Research ArticleCorrelation of VLF-EM Data with RadiometricMeasurements Implications for Uranium Exploration aroundBeldih South Purulia Shear Zone India
Saurabh Mittal S P Sharma Arkoprovo Biswas and D Sengupta
Department of Geology amp Geophysics Indian Institute of Technology Kharagpur Kharagpur West Bengal 721302 India
Correspondence should be addressed to Saurabh Mittal saurabhmittalggiitkgpernetin
Received 22 October 2013 Revised 26 January 2014 Accepted 25 February 2014 Published 27 March 2014
Academic Editor Michael S Zhdanov
Copyright copy 2014 Saurabh Mittal et alThis is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited
This study is an attempt to correlate VLF-EM data with the radiometric measurements to decipher the subsurface structure and tolocate uranium mineralization in the shear zone The study area is around Beldih mine which is an open cast apatite mine locatedon the South Purulia Shear Zone VLF method has been applied to map the structure and the presence of radioactive minerals hasbeen delineated by the detection of high 120572 and 120574 counts with respect to the background radiations High radiation counts and highsurface 120574 activity are found just above the higher apparent current-density zones in all the profiles studied at various locationsindicating uranium andor thorium mineralization as well as good correlation between these techniques
1 Introduction
Radioactive minerals occur naturally in the geological envi-ronment associated with geological features like unconfor-mity contact veins shear zones and so forth [1 2] Thenature of mineralization varies from hydrothermal vein typestrata bound deposit disseminated type and brecciatedcomplex in the form of vertical dipping and horizontalsheet type structures This is dependent primarily on theprevailing geological environment and the valence state ofuranium respectively In addition the extinction coefficientof 120572 and 120573 particles and 120574 radiations determines the depthof investigation Such shallow subsurface structures canbe best delineated by very low frequency electromagneticmethod due to its advantage in detecting conducting struc-tures Uranium being a metal is highly conducting andtherefore its presence in the subsurface rocks provides anexcellent conductivity contrast between its deposit and theneighboring formations [3 4] Moreover to validate thepresence of radioactive mineralization radiometric surveyis an essential aspect which can differentiate with a betterresolution between a probable mineralization and that of
an economic prospectTheir occurrences in outcrop enhancethe background radiation of the area
The present area of study is around an open cast minein Beldih which is known for apatite deposits and mainlyconsists of quartz-magnetite-apatite rocks granite quartziteand so forth This mine is located along the South PuruliaShear Zone (SPSZ) Low gravity high magnetic anomalylow resistivity low self-potential and shallow subsurfacesignature of uranium from bore hole has also been found inand around Beldih mine [5ndash7] Considering these findingsour aim of the survey was to demarcate the actual structureof the uranium ore body and to trace its possible extensionalong the shear zone around Beldih mine To achieve this anintegrated approach was applied where very low frequency(VLF) electromagnetic and radiometric surveys were usedtogether Since the depth of investigation for VLF methoddepends on skin depth and for the radiometric methoddepends on extinction coefficient which in turn dependson the lithology of the area as well as on the energy ofthe associated particles these measurements will throwsome light in better correlation for uranium mineralizationAnother added advantage of this integrated approach is their
Hindawi Publishing CorporationInternational Journal of GeophysicsVolume 2014 Article ID 969462 13 pageshttpdxdoiorg1011552014969462
2 International Journal of Geophysics
Beldih village (N)
Dump
Dump
Dum
p
Borehole
Mine dumpKaolin zone
QuartziteGranite
Quartz-magnetite-apatite rocks
Tuffaceous rock
Altered brecciated ultramafics Radioactive zone (vertical projection from bore hole)
VLF profile
P1500P1200P1100 P1300P1400
NP1600P1700
P1800
Cultivated land
Cultivated land
Cultivated land
Cultivated land
Cultivated land
Tank
Beldih
325998400
32998400
315998400
31998400
305998400
295998400
1745998400
175998400
1755998400
176998400
1765998400
177998400
1775998400
178998400
1785998400
179998400
1795998400
1800998400
1805998400
1810998400
1815998400
1820998400
1825998400
1830998400
3998400
29998400
285998400
280998400
86∘ and minutes
86∘ and minutes
23∘
and
min
utes
23∘
and
min
utes
0 100 200
(m)Ultramafics plusmn carbonatite
Dump
Figure 1 Geological map of Beldih mine (modified after [7]) showing VLF profiles (straight lines)
rapidness and cost-effectiveness and hence they can be usedas a quick mapping and subsurface imaging tool for scanningstructures associated with uranium mineralization
2 Geology of the Area
Beldih mine is located in Purulia district of West BengalIndia along the South Purulia Shear Zone (SPSZ)This formsa part of E-W toESE-WNWtrendingTamar-Porapahar linea-ment and it extends from Tamar Ranchi district Jharkhandin the west to Porapahar Bankura district West-Bengal inthe east The lineament vis-a-vis shear zone lies between thecontact of Chotanagpur Granite Gneiss Complex (CGGC) inthe north and Singhbhum Group in the south The strati-graphic sequence of the Beldih area is represented by ultra-mafic rocks chlorite-sericite schists chlorite-mica schistsquartzites alkali granites amphibolites and Chotanagpurgranite gneiss [8 9] Quartz-apatite-magnetite rocks carbon-atite and syenites are some other significant rocks reportedfrom Beldih region [9ndash12] This part of the shear zone is alsoreferred to as BeldihndashKutni shear zone it is a small part ofSPSZwhere deformation ismore intense which crosscuts theboundaries of regional metamorphic zoning The nature ofthe shear zone has been described as ductile to brittle-ductile[13 14]The Beldih deposit is hosted by the rocks of amphibo-lite facies but the rocks in shear zone are composed of chloriteschists and hydrothermally altered rocks This mine is also
well known for its apatite mining [10 13] and recently pres-ence of uranium deposits is also reported from this mine [7]
3 Very Low Frequency Electromagnetic Survey
Very low frequency method is a semipassive electromagneticinduction method which utilizes distant high power verticaltransmitters as a source for the primary field These trans-mitters are meant for long distance marine communicationsand situated on the coastal areas worldwide They operatein the lower band (15ndash30 kHz) of communication frequencyThese signals travel a long distance and can be utilizedfor geophysical measurements several thousand km awayfrom transmitters Since the primary field is horizontal VLFmethod is ideal for the investigation of vertical and dippingconducting structures in the subsurface It is emphasizedthat in principle VLF method uses the highest frequencycompared to other electromagneticmethodsThe name ldquoverylow frequencyrdquo comes from the transmitter used for longdistance marine communication Indeed 15ndash30 kHz is verylow with regard to other communication frequencies used inradio TV and mobile communications
The ABEM Wadi VLF instrument that utilizes only amagnetic field component was used for the present studyThis instrumentmeasures the ratio of the vertical componentof the magnetic field (119867
Figure 2 Profile P1100 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
conductor and the horizontal component (119867119909) of the primary
magnetic field which dependsmostly on theVLF transmitterIf the geological strike is along119910-axis andVLF transmitter
is located in the direction of 119884-axis from the point ofobservation then the tilt angle 120572 which is the inclination ofthe major axis of the polarization ellipse and the ellipticity 119890which is the ratio of the minor to the major axis of the ellipseare calculated by the formulae [15]
tan 2120572 = plusmn2 (119867119911119867119909) cosΔ120601
1 minus (119867119911119867119909)2
119890 =
119867119911119867119909sinΔ1206011198672
1
(1)
where the phase difference Δ120601 = 120601119911minus 120601119909 in which 120601
119911is the
phase of119867119911 120601119909is the phase of119867
119909 and119867
1= |119867119911119890119894Δ120601 sin120572 +
119867119909cos120572| The tangent of the tilt angle and the ellipticity are
good approximations to the ratio of the real component of thevertical secondary magnetic field to the horizontal primarymagnetic field and to the ratio of the quadrature componentof the vertical secondary magnetic field to the horizontalprimary field respectively [16]These quantities are called thereal (= tan120572times100) and imaginary (= 119890times 100) anomaliesrespectively and they are normally expressed in percentage
It is to be noted that real and imaginary VLF anomalieslike other electromagnetic anomalies are also affected bydifferent kinds of noises such as power line disturbances aswell as cultural noises In the present case the study area
Figure 3 Profile P1200 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
is quite remote and free from cultural noise but is affectedby power line disturbances However the power distributionwas absent during day time when the measurements weretaken Hence VLF measurement is free from such noisealso Further transmitter should be selected in the directionof geological strike and measurement should be made ina profile perpendicular to the known geological strike toattain maximum signal to noise ratio or least effect of noiseon the actual data ABEM Wadi instrument automaticallycorrects the observation if transmitter direction is deviatedplusmn10 degrees from the required direction When transmitterdirection is deviated by a large amount then a ldquobad tuningsignalrdquo is displayed on the monitor of the instrument
Subsequently orientation is adjusted accordingly and correctmeasurement is recorded With these precautions in theinstrument the expected error in the measurements is lessthan 5
The strike of the formation around the Beldih mine isapproximately in the E-W direction hence a transmitter inE-Wdirectionwith frequency of 198 kHz (located in BombayIndia) was selected for E-polarization measurements VLFsurveys were performed along eight profiles oriented inN-S direction (Figure 1) (running from south to north) Thedata was acquired at 10m intervals and subsequently datawas first smoothed with 5-point averaging filter and theninterpolated at 2m intervals to increase the resolution
Figure 4 Profile P1300 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
The above mentioned interpolated (Real and imaginary)data is transformed into apparent current density distributionin the subsurface which resembles the subsurface structureKarous and Hjelt [17] developed a filtering technique to cal-culate apparent current density which produces a magneticfield identical to the measured field If119867
minus3119867minus2119867minus111986701198671
1198672 and 119867
3are the equispaced real or imaginary anomaly
at locations 119909minus3 119909minus2 119909minus1 1199090 1199091 1199092 and 119909
3 respectively
the apparent current density at 1199090and depth Δ119911 = Δ119909 can
be computed from the following relation Consider
119869119886(1199090) =
2120587
Δ119911
(minus0102119867minus3+ 0059119867
minus2minus 0561119867
minus1
+05611198671minus 0059119867
2+ 0102119867
3)
(2)
Subsequently apparent current density is computed alongwhole profile at depth Δ119911 = Δ119909 by considering otherobservations along the profile in a systematic manner Nextobservation stations are selected with 2Δ119909 spacing andfiltering is repeated to obtain apparent current density atdepth 2Δ119909 This process is repeated to obtain apparentcurrent density at various depths The main limitation of thisapproach is apparent current density which gets truncatedgradually with depth from both sides of the profile Thisimaging technique yields 8 error in the estimation of thestructure [17] However it is fast and accurate in depictingthe subsurface structure and widely used for VLF data inter-pretation We have used this imaging technique to produceapparent current density cross-sections in the present study
Figure 5 Profile P1400 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
4 Radiometric Survey
Radiometric survey was carried out using Geiger-Mullercounter to record total ambient surface radiations andScintillation counter to note the surface gamma radiationsalong the eight selected profiles where VLF survey wasperformed For better and point to point correlation withVLF data radiometric data was collected at the same stationswhere VLF data was recorded along all the profiles usingGPS receivers For precise and accurate measurements everyradiometric measurement was repeated thrice
41 Geiger-Muller Counter Total surface radiations weremeasured using a portable pulsed GM (Geiger-Muller)counter at various locations along the selected profiles aroundthe mine The GM probe is comprised of a thin end window
halogen-quenched counter which is capable of detectingalpha and beta particles and small amount of gamma radi-ations It has a dead time of 200120583s The window is 2 cmin diameter and is shielded with a 1 cm thick lead collarThe instrument is operated with five membrane push buttonswitches and the display is a 6-digit LED
For detailed radiometric survey total radiation countswere measured at every 10m intervals along the profilesexactly where the VLF data was recorded For each mea-surement the sensor of GM counter was kept approximately15 cm above the ground surface and operated for 100 secondsduring data acquisition
42 Scintillation Counter For precise measurements of the 120574radiation we have used a portable scintillator based counting
Current density ()minus11 minus8 minus4 0 4 8 12 15
200
160
120
80
40
0
40
30
20
10
0
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 6 Profile P1500 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
system This Micro-R Survey Meter Type-UR 705 is manu-factured by Nucleonix Systems Private Limited HyderabadIndia It is designed around an integrally coupled 254 times254 cm scintillator coupled to a 254 times 127 cm Photomulti-plier Tube
The measurements were taken during winter season inorder to avoid the interference of gamma-emitting radondecay products [18] The 120574 measurements were undertakensim1m above the ground surface and directly above theexposure to get a better solid angle Each measurement wasundertaken for more than 60 seconds and was repeatedthrice for better precision and optimizing the subsequentinterpretation in terms of the ambient radiation
5 Results
On eastern side of the mine area five profiles namely P1100P1200 P1300 P1400 and P1500 covering around 600mof distance (profile length) (Figure 1) were accomplishedOn the western part of mine we took three profiles P1600P1700 and P1800 covering 600m of length (Figure 1) Forinterpretation of the subsurface geometry apparent currentdensity cross-sections with depths were made using theacquired VLF data along all the profiles For this themeasured real anomalies were interpolated at 2m intervaland filtered using Karous-Hjelt filter [17] These apparentcurrent density cross-sections are presented in Figures 2ndash9
Figure 7 Profile P1600 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
below the real and imaginary anomaly plots obtained fromthe VLF data acquired in the field Results for surface gammaactivity and total surface radiations are also shown as line-plots along with VLF anomaly for every individual profile(Figures 2ndash9) Background radiation level of the region is 40counts100 sec for surface radiations and 6ndash8120583Rh for surfacegamma activity
51 Profile 1 (P1100) The cross-over of real and imaginaryanomaly line-plot along this profile indicates the presenceof conductive zone between stations 500m and 580m(Figure 2(a))This zone is clearly depicted in apparent currentdensity cross-section (Figure 2(b)) by higher values betweenstations 460m and 540m Inclination of real anomaly curve
and apparent current density contours indicate that this con-ductive structure is vertical and lying at shallow depth (sim40mbelow surface) Radiometric data suggest the presence ofradiation more than the background levels above this con-ductive zonewith peak value of 16120583Rh and 80 counts100 secfor surface gamma activity and total radiations respectivelyat station 520m
52 Profile 2 (P1200) Profile P1200 is parallel to and 96meast of profile P1100 (Figure 3) The cross-over of real andimaginary VLF anomaly along this profile indicates thepresence of conductive feature around station 550m in thenorthern end of the profile and the slope of curve suggestsit to be a thin inclined body occurring at shallow depth
International Journal of Geophysics 9
N
40
20
0
minus20
minus40
minus60Real
anom
aly
()
Imag
inar
y
50 100 150 200 250 300 350 400 450 500 600550
Distance (m)
40
20
0
minus20
minus40
minus50
minus100
minus12 minus8 minus4 0 4 8 12
Dep
th (m
)
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
30
40
50
60
70
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
6
8
10
12
0
0
0
Current density ()
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 8 Profile P1700 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
The current density contours along this profile clearly demar-cates the shape of this body between stations 510mand 570msuggesting a width of around 60m occurring below 30mfrom the surface Radiometric data recorded over this profileshows similar behavior as that at profile P1100 with peakvalues at 520m
53 Profile 3 (P1300) This profile P1300 (Figure 4) is further83m east of profile P1200 The real and imaginary anomalyplots indicate the presence of multiple conductive bodiesalong this profile and the slope of these curves suggestsvertical structures occurring near to the surface Apparent
current density cross-section also depicts the same resultshowing the presence of three broad and shallow almostvertical conductors between stations 0m and 60m 160mand 250m and 375m and 450m Similarly the radioactivityalong this profile is higher than the background throughoutthe profile with peak between 410m and 440m The peakvalue of total radiations and surface gamma activity recordedat this station is 75 counts100 sec and 19 120583Rh respectively
54 Profile 4 (P1400) Profile P1400 lies 92m east of pro-file P1300 (Figure 5) Here also the VLF anomaly curvesdepict three conductive features all being shallow and nearly
10 International Journal of Geophysics
6789
10
0
N
20
10
0
minus10
minus10minus20Real
anom
aly
()
Imag
inar
y
50 100 150 200 250 300 350 400 450 500
Distance (m)0
10
20
30
minus20
minus40
minus60
minus80
50 100 150 200 250 300 350 400 450
Distance (m)
minus14 minus10 minus6 minus2 2 6 10 14 16
Current density ()
Dep
th (m
)
30
40
50
60
70
50 100 150 200 250 300 350 400 450 500
Distance (m)0
50 100 150 200 250 300 350 400 450 500
Distance (m)0
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 9 Profile P1800 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
vertical Apparent current density cross-section shows thepresence of one conducting and two low conducting struc-tures between stations 70m and 140m 270m and 320mand 490m and 520m respectively The conductor at thesouthern part of the profile (between stations 70mand 140m)is more conductive and wider among the three Radioactivityis observed to be highest above this conductor with peakvalue of total radiation being 290 counts100 sec and that ofgamma activity being 60120583Rh at station 150m This is thehighest radioactivity recorded along all the profiles
55 Profile 5 (P1500) Profile P1500 is taken 86m awaytowards east of profile P1400 (Figure 6) VLF anomaly curves
suggest the presence of a single conductor around station400m The slope of the anomaly curves indicates a thickinclined structure Apparent current density cross-sectionconfirms the presence of inclined conductive structurebetween stations 330mm to 420m Radiometric data isobserved to be almost equal to the background levels all longthe profile with a sudden jump in value to 180 counts100 secof total radiations and 35 120583Rh surface gamma activity atstation 510m
56 Profile 6 (P1600) This profile is located in the westernside of the Beldih mine (Figure 7) VLF anomaly curves indi-cate the presence of two conductive features around stations
International Journal of Geophysics 11
86
P1500P1100 P1200 P1300 P1400
P1600P1700
P1800
18 1805 181 1815
29
295
3
305
31
176 1765
Mine dump
N
Cultivated land
Cultivated land
298
3
302
304
306
308
31312
314
316
318
32
Cultivated land
Cultivated land
Cultivated land
Beldih village (N)
Bore hole BoreholeBLD2 BLD3
Beldih
325998400
32998400
315998400
31998400
305998400
295998400
3998400
29998400
285998400
280998400
23∘
and
min
utes
1745998400
175998400
1755998400
176998400
1765998400
177998400
1775998400
178998400
1785998400
179998400
1795998400
1800998400
1805998400
1810998400
1815998400
1820998400
1825998400
1830998400
86∘ and minutes
0 100 200
(m)
Mine dumpKaolin zone
QuartziteGranite
Quartz-magnetite-apatite rocks
Tuffaceous rock
Altered brecciated ultramafics Radioactive bands (vertical projection from borehole)
VLF profile Ultramafics plusmn carbonatite
5
10
15
20
25
30
35
40
45
50
55
86∘ and minutes
23∘
and
min
utes
Tank
(120583Rh
r)
Figure 10 Surface gamma activity superimposed over geological map of the area of study
Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
240
220
200
180
Datum
0 10
S
20 (m)
N
Expected mineralized zone
260
220
200
180
Datum240
Transverse section through bore hole BLD2 Transverse section through bore hole BLD3
RL-24062m
RL
(m)
BLD2
DD-13075m DD-16355m
640m840m
BLD3
RL
(m)
RL-24234m
Altered brecciated ultramafics
Ultramafics plusmn carbonatite Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
Altered brecciated ultramafics
Ultramafics plusmn carbonatite
Figure 11 Transverse sections through bore holes BLD2 and BLD3 (after [7])
200m and 450m Apparent current density cross-sectiondepicts both of the structures between stations 150m and250m and 410m and 520m and shows that they are dippingstructures Radiometric data shows high radioactivity in thesouthern side of the profile compared to the northern sidewith peak value of total radiation and gamma activity (140counts100 sec and 28 120583Rh resp) found above the station250m
57 Profile 7 (P1700) Differing from all other profiles inprofile P1700 92mwest of P1600 (Figure 8) theVLF anomalycurves indicate a single wide conductive feature lying all overthe profile with centre at 350m Apparent current densitycross-section also shows a much wider conductive featurelying between 0m and 230m 250m and 370m and 390mand 500m ranging in current density values from 4 to10 4 to 12 and 4 to 8 respectively This shows that
12 International Journal of Geophysics
here the same conducting zone is wider than other locationsWhereas radiometric data suggests high radioactivity abovethe background level only between stations 70m and 210m
58 Profile 8 (P1800) Further 88m west of P1700 in profileP1800 (Figure 9) VLF anomaly curves indicate the presenceof two vertical conductors Current density contours alsoshow two conductive features between stations 160m and220m and 320m and 370m The first one is less conductiveas compared to the later one Radiometric data indicates highradioactivity in the southern part of the profile with threepeak regions around stations 50m 140m and 180m
6 Discussion
In the present study eight profiles were chosen on eitherside of the Beldih mine to investigate the uranium andorthorium mineralization by applying VLF-EM and radiomet-ric methods together Results show the presence of multipleisolated conductive features in the study area These con-ductive features appearing in the profile could be becauseof the presence of fractures filled with fluids hydrothermalalteration zones clay mineralization shearing and so forthThe conductive features are traced continuously well in allthe profiles showing a regular parallel trend except in profileP1400where the similar zone is identified in the southern sideof the profileThis implies that the conductive feature at P1400has shifted southward in this profile only This offset of thecurrent density anomaly (in profile P1400) could be due toeither strike slip fault or dip slip fault or subparallel faultingIn case of dip slip fault such offset can be observed only ifan inclined bed is cut by a vertical fault at right angles tothe strike and the slip is normal After erosion such an offsetcan be seen However the observed anomalies appear verticalin the current density profile and the offset or movementis lateral along the strike of the fault This happens in caseof strike-slip fault hence it appears to be the better reasonfor such lateral shift of the mineralized body This can befurther substantiated by successive structural mapping of thearea
The separation between the conductive bodies is notuniform along all the profilesThis further suggests that thesemineralized bodies have small strike length and lenticularshape This result together with the geology of the area indi-cates that the mode of mineralization may be hydrothermalalteration
Radiometric measurements indicate higher radiationsalong the profiles than the average or background radiationsobserved in the areaThe peak or elevated radiations indicatethe presence of uranium mineralization
Surface gamma activity superimposed over geologicalmap of the area of study (Figure 10) clearly depicts the coinci-dence of conductive zones and high radioactivity zones Thiscoincidence indicates the existence of alteration zones in thisarea These zones may contain radioactive mineralization asthey are also correlating with the radioactive bands identifiedby Katti et al [7] and with the bore hole data BLD2 and BLD3(Figures 10 and 11) All these identified mineralized zones are
almost parallel and have a collective strike oriented along E-W direction which is in agreement with the strike of SPSZ
7 Conclusions
VLF-EM and radiometric methods were applied togetherin this region to study the correlation between these twomethods as well as to utilize their integrated results for theexploration of uranium Results indicate good correlationbetween VLF data and radiometric dataThis is because theseradiometric signals are associated with shallow uraniummineralization which is associated with altered mineralsthat gives conductivity contrast with the neighboring rocksCoincidence of high radioactivity over conductive zonesand their correlation with radioactive bands observed inthe area confirms the presence of uranium mineralizationThus the study also suggests that these two methods can beintegrated to explore uraniumandor thoriummineralizationeffectively at low cost with the advantage of being quick andnondestructive compared to other routine methods used forsuch purposesThe study also reveals the presence of a strike-slip fault in the eastern side of the Beldih mine proving theability and advantage of this integrated approach in detectingsuch planner structures and correlating the lithology bothvertically and laterally Since these methods are quick andcost effective they can be utilized to search for shallowuranium mineralization along the SPSZ and other suchregions quickly VLF observations are sometimes affected bypower lines in such areas Gradient Resistivity Profiling andgravity and magnetic methods can be applied to aid in theinterpretation of subsurface structures
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors would like to thank the editor and anonymousreviewers for their valuable comments and suggestions toimprove the quality of the paper
References
[1] B K Bhaumik T Bhattacharya A A P S R AcharyuluD Srinivas and M K Sandilya Principles of Radiometry inRadioactive Metal Exploration Physics Lab AMD ComplexJamshedpur India 2004
[2] V Tuncer M J Unsworth W Siripunvaraporn and J ACraven ldquoExploration for unconformity-type uranium depos-its with audiomagnetotelluric data a case study from theMcArthur River mine Saskatchewan Canadardquo Geophysics vol71 no 6 pp B201ndashB209 2006
[3] J M Legault D Carriere and L Petrie ldquoSynthetic modeltesting and distributed acquisition dc resistivity results overan unconformity uranium target from the Athabasca Basinnorthern SaskatchewanrdquoTheLeading Edge vol 27 no 1 pp 46ndash51 2008
International Journal of Geophysics 13
[4] G Nimeck and R Koch ldquoA progressive geophysical explorationstrategy at the Shea Creek uranium depositrdquoThe Leading Edgevol 27 no 1 pp 52ndash63 2008
[5] A Mandal A Biswas S Mittal et al ldquoGeophysical anomaliesassociated with uranium mineralization from Beldih mineSouth Purulia Shear Zone Indiardquo Journal of the GeologicalSociety of India vol 82 no 6 pp 601ndash606 2013
[6] S P Sharma A Biswas and S Mittal ldquoDelineation of extensionof uranium mineralization zone using resistivity and VLFsur-veys around South Purulia Shear Zone Indiardquo Journal of theGeological Society of India In press
[7] V J Katti J Sen andAK Bhatt ldquoUraniumpotentiality of SouthPurulia Shear Zone in Eastern Indian Shieldrdquo in Proceedings ofthe Technical Meeting on Low Grade Uranium Ore pp 29ndash31International Atomic Energy Agency Vienna Austria 2010
[8] A Acharyya S Ray B K Chaudhuri S K Basu S K Bhaduriand A K Sanyal ldquoProterozoic rock suites along South PuruliaShear Zone eastern India evidence for rift-related settingrdquoJournal of the Geological Society of India vol 68 no 6 pp 1069ndash1086 2006
[9] Y Vapnik S Bushmin A Chattopadhyay and D Dolivo-Dobrovolsky ldquoFluid inclusion and mineralogical study of vein-type apatite ores in shear zones from the Singhbhum metallo-genetic provinceWest Bengal IndiardquoOre Geology Reviews vol32 no 1-2 pp 412ndash430 2007
[10] T K Baidya ldquoApatite-magnetite deposit in the chhotanagpurgneissic complex Panrkidih area Purulia District West Ben-galrdquo Indian Journal of Geology vol 64 pp 88ndash95 1992
[11] S K Basu ldquoAlkaline-carbonatite complex in Precambrian ofSouth Purulia Shear Zone eastern India its characteristics andmineral potentialitiesrdquo Indian Minerals vol 47 no 3 pp 179ndash194 1993
[12] A K G Roy and P R Sengupta ldquoAlkalic-carbonatitic magma-tism and associated mineralisation along the Porapahar-Tamarlineament in the Proterozoics of Purulia District West BengalrdquoIndian Journal of Earth Sciences vol 20 no 3-4 pp 193ndash2001993
[13] T K Pyne ldquoThe Proterozoic fold belt and the chhotanagpurgneissic complex in the eastern Indian Shieldmdasha tectono-metamorphic appraisalrdquo Indian Minerals vol 46 no 1 pp 25ndash34 1992
[14] S Bhattacharya ldquoDuctile shear Zone in Purulia West BengalrdquoIndian Journal of Geology vol 61 pp 172ndash178 1989
[15] B D Smith and S H Ward ldquoOn the computation of polariza-tion ellipse parametersrdquo Geophysics vol 39 pp 867ndash869 1974
[16] N R Paterson and V Ronka ldquoFive years of surveying with thevery low frequency-electromagnetics methodrdquoGeoexplorationvol 9 no 1 pp 7ndash26 1971
[17] M Karous and S E Hjelt ldquoLinear filtering of VLF dip-anglemeasurementsrdquo Geophysical Prospecting vol 31 no 5 pp 782ndash794 1983
[18] A T Ramli S Sahrone and H Wagiran ldquoTerrestrial gammaradiation dose study to determine the baseline for environ-mental radiological health practices in Melaka state MalaysiardquoJournal of Radiological Protection vol 25 no 4 pp 435ndash4502005
Altered brecciated ultramafics Radioactive zone (vertical projection from bore hole)
VLF profile
P1500P1200P1100 P1300P1400
NP1600P1700
P1800
Cultivated land
Cultivated land
Cultivated land
Cultivated land
Cultivated land
Tank
Beldih
325998400
32998400
315998400
31998400
305998400
295998400
1745998400
175998400
1755998400
176998400
1765998400
177998400
1775998400
178998400
1785998400
179998400
1795998400
1800998400
1805998400
1810998400
1815998400
1820998400
1825998400
1830998400
3998400
29998400
285998400
280998400
86∘ and minutes
86∘ and minutes
23∘
and
min
utes
23∘
and
min
utes
0 100 200
(m)Ultramafics plusmn carbonatite
Dump
Figure 1 Geological map of Beldih mine (modified after [7]) showing VLF profiles (straight lines)
rapidness and cost-effectiveness and hence they can be usedas a quick mapping and subsurface imaging tool for scanningstructures associated with uranium mineralization
2 Geology of the Area
Beldih mine is located in Purulia district of West BengalIndia along the South Purulia Shear Zone (SPSZ)This formsa part of E-W toESE-WNWtrendingTamar-Porapahar linea-ment and it extends from Tamar Ranchi district Jharkhandin the west to Porapahar Bankura district West-Bengal inthe east The lineament vis-a-vis shear zone lies between thecontact of Chotanagpur Granite Gneiss Complex (CGGC) inthe north and Singhbhum Group in the south The strati-graphic sequence of the Beldih area is represented by ultra-mafic rocks chlorite-sericite schists chlorite-mica schistsquartzites alkali granites amphibolites and Chotanagpurgranite gneiss [8 9] Quartz-apatite-magnetite rocks carbon-atite and syenites are some other significant rocks reportedfrom Beldih region [9ndash12] This part of the shear zone is alsoreferred to as BeldihndashKutni shear zone it is a small part ofSPSZwhere deformation ismore intense which crosscuts theboundaries of regional metamorphic zoning The nature ofthe shear zone has been described as ductile to brittle-ductile[13 14]The Beldih deposit is hosted by the rocks of amphibo-lite facies but the rocks in shear zone are composed of chloriteschists and hydrothermally altered rocks This mine is also
well known for its apatite mining [10 13] and recently pres-ence of uranium deposits is also reported from this mine [7]
3 Very Low Frequency Electromagnetic Survey
Very low frequency method is a semipassive electromagneticinduction method which utilizes distant high power verticaltransmitters as a source for the primary field These trans-mitters are meant for long distance marine communicationsand situated on the coastal areas worldwide They operatein the lower band (15ndash30 kHz) of communication frequencyThese signals travel a long distance and can be utilizedfor geophysical measurements several thousand km awayfrom transmitters Since the primary field is horizontal VLFmethod is ideal for the investigation of vertical and dippingconducting structures in the subsurface It is emphasizedthat in principle VLF method uses the highest frequencycompared to other electromagneticmethodsThe name ldquoverylow frequencyrdquo comes from the transmitter used for longdistance marine communication Indeed 15ndash30 kHz is verylow with regard to other communication frequencies used inradio TV and mobile communications
The ABEM Wadi VLF instrument that utilizes only amagnetic field component was used for the present studyThis instrumentmeasures the ratio of the vertical componentof the magnetic field (119867
Figure 2 Profile P1100 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
conductor and the horizontal component (119867119909) of the primary
magnetic field which dependsmostly on theVLF transmitterIf the geological strike is along119910-axis andVLF transmitter
is located in the direction of 119884-axis from the point ofobservation then the tilt angle 120572 which is the inclination ofthe major axis of the polarization ellipse and the ellipticity 119890which is the ratio of the minor to the major axis of the ellipseare calculated by the formulae [15]
tan 2120572 = plusmn2 (119867119911119867119909) cosΔ120601
1 minus (119867119911119867119909)2
119890 =
119867119911119867119909sinΔ1206011198672
1
(1)
where the phase difference Δ120601 = 120601119911minus 120601119909 in which 120601
119911is the
phase of119867119911 120601119909is the phase of119867
119909 and119867
1= |119867119911119890119894Δ120601 sin120572 +
119867119909cos120572| The tangent of the tilt angle and the ellipticity are
good approximations to the ratio of the real component of thevertical secondary magnetic field to the horizontal primarymagnetic field and to the ratio of the quadrature componentof the vertical secondary magnetic field to the horizontalprimary field respectively [16]These quantities are called thereal (= tan120572times100) and imaginary (= 119890times 100) anomaliesrespectively and they are normally expressed in percentage
It is to be noted that real and imaginary VLF anomalieslike other electromagnetic anomalies are also affected bydifferent kinds of noises such as power line disturbances aswell as cultural noises In the present case the study area
Figure 3 Profile P1200 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
is quite remote and free from cultural noise but is affectedby power line disturbances However the power distributionwas absent during day time when the measurements weretaken Hence VLF measurement is free from such noisealso Further transmitter should be selected in the directionof geological strike and measurement should be made ina profile perpendicular to the known geological strike toattain maximum signal to noise ratio or least effect of noiseon the actual data ABEM Wadi instrument automaticallycorrects the observation if transmitter direction is deviatedplusmn10 degrees from the required direction When transmitterdirection is deviated by a large amount then a ldquobad tuningsignalrdquo is displayed on the monitor of the instrument
Subsequently orientation is adjusted accordingly and correctmeasurement is recorded With these precautions in theinstrument the expected error in the measurements is lessthan 5
The strike of the formation around the Beldih mine isapproximately in the E-W direction hence a transmitter inE-Wdirectionwith frequency of 198 kHz (located in BombayIndia) was selected for E-polarization measurements VLFsurveys were performed along eight profiles oriented inN-S direction (Figure 1) (running from south to north) Thedata was acquired at 10m intervals and subsequently datawas first smoothed with 5-point averaging filter and theninterpolated at 2m intervals to increase the resolution
Figure 4 Profile P1300 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
The above mentioned interpolated (Real and imaginary)data is transformed into apparent current density distributionin the subsurface which resembles the subsurface structureKarous and Hjelt [17] developed a filtering technique to cal-culate apparent current density which produces a magneticfield identical to the measured field If119867
minus3119867minus2119867minus111986701198671
1198672 and 119867
3are the equispaced real or imaginary anomaly
at locations 119909minus3 119909minus2 119909minus1 1199090 1199091 1199092 and 119909
3 respectively
the apparent current density at 1199090and depth Δ119911 = Δ119909 can
be computed from the following relation Consider
119869119886(1199090) =
2120587
Δ119911
(minus0102119867minus3+ 0059119867
minus2minus 0561119867
minus1
+05611198671minus 0059119867
2+ 0102119867
3)
(2)
Subsequently apparent current density is computed alongwhole profile at depth Δ119911 = Δ119909 by considering otherobservations along the profile in a systematic manner Nextobservation stations are selected with 2Δ119909 spacing andfiltering is repeated to obtain apparent current density atdepth 2Δ119909 This process is repeated to obtain apparentcurrent density at various depths The main limitation of thisapproach is apparent current density which gets truncatedgradually with depth from both sides of the profile Thisimaging technique yields 8 error in the estimation of thestructure [17] However it is fast and accurate in depictingthe subsurface structure and widely used for VLF data inter-pretation We have used this imaging technique to produceapparent current density cross-sections in the present study
Figure 5 Profile P1400 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
4 Radiometric Survey
Radiometric survey was carried out using Geiger-Mullercounter to record total ambient surface radiations andScintillation counter to note the surface gamma radiationsalong the eight selected profiles where VLF survey wasperformed For better and point to point correlation withVLF data radiometric data was collected at the same stationswhere VLF data was recorded along all the profiles usingGPS receivers For precise and accurate measurements everyradiometric measurement was repeated thrice
41 Geiger-Muller Counter Total surface radiations weremeasured using a portable pulsed GM (Geiger-Muller)counter at various locations along the selected profiles aroundthe mine The GM probe is comprised of a thin end window
halogen-quenched counter which is capable of detectingalpha and beta particles and small amount of gamma radi-ations It has a dead time of 200120583s The window is 2 cmin diameter and is shielded with a 1 cm thick lead collarThe instrument is operated with five membrane push buttonswitches and the display is a 6-digit LED
For detailed radiometric survey total radiation countswere measured at every 10m intervals along the profilesexactly where the VLF data was recorded For each mea-surement the sensor of GM counter was kept approximately15 cm above the ground surface and operated for 100 secondsduring data acquisition
42 Scintillation Counter For precise measurements of the 120574radiation we have used a portable scintillator based counting
Current density ()minus11 minus8 minus4 0 4 8 12 15
200
160
120
80
40
0
40
30
20
10
0
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 6 Profile P1500 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
system This Micro-R Survey Meter Type-UR 705 is manu-factured by Nucleonix Systems Private Limited HyderabadIndia It is designed around an integrally coupled 254 times254 cm scintillator coupled to a 254 times 127 cm Photomulti-plier Tube
The measurements were taken during winter season inorder to avoid the interference of gamma-emitting radondecay products [18] The 120574 measurements were undertakensim1m above the ground surface and directly above theexposure to get a better solid angle Each measurement wasundertaken for more than 60 seconds and was repeatedthrice for better precision and optimizing the subsequentinterpretation in terms of the ambient radiation
5 Results
On eastern side of the mine area five profiles namely P1100P1200 P1300 P1400 and P1500 covering around 600mof distance (profile length) (Figure 1) were accomplishedOn the western part of mine we took three profiles P1600P1700 and P1800 covering 600m of length (Figure 1) Forinterpretation of the subsurface geometry apparent currentdensity cross-sections with depths were made using theacquired VLF data along all the profiles For this themeasured real anomalies were interpolated at 2m intervaland filtered using Karous-Hjelt filter [17] These apparentcurrent density cross-sections are presented in Figures 2ndash9
Figure 7 Profile P1600 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
below the real and imaginary anomaly plots obtained fromthe VLF data acquired in the field Results for surface gammaactivity and total surface radiations are also shown as line-plots along with VLF anomaly for every individual profile(Figures 2ndash9) Background radiation level of the region is 40counts100 sec for surface radiations and 6ndash8120583Rh for surfacegamma activity
51 Profile 1 (P1100) The cross-over of real and imaginaryanomaly line-plot along this profile indicates the presenceof conductive zone between stations 500m and 580m(Figure 2(a))This zone is clearly depicted in apparent currentdensity cross-section (Figure 2(b)) by higher values betweenstations 460m and 540m Inclination of real anomaly curve
and apparent current density contours indicate that this con-ductive structure is vertical and lying at shallow depth (sim40mbelow surface) Radiometric data suggest the presence ofradiation more than the background levels above this con-ductive zonewith peak value of 16120583Rh and 80 counts100 secfor surface gamma activity and total radiations respectivelyat station 520m
52 Profile 2 (P1200) Profile P1200 is parallel to and 96meast of profile P1100 (Figure 3) The cross-over of real andimaginary VLF anomaly along this profile indicates thepresence of conductive feature around station 550m in thenorthern end of the profile and the slope of curve suggestsit to be a thin inclined body occurring at shallow depth
International Journal of Geophysics 9
N
40
20
0
minus20
minus40
minus60Real
anom
aly
()
Imag
inar
y
50 100 150 200 250 300 350 400 450 500 600550
Distance (m)
40
20
0
minus20
minus40
minus50
minus100
minus12 minus8 minus4 0 4 8 12
Dep
th (m
)
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
30
40
50
60
70
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
6
8
10
12
0
0
0
Current density ()
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 8 Profile P1700 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
The current density contours along this profile clearly demar-cates the shape of this body between stations 510mand 570msuggesting a width of around 60m occurring below 30mfrom the surface Radiometric data recorded over this profileshows similar behavior as that at profile P1100 with peakvalues at 520m
53 Profile 3 (P1300) This profile P1300 (Figure 4) is further83m east of profile P1200 The real and imaginary anomalyplots indicate the presence of multiple conductive bodiesalong this profile and the slope of these curves suggestsvertical structures occurring near to the surface Apparent
current density cross-section also depicts the same resultshowing the presence of three broad and shallow almostvertical conductors between stations 0m and 60m 160mand 250m and 375m and 450m Similarly the radioactivityalong this profile is higher than the background throughoutthe profile with peak between 410m and 440m The peakvalue of total radiations and surface gamma activity recordedat this station is 75 counts100 sec and 19 120583Rh respectively
54 Profile 4 (P1400) Profile P1400 lies 92m east of pro-file P1300 (Figure 5) Here also the VLF anomaly curvesdepict three conductive features all being shallow and nearly
10 International Journal of Geophysics
6789
10
0
N
20
10
0
minus10
minus10minus20Real
anom
aly
()
Imag
inar
y
50 100 150 200 250 300 350 400 450 500
Distance (m)0
10
20
30
minus20
minus40
minus60
minus80
50 100 150 200 250 300 350 400 450
Distance (m)
minus14 minus10 minus6 minus2 2 6 10 14 16
Current density ()
Dep
th (m
)
30
40
50
60
70
50 100 150 200 250 300 350 400 450 500
Distance (m)0
50 100 150 200 250 300 350 400 450 500
Distance (m)0
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 9 Profile P1800 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
vertical Apparent current density cross-section shows thepresence of one conducting and two low conducting struc-tures between stations 70m and 140m 270m and 320mand 490m and 520m respectively The conductor at thesouthern part of the profile (between stations 70mand 140m)is more conductive and wider among the three Radioactivityis observed to be highest above this conductor with peakvalue of total radiation being 290 counts100 sec and that ofgamma activity being 60120583Rh at station 150m This is thehighest radioactivity recorded along all the profiles
55 Profile 5 (P1500) Profile P1500 is taken 86m awaytowards east of profile P1400 (Figure 6) VLF anomaly curves
suggest the presence of a single conductor around station400m The slope of the anomaly curves indicates a thickinclined structure Apparent current density cross-sectionconfirms the presence of inclined conductive structurebetween stations 330mm to 420m Radiometric data isobserved to be almost equal to the background levels all longthe profile with a sudden jump in value to 180 counts100 secof total radiations and 35 120583Rh surface gamma activity atstation 510m
56 Profile 6 (P1600) This profile is located in the westernside of the Beldih mine (Figure 7) VLF anomaly curves indi-cate the presence of two conductive features around stations
International Journal of Geophysics 11
86
P1500P1100 P1200 P1300 P1400
P1600P1700
P1800
18 1805 181 1815
29
295
3
305
31
176 1765
Mine dump
N
Cultivated land
Cultivated land
298
3
302
304
306
308
31312
314
316
318
32
Cultivated land
Cultivated land
Cultivated land
Beldih village (N)
Bore hole BoreholeBLD2 BLD3
Beldih
325998400
32998400
315998400
31998400
305998400
295998400
3998400
29998400
285998400
280998400
23∘
and
min
utes
1745998400
175998400
1755998400
176998400
1765998400
177998400
1775998400
178998400
1785998400
179998400
1795998400
1800998400
1805998400
1810998400
1815998400
1820998400
1825998400
1830998400
86∘ and minutes
0 100 200
(m)
Mine dumpKaolin zone
QuartziteGranite
Quartz-magnetite-apatite rocks
Tuffaceous rock
Altered brecciated ultramafics Radioactive bands (vertical projection from borehole)
VLF profile Ultramafics plusmn carbonatite
5
10
15
20
25
30
35
40
45
50
55
86∘ and minutes
23∘
and
min
utes
Tank
(120583Rh
r)
Figure 10 Surface gamma activity superimposed over geological map of the area of study
Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
240
220
200
180
Datum
0 10
S
20 (m)
N
Expected mineralized zone
260
220
200
180
Datum240
Transverse section through bore hole BLD2 Transverse section through bore hole BLD3
RL-24062m
RL
(m)
BLD2
DD-13075m DD-16355m
640m840m
BLD3
RL
(m)
RL-24234m
Altered brecciated ultramafics
Ultramafics plusmn carbonatite Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
Altered brecciated ultramafics
Ultramafics plusmn carbonatite
Figure 11 Transverse sections through bore holes BLD2 and BLD3 (after [7])
200m and 450m Apparent current density cross-sectiondepicts both of the structures between stations 150m and250m and 410m and 520m and shows that they are dippingstructures Radiometric data shows high radioactivity in thesouthern side of the profile compared to the northern sidewith peak value of total radiation and gamma activity (140counts100 sec and 28 120583Rh resp) found above the station250m
57 Profile 7 (P1700) Differing from all other profiles inprofile P1700 92mwest of P1600 (Figure 8) theVLF anomalycurves indicate a single wide conductive feature lying all overthe profile with centre at 350m Apparent current densitycross-section also shows a much wider conductive featurelying between 0m and 230m 250m and 370m and 390mand 500m ranging in current density values from 4 to10 4 to 12 and 4 to 8 respectively This shows that
12 International Journal of Geophysics
here the same conducting zone is wider than other locationsWhereas radiometric data suggests high radioactivity abovethe background level only between stations 70m and 210m
58 Profile 8 (P1800) Further 88m west of P1700 in profileP1800 (Figure 9) VLF anomaly curves indicate the presenceof two vertical conductors Current density contours alsoshow two conductive features between stations 160m and220m and 320m and 370m The first one is less conductiveas compared to the later one Radiometric data indicates highradioactivity in the southern part of the profile with threepeak regions around stations 50m 140m and 180m
6 Discussion
In the present study eight profiles were chosen on eitherside of the Beldih mine to investigate the uranium andorthorium mineralization by applying VLF-EM and radiomet-ric methods together Results show the presence of multipleisolated conductive features in the study area These con-ductive features appearing in the profile could be becauseof the presence of fractures filled with fluids hydrothermalalteration zones clay mineralization shearing and so forthThe conductive features are traced continuously well in allthe profiles showing a regular parallel trend except in profileP1400where the similar zone is identified in the southern sideof the profileThis implies that the conductive feature at P1400has shifted southward in this profile only This offset of thecurrent density anomaly (in profile P1400) could be due toeither strike slip fault or dip slip fault or subparallel faultingIn case of dip slip fault such offset can be observed only ifan inclined bed is cut by a vertical fault at right angles tothe strike and the slip is normal After erosion such an offsetcan be seen However the observed anomalies appear verticalin the current density profile and the offset or movementis lateral along the strike of the fault This happens in caseof strike-slip fault hence it appears to be the better reasonfor such lateral shift of the mineralized body This can befurther substantiated by successive structural mapping of thearea
The separation between the conductive bodies is notuniform along all the profilesThis further suggests that thesemineralized bodies have small strike length and lenticularshape This result together with the geology of the area indi-cates that the mode of mineralization may be hydrothermalalteration
Radiometric measurements indicate higher radiationsalong the profiles than the average or background radiationsobserved in the areaThe peak or elevated radiations indicatethe presence of uranium mineralization
Surface gamma activity superimposed over geologicalmap of the area of study (Figure 10) clearly depicts the coinci-dence of conductive zones and high radioactivity zones Thiscoincidence indicates the existence of alteration zones in thisarea These zones may contain radioactive mineralization asthey are also correlating with the radioactive bands identifiedby Katti et al [7] and with the bore hole data BLD2 and BLD3(Figures 10 and 11) All these identified mineralized zones are
almost parallel and have a collective strike oriented along E-W direction which is in agreement with the strike of SPSZ
7 Conclusions
VLF-EM and radiometric methods were applied togetherin this region to study the correlation between these twomethods as well as to utilize their integrated results for theexploration of uranium Results indicate good correlationbetween VLF data and radiometric dataThis is because theseradiometric signals are associated with shallow uraniummineralization which is associated with altered mineralsthat gives conductivity contrast with the neighboring rocksCoincidence of high radioactivity over conductive zonesand their correlation with radioactive bands observed inthe area confirms the presence of uranium mineralizationThus the study also suggests that these two methods can beintegrated to explore uraniumandor thoriummineralizationeffectively at low cost with the advantage of being quick andnondestructive compared to other routine methods used forsuch purposesThe study also reveals the presence of a strike-slip fault in the eastern side of the Beldih mine proving theability and advantage of this integrated approach in detectingsuch planner structures and correlating the lithology bothvertically and laterally Since these methods are quick andcost effective they can be utilized to search for shallowuranium mineralization along the SPSZ and other suchregions quickly VLF observations are sometimes affected bypower lines in such areas Gradient Resistivity Profiling andgravity and magnetic methods can be applied to aid in theinterpretation of subsurface structures
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors would like to thank the editor and anonymousreviewers for their valuable comments and suggestions toimprove the quality of the paper
References
[1] B K Bhaumik T Bhattacharya A A P S R AcharyuluD Srinivas and M K Sandilya Principles of Radiometry inRadioactive Metal Exploration Physics Lab AMD ComplexJamshedpur India 2004
[2] V Tuncer M J Unsworth W Siripunvaraporn and J ACraven ldquoExploration for unconformity-type uranium depos-its with audiomagnetotelluric data a case study from theMcArthur River mine Saskatchewan Canadardquo Geophysics vol71 no 6 pp B201ndashB209 2006
[3] J M Legault D Carriere and L Petrie ldquoSynthetic modeltesting and distributed acquisition dc resistivity results overan unconformity uranium target from the Athabasca Basinnorthern SaskatchewanrdquoTheLeading Edge vol 27 no 1 pp 46ndash51 2008
International Journal of Geophysics 13
[4] G Nimeck and R Koch ldquoA progressive geophysical explorationstrategy at the Shea Creek uranium depositrdquoThe Leading Edgevol 27 no 1 pp 52ndash63 2008
[5] A Mandal A Biswas S Mittal et al ldquoGeophysical anomaliesassociated with uranium mineralization from Beldih mineSouth Purulia Shear Zone Indiardquo Journal of the GeologicalSociety of India vol 82 no 6 pp 601ndash606 2013
[6] S P Sharma A Biswas and S Mittal ldquoDelineation of extensionof uranium mineralization zone using resistivity and VLFsur-veys around South Purulia Shear Zone Indiardquo Journal of theGeological Society of India In press
[7] V J Katti J Sen andAK Bhatt ldquoUraniumpotentiality of SouthPurulia Shear Zone in Eastern Indian Shieldrdquo in Proceedings ofthe Technical Meeting on Low Grade Uranium Ore pp 29ndash31International Atomic Energy Agency Vienna Austria 2010
[8] A Acharyya S Ray B K Chaudhuri S K Basu S K Bhaduriand A K Sanyal ldquoProterozoic rock suites along South PuruliaShear Zone eastern India evidence for rift-related settingrdquoJournal of the Geological Society of India vol 68 no 6 pp 1069ndash1086 2006
[9] Y Vapnik S Bushmin A Chattopadhyay and D Dolivo-Dobrovolsky ldquoFluid inclusion and mineralogical study of vein-type apatite ores in shear zones from the Singhbhum metallo-genetic provinceWest Bengal IndiardquoOre Geology Reviews vol32 no 1-2 pp 412ndash430 2007
[10] T K Baidya ldquoApatite-magnetite deposit in the chhotanagpurgneissic complex Panrkidih area Purulia District West Ben-galrdquo Indian Journal of Geology vol 64 pp 88ndash95 1992
[11] S K Basu ldquoAlkaline-carbonatite complex in Precambrian ofSouth Purulia Shear Zone eastern India its characteristics andmineral potentialitiesrdquo Indian Minerals vol 47 no 3 pp 179ndash194 1993
[12] A K G Roy and P R Sengupta ldquoAlkalic-carbonatitic magma-tism and associated mineralisation along the Porapahar-Tamarlineament in the Proterozoics of Purulia District West BengalrdquoIndian Journal of Earth Sciences vol 20 no 3-4 pp 193ndash2001993
[13] T K Pyne ldquoThe Proterozoic fold belt and the chhotanagpurgneissic complex in the eastern Indian Shieldmdasha tectono-metamorphic appraisalrdquo Indian Minerals vol 46 no 1 pp 25ndash34 1992
[14] S Bhattacharya ldquoDuctile shear Zone in Purulia West BengalrdquoIndian Journal of Geology vol 61 pp 172ndash178 1989
[15] B D Smith and S H Ward ldquoOn the computation of polariza-tion ellipse parametersrdquo Geophysics vol 39 pp 867ndash869 1974
[16] N R Paterson and V Ronka ldquoFive years of surveying with thevery low frequency-electromagnetics methodrdquoGeoexplorationvol 9 no 1 pp 7ndash26 1971
[17] M Karous and S E Hjelt ldquoLinear filtering of VLF dip-anglemeasurementsrdquo Geophysical Prospecting vol 31 no 5 pp 782ndash794 1983
[18] A T Ramli S Sahrone and H Wagiran ldquoTerrestrial gammaradiation dose study to determine the baseline for environ-mental radiological health practices in Melaka state MalaysiardquoJournal of Radiological Protection vol 25 no 4 pp 435ndash4502005
Figure 2 Profile P1100 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
conductor and the horizontal component (119867119909) of the primary
magnetic field which dependsmostly on theVLF transmitterIf the geological strike is along119910-axis andVLF transmitter
is located in the direction of 119884-axis from the point ofobservation then the tilt angle 120572 which is the inclination ofthe major axis of the polarization ellipse and the ellipticity 119890which is the ratio of the minor to the major axis of the ellipseare calculated by the formulae [15]
tan 2120572 = plusmn2 (119867119911119867119909) cosΔ120601
1 minus (119867119911119867119909)2
119890 =
119867119911119867119909sinΔ1206011198672
1
(1)
where the phase difference Δ120601 = 120601119911minus 120601119909 in which 120601
119911is the
phase of119867119911 120601119909is the phase of119867
119909 and119867
1= |119867119911119890119894Δ120601 sin120572 +
119867119909cos120572| The tangent of the tilt angle and the ellipticity are
good approximations to the ratio of the real component of thevertical secondary magnetic field to the horizontal primarymagnetic field and to the ratio of the quadrature componentof the vertical secondary magnetic field to the horizontalprimary field respectively [16]These quantities are called thereal (= tan120572times100) and imaginary (= 119890times 100) anomaliesrespectively and they are normally expressed in percentage
It is to be noted that real and imaginary VLF anomalieslike other electromagnetic anomalies are also affected bydifferent kinds of noises such as power line disturbances aswell as cultural noises In the present case the study area
Figure 3 Profile P1200 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
is quite remote and free from cultural noise but is affectedby power line disturbances However the power distributionwas absent during day time when the measurements weretaken Hence VLF measurement is free from such noisealso Further transmitter should be selected in the directionof geological strike and measurement should be made ina profile perpendicular to the known geological strike toattain maximum signal to noise ratio or least effect of noiseon the actual data ABEM Wadi instrument automaticallycorrects the observation if transmitter direction is deviatedplusmn10 degrees from the required direction When transmitterdirection is deviated by a large amount then a ldquobad tuningsignalrdquo is displayed on the monitor of the instrument
Subsequently orientation is adjusted accordingly and correctmeasurement is recorded With these precautions in theinstrument the expected error in the measurements is lessthan 5
The strike of the formation around the Beldih mine isapproximately in the E-W direction hence a transmitter inE-Wdirectionwith frequency of 198 kHz (located in BombayIndia) was selected for E-polarization measurements VLFsurveys were performed along eight profiles oriented inN-S direction (Figure 1) (running from south to north) Thedata was acquired at 10m intervals and subsequently datawas first smoothed with 5-point averaging filter and theninterpolated at 2m intervals to increase the resolution
Figure 4 Profile P1300 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
The above mentioned interpolated (Real and imaginary)data is transformed into apparent current density distributionin the subsurface which resembles the subsurface structureKarous and Hjelt [17] developed a filtering technique to cal-culate apparent current density which produces a magneticfield identical to the measured field If119867
minus3119867minus2119867minus111986701198671
1198672 and 119867
3are the equispaced real or imaginary anomaly
at locations 119909minus3 119909minus2 119909minus1 1199090 1199091 1199092 and 119909
3 respectively
the apparent current density at 1199090and depth Δ119911 = Δ119909 can
be computed from the following relation Consider
119869119886(1199090) =
2120587
Δ119911
(minus0102119867minus3+ 0059119867
minus2minus 0561119867
minus1
+05611198671minus 0059119867
2+ 0102119867
3)
(2)
Subsequently apparent current density is computed alongwhole profile at depth Δ119911 = Δ119909 by considering otherobservations along the profile in a systematic manner Nextobservation stations are selected with 2Δ119909 spacing andfiltering is repeated to obtain apparent current density atdepth 2Δ119909 This process is repeated to obtain apparentcurrent density at various depths The main limitation of thisapproach is apparent current density which gets truncatedgradually with depth from both sides of the profile Thisimaging technique yields 8 error in the estimation of thestructure [17] However it is fast and accurate in depictingthe subsurface structure and widely used for VLF data inter-pretation We have used this imaging technique to produceapparent current density cross-sections in the present study
Figure 5 Profile P1400 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
4 Radiometric Survey
Radiometric survey was carried out using Geiger-Mullercounter to record total ambient surface radiations andScintillation counter to note the surface gamma radiationsalong the eight selected profiles where VLF survey wasperformed For better and point to point correlation withVLF data radiometric data was collected at the same stationswhere VLF data was recorded along all the profiles usingGPS receivers For precise and accurate measurements everyradiometric measurement was repeated thrice
41 Geiger-Muller Counter Total surface radiations weremeasured using a portable pulsed GM (Geiger-Muller)counter at various locations along the selected profiles aroundthe mine The GM probe is comprised of a thin end window
halogen-quenched counter which is capable of detectingalpha and beta particles and small amount of gamma radi-ations It has a dead time of 200120583s The window is 2 cmin diameter and is shielded with a 1 cm thick lead collarThe instrument is operated with five membrane push buttonswitches and the display is a 6-digit LED
For detailed radiometric survey total radiation countswere measured at every 10m intervals along the profilesexactly where the VLF data was recorded For each mea-surement the sensor of GM counter was kept approximately15 cm above the ground surface and operated for 100 secondsduring data acquisition
42 Scintillation Counter For precise measurements of the 120574radiation we have used a portable scintillator based counting
Current density ()minus11 minus8 minus4 0 4 8 12 15
200
160
120
80
40
0
40
30
20
10
0
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 6 Profile P1500 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
system This Micro-R Survey Meter Type-UR 705 is manu-factured by Nucleonix Systems Private Limited HyderabadIndia It is designed around an integrally coupled 254 times254 cm scintillator coupled to a 254 times 127 cm Photomulti-plier Tube
The measurements were taken during winter season inorder to avoid the interference of gamma-emitting radondecay products [18] The 120574 measurements were undertakensim1m above the ground surface and directly above theexposure to get a better solid angle Each measurement wasundertaken for more than 60 seconds and was repeatedthrice for better precision and optimizing the subsequentinterpretation in terms of the ambient radiation
5 Results
On eastern side of the mine area five profiles namely P1100P1200 P1300 P1400 and P1500 covering around 600mof distance (profile length) (Figure 1) were accomplishedOn the western part of mine we took three profiles P1600P1700 and P1800 covering 600m of length (Figure 1) Forinterpretation of the subsurface geometry apparent currentdensity cross-sections with depths were made using theacquired VLF data along all the profiles For this themeasured real anomalies were interpolated at 2m intervaland filtered using Karous-Hjelt filter [17] These apparentcurrent density cross-sections are presented in Figures 2ndash9
Figure 7 Profile P1600 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
below the real and imaginary anomaly plots obtained fromthe VLF data acquired in the field Results for surface gammaactivity and total surface radiations are also shown as line-plots along with VLF anomaly for every individual profile(Figures 2ndash9) Background radiation level of the region is 40counts100 sec for surface radiations and 6ndash8120583Rh for surfacegamma activity
51 Profile 1 (P1100) The cross-over of real and imaginaryanomaly line-plot along this profile indicates the presenceof conductive zone between stations 500m and 580m(Figure 2(a))This zone is clearly depicted in apparent currentdensity cross-section (Figure 2(b)) by higher values betweenstations 460m and 540m Inclination of real anomaly curve
and apparent current density contours indicate that this con-ductive structure is vertical and lying at shallow depth (sim40mbelow surface) Radiometric data suggest the presence ofradiation more than the background levels above this con-ductive zonewith peak value of 16120583Rh and 80 counts100 secfor surface gamma activity and total radiations respectivelyat station 520m
52 Profile 2 (P1200) Profile P1200 is parallel to and 96meast of profile P1100 (Figure 3) The cross-over of real andimaginary VLF anomaly along this profile indicates thepresence of conductive feature around station 550m in thenorthern end of the profile and the slope of curve suggestsit to be a thin inclined body occurring at shallow depth
International Journal of Geophysics 9
N
40
20
0
minus20
minus40
minus60Real
anom
aly
()
Imag
inar
y
50 100 150 200 250 300 350 400 450 500 600550
Distance (m)
40
20
0
minus20
minus40
minus50
minus100
minus12 minus8 minus4 0 4 8 12
Dep
th (m
)
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
30
40
50
60
70
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
6
8
10
12
0
0
0
Current density ()
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 8 Profile P1700 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
The current density contours along this profile clearly demar-cates the shape of this body between stations 510mand 570msuggesting a width of around 60m occurring below 30mfrom the surface Radiometric data recorded over this profileshows similar behavior as that at profile P1100 with peakvalues at 520m
53 Profile 3 (P1300) This profile P1300 (Figure 4) is further83m east of profile P1200 The real and imaginary anomalyplots indicate the presence of multiple conductive bodiesalong this profile and the slope of these curves suggestsvertical structures occurring near to the surface Apparent
current density cross-section also depicts the same resultshowing the presence of three broad and shallow almostvertical conductors between stations 0m and 60m 160mand 250m and 375m and 450m Similarly the radioactivityalong this profile is higher than the background throughoutthe profile with peak between 410m and 440m The peakvalue of total radiations and surface gamma activity recordedat this station is 75 counts100 sec and 19 120583Rh respectively
54 Profile 4 (P1400) Profile P1400 lies 92m east of pro-file P1300 (Figure 5) Here also the VLF anomaly curvesdepict three conductive features all being shallow and nearly
10 International Journal of Geophysics
6789
10
0
N
20
10
0
minus10
minus10minus20Real
anom
aly
()
Imag
inar
y
50 100 150 200 250 300 350 400 450 500
Distance (m)0
10
20
30
minus20
minus40
minus60
minus80
50 100 150 200 250 300 350 400 450
Distance (m)
minus14 minus10 minus6 minus2 2 6 10 14 16
Current density ()
Dep
th (m
)
30
40
50
60
70
50 100 150 200 250 300 350 400 450 500
Distance (m)0
50 100 150 200 250 300 350 400 450 500
Distance (m)0
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 9 Profile P1800 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
vertical Apparent current density cross-section shows thepresence of one conducting and two low conducting struc-tures between stations 70m and 140m 270m and 320mand 490m and 520m respectively The conductor at thesouthern part of the profile (between stations 70mand 140m)is more conductive and wider among the three Radioactivityis observed to be highest above this conductor with peakvalue of total radiation being 290 counts100 sec and that ofgamma activity being 60120583Rh at station 150m This is thehighest radioactivity recorded along all the profiles
55 Profile 5 (P1500) Profile P1500 is taken 86m awaytowards east of profile P1400 (Figure 6) VLF anomaly curves
suggest the presence of a single conductor around station400m The slope of the anomaly curves indicates a thickinclined structure Apparent current density cross-sectionconfirms the presence of inclined conductive structurebetween stations 330mm to 420m Radiometric data isobserved to be almost equal to the background levels all longthe profile with a sudden jump in value to 180 counts100 secof total radiations and 35 120583Rh surface gamma activity atstation 510m
56 Profile 6 (P1600) This profile is located in the westernside of the Beldih mine (Figure 7) VLF anomaly curves indi-cate the presence of two conductive features around stations
International Journal of Geophysics 11
86
P1500P1100 P1200 P1300 P1400
P1600P1700
P1800
18 1805 181 1815
29
295
3
305
31
176 1765
Mine dump
N
Cultivated land
Cultivated land
298
3
302
304
306
308
31312
314
316
318
32
Cultivated land
Cultivated land
Cultivated land
Beldih village (N)
Bore hole BoreholeBLD2 BLD3
Beldih
325998400
32998400
315998400
31998400
305998400
295998400
3998400
29998400
285998400
280998400
23∘
and
min
utes
1745998400
175998400
1755998400
176998400
1765998400
177998400
1775998400
178998400
1785998400
179998400
1795998400
1800998400
1805998400
1810998400
1815998400
1820998400
1825998400
1830998400
86∘ and minutes
0 100 200
(m)
Mine dumpKaolin zone
QuartziteGranite
Quartz-magnetite-apatite rocks
Tuffaceous rock
Altered brecciated ultramafics Radioactive bands (vertical projection from borehole)
VLF profile Ultramafics plusmn carbonatite
5
10
15
20
25
30
35
40
45
50
55
86∘ and minutes
23∘
and
min
utes
Tank
(120583Rh
r)
Figure 10 Surface gamma activity superimposed over geological map of the area of study
Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
240
220
200
180
Datum
0 10
S
20 (m)
N
Expected mineralized zone
260
220
200
180
Datum240
Transverse section through bore hole BLD2 Transverse section through bore hole BLD3
RL-24062m
RL
(m)
BLD2
DD-13075m DD-16355m
640m840m
BLD3
RL
(m)
RL-24234m
Altered brecciated ultramafics
Ultramafics plusmn carbonatite Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
Altered brecciated ultramafics
Ultramafics plusmn carbonatite
Figure 11 Transverse sections through bore holes BLD2 and BLD3 (after [7])
200m and 450m Apparent current density cross-sectiondepicts both of the structures between stations 150m and250m and 410m and 520m and shows that they are dippingstructures Radiometric data shows high radioactivity in thesouthern side of the profile compared to the northern sidewith peak value of total radiation and gamma activity (140counts100 sec and 28 120583Rh resp) found above the station250m
57 Profile 7 (P1700) Differing from all other profiles inprofile P1700 92mwest of P1600 (Figure 8) theVLF anomalycurves indicate a single wide conductive feature lying all overthe profile with centre at 350m Apparent current densitycross-section also shows a much wider conductive featurelying between 0m and 230m 250m and 370m and 390mand 500m ranging in current density values from 4 to10 4 to 12 and 4 to 8 respectively This shows that
12 International Journal of Geophysics
here the same conducting zone is wider than other locationsWhereas radiometric data suggests high radioactivity abovethe background level only between stations 70m and 210m
58 Profile 8 (P1800) Further 88m west of P1700 in profileP1800 (Figure 9) VLF anomaly curves indicate the presenceof two vertical conductors Current density contours alsoshow two conductive features between stations 160m and220m and 320m and 370m The first one is less conductiveas compared to the later one Radiometric data indicates highradioactivity in the southern part of the profile with threepeak regions around stations 50m 140m and 180m
6 Discussion
In the present study eight profiles were chosen on eitherside of the Beldih mine to investigate the uranium andorthorium mineralization by applying VLF-EM and radiomet-ric methods together Results show the presence of multipleisolated conductive features in the study area These con-ductive features appearing in the profile could be becauseof the presence of fractures filled with fluids hydrothermalalteration zones clay mineralization shearing and so forthThe conductive features are traced continuously well in allthe profiles showing a regular parallel trend except in profileP1400where the similar zone is identified in the southern sideof the profileThis implies that the conductive feature at P1400has shifted southward in this profile only This offset of thecurrent density anomaly (in profile P1400) could be due toeither strike slip fault or dip slip fault or subparallel faultingIn case of dip slip fault such offset can be observed only ifan inclined bed is cut by a vertical fault at right angles tothe strike and the slip is normal After erosion such an offsetcan be seen However the observed anomalies appear verticalin the current density profile and the offset or movementis lateral along the strike of the fault This happens in caseof strike-slip fault hence it appears to be the better reasonfor such lateral shift of the mineralized body This can befurther substantiated by successive structural mapping of thearea
The separation between the conductive bodies is notuniform along all the profilesThis further suggests that thesemineralized bodies have small strike length and lenticularshape This result together with the geology of the area indi-cates that the mode of mineralization may be hydrothermalalteration
Radiometric measurements indicate higher radiationsalong the profiles than the average or background radiationsobserved in the areaThe peak or elevated radiations indicatethe presence of uranium mineralization
Surface gamma activity superimposed over geologicalmap of the area of study (Figure 10) clearly depicts the coinci-dence of conductive zones and high radioactivity zones Thiscoincidence indicates the existence of alteration zones in thisarea These zones may contain radioactive mineralization asthey are also correlating with the radioactive bands identifiedby Katti et al [7] and with the bore hole data BLD2 and BLD3(Figures 10 and 11) All these identified mineralized zones are
almost parallel and have a collective strike oriented along E-W direction which is in agreement with the strike of SPSZ
7 Conclusions
VLF-EM and radiometric methods were applied togetherin this region to study the correlation between these twomethods as well as to utilize their integrated results for theexploration of uranium Results indicate good correlationbetween VLF data and radiometric dataThis is because theseradiometric signals are associated with shallow uraniummineralization which is associated with altered mineralsthat gives conductivity contrast with the neighboring rocksCoincidence of high radioactivity over conductive zonesand their correlation with radioactive bands observed inthe area confirms the presence of uranium mineralizationThus the study also suggests that these two methods can beintegrated to explore uraniumandor thoriummineralizationeffectively at low cost with the advantage of being quick andnondestructive compared to other routine methods used forsuch purposesThe study also reveals the presence of a strike-slip fault in the eastern side of the Beldih mine proving theability and advantage of this integrated approach in detectingsuch planner structures and correlating the lithology bothvertically and laterally Since these methods are quick andcost effective they can be utilized to search for shallowuranium mineralization along the SPSZ and other suchregions quickly VLF observations are sometimes affected bypower lines in such areas Gradient Resistivity Profiling andgravity and magnetic methods can be applied to aid in theinterpretation of subsurface structures
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors would like to thank the editor and anonymousreviewers for their valuable comments and suggestions toimprove the quality of the paper
References
[1] B K Bhaumik T Bhattacharya A A P S R AcharyuluD Srinivas and M K Sandilya Principles of Radiometry inRadioactive Metal Exploration Physics Lab AMD ComplexJamshedpur India 2004
[2] V Tuncer M J Unsworth W Siripunvaraporn and J ACraven ldquoExploration for unconformity-type uranium depos-its with audiomagnetotelluric data a case study from theMcArthur River mine Saskatchewan Canadardquo Geophysics vol71 no 6 pp B201ndashB209 2006
[3] J M Legault D Carriere and L Petrie ldquoSynthetic modeltesting and distributed acquisition dc resistivity results overan unconformity uranium target from the Athabasca Basinnorthern SaskatchewanrdquoTheLeading Edge vol 27 no 1 pp 46ndash51 2008
International Journal of Geophysics 13
[4] G Nimeck and R Koch ldquoA progressive geophysical explorationstrategy at the Shea Creek uranium depositrdquoThe Leading Edgevol 27 no 1 pp 52ndash63 2008
[5] A Mandal A Biswas S Mittal et al ldquoGeophysical anomaliesassociated with uranium mineralization from Beldih mineSouth Purulia Shear Zone Indiardquo Journal of the GeologicalSociety of India vol 82 no 6 pp 601ndash606 2013
[6] S P Sharma A Biswas and S Mittal ldquoDelineation of extensionof uranium mineralization zone using resistivity and VLFsur-veys around South Purulia Shear Zone Indiardquo Journal of theGeological Society of India In press
[7] V J Katti J Sen andAK Bhatt ldquoUraniumpotentiality of SouthPurulia Shear Zone in Eastern Indian Shieldrdquo in Proceedings ofthe Technical Meeting on Low Grade Uranium Ore pp 29ndash31International Atomic Energy Agency Vienna Austria 2010
[8] A Acharyya S Ray B K Chaudhuri S K Basu S K Bhaduriand A K Sanyal ldquoProterozoic rock suites along South PuruliaShear Zone eastern India evidence for rift-related settingrdquoJournal of the Geological Society of India vol 68 no 6 pp 1069ndash1086 2006
[9] Y Vapnik S Bushmin A Chattopadhyay and D Dolivo-Dobrovolsky ldquoFluid inclusion and mineralogical study of vein-type apatite ores in shear zones from the Singhbhum metallo-genetic provinceWest Bengal IndiardquoOre Geology Reviews vol32 no 1-2 pp 412ndash430 2007
[10] T K Baidya ldquoApatite-magnetite deposit in the chhotanagpurgneissic complex Panrkidih area Purulia District West Ben-galrdquo Indian Journal of Geology vol 64 pp 88ndash95 1992
[11] S K Basu ldquoAlkaline-carbonatite complex in Precambrian ofSouth Purulia Shear Zone eastern India its characteristics andmineral potentialitiesrdquo Indian Minerals vol 47 no 3 pp 179ndash194 1993
[12] A K G Roy and P R Sengupta ldquoAlkalic-carbonatitic magma-tism and associated mineralisation along the Porapahar-Tamarlineament in the Proterozoics of Purulia District West BengalrdquoIndian Journal of Earth Sciences vol 20 no 3-4 pp 193ndash2001993
[13] T K Pyne ldquoThe Proterozoic fold belt and the chhotanagpurgneissic complex in the eastern Indian Shieldmdasha tectono-metamorphic appraisalrdquo Indian Minerals vol 46 no 1 pp 25ndash34 1992
[14] S Bhattacharya ldquoDuctile shear Zone in Purulia West BengalrdquoIndian Journal of Geology vol 61 pp 172ndash178 1989
[15] B D Smith and S H Ward ldquoOn the computation of polariza-tion ellipse parametersrdquo Geophysics vol 39 pp 867ndash869 1974
[16] N R Paterson and V Ronka ldquoFive years of surveying with thevery low frequency-electromagnetics methodrdquoGeoexplorationvol 9 no 1 pp 7ndash26 1971
[17] M Karous and S E Hjelt ldquoLinear filtering of VLF dip-anglemeasurementsrdquo Geophysical Prospecting vol 31 no 5 pp 782ndash794 1983
[18] A T Ramli S Sahrone and H Wagiran ldquoTerrestrial gammaradiation dose study to determine the baseline for environ-mental radiological health practices in Melaka state MalaysiardquoJournal of Radiological Protection vol 25 no 4 pp 435ndash4502005
Figure 3 Profile P1200 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
is quite remote and free from cultural noise but is affectedby power line disturbances However the power distributionwas absent during day time when the measurements weretaken Hence VLF measurement is free from such noisealso Further transmitter should be selected in the directionof geological strike and measurement should be made ina profile perpendicular to the known geological strike toattain maximum signal to noise ratio or least effect of noiseon the actual data ABEM Wadi instrument automaticallycorrects the observation if transmitter direction is deviatedplusmn10 degrees from the required direction When transmitterdirection is deviated by a large amount then a ldquobad tuningsignalrdquo is displayed on the monitor of the instrument
Subsequently orientation is adjusted accordingly and correctmeasurement is recorded With these precautions in theinstrument the expected error in the measurements is lessthan 5
The strike of the formation around the Beldih mine isapproximately in the E-W direction hence a transmitter inE-Wdirectionwith frequency of 198 kHz (located in BombayIndia) was selected for E-polarization measurements VLFsurveys were performed along eight profiles oriented inN-S direction (Figure 1) (running from south to north) Thedata was acquired at 10m intervals and subsequently datawas first smoothed with 5-point averaging filter and theninterpolated at 2m intervals to increase the resolution
Figure 4 Profile P1300 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
The above mentioned interpolated (Real and imaginary)data is transformed into apparent current density distributionin the subsurface which resembles the subsurface structureKarous and Hjelt [17] developed a filtering technique to cal-culate apparent current density which produces a magneticfield identical to the measured field If119867
minus3119867minus2119867minus111986701198671
1198672 and 119867
3are the equispaced real or imaginary anomaly
at locations 119909minus3 119909minus2 119909minus1 1199090 1199091 1199092 and 119909
3 respectively
the apparent current density at 1199090and depth Δ119911 = Δ119909 can
be computed from the following relation Consider
119869119886(1199090) =
2120587
Δ119911
(minus0102119867minus3+ 0059119867
minus2minus 0561119867
minus1
+05611198671minus 0059119867
2+ 0102119867
3)
(2)
Subsequently apparent current density is computed alongwhole profile at depth Δ119911 = Δ119909 by considering otherobservations along the profile in a systematic manner Nextobservation stations are selected with 2Δ119909 spacing andfiltering is repeated to obtain apparent current density atdepth 2Δ119909 This process is repeated to obtain apparentcurrent density at various depths The main limitation of thisapproach is apparent current density which gets truncatedgradually with depth from both sides of the profile Thisimaging technique yields 8 error in the estimation of thestructure [17] However it is fast and accurate in depictingthe subsurface structure and widely used for VLF data inter-pretation We have used this imaging technique to produceapparent current density cross-sections in the present study
Figure 5 Profile P1400 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
4 Radiometric Survey
Radiometric survey was carried out using Geiger-Mullercounter to record total ambient surface radiations andScintillation counter to note the surface gamma radiationsalong the eight selected profiles where VLF survey wasperformed For better and point to point correlation withVLF data radiometric data was collected at the same stationswhere VLF data was recorded along all the profiles usingGPS receivers For precise and accurate measurements everyradiometric measurement was repeated thrice
41 Geiger-Muller Counter Total surface radiations weremeasured using a portable pulsed GM (Geiger-Muller)counter at various locations along the selected profiles aroundthe mine The GM probe is comprised of a thin end window
halogen-quenched counter which is capable of detectingalpha and beta particles and small amount of gamma radi-ations It has a dead time of 200120583s The window is 2 cmin diameter and is shielded with a 1 cm thick lead collarThe instrument is operated with five membrane push buttonswitches and the display is a 6-digit LED
For detailed radiometric survey total radiation countswere measured at every 10m intervals along the profilesexactly where the VLF data was recorded For each mea-surement the sensor of GM counter was kept approximately15 cm above the ground surface and operated for 100 secondsduring data acquisition
42 Scintillation Counter For precise measurements of the 120574radiation we have used a portable scintillator based counting
Current density ()minus11 minus8 minus4 0 4 8 12 15
200
160
120
80
40
0
40
30
20
10
0
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 6 Profile P1500 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
system This Micro-R Survey Meter Type-UR 705 is manu-factured by Nucleonix Systems Private Limited HyderabadIndia It is designed around an integrally coupled 254 times254 cm scintillator coupled to a 254 times 127 cm Photomulti-plier Tube
The measurements were taken during winter season inorder to avoid the interference of gamma-emitting radondecay products [18] The 120574 measurements were undertakensim1m above the ground surface and directly above theexposure to get a better solid angle Each measurement wasundertaken for more than 60 seconds and was repeatedthrice for better precision and optimizing the subsequentinterpretation in terms of the ambient radiation
5 Results
On eastern side of the mine area five profiles namely P1100P1200 P1300 P1400 and P1500 covering around 600mof distance (profile length) (Figure 1) were accomplishedOn the western part of mine we took three profiles P1600P1700 and P1800 covering 600m of length (Figure 1) Forinterpretation of the subsurface geometry apparent currentdensity cross-sections with depths were made using theacquired VLF data along all the profiles For this themeasured real anomalies were interpolated at 2m intervaland filtered using Karous-Hjelt filter [17] These apparentcurrent density cross-sections are presented in Figures 2ndash9
Figure 7 Profile P1600 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
below the real and imaginary anomaly plots obtained fromthe VLF data acquired in the field Results for surface gammaactivity and total surface radiations are also shown as line-plots along with VLF anomaly for every individual profile(Figures 2ndash9) Background radiation level of the region is 40counts100 sec for surface radiations and 6ndash8120583Rh for surfacegamma activity
51 Profile 1 (P1100) The cross-over of real and imaginaryanomaly line-plot along this profile indicates the presenceof conductive zone between stations 500m and 580m(Figure 2(a))This zone is clearly depicted in apparent currentdensity cross-section (Figure 2(b)) by higher values betweenstations 460m and 540m Inclination of real anomaly curve
and apparent current density contours indicate that this con-ductive structure is vertical and lying at shallow depth (sim40mbelow surface) Radiometric data suggest the presence ofradiation more than the background levels above this con-ductive zonewith peak value of 16120583Rh and 80 counts100 secfor surface gamma activity and total radiations respectivelyat station 520m
52 Profile 2 (P1200) Profile P1200 is parallel to and 96meast of profile P1100 (Figure 3) The cross-over of real andimaginary VLF anomaly along this profile indicates thepresence of conductive feature around station 550m in thenorthern end of the profile and the slope of curve suggestsit to be a thin inclined body occurring at shallow depth
International Journal of Geophysics 9
N
40
20
0
minus20
minus40
minus60Real
anom
aly
()
Imag
inar
y
50 100 150 200 250 300 350 400 450 500 600550
Distance (m)
40
20
0
minus20
minus40
minus50
minus100
minus12 minus8 minus4 0 4 8 12
Dep
th (m
)
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
30
40
50
60
70
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
6
8
10
12
0
0
0
Current density ()
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 8 Profile P1700 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
The current density contours along this profile clearly demar-cates the shape of this body between stations 510mand 570msuggesting a width of around 60m occurring below 30mfrom the surface Radiometric data recorded over this profileshows similar behavior as that at profile P1100 with peakvalues at 520m
53 Profile 3 (P1300) This profile P1300 (Figure 4) is further83m east of profile P1200 The real and imaginary anomalyplots indicate the presence of multiple conductive bodiesalong this profile and the slope of these curves suggestsvertical structures occurring near to the surface Apparent
current density cross-section also depicts the same resultshowing the presence of three broad and shallow almostvertical conductors between stations 0m and 60m 160mand 250m and 375m and 450m Similarly the radioactivityalong this profile is higher than the background throughoutthe profile with peak between 410m and 440m The peakvalue of total radiations and surface gamma activity recordedat this station is 75 counts100 sec and 19 120583Rh respectively
54 Profile 4 (P1400) Profile P1400 lies 92m east of pro-file P1300 (Figure 5) Here also the VLF anomaly curvesdepict three conductive features all being shallow and nearly
10 International Journal of Geophysics
6789
10
0
N
20
10
0
minus10
minus10minus20Real
anom
aly
()
Imag
inar
y
50 100 150 200 250 300 350 400 450 500
Distance (m)0
10
20
30
minus20
minus40
minus60
minus80
50 100 150 200 250 300 350 400 450
Distance (m)
minus14 minus10 minus6 minus2 2 6 10 14 16
Current density ()
Dep
th (m
)
30
40
50
60
70
50 100 150 200 250 300 350 400 450 500
Distance (m)0
50 100 150 200 250 300 350 400 450 500
Distance (m)0
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 9 Profile P1800 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
vertical Apparent current density cross-section shows thepresence of one conducting and two low conducting struc-tures between stations 70m and 140m 270m and 320mand 490m and 520m respectively The conductor at thesouthern part of the profile (between stations 70mand 140m)is more conductive and wider among the three Radioactivityis observed to be highest above this conductor with peakvalue of total radiation being 290 counts100 sec and that ofgamma activity being 60120583Rh at station 150m This is thehighest radioactivity recorded along all the profiles
55 Profile 5 (P1500) Profile P1500 is taken 86m awaytowards east of profile P1400 (Figure 6) VLF anomaly curves
suggest the presence of a single conductor around station400m The slope of the anomaly curves indicates a thickinclined structure Apparent current density cross-sectionconfirms the presence of inclined conductive structurebetween stations 330mm to 420m Radiometric data isobserved to be almost equal to the background levels all longthe profile with a sudden jump in value to 180 counts100 secof total radiations and 35 120583Rh surface gamma activity atstation 510m
56 Profile 6 (P1600) This profile is located in the westernside of the Beldih mine (Figure 7) VLF anomaly curves indi-cate the presence of two conductive features around stations
International Journal of Geophysics 11
86
P1500P1100 P1200 P1300 P1400
P1600P1700
P1800
18 1805 181 1815
29
295
3
305
31
176 1765
Mine dump
N
Cultivated land
Cultivated land
298
3
302
304
306
308
31312
314
316
318
32
Cultivated land
Cultivated land
Cultivated land
Beldih village (N)
Bore hole BoreholeBLD2 BLD3
Beldih
325998400
32998400
315998400
31998400
305998400
295998400
3998400
29998400
285998400
280998400
23∘
and
min
utes
1745998400
175998400
1755998400
176998400
1765998400
177998400
1775998400
178998400
1785998400
179998400
1795998400
1800998400
1805998400
1810998400
1815998400
1820998400
1825998400
1830998400
86∘ and minutes
0 100 200
(m)
Mine dumpKaolin zone
QuartziteGranite
Quartz-magnetite-apatite rocks
Tuffaceous rock
Altered brecciated ultramafics Radioactive bands (vertical projection from borehole)
VLF profile Ultramafics plusmn carbonatite
5
10
15
20
25
30
35
40
45
50
55
86∘ and minutes
23∘
and
min
utes
Tank
(120583Rh
r)
Figure 10 Surface gamma activity superimposed over geological map of the area of study
Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
240
220
200
180
Datum
0 10
S
20 (m)
N
Expected mineralized zone
260
220
200
180
Datum240
Transverse section through bore hole BLD2 Transverse section through bore hole BLD3
RL-24062m
RL
(m)
BLD2
DD-13075m DD-16355m
640m840m
BLD3
RL
(m)
RL-24234m
Altered brecciated ultramafics
Ultramafics plusmn carbonatite Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
Altered brecciated ultramafics
Ultramafics plusmn carbonatite
Figure 11 Transverse sections through bore holes BLD2 and BLD3 (after [7])
200m and 450m Apparent current density cross-sectiondepicts both of the structures between stations 150m and250m and 410m and 520m and shows that they are dippingstructures Radiometric data shows high radioactivity in thesouthern side of the profile compared to the northern sidewith peak value of total radiation and gamma activity (140counts100 sec and 28 120583Rh resp) found above the station250m
57 Profile 7 (P1700) Differing from all other profiles inprofile P1700 92mwest of P1600 (Figure 8) theVLF anomalycurves indicate a single wide conductive feature lying all overthe profile with centre at 350m Apparent current densitycross-section also shows a much wider conductive featurelying between 0m and 230m 250m and 370m and 390mand 500m ranging in current density values from 4 to10 4 to 12 and 4 to 8 respectively This shows that
12 International Journal of Geophysics
here the same conducting zone is wider than other locationsWhereas radiometric data suggests high radioactivity abovethe background level only between stations 70m and 210m
58 Profile 8 (P1800) Further 88m west of P1700 in profileP1800 (Figure 9) VLF anomaly curves indicate the presenceof two vertical conductors Current density contours alsoshow two conductive features between stations 160m and220m and 320m and 370m The first one is less conductiveas compared to the later one Radiometric data indicates highradioactivity in the southern part of the profile with threepeak regions around stations 50m 140m and 180m
6 Discussion
In the present study eight profiles were chosen on eitherside of the Beldih mine to investigate the uranium andorthorium mineralization by applying VLF-EM and radiomet-ric methods together Results show the presence of multipleisolated conductive features in the study area These con-ductive features appearing in the profile could be becauseof the presence of fractures filled with fluids hydrothermalalteration zones clay mineralization shearing and so forthThe conductive features are traced continuously well in allthe profiles showing a regular parallel trend except in profileP1400where the similar zone is identified in the southern sideof the profileThis implies that the conductive feature at P1400has shifted southward in this profile only This offset of thecurrent density anomaly (in profile P1400) could be due toeither strike slip fault or dip slip fault or subparallel faultingIn case of dip slip fault such offset can be observed only ifan inclined bed is cut by a vertical fault at right angles tothe strike and the slip is normal After erosion such an offsetcan be seen However the observed anomalies appear verticalin the current density profile and the offset or movementis lateral along the strike of the fault This happens in caseof strike-slip fault hence it appears to be the better reasonfor such lateral shift of the mineralized body This can befurther substantiated by successive structural mapping of thearea
The separation between the conductive bodies is notuniform along all the profilesThis further suggests that thesemineralized bodies have small strike length and lenticularshape This result together with the geology of the area indi-cates that the mode of mineralization may be hydrothermalalteration
Radiometric measurements indicate higher radiationsalong the profiles than the average or background radiationsobserved in the areaThe peak or elevated radiations indicatethe presence of uranium mineralization
Surface gamma activity superimposed over geologicalmap of the area of study (Figure 10) clearly depicts the coinci-dence of conductive zones and high radioactivity zones Thiscoincidence indicates the existence of alteration zones in thisarea These zones may contain radioactive mineralization asthey are also correlating with the radioactive bands identifiedby Katti et al [7] and with the bore hole data BLD2 and BLD3(Figures 10 and 11) All these identified mineralized zones are
almost parallel and have a collective strike oriented along E-W direction which is in agreement with the strike of SPSZ
7 Conclusions
VLF-EM and radiometric methods were applied togetherin this region to study the correlation between these twomethods as well as to utilize their integrated results for theexploration of uranium Results indicate good correlationbetween VLF data and radiometric dataThis is because theseradiometric signals are associated with shallow uraniummineralization which is associated with altered mineralsthat gives conductivity contrast with the neighboring rocksCoincidence of high radioactivity over conductive zonesand their correlation with radioactive bands observed inthe area confirms the presence of uranium mineralizationThus the study also suggests that these two methods can beintegrated to explore uraniumandor thoriummineralizationeffectively at low cost with the advantage of being quick andnondestructive compared to other routine methods used forsuch purposesThe study also reveals the presence of a strike-slip fault in the eastern side of the Beldih mine proving theability and advantage of this integrated approach in detectingsuch planner structures and correlating the lithology bothvertically and laterally Since these methods are quick andcost effective they can be utilized to search for shallowuranium mineralization along the SPSZ and other suchregions quickly VLF observations are sometimes affected bypower lines in such areas Gradient Resistivity Profiling andgravity and magnetic methods can be applied to aid in theinterpretation of subsurface structures
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors would like to thank the editor and anonymousreviewers for their valuable comments and suggestions toimprove the quality of the paper
References
[1] B K Bhaumik T Bhattacharya A A P S R AcharyuluD Srinivas and M K Sandilya Principles of Radiometry inRadioactive Metal Exploration Physics Lab AMD ComplexJamshedpur India 2004
[2] V Tuncer M J Unsworth W Siripunvaraporn and J ACraven ldquoExploration for unconformity-type uranium depos-its with audiomagnetotelluric data a case study from theMcArthur River mine Saskatchewan Canadardquo Geophysics vol71 no 6 pp B201ndashB209 2006
[3] J M Legault D Carriere and L Petrie ldquoSynthetic modeltesting and distributed acquisition dc resistivity results overan unconformity uranium target from the Athabasca Basinnorthern SaskatchewanrdquoTheLeading Edge vol 27 no 1 pp 46ndash51 2008
International Journal of Geophysics 13
[4] G Nimeck and R Koch ldquoA progressive geophysical explorationstrategy at the Shea Creek uranium depositrdquoThe Leading Edgevol 27 no 1 pp 52ndash63 2008
[5] A Mandal A Biswas S Mittal et al ldquoGeophysical anomaliesassociated with uranium mineralization from Beldih mineSouth Purulia Shear Zone Indiardquo Journal of the GeologicalSociety of India vol 82 no 6 pp 601ndash606 2013
[6] S P Sharma A Biswas and S Mittal ldquoDelineation of extensionof uranium mineralization zone using resistivity and VLFsur-veys around South Purulia Shear Zone Indiardquo Journal of theGeological Society of India In press
[7] V J Katti J Sen andAK Bhatt ldquoUraniumpotentiality of SouthPurulia Shear Zone in Eastern Indian Shieldrdquo in Proceedings ofthe Technical Meeting on Low Grade Uranium Ore pp 29ndash31International Atomic Energy Agency Vienna Austria 2010
[8] A Acharyya S Ray B K Chaudhuri S K Basu S K Bhaduriand A K Sanyal ldquoProterozoic rock suites along South PuruliaShear Zone eastern India evidence for rift-related settingrdquoJournal of the Geological Society of India vol 68 no 6 pp 1069ndash1086 2006
[9] Y Vapnik S Bushmin A Chattopadhyay and D Dolivo-Dobrovolsky ldquoFluid inclusion and mineralogical study of vein-type apatite ores in shear zones from the Singhbhum metallo-genetic provinceWest Bengal IndiardquoOre Geology Reviews vol32 no 1-2 pp 412ndash430 2007
[10] T K Baidya ldquoApatite-magnetite deposit in the chhotanagpurgneissic complex Panrkidih area Purulia District West Ben-galrdquo Indian Journal of Geology vol 64 pp 88ndash95 1992
[11] S K Basu ldquoAlkaline-carbonatite complex in Precambrian ofSouth Purulia Shear Zone eastern India its characteristics andmineral potentialitiesrdquo Indian Minerals vol 47 no 3 pp 179ndash194 1993
[12] A K G Roy and P R Sengupta ldquoAlkalic-carbonatitic magma-tism and associated mineralisation along the Porapahar-Tamarlineament in the Proterozoics of Purulia District West BengalrdquoIndian Journal of Earth Sciences vol 20 no 3-4 pp 193ndash2001993
[13] T K Pyne ldquoThe Proterozoic fold belt and the chhotanagpurgneissic complex in the eastern Indian Shieldmdasha tectono-metamorphic appraisalrdquo Indian Minerals vol 46 no 1 pp 25ndash34 1992
[14] S Bhattacharya ldquoDuctile shear Zone in Purulia West BengalrdquoIndian Journal of Geology vol 61 pp 172ndash178 1989
[15] B D Smith and S H Ward ldquoOn the computation of polariza-tion ellipse parametersrdquo Geophysics vol 39 pp 867ndash869 1974
[16] N R Paterson and V Ronka ldquoFive years of surveying with thevery low frequency-electromagnetics methodrdquoGeoexplorationvol 9 no 1 pp 7ndash26 1971
[17] M Karous and S E Hjelt ldquoLinear filtering of VLF dip-anglemeasurementsrdquo Geophysical Prospecting vol 31 no 5 pp 782ndash794 1983
[18] A T Ramli S Sahrone and H Wagiran ldquoTerrestrial gammaradiation dose study to determine the baseline for environ-mental radiological health practices in Melaka state MalaysiardquoJournal of Radiological Protection vol 25 no 4 pp 435ndash4502005
Figure 4 Profile P1300 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
The above mentioned interpolated (Real and imaginary)data is transformed into apparent current density distributionin the subsurface which resembles the subsurface structureKarous and Hjelt [17] developed a filtering technique to cal-culate apparent current density which produces a magneticfield identical to the measured field If119867
minus3119867minus2119867minus111986701198671
1198672 and 119867
3are the equispaced real or imaginary anomaly
at locations 119909minus3 119909minus2 119909minus1 1199090 1199091 1199092 and 119909
3 respectively
the apparent current density at 1199090and depth Δ119911 = Δ119909 can
be computed from the following relation Consider
119869119886(1199090) =
2120587
Δ119911
(minus0102119867minus3+ 0059119867
minus2minus 0561119867
minus1
+05611198671minus 0059119867
2+ 0102119867
3)
(2)
Subsequently apparent current density is computed alongwhole profile at depth Δ119911 = Δ119909 by considering otherobservations along the profile in a systematic manner Nextobservation stations are selected with 2Δ119909 spacing andfiltering is repeated to obtain apparent current density atdepth 2Δ119909 This process is repeated to obtain apparentcurrent density at various depths The main limitation of thisapproach is apparent current density which gets truncatedgradually with depth from both sides of the profile Thisimaging technique yields 8 error in the estimation of thestructure [17] However it is fast and accurate in depictingthe subsurface structure and widely used for VLF data inter-pretation We have used this imaging technique to produceapparent current density cross-sections in the present study
Figure 5 Profile P1400 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
4 Radiometric Survey
Radiometric survey was carried out using Geiger-Mullercounter to record total ambient surface radiations andScintillation counter to note the surface gamma radiationsalong the eight selected profiles where VLF survey wasperformed For better and point to point correlation withVLF data radiometric data was collected at the same stationswhere VLF data was recorded along all the profiles usingGPS receivers For precise and accurate measurements everyradiometric measurement was repeated thrice
41 Geiger-Muller Counter Total surface radiations weremeasured using a portable pulsed GM (Geiger-Muller)counter at various locations along the selected profiles aroundthe mine The GM probe is comprised of a thin end window
halogen-quenched counter which is capable of detectingalpha and beta particles and small amount of gamma radi-ations It has a dead time of 200120583s The window is 2 cmin diameter and is shielded with a 1 cm thick lead collarThe instrument is operated with five membrane push buttonswitches and the display is a 6-digit LED
For detailed radiometric survey total radiation countswere measured at every 10m intervals along the profilesexactly where the VLF data was recorded For each mea-surement the sensor of GM counter was kept approximately15 cm above the ground surface and operated for 100 secondsduring data acquisition
42 Scintillation Counter For precise measurements of the 120574radiation we have used a portable scintillator based counting
Current density ()minus11 minus8 minus4 0 4 8 12 15
200
160
120
80
40
0
40
30
20
10
0
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 6 Profile P1500 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
system This Micro-R Survey Meter Type-UR 705 is manu-factured by Nucleonix Systems Private Limited HyderabadIndia It is designed around an integrally coupled 254 times254 cm scintillator coupled to a 254 times 127 cm Photomulti-plier Tube
The measurements were taken during winter season inorder to avoid the interference of gamma-emitting radondecay products [18] The 120574 measurements were undertakensim1m above the ground surface and directly above theexposure to get a better solid angle Each measurement wasundertaken for more than 60 seconds and was repeatedthrice for better precision and optimizing the subsequentinterpretation in terms of the ambient radiation
5 Results
On eastern side of the mine area five profiles namely P1100P1200 P1300 P1400 and P1500 covering around 600mof distance (profile length) (Figure 1) were accomplishedOn the western part of mine we took three profiles P1600P1700 and P1800 covering 600m of length (Figure 1) Forinterpretation of the subsurface geometry apparent currentdensity cross-sections with depths were made using theacquired VLF data along all the profiles For this themeasured real anomalies were interpolated at 2m intervaland filtered using Karous-Hjelt filter [17] These apparentcurrent density cross-sections are presented in Figures 2ndash9
Figure 7 Profile P1600 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
below the real and imaginary anomaly plots obtained fromthe VLF data acquired in the field Results for surface gammaactivity and total surface radiations are also shown as line-plots along with VLF anomaly for every individual profile(Figures 2ndash9) Background radiation level of the region is 40counts100 sec for surface radiations and 6ndash8120583Rh for surfacegamma activity
51 Profile 1 (P1100) The cross-over of real and imaginaryanomaly line-plot along this profile indicates the presenceof conductive zone between stations 500m and 580m(Figure 2(a))This zone is clearly depicted in apparent currentdensity cross-section (Figure 2(b)) by higher values betweenstations 460m and 540m Inclination of real anomaly curve
and apparent current density contours indicate that this con-ductive structure is vertical and lying at shallow depth (sim40mbelow surface) Radiometric data suggest the presence ofradiation more than the background levels above this con-ductive zonewith peak value of 16120583Rh and 80 counts100 secfor surface gamma activity and total radiations respectivelyat station 520m
52 Profile 2 (P1200) Profile P1200 is parallel to and 96meast of profile P1100 (Figure 3) The cross-over of real andimaginary VLF anomaly along this profile indicates thepresence of conductive feature around station 550m in thenorthern end of the profile and the slope of curve suggestsit to be a thin inclined body occurring at shallow depth
International Journal of Geophysics 9
N
40
20
0
minus20
minus40
minus60Real
anom
aly
()
Imag
inar
y
50 100 150 200 250 300 350 400 450 500 600550
Distance (m)
40
20
0
minus20
minus40
minus50
minus100
minus12 minus8 minus4 0 4 8 12
Dep
th (m
)
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
30
40
50
60
70
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
6
8
10
12
0
0
0
Current density ()
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 8 Profile P1700 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
The current density contours along this profile clearly demar-cates the shape of this body between stations 510mand 570msuggesting a width of around 60m occurring below 30mfrom the surface Radiometric data recorded over this profileshows similar behavior as that at profile P1100 with peakvalues at 520m
53 Profile 3 (P1300) This profile P1300 (Figure 4) is further83m east of profile P1200 The real and imaginary anomalyplots indicate the presence of multiple conductive bodiesalong this profile and the slope of these curves suggestsvertical structures occurring near to the surface Apparent
current density cross-section also depicts the same resultshowing the presence of three broad and shallow almostvertical conductors between stations 0m and 60m 160mand 250m and 375m and 450m Similarly the radioactivityalong this profile is higher than the background throughoutthe profile with peak between 410m and 440m The peakvalue of total radiations and surface gamma activity recordedat this station is 75 counts100 sec and 19 120583Rh respectively
54 Profile 4 (P1400) Profile P1400 lies 92m east of pro-file P1300 (Figure 5) Here also the VLF anomaly curvesdepict three conductive features all being shallow and nearly
10 International Journal of Geophysics
6789
10
0
N
20
10
0
minus10
minus10minus20Real
anom
aly
()
Imag
inar
y
50 100 150 200 250 300 350 400 450 500
Distance (m)0
10
20
30
minus20
minus40
minus60
minus80
50 100 150 200 250 300 350 400 450
Distance (m)
minus14 minus10 minus6 minus2 2 6 10 14 16
Current density ()
Dep
th (m
)
30
40
50
60
70
50 100 150 200 250 300 350 400 450 500
Distance (m)0
50 100 150 200 250 300 350 400 450 500
Distance (m)0
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 9 Profile P1800 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
vertical Apparent current density cross-section shows thepresence of one conducting and two low conducting struc-tures between stations 70m and 140m 270m and 320mand 490m and 520m respectively The conductor at thesouthern part of the profile (between stations 70mand 140m)is more conductive and wider among the three Radioactivityis observed to be highest above this conductor with peakvalue of total radiation being 290 counts100 sec and that ofgamma activity being 60120583Rh at station 150m This is thehighest radioactivity recorded along all the profiles
55 Profile 5 (P1500) Profile P1500 is taken 86m awaytowards east of profile P1400 (Figure 6) VLF anomaly curves
suggest the presence of a single conductor around station400m The slope of the anomaly curves indicates a thickinclined structure Apparent current density cross-sectionconfirms the presence of inclined conductive structurebetween stations 330mm to 420m Radiometric data isobserved to be almost equal to the background levels all longthe profile with a sudden jump in value to 180 counts100 secof total radiations and 35 120583Rh surface gamma activity atstation 510m
56 Profile 6 (P1600) This profile is located in the westernside of the Beldih mine (Figure 7) VLF anomaly curves indi-cate the presence of two conductive features around stations
International Journal of Geophysics 11
86
P1500P1100 P1200 P1300 P1400
P1600P1700
P1800
18 1805 181 1815
29
295
3
305
31
176 1765
Mine dump
N
Cultivated land
Cultivated land
298
3
302
304
306
308
31312
314
316
318
32
Cultivated land
Cultivated land
Cultivated land
Beldih village (N)
Bore hole BoreholeBLD2 BLD3
Beldih
325998400
32998400
315998400
31998400
305998400
295998400
3998400
29998400
285998400
280998400
23∘
and
min
utes
1745998400
175998400
1755998400
176998400
1765998400
177998400
1775998400
178998400
1785998400
179998400
1795998400
1800998400
1805998400
1810998400
1815998400
1820998400
1825998400
1830998400
86∘ and minutes
0 100 200
(m)
Mine dumpKaolin zone
QuartziteGranite
Quartz-magnetite-apatite rocks
Tuffaceous rock
Altered brecciated ultramafics Radioactive bands (vertical projection from borehole)
VLF profile Ultramafics plusmn carbonatite
5
10
15
20
25
30
35
40
45
50
55
86∘ and minutes
23∘
and
min
utes
Tank
(120583Rh
r)
Figure 10 Surface gamma activity superimposed over geological map of the area of study
Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
240
220
200
180
Datum
0 10
S
20 (m)
N
Expected mineralized zone
260
220
200
180
Datum240
Transverse section through bore hole BLD2 Transverse section through bore hole BLD3
RL-24062m
RL
(m)
BLD2
DD-13075m DD-16355m
640m840m
BLD3
RL
(m)
RL-24234m
Altered brecciated ultramafics
Ultramafics plusmn carbonatite Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
Altered brecciated ultramafics
Ultramafics plusmn carbonatite
Figure 11 Transverse sections through bore holes BLD2 and BLD3 (after [7])
200m and 450m Apparent current density cross-sectiondepicts both of the structures between stations 150m and250m and 410m and 520m and shows that they are dippingstructures Radiometric data shows high radioactivity in thesouthern side of the profile compared to the northern sidewith peak value of total radiation and gamma activity (140counts100 sec and 28 120583Rh resp) found above the station250m
57 Profile 7 (P1700) Differing from all other profiles inprofile P1700 92mwest of P1600 (Figure 8) theVLF anomalycurves indicate a single wide conductive feature lying all overthe profile with centre at 350m Apparent current densitycross-section also shows a much wider conductive featurelying between 0m and 230m 250m and 370m and 390mand 500m ranging in current density values from 4 to10 4 to 12 and 4 to 8 respectively This shows that
12 International Journal of Geophysics
here the same conducting zone is wider than other locationsWhereas radiometric data suggests high radioactivity abovethe background level only between stations 70m and 210m
58 Profile 8 (P1800) Further 88m west of P1700 in profileP1800 (Figure 9) VLF anomaly curves indicate the presenceof two vertical conductors Current density contours alsoshow two conductive features between stations 160m and220m and 320m and 370m The first one is less conductiveas compared to the later one Radiometric data indicates highradioactivity in the southern part of the profile with threepeak regions around stations 50m 140m and 180m
6 Discussion
In the present study eight profiles were chosen on eitherside of the Beldih mine to investigate the uranium andorthorium mineralization by applying VLF-EM and radiomet-ric methods together Results show the presence of multipleisolated conductive features in the study area These con-ductive features appearing in the profile could be becauseof the presence of fractures filled with fluids hydrothermalalteration zones clay mineralization shearing and so forthThe conductive features are traced continuously well in allthe profiles showing a regular parallel trend except in profileP1400where the similar zone is identified in the southern sideof the profileThis implies that the conductive feature at P1400has shifted southward in this profile only This offset of thecurrent density anomaly (in profile P1400) could be due toeither strike slip fault or dip slip fault or subparallel faultingIn case of dip slip fault such offset can be observed only ifan inclined bed is cut by a vertical fault at right angles tothe strike and the slip is normal After erosion such an offsetcan be seen However the observed anomalies appear verticalin the current density profile and the offset or movementis lateral along the strike of the fault This happens in caseof strike-slip fault hence it appears to be the better reasonfor such lateral shift of the mineralized body This can befurther substantiated by successive structural mapping of thearea
The separation between the conductive bodies is notuniform along all the profilesThis further suggests that thesemineralized bodies have small strike length and lenticularshape This result together with the geology of the area indi-cates that the mode of mineralization may be hydrothermalalteration
Radiometric measurements indicate higher radiationsalong the profiles than the average or background radiationsobserved in the areaThe peak or elevated radiations indicatethe presence of uranium mineralization
Surface gamma activity superimposed over geologicalmap of the area of study (Figure 10) clearly depicts the coinci-dence of conductive zones and high radioactivity zones Thiscoincidence indicates the existence of alteration zones in thisarea These zones may contain radioactive mineralization asthey are also correlating with the radioactive bands identifiedby Katti et al [7] and with the bore hole data BLD2 and BLD3(Figures 10 and 11) All these identified mineralized zones are
almost parallel and have a collective strike oriented along E-W direction which is in agreement with the strike of SPSZ
7 Conclusions
VLF-EM and radiometric methods were applied togetherin this region to study the correlation between these twomethods as well as to utilize their integrated results for theexploration of uranium Results indicate good correlationbetween VLF data and radiometric dataThis is because theseradiometric signals are associated with shallow uraniummineralization which is associated with altered mineralsthat gives conductivity contrast with the neighboring rocksCoincidence of high radioactivity over conductive zonesand their correlation with radioactive bands observed inthe area confirms the presence of uranium mineralizationThus the study also suggests that these two methods can beintegrated to explore uraniumandor thoriummineralizationeffectively at low cost with the advantage of being quick andnondestructive compared to other routine methods used forsuch purposesThe study also reveals the presence of a strike-slip fault in the eastern side of the Beldih mine proving theability and advantage of this integrated approach in detectingsuch planner structures and correlating the lithology bothvertically and laterally Since these methods are quick andcost effective they can be utilized to search for shallowuranium mineralization along the SPSZ and other suchregions quickly VLF observations are sometimes affected bypower lines in such areas Gradient Resistivity Profiling andgravity and magnetic methods can be applied to aid in theinterpretation of subsurface structures
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors would like to thank the editor and anonymousreviewers for their valuable comments and suggestions toimprove the quality of the paper
References
[1] B K Bhaumik T Bhattacharya A A P S R AcharyuluD Srinivas and M K Sandilya Principles of Radiometry inRadioactive Metal Exploration Physics Lab AMD ComplexJamshedpur India 2004
[2] V Tuncer M J Unsworth W Siripunvaraporn and J ACraven ldquoExploration for unconformity-type uranium depos-its with audiomagnetotelluric data a case study from theMcArthur River mine Saskatchewan Canadardquo Geophysics vol71 no 6 pp B201ndashB209 2006
[3] J M Legault D Carriere and L Petrie ldquoSynthetic modeltesting and distributed acquisition dc resistivity results overan unconformity uranium target from the Athabasca Basinnorthern SaskatchewanrdquoTheLeading Edge vol 27 no 1 pp 46ndash51 2008
International Journal of Geophysics 13
[4] G Nimeck and R Koch ldquoA progressive geophysical explorationstrategy at the Shea Creek uranium depositrdquoThe Leading Edgevol 27 no 1 pp 52ndash63 2008
[5] A Mandal A Biswas S Mittal et al ldquoGeophysical anomaliesassociated with uranium mineralization from Beldih mineSouth Purulia Shear Zone Indiardquo Journal of the GeologicalSociety of India vol 82 no 6 pp 601ndash606 2013
[6] S P Sharma A Biswas and S Mittal ldquoDelineation of extensionof uranium mineralization zone using resistivity and VLFsur-veys around South Purulia Shear Zone Indiardquo Journal of theGeological Society of India In press
[7] V J Katti J Sen andAK Bhatt ldquoUraniumpotentiality of SouthPurulia Shear Zone in Eastern Indian Shieldrdquo in Proceedings ofthe Technical Meeting on Low Grade Uranium Ore pp 29ndash31International Atomic Energy Agency Vienna Austria 2010
[8] A Acharyya S Ray B K Chaudhuri S K Basu S K Bhaduriand A K Sanyal ldquoProterozoic rock suites along South PuruliaShear Zone eastern India evidence for rift-related settingrdquoJournal of the Geological Society of India vol 68 no 6 pp 1069ndash1086 2006
[9] Y Vapnik S Bushmin A Chattopadhyay and D Dolivo-Dobrovolsky ldquoFluid inclusion and mineralogical study of vein-type apatite ores in shear zones from the Singhbhum metallo-genetic provinceWest Bengal IndiardquoOre Geology Reviews vol32 no 1-2 pp 412ndash430 2007
[10] T K Baidya ldquoApatite-magnetite deposit in the chhotanagpurgneissic complex Panrkidih area Purulia District West Ben-galrdquo Indian Journal of Geology vol 64 pp 88ndash95 1992
[11] S K Basu ldquoAlkaline-carbonatite complex in Precambrian ofSouth Purulia Shear Zone eastern India its characteristics andmineral potentialitiesrdquo Indian Minerals vol 47 no 3 pp 179ndash194 1993
[12] A K G Roy and P R Sengupta ldquoAlkalic-carbonatitic magma-tism and associated mineralisation along the Porapahar-Tamarlineament in the Proterozoics of Purulia District West BengalrdquoIndian Journal of Earth Sciences vol 20 no 3-4 pp 193ndash2001993
[13] T K Pyne ldquoThe Proterozoic fold belt and the chhotanagpurgneissic complex in the eastern Indian Shieldmdasha tectono-metamorphic appraisalrdquo Indian Minerals vol 46 no 1 pp 25ndash34 1992
[14] S Bhattacharya ldquoDuctile shear Zone in Purulia West BengalrdquoIndian Journal of Geology vol 61 pp 172ndash178 1989
[15] B D Smith and S H Ward ldquoOn the computation of polariza-tion ellipse parametersrdquo Geophysics vol 39 pp 867ndash869 1974
[16] N R Paterson and V Ronka ldquoFive years of surveying with thevery low frequency-electromagnetics methodrdquoGeoexplorationvol 9 no 1 pp 7ndash26 1971
[17] M Karous and S E Hjelt ldquoLinear filtering of VLF dip-anglemeasurementsrdquo Geophysical Prospecting vol 31 no 5 pp 782ndash794 1983
[18] A T Ramli S Sahrone and H Wagiran ldquoTerrestrial gammaradiation dose study to determine the baseline for environ-mental radiological health practices in Melaka state MalaysiardquoJournal of Radiological Protection vol 25 no 4 pp 435ndash4502005
Figure 5 Profile P1400 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
4 Radiometric Survey
Radiometric survey was carried out using Geiger-Mullercounter to record total ambient surface radiations andScintillation counter to note the surface gamma radiationsalong the eight selected profiles where VLF survey wasperformed For better and point to point correlation withVLF data radiometric data was collected at the same stationswhere VLF data was recorded along all the profiles usingGPS receivers For precise and accurate measurements everyradiometric measurement was repeated thrice
41 Geiger-Muller Counter Total surface radiations weremeasured using a portable pulsed GM (Geiger-Muller)counter at various locations along the selected profiles aroundthe mine The GM probe is comprised of a thin end window
halogen-quenched counter which is capable of detectingalpha and beta particles and small amount of gamma radi-ations It has a dead time of 200120583s The window is 2 cmin diameter and is shielded with a 1 cm thick lead collarThe instrument is operated with five membrane push buttonswitches and the display is a 6-digit LED
For detailed radiometric survey total radiation countswere measured at every 10m intervals along the profilesexactly where the VLF data was recorded For each mea-surement the sensor of GM counter was kept approximately15 cm above the ground surface and operated for 100 secondsduring data acquisition
42 Scintillation Counter For precise measurements of the 120574radiation we have used a portable scintillator based counting
Current density ()minus11 minus8 minus4 0 4 8 12 15
200
160
120
80
40
0
40
30
20
10
0
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 6 Profile P1500 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
system This Micro-R Survey Meter Type-UR 705 is manu-factured by Nucleonix Systems Private Limited HyderabadIndia It is designed around an integrally coupled 254 times254 cm scintillator coupled to a 254 times 127 cm Photomulti-plier Tube
The measurements were taken during winter season inorder to avoid the interference of gamma-emitting radondecay products [18] The 120574 measurements were undertakensim1m above the ground surface and directly above theexposure to get a better solid angle Each measurement wasundertaken for more than 60 seconds and was repeatedthrice for better precision and optimizing the subsequentinterpretation in terms of the ambient radiation
5 Results
On eastern side of the mine area five profiles namely P1100P1200 P1300 P1400 and P1500 covering around 600mof distance (profile length) (Figure 1) were accomplishedOn the western part of mine we took three profiles P1600P1700 and P1800 covering 600m of length (Figure 1) Forinterpretation of the subsurface geometry apparent currentdensity cross-sections with depths were made using theacquired VLF data along all the profiles For this themeasured real anomalies were interpolated at 2m intervaland filtered using Karous-Hjelt filter [17] These apparentcurrent density cross-sections are presented in Figures 2ndash9
Figure 7 Profile P1600 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
below the real and imaginary anomaly plots obtained fromthe VLF data acquired in the field Results for surface gammaactivity and total surface radiations are also shown as line-plots along with VLF anomaly for every individual profile(Figures 2ndash9) Background radiation level of the region is 40counts100 sec for surface radiations and 6ndash8120583Rh for surfacegamma activity
51 Profile 1 (P1100) The cross-over of real and imaginaryanomaly line-plot along this profile indicates the presenceof conductive zone between stations 500m and 580m(Figure 2(a))This zone is clearly depicted in apparent currentdensity cross-section (Figure 2(b)) by higher values betweenstations 460m and 540m Inclination of real anomaly curve
and apparent current density contours indicate that this con-ductive structure is vertical and lying at shallow depth (sim40mbelow surface) Radiometric data suggest the presence ofradiation more than the background levels above this con-ductive zonewith peak value of 16120583Rh and 80 counts100 secfor surface gamma activity and total radiations respectivelyat station 520m
52 Profile 2 (P1200) Profile P1200 is parallel to and 96meast of profile P1100 (Figure 3) The cross-over of real andimaginary VLF anomaly along this profile indicates thepresence of conductive feature around station 550m in thenorthern end of the profile and the slope of curve suggestsit to be a thin inclined body occurring at shallow depth
International Journal of Geophysics 9
N
40
20
0
minus20
minus40
minus60Real
anom
aly
()
Imag
inar
y
50 100 150 200 250 300 350 400 450 500 600550
Distance (m)
40
20
0
minus20
minus40
minus50
minus100
minus12 minus8 minus4 0 4 8 12
Dep
th (m
)
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
30
40
50
60
70
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
6
8
10
12
0
0
0
Current density ()
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 8 Profile P1700 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
The current density contours along this profile clearly demar-cates the shape of this body between stations 510mand 570msuggesting a width of around 60m occurring below 30mfrom the surface Radiometric data recorded over this profileshows similar behavior as that at profile P1100 with peakvalues at 520m
53 Profile 3 (P1300) This profile P1300 (Figure 4) is further83m east of profile P1200 The real and imaginary anomalyplots indicate the presence of multiple conductive bodiesalong this profile and the slope of these curves suggestsvertical structures occurring near to the surface Apparent
current density cross-section also depicts the same resultshowing the presence of three broad and shallow almostvertical conductors between stations 0m and 60m 160mand 250m and 375m and 450m Similarly the radioactivityalong this profile is higher than the background throughoutthe profile with peak between 410m and 440m The peakvalue of total radiations and surface gamma activity recordedat this station is 75 counts100 sec and 19 120583Rh respectively
54 Profile 4 (P1400) Profile P1400 lies 92m east of pro-file P1300 (Figure 5) Here also the VLF anomaly curvesdepict three conductive features all being shallow and nearly
10 International Journal of Geophysics
6789
10
0
N
20
10
0
minus10
minus10minus20Real
anom
aly
()
Imag
inar
y
50 100 150 200 250 300 350 400 450 500
Distance (m)0
10
20
30
minus20
minus40
minus60
minus80
50 100 150 200 250 300 350 400 450
Distance (m)
minus14 minus10 minus6 minus2 2 6 10 14 16
Current density ()
Dep
th (m
)
30
40
50
60
70
50 100 150 200 250 300 350 400 450 500
Distance (m)0
50 100 150 200 250 300 350 400 450 500
Distance (m)0
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 9 Profile P1800 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
vertical Apparent current density cross-section shows thepresence of one conducting and two low conducting struc-tures between stations 70m and 140m 270m and 320mand 490m and 520m respectively The conductor at thesouthern part of the profile (between stations 70mand 140m)is more conductive and wider among the three Radioactivityis observed to be highest above this conductor with peakvalue of total radiation being 290 counts100 sec and that ofgamma activity being 60120583Rh at station 150m This is thehighest radioactivity recorded along all the profiles
55 Profile 5 (P1500) Profile P1500 is taken 86m awaytowards east of profile P1400 (Figure 6) VLF anomaly curves
suggest the presence of a single conductor around station400m The slope of the anomaly curves indicates a thickinclined structure Apparent current density cross-sectionconfirms the presence of inclined conductive structurebetween stations 330mm to 420m Radiometric data isobserved to be almost equal to the background levels all longthe profile with a sudden jump in value to 180 counts100 secof total radiations and 35 120583Rh surface gamma activity atstation 510m
56 Profile 6 (P1600) This profile is located in the westernside of the Beldih mine (Figure 7) VLF anomaly curves indi-cate the presence of two conductive features around stations
International Journal of Geophysics 11
86
P1500P1100 P1200 P1300 P1400
P1600P1700
P1800
18 1805 181 1815
29
295
3
305
31
176 1765
Mine dump
N
Cultivated land
Cultivated land
298
3
302
304
306
308
31312
314
316
318
32
Cultivated land
Cultivated land
Cultivated land
Beldih village (N)
Bore hole BoreholeBLD2 BLD3
Beldih
325998400
32998400
315998400
31998400
305998400
295998400
3998400
29998400
285998400
280998400
23∘
and
min
utes
1745998400
175998400
1755998400
176998400
1765998400
177998400
1775998400
178998400
1785998400
179998400
1795998400
1800998400
1805998400
1810998400
1815998400
1820998400
1825998400
1830998400
86∘ and minutes
0 100 200
(m)
Mine dumpKaolin zone
QuartziteGranite
Quartz-magnetite-apatite rocks
Tuffaceous rock
Altered brecciated ultramafics Radioactive bands (vertical projection from borehole)
VLF profile Ultramafics plusmn carbonatite
5
10
15
20
25
30
35
40
45
50
55
86∘ and minutes
23∘
and
min
utes
Tank
(120583Rh
r)
Figure 10 Surface gamma activity superimposed over geological map of the area of study
Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
240
220
200
180
Datum
0 10
S
20 (m)
N
Expected mineralized zone
260
220
200
180
Datum240
Transverse section through bore hole BLD2 Transverse section through bore hole BLD3
RL-24062m
RL
(m)
BLD2
DD-13075m DD-16355m
640m840m
BLD3
RL
(m)
RL-24234m
Altered brecciated ultramafics
Ultramafics plusmn carbonatite Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
Altered brecciated ultramafics
Ultramafics plusmn carbonatite
Figure 11 Transverse sections through bore holes BLD2 and BLD3 (after [7])
200m and 450m Apparent current density cross-sectiondepicts both of the structures between stations 150m and250m and 410m and 520m and shows that they are dippingstructures Radiometric data shows high radioactivity in thesouthern side of the profile compared to the northern sidewith peak value of total radiation and gamma activity (140counts100 sec and 28 120583Rh resp) found above the station250m
57 Profile 7 (P1700) Differing from all other profiles inprofile P1700 92mwest of P1600 (Figure 8) theVLF anomalycurves indicate a single wide conductive feature lying all overthe profile with centre at 350m Apparent current densitycross-section also shows a much wider conductive featurelying between 0m and 230m 250m and 370m and 390mand 500m ranging in current density values from 4 to10 4 to 12 and 4 to 8 respectively This shows that
12 International Journal of Geophysics
here the same conducting zone is wider than other locationsWhereas radiometric data suggests high radioactivity abovethe background level only between stations 70m and 210m
58 Profile 8 (P1800) Further 88m west of P1700 in profileP1800 (Figure 9) VLF anomaly curves indicate the presenceof two vertical conductors Current density contours alsoshow two conductive features between stations 160m and220m and 320m and 370m The first one is less conductiveas compared to the later one Radiometric data indicates highradioactivity in the southern part of the profile with threepeak regions around stations 50m 140m and 180m
6 Discussion
In the present study eight profiles were chosen on eitherside of the Beldih mine to investigate the uranium andorthorium mineralization by applying VLF-EM and radiomet-ric methods together Results show the presence of multipleisolated conductive features in the study area These con-ductive features appearing in the profile could be becauseof the presence of fractures filled with fluids hydrothermalalteration zones clay mineralization shearing and so forthThe conductive features are traced continuously well in allthe profiles showing a regular parallel trend except in profileP1400where the similar zone is identified in the southern sideof the profileThis implies that the conductive feature at P1400has shifted southward in this profile only This offset of thecurrent density anomaly (in profile P1400) could be due toeither strike slip fault or dip slip fault or subparallel faultingIn case of dip slip fault such offset can be observed only ifan inclined bed is cut by a vertical fault at right angles tothe strike and the slip is normal After erosion such an offsetcan be seen However the observed anomalies appear verticalin the current density profile and the offset or movementis lateral along the strike of the fault This happens in caseof strike-slip fault hence it appears to be the better reasonfor such lateral shift of the mineralized body This can befurther substantiated by successive structural mapping of thearea
The separation between the conductive bodies is notuniform along all the profilesThis further suggests that thesemineralized bodies have small strike length and lenticularshape This result together with the geology of the area indi-cates that the mode of mineralization may be hydrothermalalteration
Radiometric measurements indicate higher radiationsalong the profiles than the average or background radiationsobserved in the areaThe peak or elevated radiations indicatethe presence of uranium mineralization
Surface gamma activity superimposed over geologicalmap of the area of study (Figure 10) clearly depicts the coinci-dence of conductive zones and high radioactivity zones Thiscoincidence indicates the existence of alteration zones in thisarea These zones may contain radioactive mineralization asthey are also correlating with the radioactive bands identifiedby Katti et al [7] and with the bore hole data BLD2 and BLD3(Figures 10 and 11) All these identified mineralized zones are
almost parallel and have a collective strike oriented along E-W direction which is in agreement with the strike of SPSZ
7 Conclusions
VLF-EM and radiometric methods were applied togetherin this region to study the correlation between these twomethods as well as to utilize their integrated results for theexploration of uranium Results indicate good correlationbetween VLF data and radiometric dataThis is because theseradiometric signals are associated with shallow uraniummineralization which is associated with altered mineralsthat gives conductivity contrast with the neighboring rocksCoincidence of high radioactivity over conductive zonesand their correlation with radioactive bands observed inthe area confirms the presence of uranium mineralizationThus the study also suggests that these two methods can beintegrated to explore uraniumandor thoriummineralizationeffectively at low cost with the advantage of being quick andnondestructive compared to other routine methods used forsuch purposesThe study also reveals the presence of a strike-slip fault in the eastern side of the Beldih mine proving theability and advantage of this integrated approach in detectingsuch planner structures and correlating the lithology bothvertically and laterally Since these methods are quick andcost effective they can be utilized to search for shallowuranium mineralization along the SPSZ and other suchregions quickly VLF observations are sometimes affected bypower lines in such areas Gradient Resistivity Profiling andgravity and magnetic methods can be applied to aid in theinterpretation of subsurface structures
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors would like to thank the editor and anonymousreviewers for their valuable comments and suggestions toimprove the quality of the paper
References
[1] B K Bhaumik T Bhattacharya A A P S R AcharyuluD Srinivas and M K Sandilya Principles of Radiometry inRadioactive Metal Exploration Physics Lab AMD ComplexJamshedpur India 2004
[2] V Tuncer M J Unsworth W Siripunvaraporn and J ACraven ldquoExploration for unconformity-type uranium depos-its with audiomagnetotelluric data a case study from theMcArthur River mine Saskatchewan Canadardquo Geophysics vol71 no 6 pp B201ndashB209 2006
[3] J M Legault D Carriere and L Petrie ldquoSynthetic modeltesting and distributed acquisition dc resistivity results overan unconformity uranium target from the Athabasca Basinnorthern SaskatchewanrdquoTheLeading Edge vol 27 no 1 pp 46ndash51 2008
International Journal of Geophysics 13
[4] G Nimeck and R Koch ldquoA progressive geophysical explorationstrategy at the Shea Creek uranium depositrdquoThe Leading Edgevol 27 no 1 pp 52ndash63 2008
[5] A Mandal A Biswas S Mittal et al ldquoGeophysical anomaliesassociated with uranium mineralization from Beldih mineSouth Purulia Shear Zone Indiardquo Journal of the GeologicalSociety of India vol 82 no 6 pp 601ndash606 2013
[6] S P Sharma A Biswas and S Mittal ldquoDelineation of extensionof uranium mineralization zone using resistivity and VLFsur-veys around South Purulia Shear Zone Indiardquo Journal of theGeological Society of India In press
[7] V J Katti J Sen andAK Bhatt ldquoUraniumpotentiality of SouthPurulia Shear Zone in Eastern Indian Shieldrdquo in Proceedings ofthe Technical Meeting on Low Grade Uranium Ore pp 29ndash31International Atomic Energy Agency Vienna Austria 2010
[8] A Acharyya S Ray B K Chaudhuri S K Basu S K Bhaduriand A K Sanyal ldquoProterozoic rock suites along South PuruliaShear Zone eastern India evidence for rift-related settingrdquoJournal of the Geological Society of India vol 68 no 6 pp 1069ndash1086 2006
[9] Y Vapnik S Bushmin A Chattopadhyay and D Dolivo-Dobrovolsky ldquoFluid inclusion and mineralogical study of vein-type apatite ores in shear zones from the Singhbhum metallo-genetic provinceWest Bengal IndiardquoOre Geology Reviews vol32 no 1-2 pp 412ndash430 2007
[10] T K Baidya ldquoApatite-magnetite deposit in the chhotanagpurgneissic complex Panrkidih area Purulia District West Ben-galrdquo Indian Journal of Geology vol 64 pp 88ndash95 1992
[11] S K Basu ldquoAlkaline-carbonatite complex in Precambrian ofSouth Purulia Shear Zone eastern India its characteristics andmineral potentialitiesrdquo Indian Minerals vol 47 no 3 pp 179ndash194 1993
[12] A K G Roy and P R Sengupta ldquoAlkalic-carbonatitic magma-tism and associated mineralisation along the Porapahar-Tamarlineament in the Proterozoics of Purulia District West BengalrdquoIndian Journal of Earth Sciences vol 20 no 3-4 pp 193ndash2001993
[13] T K Pyne ldquoThe Proterozoic fold belt and the chhotanagpurgneissic complex in the eastern Indian Shieldmdasha tectono-metamorphic appraisalrdquo Indian Minerals vol 46 no 1 pp 25ndash34 1992
[14] S Bhattacharya ldquoDuctile shear Zone in Purulia West BengalrdquoIndian Journal of Geology vol 61 pp 172ndash178 1989
[15] B D Smith and S H Ward ldquoOn the computation of polariza-tion ellipse parametersrdquo Geophysics vol 39 pp 867ndash869 1974
[16] N R Paterson and V Ronka ldquoFive years of surveying with thevery low frequency-electromagnetics methodrdquoGeoexplorationvol 9 no 1 pp 7ndash26 1971
[17] M Karous and S E Hjelt ldquoLinear filtering of VLF dip-anglemeasurementsrdquo Geophysical Prospecting vol 31 no 5 pp 782ndash794 1983
[18] A T Ramli S Sahrone and H Wagiran ldquoTerrestrial gammaradiation dose study to determine the baseline for environ-mental radiological health practices in Melaka state MalaysiardquoJournal of Radiological Protection vol 25 no 4 pp 435ndash4502005
Current density ()minus11 minus8 minus4 0 4 8 12 15
200
160
120
80
40
0
40
30
20
10
0
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 6 Profile P1500 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
system This Micro-R Survey Meter Type-UR 705 is manu-factured by Nucleonix Systems Private Limited HyderabadIndia It is designed around an integrally coupled 254 times254 cm scintillator coupled to a 254 times 127 cm Photomulti-plier Tube
The measurements were taken during winter season inorder to avoid the interference of gamma-emitting radondecay products [18] The 120574 measurements were undertakensim1m above the ground surface and directly above theexposure to get a better solid angle Each measurement wasundertaken for more than 60 seconds and was repeatedthrice for better precision and optimizing the subsequentinterpretation in terms of the ambient radiation
5 Results
On eastern side of the mine area five profiles namely P1100P1200 P1300 P1400 and P1500 covering around 600mof distance (profile length) (Figure 1) were accomplishedOn the western part of mine we took three profiles P1600P1700 and P1800 covering 600m of length (Figure 1) Forinterpretation of the subsurface geometry apparent currentdensity cross-sections with depths were made using theacquired VLF data along all the profiles For this themeasured real anomalies were interpolated at 2m intervaland filtered using Karous-Hjelt filter [17] These apparentcurrent density cross-sections are presented in Figures 2ndash9
Figure 7 Profile P1600 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
below the real and imaginary anomaly plots obtained fromthe VLF data acquired in the field Results for surface gammaactivity and total surface radiations are also shown as line-plots along with VLF anomaly for every individual profile(Figures 2ndash9) Background radiation level of the region is 40counts100 sec for surface radiations and 6ndash8120583Rh for surfacegamma activity
51 Profile 1 (P1100) The cross-over of real and imaginaryanomaly line-plot along this profile indicates the presenceof conductive zone between stations 500m and 580m(Figure 2(a))This zone is clearly depicted in apparent currentdensity cross-section (Figure 2(b)) by higher values betweenstations 460m and 540m Inclination of real anomaly curve
and apparent current density contours indicate that this con-ductive structure is vertical and lying at shallow depth (sim40mbelow surface) Radiometric data suggest the presence ofradiation more than the background levels above this con-ductive zonewith peak value of 16120583Rh and 80 counts100 secfor surface gamma activity and total radiations respectivelyat station 520m
52 Profile 2 (P1200) Profile P1200 is parallel to and 96meast of profile P1100 (Figure 3) The cross-over of real andimaginary VLF anomaly along this profile indicates thepresence of conductive feature around station 550m in thenorthern end of the profile and the slope of curve suggestsit to be a thin inclined body occurring at shallow depth
International Journal of Geophysics 9
N
40
20
0
minus20
minus40
minus60Real
anom
aly
()
Imag
inar
y
50 100 150 200 250 300 350 400 450 500 600550
Distance (m)
40
20
0
minus20
minus40
minus50
minus100
minus12 minus8 minus4 0 4 8 12
Dep
th (m
)
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
30
40
50
60
70
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
6
8
10
12
0
0
0
Current density ()
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 8 Profile P1700 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
The current density contours along this profile clearly demar-cates the shape of this body between stations 510mand 570msuggesting a width of around 60m occurring below 30mfrom the surface Radiometric data recorded over this profileshows similar behavior as that at profile P1100 with peakvalues at 520m
53 Profile 3 (P1300) This profile P1300 (Figure 4) is further83m east of profile P1200 The real and imaginary anomalyplots indicate the presence of multiple conductive bodiesalong this profile and the slope of these curves suggestsvertical structures occurring near to the surface Apparent
current density cross-section also depicts the same resultshowing the presence of three broad and shallow almostvertical conductors between stations 0m and 60m 160mand 250m and 375m and 450m Similarly the radioactivityalong this profile is higher than the background throughoutthe profile with peak between 410m and 440m The peakvalue of total radiations and surface gamma activity recordedat this station is 75 counts100 sec and 19 120583Rh respectively
54 Profile 4 (P1400) Profile P1400 lies 92m east of pro-file P1300 (Figure 5) Here also the VLF anomaly curvesdepict three conductive features all being shallow and nearly
10 International Journal of Geophysics
6789
10
0
N
20
10
0
minus10
minus10minus20Real
anom
aly
()
Imag
inar
y
50 100 150 200 250 300 350 400 450 500
Distance (m)0
10
20
30
minus20
minus40
minus60
minus80
50 100 150 200 250 300 350 400 450
Distance (m)
minus14 minus10 minus6 minus2 2 6 10 14 16
Current density ()
Dep
th (m
)
30
40
50
60
70
50 100 150 200 250 300 350 400 450 500
Distance (m)0
50 100 150 200 250 300 350 400 450 500
Distance (m)0
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 9 Profile P1800 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
vertical Apparent current density cross-section shows thepresence of one conducting and two low conducting struc-tures between stations 70m and 140m 270m and 320mand 490m and 520m respectively The conductor at thesouthern part of the profile (between stations 70mand 140m)is more conductive and wider among the three Radioactivityis observed to be highest above this conductor with peakvalue of total radiation being 290 counts100 sec and that ofgamma activity being 60120583Rh at station 150m This is thehighest radioactivity recorded along all the profiles
55 Profile 5 (P1500) Profile P1500 is taken 86m awaytowards east of profile P1400 (Figure 6) VLF anomaly curves
suggest the presence of a single conductor around station400m The slope of the anomaly curves indicates a thickinclined structure Apparent current density cross-sectionconfirms the presence of inclined conductive structurebetween stations 330mm to 420m Radiometric data isobserved to be almost equal to the background levels all longthe profile with a sudden jump in value to 180 counts100 secof total radiations and 35 120583Rh surface gamma activity atstation 510m
56 Profile 6 (P1600) This profile is located in the westernside of the Beldih mine (Figure 7) VLF anomaly curves indi-cate the presence of two conductive features around stations
International Journal of Geophysics 11
86
P1500P1100 P1200 P1300 P1400
P1600P1700
P1800
18 1805 181 1815
29
295
3
305
31
176 1765
Mine dump
N
Cultivated land
Cultivated land
298
3
302
304
306
308
31312
314
316
318
32
Cultivated land
Cultivated land
Cultivated land
Beldih village (N)
Bore hole BoreholeBLD2 BLD3
Beldih
325998400
32998400
315998400
31998400
305998400
295998400
3998400
29998400
285998400
280998400
23∘
and
min
utes
1745998400
175998400
1755998400
176998400
1765998400
177998400
1775998400
178998400
1785998400
179998400
1795998400
1800998400
1805998400
1810998400
1815998400
1820998400
1825998400
1830998400
86∘ and minutes
0 100 200
(m)
Mine dumpKaolin zone
QuartziteGranite
Quartz-magnetite-apatite rocks
Tuffaceous rock
Altered brecciated ultramafics Radioactive bands (vertical projection from borehole)
VLF profile Ultramafics plusmn carbonatite
5
10
15
20
25
30
35
40
45
50
55
86∘ and minutes
23∘
and
min
utes
Tank
(120583Rh
r)
Figure 10 Surface gamma activity superimposed over geological map of the area of study
Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
240
220
200
180
Datum
0 10
S
20 (m)
N
Expected mineralized zone
260
220
200
180
Datum240
Transverse section through bore hole BLD2 Transverse section through bore hole BLD3
RL-24062m
RL
(m)
BLD2
DD-13075m DD-16355m
640m840m
BLD3
RL
(m)
RL-24234m
Altered brecciated ultramafics
Ultramafics plusmn carbonatite Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
Altered brecciated ultramafics
Ultramafics plusmn carbonatite
Figure 11 Transverse sections through bore holes BLD2 and BLD3 (after [7])
200m and 450m Apparent current density cross-sectiondepicts both of the structures between stations 150m and250m and 410m and 520m and shows that they are dippingstructures Radiometric data shows high radioactivity in thesouthern side of the profile compared to the northern sidewith peak value of total radiation and gamma activity (140counts100 sec and 28 120583Rh resp) found above the station250m
57 Profile 7 (P1700) Differing from all other profiles inprofile P1700 92mwest of P1600 (Figure 8) theVLF anomalycurves indicate a single wide conductive feature lying all overthe profile with centre at 350m Apparent current densitycross-section also shows a much wider conductive featurelying between 0m and 230m 250m and 370m and 390mand 500m ranging in current density values from 4 to10 4 to 12 and 4 to 8 respectively This shows that
12 International Journal of Geophysics
here the same conducting zone is wider than other locationsWhereas radiometric data suggests high radioactivity abovethe background level only between stations 70m and 210m
58 Profile 8 (P1800) Further 88m west of P1700 in profileP1800 (Figure 9) VLF anomaly curves indicate the presenceof two vertical conductors Current density contours alsoshow two conductive features between stations 160m and220m and 320m and 370m The first one is less conductiveas compared to the later one Radiometric data indicates highradioactivity in the southern part of the profile with threepeak regions around stations 50m 140m and 180m
6 Discussion
In the present study eight profiles were chosen on eitherside of the Beldih mine to investigate the uranium andorthorium mineralization by applying VLF-EM and radiomet-ric methods together Results show the presence of multipleisolated conductive features in the study area These con-ductive features appearing in the profile could be becauseof the presence of fractures filled with fluids hydrothermalalteration zones clay mineralization shearing and so forthThe conductive features are traced continuously well in allthe profiles showing a regular parallel trend except in profileP1400where the similar zone is identified in the southern sideof the profileThis implies that the conductive feature at P1400has shifted southward in this profile only This offset of thecurrent density anomaly (in profile P1400) could be due toeither strike slip fault or dip slip fault or subparallel faultingIn case of dip slip fault such offset can be observed only ifan inclined bed is cut by a vertical fault at right angles tothe strike and the slip is normal After erosion such an offsetcan be seen However the observed anomalies appear verticalin the current density profile and the offset or movementis lateral along the strike of the fault This happens in caseof strike-slip fault hence it appears to be the better reasonfor such lateral shift of the mineralized body This can befurther substantiated by successive structural mapping of thearea
The separation between the conductive bodies is notuniform along all the profilesThis further suggests that thesemineralized bodies have small strike length and lenticularshape This result together with the geology of the area indi-cates that the mode of mineralization may be hydrothermalalteration
Radiometric measurements indicate higher radiationsalong the profiles than the average or background radiationsobserved in the areaThe peak or elevated radiations indicatethe presence of uranium mineralization
Surface gamma activity superimposed over geologicalmap of the area of study (Figure 10) clearly depicts the coinci-dence of conductive zones and high radioactivity zones Thiscoincidence indicates the existence of alteration zones in thisarea These zones may contain radioactive mineralization asthey are also correlating with the radioactive bands identifiedby Katti et al [7] and with the bore hole data BLD2 and BLD3(Figures 10 and 11) All these identified mineralized zones are
almost parallel and have a collective strike oriented along E-W direction which is in agreement with the strike of SPSZ
7 Conclusions
VLF-EM and radiometric methods were applied togetherin this region to study the correlation between these twomethods as well as to utilize their integrated results for theexploration of uranium Results indicate good correlationbetween VLF data and radiometric dataThis is because theseradiometric signals are associated with shallow uraniummineralization which is associated with altered mineralsthat gives conductivity contrast with the neighboring rocksCoincidence of high radioactivity over conductive zonesand their correlation with radioactive bands observed inthe area confirms the presence of uranium mineralizationThus the study also suggests that these two methods can beintegrated to explore uraniumandor thoriummineralizationeffectively at low cost with the advantage of being quick andnondestructive compared to other routine methods used forsuch purposesThe study also reveals the presence of a strike-slip fault in the eastern side of the Beldih mine proving theability and advantage of this integrated approach in detectingsuch planner structures and correlating the lithology bothvertically and laterally Since these methods are quick andcost effective they can be utilized to search for shallowuranium mineralization along the SPSZ and other suchregions quickly VLF observations are sometimes affected bypower lines in such areas Gradient Resistivity Profiling andgravity and magnetic methods can be applied to aid in theinterpretation of subsurface structures
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors would like to thank the editor and anonymousreviewers for their valuable comments and suggestions toimprove the quality of the paper
References
[1] B K Bhaumik T Bhattacharya A A P S R AcharyuluD Srinivas and M K Sandilya Principles of Radiometry inRadioactive Metal Exploration Physics Lab AMD ComplexJamshedpur India 2004
[2] V Tuncer M J Unsworth W Siripunvaraporn and J ACraven ldquoExploration for unconformity-type uranium depos-its with audiomagnetotelluric data a case study from theMcArthur River mine Saskatchewan Canadardquo Geophysics vol71 no 6 pp B201ndashB209 2006
[3] J M Legault D Carriere and L Petrie ldquoSynthetic modeltesting and distributed acquisition dc resistivity results overan unconformity uranium target from the Athabasca Basinnorthern SaskatchewanrdquoTheLeading Edge vol 27 no 1 pp 46ndash51 2008
International Journal of Geophysics 13
[4] G Nimeck and R Koch ldquoA progressive geophysical explorationstrategy at the Shea Creek uranium depositrdquoThe Leading Edgevol 27 no 1 pp 52ndash63 2008
[5] A Mandal A Biswas S Mittal et al ldquoGeophysical anomaliesassociated with uranium mineralization from Beldih mineSouth Purulia Shear Zone Indiardquo Journal of the GeologicalSociety of India vol 82 no 6 pp 601ndash606 2013
[6] S P Sharma A Biswas and S Mittal ldquoDelineation of extensionof uranium mineralization zone using resistivity and VLFsur-veys around South Purulia Shear Zone Indiardquo Journal of theGeological Society of India In press
[7] V J Katti J Sen andAK Bhatt ldquoUraniumpotentiality of SouthPurulia Shear Zone in Eastern Indian Shieldrdquo in Proceedings ofthe Technical Meeting on Low Grade Uranium Ore pp 29ndash31International Atomic Energy Agency Vienna Austria 2010
[8] A Acharyya S Ray B K Chaudhuri S K Basu S K Bhaduriand A K Sanyal ldquoProterozoic rock suites along South PuruliaShear Zone eastern India evidence for rift-related settingrdquoJournal of the Geological Society of India vol 68 no 6 pp 1069ndash1086 2006
[9] Y Vapnik S Bushmin A Chattopadhyay and D Dolivo-Dobrovolsky ldquoFluid inclusion and mineralogical study of vein-type apatite ores in shear zones from the Singhbhum metallo-genetic provinceWest Bengal IndiardquoOre Geology Reviews vol32 no 1-2 pp 412ndash430 2007
[10] T K Baidya ldquoApatite-magnetite deposit in the chhotanagpurgneissic complex Panrkidih area Purulia District West Ben-galrdquo Indian Journal of Geology vol 64 pp 88ndash95 1992
[11] S K Basu ldquoAlkaline-carbonatite complex in Precambrian ofSouth Purulia Shear Zone eastern India its characteristics andmineral potentialitiesrdquo Indian Minerals vol 47 no 3 pp 179ndash194 1993
[12] A K G Roy and P R Sengupta ldquoAlkalic-carbonatitic magma-tism and associated mineralisation along the Porapahar-Tamarlineament in the Proterozoics of Purulia District West BengalrdquoIndian Journal of Earth Sciences vol 20 no 3-4 pp 193ndash2001993
[13] T K Pyne ldquoThe Proterozoic fold belt and the chhotanagpurgneissic complex in the eastern Indian Shieldmdasha tectono-metamorphic appraisalrdquo Indian Minerals vol 46 no 1 pp 25ndash34 1992
[14] S Bhattacharya ldquoDuctile shear Zone in Purulia West BengalrdquoIndian Journal of Geology vol 61 pp 172ndash178 1989
[15] B D Smith and S H Ward ldquoOn the computation of polariza-tion ellipse parametersrdquo Geophysics vol 39 pp 867ndash869 1974
[16] N R Paterson and V Ronka ldquoFive years of surveying with thevery low frequency-electromagnetics methodrdquoGeoexplorationvol 9 no 1 pp 7ndash26 1971
[17] M Karous and S E Hjelt ldquoLinear filtering of VLF dip-anglemeasurementsrdquo Geophysical Prospecting vol 31 no 5 pp 782ndash794 1983
[18] A T Ramli S Sahrone and H Wagiran ldquoTerrestrial gammaradiation dose study to determine the baseline for environ-mental radiological health practices in Melaka state MalaysiardquoJournal of Radiological Protection vol 25 no 4 pp 435ndash4502005
Figure 7 Profile P1600 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
below the real and imaginary anomaly plots obtained fromthe VLF data acquired in the field Results for surface gammaactivity and total surface radiations are also shown as line-plots along with VLF anomaly for every individual profile(Figures 2ndash9) Background radiation level of the region is 40counts100 sec for surface radiations and 6ndash8120583Rh for surfacegamma activity
51 Profile 1 (P1100) The cross-over of real and imaginaryanomaly line-plot along this profile indicates the presenceof conductive zone between stations 500m and 580m(Figure 2(a))This zone is clearly depicted in apparent currentdensity cross-section (Figure 2(b)) by higher values betweenstations 460m and 540m Inclination of real anomaly curve
and apparent current density contours indicate that this con-ductive structure is vertical and lying at shallow depth (sim40mbelow surface) Radiometric data suggest the presence ofradiation more than the background levels above this con-ductive zonewith peak value of 16120583Rh and 80 counts100 secfor surface gamma activity and total radiations respectivelyat station 520m
52 Profile 2 (P1200) Profile P1200 is parallel to and 96meast of profile P1100 (Figure 3) The cross-over of real andimaginary VLF anomaly along this profile indicates thepresence of conductive feature around station 550m in thenorthern end of the profile and the slope of curve suggestsit to be a thin inclined body occurring at shallow depth
International Journal of Geophysics 9
N
40
20
0
minus20
minus40
minus60Real
anom
aly
()
Imag
inar
y
50 100 150 200 250 300 350 400 450 500 600550
Distance (m)
40
20
0
minus20
minus40
minus50
minus100
minus12 minus8 minus4 0 4 8 12
Dep
th (m
)
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
30
40
50
60
70
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
50 100 150 200 250 300 350 400 450 500 550
Distance (m)
6
8
10
12
0
0
0
Current density ()
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 8 Profile P1700 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
The current density contours along this profile clearly demar-cates the shape of this body between stations 510mand 570msuggesting a width of around 60m occurring below 30mfrom the surface Radiometric data recorded over this profileshows similar behavior as that at profile P1100 with peakvalues at 520m
53 Profile 3 (P1300) This profile P1300 (Figure 4) is further83m east of profile P1200 The real and imaginary anomalyplots indicate the presence of multiple conductive bodiesalong this profile and the slope of these curves suggestsvertical structures occurring near to the surface Apparent
current density cross-section also depicts the same resultshowing the presence of three broad and shallow almostvertical conductors between stations 0m and 60m 160mand 250m and 375m and 450m Similarly the radioactivityalong this profile is higher than the background throughoutthe profile with peak between 410m and 440m The peakvalue of total radiations and surface gamma activity recordedat this station is 75 counts100 sec and 19 120583Rh respectively
54 Profile 4 (P1400) Profile P1400 lies 92m east of pro-file P1300 (Figure 5) Here also the VLF anomaly curvesdepict three conductive features all being shallow and nearly
10 International Journal of Geophysics
6789
10
0
N
20
10
0
minus10
minus10minus20Real
anom
aly
()
Imag
inar
y
50 100 150 200 250 300 350 400 450 500
Distance (m)0
10
20
30
minus20
minus40
minus60
minus80
50 100 150 200 250 300 350 400 450
Distance (m)
minus14 minus10 minus6 minus2 2 6 10 14 16
Current density ()
Dep
th (m
)
30
40
50
60
70
50 100 150 200 250 300 350 400 450 500
Distance (m)0
50 100 150 200 250 300 350 400 450 500
Distance (m)0
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 9 Profile P1800 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
vertical Apparent current density cross-section shows thepresence of one conducting and two low conducting struc-tures between stations 70m and 140m 270m and 320mand 490m and 520m respectively The conductor at thesouthern part of the profile (between stations 70mand 140m)is more conductive and wider among the three Radioactivityis observed to be highest above this conductor with peakvalue of total radiation being 290 counts100 sec and that ofgamma activity being 60120583Rh at station 150m This is thehighest radioactivity recorded along all the profiles
55 Profile 5 (P1500) Profile P1500 is taken 86m awaytowards east of profile P1400 (Figure 6) VLF anomaly curves
suggest the presence of a single conductor around station400m The slope of the anomaly curves indicates a thickinclined structure Apparent current density cross-sectionconfirms the presence of inclined conductive structurebetween stations 330mm to 420m Radiometric data isobserved to be almost equal to the background levels all longthe profile with a sudden jump in value to 180 counts100 secof total radiations and 35 120583Rh surface gamma activity atstation 510m
56 Profile 6 (P1600) This profile is located in the westernside of the Beldih mine (Figure 7) VLF anomaly curves indi-cate the presence of two conductive features around stations
International Journal of Geophysics 11
86
P1500P1100 P1200 P1300 P1400
P1600P1700
P1800
18 1805 181 1815
29
295
3
305
31
176 1765
Mine dump
N
Cultivated land
Cultivated land
298
3
302
304
306
308
31312
314
316
318
32
Cultivated land
Cultivated land
Cultivated land
Beldih village (N)
Bore hole BoreholeBLD2 BLD3
Beldih
325998400
32998400
315998400
31998400
305998400
295998400
3998400
29998400
285998400
280998400
23∘
and
min
utes
1745998400
175998400
1755998400
176998400
1765998400
177998400
1775998400
178998400
1785998400
179998400
1795998400
1800998400
1805998400
1810998400
1815998400
1820998400
1825998400
1830998400
86∘ and minutes
0 100 200
(m)
Mine dumpKaolin zone
QuartziteGranite
Quartz-magnetite-apatite rocks
Tuffaceous rock
Altered brecciated ultramafics Radioactive bands (vertical projection from borehole)
VLF profile Ultramafics plusmn carbonatite
5
10
15
20
25
30
35
40
45
50
55
86∘ and minutes
23∘
and
min
utes
Tank
(120583Rh
r)
Figure 10 Surface gamma activity superimposed over geological map of the area of study
Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
240
220
200
180
Datum
0 10
S
20 (m)
N
Expected mineralized zone
260
220
200
180
Datum240
Transverse section through bore hole BLD2 Transverse section through bore hole BLD3
RL-24062m
RL
(m)
BLD2
DD-13075m DD-16355m
640m840m
BLD3
RL
(m)
RL-24234m
Altered brecciated ultramafics
Ultramafics plusmn carbonatite Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
Altered brecciated ultramafics
Ultramafics plusmn carbonatite
Figure 11 Transverse sections through bore holes BLD2 and BLD3 (after [7])
200m and 450m Apparent current density cross-sectiondepicts both of the structures between stations 150m and250m and 410m and 520m and shows that they are dippingstructures Radiometric data shows high radioactivity in thesouthern side of the profile compared to the northern sidewith peak value of total radiation and gamma activity (140counts100 sec and 28 120583Rh resp) found above the station250m
57 Profile 7 (P1700) Differing from all other profiles inprofile P1700 92mwest of P1600 (Figure 8) theVLF anomalycurves indicate a single wide conductive feature lying all overthe profile with centre at 350m Apparent current densitycross-section also shows a much wider conductive featurelying between 0m and 230m 250m and 370m and 390mand 500m ranging in current density values from 4 to10 4 to 12 and 4 to 8 respectively This shows that
12 International Journal of Geophysics
here the same conducting zone is wider than other locationsWhereas radiometric data suggests high radioactivity abovethe background level only between stations 70m and 210m
58 Profile 8 (P1800) Further 88m west of P1700 in profileP1800 (Figure 9) VLF anomaly curves indicate the presenceof two vertical conductors Current density contours alsoshow two conductive features between stations 160m and220m and 320m and 370m The first one is less conductiveas compared to the later one Radiometric data indicates highradioactivity in the southern part of the profile with threepeak regions around stations 50m 140m and 180m
6 Discussion
In the present study eight profiles were chosen on eitherside of the Beldih mine to investigate the uranium andorthorium mineralization by applying VLF-EM and radiomet-ric methods together Results show the presence of multipleisolated conductive features in the study area These con-ductive features appearing in the profile could be becauseof the presence of fractures filled with fluids hydrothermalalteration zones clay mineralization shearing and so forthThe conductive features are traced continuously well in allthe profiles showing a regular parallel trend except in profileP1400where the similar zone is identified in the southern sideof the profileThis implies that the conductive feature at P1400has shifted southward in this profile only This offset of thecurrent density anomaly (in profile P1400) could be due toeither strike slip fault or dip slip fault or subparallel faultingIn case of dip slip fault such offset can be observed only ifan inclined bed is cut by a vertical fault at right angles tothe strike and the slip is normal After erosion such an offsetcan be seen However the observed anomalies appear verticalin the current density profile and the offset or movementis lateral along the strike of the fault This happens in caseof strike-slip fault hence it appears to be the better reasonfor such lateral shift of the mineralized body This can befurther substantiated by successive structural mapping of thearea
The separation between the conductive bodies is notuniform along all the profilesThis further suggests that thesemineralized bodies have small strike length and lenticularshape This result together with the geology of the area indi-cates that the mode of mineralization may be hydrothermalalteration
Radiometric measurements indicate higher radiationsalong the profiles than the average or background radiationsobserved in the areaThe peak or elevated radiations indicatethe presence of uranium mineralization
Surface gamma activity superimposed over geologicalmap of the area of study (Figure 10) clearly depicts the coinci-dence of conductive zones and high radioactivity zones Thiscoincidence indicates the existence of alteration zones in thisarea These zones may contain radioactive mineralization asthey are also correlating with the radioactive bands identifiedby Katti et al [7] and with the bore hole data BLD2 and BLD3(Figures 10 and 11) All these identified mineralized zones are
almost parallel and have a collective strike oriented along E-W direction which is in agreement with the strike of SPSZ
7 Conclusions
VLF-EM and radiometric methods were applied togetherin this region to study the correlation between these twomethods as well as to utilize their integrated results for theexploration of uranium Results indicate good correlationbetween VLF data and radiometric dataThis is because theseradiometric signals are associated with shallow uraniummineralization which is associated with altered mineralsthat gives conductivity contrast with the neighboring rocksCoincidence of high radioactivity over conductive zonesand their correlation with radioactive bands observed inthe area confirms the presence of uranium mineralizationThus the study also suggests that these two methods can beintegrated to explore uraniumandor thoriummineralizationeffectively at low cost with the advantage of being quick andnondestructive compared to other routine methods used forsuch purposesThe study also reveals the presence of a strike-slip fault in the eastern side of the Beldih mine proving theability and advantage of this integrated approach in detectingsuch planner structures and correlating the lithology bothvertically and laterally Since these methods are quick andcost effective they can be utilized to search for shallowuranium mineralization along the SPSZ and other suchregions quickly VLF observations are sometimes affected bypower lines in such areas Gradient Resistivity Profiling andgravity and magnetic methods can be applied to aid in theinterpretation of subsurface structures
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors would like to thank the editor and anonymousreviewers for their valuable comments and suggestions toimprove the quality of the paper
References
[1] B K Bhaumik T Bhattacharya A A P S R AcharyuluD Srinivas and M K Sandilya Principles of Radiometry inRadioactive Metal Exploration Physics Lab AMD ComplexJamshedpur India 2004
[2] V Tuncer M J Unsworth W Siripunvaraporn and J ACraven ldquoExploration for unconformity-type uranium depos-its with audiomagnetotelluric data a case study from theMcArthur River mine Saskatchewan Canadardquo Geophysics vol71 no 6 pp B201ndashB209 2006
[3] J M Legault D Carriere and L Petrie ldquoSynthetic modeltesting and distributed acquisition dc resistivity results overan unconformity uranium target from the Athabasca Basinnorthern SaskatchewanrdquoTheLeading Edge vol 27 no 1 pp 46ndash51 2008
International Journal of Geophysics 13
[4] G Nimeck and R Koch ldquoA progressive geophysical explorationstrategy at the Shea Creek uranium depositrdquoThe Leading Edgevol 27 no 1 pp 52ndash63 2008
[5] A Mandal A Biswas S Mittal et al ldquoGeophysical anomaliesassociated with uranium mineralization from Beldih mineSouth Purulia Shear Zone Indiardquo Journal of the GeologicalSociety of India vol 82 no 6 pp 601ndash606 2013
[6] S P Sharma A Biswas and S Mittal ldquoDelineation of extensionof uranium mineralization zone using resistivity and VLFsur-veys around South Purulia Shear Zone Indiardquo Journal of theGeological Society of India In press
[7] V J Katti J Sen andAK Bhatt ldquoUraniumpotentiality of SouthPurulia Shear Zone in Eastern Indian Shieldrdquo in Proceedings ofthe Technical Meeting on Low Grade Uranium Ore pp 29ndash31International Atomic Energy Agency Vienna Austria 2010
[8] A Acharyya S Ray B K Chaudhuri S K Basu S K Bhaduriand A K Sanyal ldquoProterozoic rock suites along South PuruliaShear Zone eastern India evidence for rift-related settingrdquoJournal of the Geological Society of India vol 68 no 6 pp 1069ndash1086 2006
[9] Y Vapnik S Bushmin A Chattopadhyay and D Dolivo-Dobrovolsky ldquoFluid inclusion and mineralogical study of vein-type apatite ores in shear zones from the Singhbhum metallo-genetic provinceWest Bengal IndiardquoOre Geology Reviews vol32 no 1-2 pp 412ndash430 2007
[10] T K Baidya ldquoApatite-magnetite deposit in the chhotanagpurgneissic complex Panrkidih area Purulia District West Ben-galrdquo Indian Journal of Geology vol 64 pp 88ndash95 1992
[11] S K Basu ldquoAlkaline-carbonatite complex in Precambrian ofSouth Purulia Shear Zone eastern India its characteristics andmineral potentialitiesrdquo Indian Minerals vol 47 no 3 pp 179ndash194 1993
[12] A K G Roy and P R Sengupta ldquoAlkalic-carbonatitic magma-tism and associated mineralisation along the Porapahar-Tamarlineament in the Proterozoics of Purulia District West BengalrdquoIndian Journal of Earth Sciences vol 20 no 3-4 pp 193ndash2001993
[13] T K Pyne ldquoThe Proterozoic fold belt and the chhotanagpurgneissic complex in the eastern Indian Shieldmdasha tectono-metamorphic appraisalrdquo Indian Minerals vol 46 no 1 pp 25ndash34 1992
[14] S Bhattacharya ldquoDuctile shear Zone in Purulia West BengalrdquoIndian Journal of Geology vol 61 pp 172ndash178 1989
[15] B D Smith and S H Ward ldquoOn the computation of polariza-tion ellipse parametersrdquo Geophysics vol 39 pp 867ndash869 1974
[16] N R Paterson and V Ronka ldquoFive years of surveying with thevery low frequency-electromagnetics methodrdquoGeoexplorationvol 9 no 1 pp 7ndash26 1971
[17] M Karous and S E Hjelt ldquoLinear filtering of VLF dip-anglemeasurementsrdquo Geophysical Prospecting vol 31 no 5 pp 782ndash794 1983
[18] A T Ramli S Sahrone and H Wagiran ldquoTerrestrial gammaradiation dose study to determine the baseline for environ-mental radiological health practices in Melaka state MalaysiardquoJournal of Radiological Protection vol 25 no 4 pp 435ndash4502005
Figure 8 Profile P1700 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
The current density contours along this profile clearly demar-cates the shape of this body between stations 510mand 570msuggesting a width of around 60m occurring below 30mfrom the surface Radiometric data recorded over this profileshows similar behavior as that at profile P1100 with peakvalues at 520m
53 Profile 3 (P1300) This profile P1300 (Figure 4) is further83m east of profile P1200 The real and imaginary anomalyplots indicate the presence of multiple conductive bodiesalong this profile and the slope of these curves suggestsvertical structures occurring near to the surface Apparent
current density cross-section also depicts the same resultshowing the presence of three broad and shallow almostvertical conductors between stations 0m and 60m 160mand 250m and 375m and 450m Similarly the radioactivityalong this profile is higher than the background throughoutthe profile with peak between 410m and 440m The peakvalue of total radiations and surface gamma activity recordedat this station is 75 counts100 sec and 19 120583Rh respectively
54 Profile 4 (P1400) Profile P1400 lies 92m east of pro-file P1300 (Figure 5) Here also the VLF anomaly curvesdepict three conductive features all being shallow and nearly
10 International Journal of Geophysics
6789
10
0
N
20
10
0
minus10
minus10minus20Real
anom
aly
()
Imag
inar
y
50 100 150 200 250 300 350 400 450 500
Distance (m)0
10
20
30
minus20
minus40
minus60
minus80
50 100 150 200 250 300 350 400 450
Distance (m)
minus14 minus10 minus6 minus2 2 6 10 14 16
Current density ()
Dep
th (m
)
30
40
50
60
70
50 100 150 200 250 300 350 400 450 500
Distance (m)0
50 100 150 200 250 300 350 400 450 500
Distance (m)0
(a)
(b)
(c)
(d)
anom
aly
()
(120583Rh
)(C
ount
s100
s)
Figure 9 Profile P1800 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
vertical Apparent current density cross-section shows thepresence of one conducting and two low conducting struc-tures between stations 70m and 140m 270m and 320mand 490m and 520m respectively The conductor at thesouthern part of the profile (between stations 70mand 140m)is more conductive and wider among the three Radioactivityis observed to be highest above this conductor with peakvalue of total radiation being 290 counts100 sec and that ofgamma activity being 60120583Rh at station 150m This is thehighest radioactivity recorded along all the profiles
55 Profile 5 (P1500) Profile P1500 is taken 86m awaytowards east of profile P1400 (Figure 6) VLF anomaly curves
suggest the presence of a single conductor around station400m The slope of the anomaly curves indicates a thickinclined structure Apparent current density cross-sectionconfirms the presence of inclined conductive structurebetween stations 330mm to 420m Radiometric data isobserved to be almost equal to the background levels all longthe profile with a sudden jump in value to 180 counts100 secof total radiations and 35 120583Rh surface gamma activity atstation 510m
56 Profile 6 (P1600) This profile is located in the westernside of the Beldih mine (Figure 7) VLF anomaly curves indi-cate the presence of two conductive features around stations
International Journal of Geophysics 11
86
P1500P1100 P1200 P1300 P1400
P1600P1700
P1800
18 1805 181 1815
29
295
3
305
31
176 1765
Mine dump
N
Cultivated land
Cultivated land
298
3
302
304
306
308
31312
314
316
318
32
Cultivated land
Cultivated land
Cultivated land
Beldih village (N)
Bore hole BoreholeBLD2 BLD3
Beldih
325998400
32998400
315998400
31998400
305998400
295998400
3998400
29998400
285998400
280998400
23∘
and
min
utes
1745998400
175998400
1755998400
176998400
1765998400
177998400
1775998400
178998400
1785998400
179998400
1795998400
1800998400
1805998400
1810998400
1815998400
1820998400
1825998400
1830998400
86∘ and minutes
0 100 200
(m)
Mine dumpKaolin zone
QuartziteGranite
Quartz-magnetite-apatite rocks
Tuffaceous rock
Altered brecciated ultramafics Radioactive bands (vertical projection from borehole)
VLF profile Ultramafics plusmn carbonatite
5
10
15
20
25
30
35
40
45
50
55
86∘ and minutes
23∘
and
min
utes
Tank
(120583Rh
r)
Figure 10 Surface gamma activity superimposed over geological map of the area of study
Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
240
220
200
180
Datum
0 10
S
20 (m)
N
Expected mineralized zone
260
220
200
180
Datum240
Transverse section through bore hole BLD2 Transverse section through bore hole BLD3
RL-24062m
RL
(m)
BLD2
DD-13075m DD-16355m
640m840m
BLD3
RL
(m)
RL-24234m
Altered brecciated ultramafics
Ultramafics plusmn carbonatite Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
Altered brecciated ultramafics
Ultramafics plusmn carbonatite
Figure 11 Transverse sections through bore holes BLD2 and BLD3 (after [7])
200m and 450m Apparent current density cross-sectiondepicts both of the structures between stations 150m and250m and 410m and 520m and shows that they are dippingstructures Radiometric data shows high radioactivity in thesouthern side of the profile compared to the northern sidewith peak value of total radiation and gamma activity (140counts100 sec and 28 120583Rh resp) found above the station250m
57 Profile 7 (P1700) Differing from all other profiles inprofile P1700 92mwest of P1600 (Figure 8) theVLF anomalycurves indicate a single wide conductive feature lying all overthe profile with centre at 350m Apparent current densitycross-section also shows a much wider conductive featurelying between 0m and 230m 250m and 370m and 390mand 500m ranging in current density values from 4 to10 4 to 12 and 4 to 8 respectively This shows that
12 International Journal of Geophysics
here the same conducting zone is wider than other locationsWhereas radiometric data suggests high radioactivity abovethe background level only between stations 70m and 210m
58 Profile 8 (P1800) Further 88m west of P1700 in profileP1800 (Figure 9) VLF anomaly curves indicate the presenceof two vertical conductors Current density contours alsoshow two conductive features between stations 160m and220m and 320m and 370m The first one is less conductiveas compared to the later one Radiometric data indicates highradioactivity in the southern part of the profile with threepeak regions around stations 50m 140m and 180m
6 Discussion
In the present study eight profiles were chosen on eitherside of the Beldih mine to investigate the uranium andorthorium mineralization by applying VLF-EM and radiomet-ric methods together Results show the presence of multipleisolated conductive features in the study area These con-ductive features appearing in the profile could be becauseof the presence of fractures filled with fluids hydrothermalalteration zones clay mineralization shearing and so forthThe conductive features are traced continuously well in allthe profiles showing a regular parallel trend except in profileP1400where the similar zone is identified in the southern sideof the profileThis implies that the conductive feature at P1400has shifted southward in this profile only This offset of thecurrent density anomaly (in profile P1400) could be due toeither strike slip fault or dip slip fault or subparallel faultingIn case of dip slip fault such offset can be observed only ifan inclined bed is cut by a vertical fault at right angles tothe strike and the slip is normal After erosion such an offsetcan be seen However the observed anomalies appear verticalin the current density profile and the offset or movementis lateral along the strike of the fault This happens in caseof strike-slip fault hence it appears to be the better reasonfor such lateral shift of the mineralized body This can befurther substantiated by successive structural mapping of thearea
The separation between the conductive bodies is notuniform along all the profilesThis further suggests that thesemineralized bodies have small strike length and lenticularshape This result together with the geology of the area indi-cates that the mode of mineralization may be hydrothermalalteration
Radiometric measurements indicate higher radiationsalong the profiles than the average or background radiationsobserved in the areaThe peak or elevated radiations indicatethe presence of uranium mineralization
Surface gamma activity superimposed over geologicalmap of the area of study (Figure 10) clearly depicts the coinci-dence of conductive zones and high radioactivity zones Thiscoincidence indicates the existence of alteration zones in thisarea These zones may contain radioactive mineralization asthey are also correlating with the radioactive bands identifiedby Katti et al [7] and with the bore hole data BLD2 and BLD3(Figures 10 and 11) All these identified mineralized zones are
almost parallel and have a collective strike oriented along E-W direction which is in agreement with the strike of SPSZ
7 Conclusions
VLF-EM and radiometric methods were applied togetherin this region to study the correlation between these twomethods as well as to utilize their integrated results for theexploration of uranium Results indicate good correlationbetween VLF data and radiometric dataThis is because theseradiometric signals are associated with shallow uraniummineralization which is associated with altered mineralsthat gives conductivity contrast with the neighboring rocksCoincidence of high radioactivity over conductive zonesand their correlation with radioactive bands observed inthe area confirms the presence of uranium mineralizationThus the study also suggests that these two methods can beintegrated to explore uraniumandor thoriummineralizationeffectively at low cost with the advantage of being quick andnondestructive compared to other routine methods used forsuch purposesThe study also reveals the presence of a strike-slip fault in the eastern side of the Beldih mine proving theability and advantage of this integrated approach in detectingsuch planner structures and correlating the lithology bothvertically and laterally Since these methods are quick andcost effective they can be utilized to search for shallowuranium mineralization along the SPSZ and other suchregions quickly VLF observations are sometimes affected bypower lines in such areas Gradient Resistivity Profiling andgravity and magnetic methods can be applied to aid in theinterpretation of subsurface structures
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors would like to thank the editor and anonymousreviewers for their valuable comments and suggestions toimprove the quality of the paper
References
[1] B K Bhaumik T Bhattacharya A A P S R AcharyuluD Srinivas and M K Sandilya Principles of Radiometry inRadioactive Metal Exploration Physics Lab AMD ComplexJamshedpur India 2004
[2] V Tuncer M J Unsworth W Siripunvaraporn and J ACraven ldquoExploration for unconformity-type uranium depos-its with audiomagnetotelluric data a case study from theMcArthur River mine Saskatchewan Canadardquo Geophysics vol71 no 6 pp B201ndashB209 2006
[3] J M Legault D Carriere and L Petrie ldquoSynthetic modeltesting and distributed acquisition dc resistivity results overan unconformity uranium target from the Athabasca Basinnorthern SaskatchewanrdquoTheLeading Edge vol 27 no 1 pp 46ndash51 2008
International Journal of Geophysics 13
[4] G Nimeck and R Koch ldquoA progressive geophysical explorationstrategy at the Shea Creek uranium depositrdquoThe Leading Edgevol 27 no 1 pp 52ndash63 2008
[5] A Mandal A Biswas S Mittal et al ldquoGeophysical anomaliesassociated with uranium mineralization from Beldih mineSouth Purulia Shear Zone Indiardquo Journal of the GeologicalSociety of India vol 82 no 6 pp 601ndash606 2013
[6] S P Sharma A Biswas and S Mittal ldquoDelineation of extensionof uranium mineralization zone using resistivity and VLFsur-veys around South Purulia Shear Zone Indiardquo Journal of theGeological Society of India In press
[7] V J Katti J Sen andAK Bhatt ldquoUraniumpotentiality of SouthPurulia Shear Zone in Eastern Indian Shieldrdquo in Proceedings ofthe Technical Meeting on Low Grade Uranium Ore pp 29ndash31International Atomic Energy Agency Vienna Austria 2010
[8] A Acharyya S Ray B K Chaudhuri S K Basu S K Bhaduriand A K Sanyal ldquoProterozoic rock suites along South PuruliaShear Zone eastern India evidence for rift-related settingrdquoJournal of the Geological Society of India vol 68 no 6 pp 1069ndash1086 2006
[9] Y Vapnik S Bushmin A Chattopadhyay and D Dolivo-Dobrovolsky ldquoFluid inclusion and mineralogical study of vein-type apatite ores in shear zones from the Singhbhum metallo-genetic provinceWest Bengal IndiardquoOre Geology Reviews vol32 no 1-2 pp 412ndash430 2007
[10] T K Baidya ldquoApatite-magnetite deposit in the chhotanagpurgneissic complex Panrkidih area Purulia District West Ben-galrdquo Indian Journal of Geology vol 64 pp 88ndash95 1992
[11] S K Basu ldquoAlkaline-carbonatite complex in Precambrian ofSouth Purulia Shear Zone eastern India its characteristics andmineral potentialitiesrdquo Indian Minerals vol 47 no 3 pp 179ndash194 1993
[12] A K G Roy and P R Sengupta ldquoAlkalic-carbonatitic magma-tism and associated mineralisation along the Porapahar-Tamarlineament in the Proterozoics of Purulia District West BengalrdquoIndian Journal of Earth Sciences vol 20 no 3-4 pp 193ndash2001993
[13] T K Pyne ldquoThe Proterozoic fold belt and the chhotanagpurgneissic complex in the eastern Indian Shieldmdasha tectono-metamorphic appraisalrdquo Indian Minerals vol 46 no 1 pp 25ndash34 1992
[14] S Bhattacharya ldquoDuctile shear Zone in Purulia West BengalrdquoIndian Journal of Geology vol 61 pp 172ndash178 1989
[15] B D Smith and S H Ward ldquoOn the computation of polariza-tion ellipse parametersrdquo Geophysics vol 39 pp 867ndash869 1974
[16] N R Paterson and V Ronka ldquoFive years of surveying with thevery low frequency-electromagnetics methodrdquoGeoexplorationvol 9 no 1 pp 7ndash26 1971
[17] M Karous and S E Hjelt ldquoLinear filtering of VLF dip-anglemeasurementsrdquo Geophysical Prospecting vol 31 no 5 pp 782ndash794 1983
[18] A T Ramli S Sahrone and H Wagiran ldquoTerrestrial gammaradiation dose study to determine the baseline for environ-mental radiological health practices in Melaka state MalaysiardquoJournal of Radiological Protection vol 25 no 4 pp 435ndash4502005
Figure 9 Profile P1800 (a) VLF anomaly (real by solid line and imaginary by dashed line) (b) pseudo current density cross-section alongprofile P1100 and (c) surface radiation and (d) surface gamma activity
vertical Apparent current density cross-section shows thepresence of one conducting and two low conducting struc-tures between stations 70m and 140m 270m and 320mand 490m and 520m respectively The conductor at thesouthern part of the profile (between stations 70mand 140m)is more conductive and wider among the three Radioactivityis observed to be highest above this conductor with peakvalue of total radiation being 290 counts100 sec and that ofgamma activity being 60120583Rh at station 150m This is thehighest radioactivity recorded along all the profiles
55 Profile 5 (P1500) Profile P1500 is taken 86m awaytowards east of profile P1400 (Figure 6) VLF anomaly curves
suggest the presence of a single conductor around station400m The slope of the anomaly curves indicates a thickinclined structure Apparent current density cross-sectionconfirms the presence of inclined conductive structurebetween stations 330mm to 420m Radiometric data isobserved to be almost equal to the background levels all longthe profile with a sudden jump in value to 180 counts100 secof total radiations and 35 120583Rh surface gamma activity atstation 510m
56 Profile 6 (P1600) This profile is located in the westernside of the Beldih mine (Figure 7) VLF anomaly curves indi-cate the presence of two conductive features around stations
International Journal of Geophysics 11
86
P1500P1100 P1200 P1300 P1400
P1600P1700
P1800
18 1805 181 1815
29
295
3
305
31
176 1765
Mine dump
N
Cultivated land
Cultivated land
298
3
302
304
306
308
31312
314
316
318
32
Cultivated land
Cultivated land
Cultivated land
Beldih village (N)
Bore hole BoreholeBLD2 BLD3
Beldih
325998400
32998400
315998400
31998400
305998400
295998400
3998400
29998400
285998400
280998400
23∘
and
min
utes
1745998400
175998400
1755998400
176998400
1765998400
177998400
1775998400
178998400
1785998400
179998400
1795998400
1800998400
1805998400
1810998400
1815998400
1820998400
1825998400
1830998400
86∘ and minutes
0 100 200
(m)
Mine dumpKaolin zone
QuartziteGranite
Quartz-magnetite-apatite rocks
Tuffaceous rock
Altered brecciated ultramafics Radioactive bands (vertical projection from borehole)
VLF profile Ultramafics plusmn carbonatite
5
10
15
20
25
30
35
40
45
50
55
86∘ and minutes
23∘
and
min
utes
Tank
(120583Rh
r)
Figure 10 Surface gamma activity superimposed over geological map of the area of study
Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
240
220
200
180
Datum
0 10
S
20 (m)
N
Expected mineralized zone
260
220
200
180
Datum240
Transverse section through bore hole BLD2 Transverse section through bore hole BLD3
RL-24062m
RL
(m)
BLD2
DD-13075m DD-16355m
640m840m
BLD3
RL
(m)
RL-24234m
Altered brecciated ultramafics
Ultramafics plusmn carbonatite Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
Altered brecciated ultramafics
Ultramafics plusmn carbonatite
Figure 11 Transverse sections through bore holes BLD2 and BLD3 (after [7])
200m and 450m Apparent current density cross-sectiondepicts both of the structures between stations 150m and250m and 410m and 520m and shows that they are dippingstructures Radiometric data shows high radioactivity in thesouthern side of the profile compared to the northern sidewith peak value of total radiation and gamma activity (140counts100 sec and 28 120583Rh resp) found above the station250m
57 Profile 7 (P1700) Differing from all other profiles inprofile P1700 92mwest of P1600 (Figure 8) theVLF anomalycurves indicate a single wide conductive feature lying all overthe profile with centre at 350m Apparent current densitycross-section also shows a much wider conductive featurelying between 0m and 230m 250m and 370m and 390mand 500m ranging in current density values from 4 to10 4 to 12 and 4 to 8 respectively This shows that
12 International Journal of Geophysics
here the same conducting zone is wider than other locationsWhereas radiometric data suggests high radioactivity abovethe background level only between stations 70m and 210m
58 Profile 8 (P1800) Further 88m west of P1700 in profileP1800 (Figure 9) VLF anomaly curves indicate the presenceof two vertical conductors Current density contours alsoshow two conductive features between stations 160m and220m and 320m and 370m The first one is less conductiveas compared to the later one Radiometric data indicates highradioactivity in the southern part of the profile with threepeak regions around stations 50m 140m and 180m
6 Discussion
In the present study eight profiles were chosen on eitherside of the Beldih mine to investigate the uranium andorthorium mineralization by applying VLF-EM and radiomet-ric methods together Results show the presence of multipleisolated conductive features in the study area These con-ductive features appearing in the profile could be becauseof the presence of fractures filled with fluids hydrothermalalteration zones clay mineralization shearing and so forthThe conductive features are traced continuously well in allthe profiles showing a regular parallel trend except in profileP1400where the similar zone is identified in the southern sideof the profileThis implies that the conductive feature at P1400has shifted southward in this profile only This offset of thecurrent density anomaly (in profile P1400) could be due toeither strike slip fault or dip slip fault or subparallel faultingIn case of dip slip fault such offset can be observed only ifan inclined bed is cut by a vertical fault at right angles tothe strike and the slip is normal After erosion such an offsetcan be seen However the observed anomalies appear verticalin the current density profile and the offset or movementis lateral along the strike of the fault This happens in caseof strike-slip fault hence it appears to be the better reasonfor such lateral shift of the mineralized body This can befurther substantiated by successive structural mapping of thearea
The separation between the conductive bodies is notuniform along all the profilesThis further suggests that thesemineralized bodies have small strike length and lenticularshape This result together with the geology of the area indi-cates that the mode of mineralization may be hydrothermalalteration
Radiometric measurements indicate higher radiationsalong the profiles than the average or background radiationsobserved in the areaThe peak or elevated radiations indicatethe presence of uranium mineralization
Surface gamma activity superimposed over geologicalmap of the area of study (Figure 10) clearly depicts the coinci-dence of conductive zones and high radioactivity zones Thiscoincidence indicates the existence of alteration zones in thisarea These zones may contain radioactive mineralization asthey are also correlating with the radioactive bands identifiedby Katti et al [7] and with the bore hole data BLD2 and BLD3(Figures 10 and 11) All these identified mineralized zones are
almost parallel and have a collective strike oriented along E-W direction which is in agreement with the strike of SPSZ
7 Conclusions
VLF-EM and radiometric methods were applied togetherin this region to study the correlation between these twomethods as well as to utilize their integrated results for theexploration of uranium Results indicate good correlationbetween VLF data and radiometric dataThis is because theseradiometric signals are associated with shallow uraniummineralization which is associated with altered mineralsthat gives conductivity contrast with the neighboring rocksCoincidence of high radioactivity over conductive zonesand their correlation with radioactive bands observed inthe area confirms the presence of uranium mineralizationThus the study also suggests that these two methods can beintegrated to explore uraniumandor thoriummineralizationeffectively at low cost with the advantage of being quick andnondestructive compared to other routine methods used forsuch purposesThe study also reveals the presence of a strike-slip fault in the eastern side of the Beldih mine proving theability and advantage of this integrated approach in detectingsuch planner structures and correlating the lithology bothvertically and laterally Since these methods are quick andcost effective they can be utilized to search for shallowuranium mineralization along the SPSZ and other suchregions quickly VLF observations are sometimes affected bypower lines in such areas Gradient Resistivity Profiling andgravity and magnetic methods can be applied to aid in theinterpretation of subsurface structures
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors would like to thank the editor and anonymousreviewers for their valuable comments and suggestions toimprove the quality of the paper
References
[1] B K Bhaumik T Bhattacharya A A P S R AcharyuluD Srinivas and M K Sandilya Principles of Radiometry inRadioactive Metal Exploration Physics Lab AMD ComplexJamshedpur India 2004
[2] V Tuncer M J Unsworth W Siripunvaraporn and J ACraven ldquoExploration for unconformity-type uranium depos-its with audiomagnetotelluric data a case study from theMcArthur River mine Saskatchewan Canadardquo Geophysics vol71 no 6 pp B201ndashB209 2006
[3] J M Legault D Carriere and L Petrie ldquoSynthetic modeltesting and distributed acquisition dc resistivity results overan unconformity uranium target from the Athabasca Basinnorthern SaskatchewanrdquoTheLeading Edge vol 27 no 1 pp 46ndash51 2008
International Journal of Geophysics 13
[4] G Nimeck and R Koch ldquoA progressive geophysical explorationstrategy at the Shea Creek uranium depositrdquoThe Leading Edgevol 27 no 1 pp 52ndash63 2008
[5] A Mandal A Biswas S Mittal et al ldquoGeophysical anomaliesassociated with uranium mineralization from Beldih mineSouth Purulia Shear Zone Indiardquo Journal of the GeologicalSociety of India vol 82 no 6 pp 601ndash606 2013
[6] S P Sharma A Biswas and S Mittal ldquoDelineation of extensionof uranium mineralization zone using resistivity and VLFsur-veys around South Purulia Shear Zone Indiardquo Journal of theGeological Society of India In press
[7] V J Katti J Sen andAK Bhatt ldquoUraniumpotentiality of SouthPurulia Shear Zone in Eastern Indian Shieldrdquo in Proceedings ofthe Technical Meeting on Low Grade Uranium Ore pp 29ndash31International Atomic Energy Agency Vienna Austria 2010
[8] A Acharyya S Ray B K Chaudhuri S K Basu S K Bhaduriand A K Sanyal ldquoProterozoic rock suites along South PuruliaShear Zone eastern India evidence for rift-related settingrdquoJournal of the Geological Society of India vol 68 no 6 pp 1069ndash1086 2006
[9] Y Vapnik S Bushmin A Chattopadhyay and D Dolivo-Dobrovolsky ldquoFluid inclusion and mineralogical study of vein-type apatite ores in shear zones from the Singhbhum metallo-genetic provinceWest Bengal IndiardquoOre Geology Reviews vol32 no 1-2 pp 412ndash430 2007
[10] T K Baidya ldquoApatite-magnetite deposit in the chhotanagpurgneissic complex Panrkidih area Purulia District West Ben-galrdquo Indian Journal of Geology vol 64 pp 88ndash95 1992
[11] S K Basu ldquoAlkaline-carbonatite complex in Precambrian ofSouth Purulia Shear Zone eastern India its characteristics andmineral potentialitiesrdquo Indian Minerals vol 47 no 3 pp 179ndash194 1993
[12] A K G Roy and P R Sengupta ldquoAlkalic-carbonatitic magma-tism and associated mineralisation along the Porapahar-Tamarlineament in the Proterozoics of Purulia District West BengalrdquoIndian Journal of Earth Sciences vol 20 no 3-4 pp 193ndash2001993
[13] T K Pyne ldquoThe Proterozoic fold belt and the chhotanagpurgneissic complex in the eastern Indian Shieldmdasha tectono-metamorphic appraisalrdquo Indian Minerals vol 46 no 1 pp 25ndash34 1992
[14] S Bhattacharya ldquoDuctile shear Zone in Purulia West BengalrdquoIndian Journal of Geology vol 61 pp 172ndash178 1989
[15] B D Smith and S H Ward ldquoOn the computation of polariza-tion ellipse parametersrdquo Geophysics vol 39 pp 867ndash869 1974
[16] N R Paterson and V Ronka ldquoFive years of surveying with thevery low frequency-electromagnetics methodrdquoGeoexplorationvol 9 no 1 pp 7ndash26 1971
[17] M Karous and S E Hjelt ldquoLinear filtering of VLF dip-anglemeasurementsrdquo Geophysical Prospecting vol 31 no 5 pp 782ndash794 1983
[18] A T Ramli S Sahrone and H Wagiran ldquoTerrestrial gammaradiation dose study to determine the baseline for environ-mental radiological health practices in Melaka state MalaysiardquoJournal of Radiological Protection vol 25 no 4 pp 435ndash4502005
Altered brecciated ultramafics Radioactive bands (vertical projection from borehole)
VLF profile Ultramafics plusmn carbonatite
5
10
15
20
25
30
35
40
45
50
55
86∘ and minutes
23∘
and
min
utes
Tank
(120583Rh
r)
Figure 10 Surface gamma activity superimposed over geological map of the area of study
Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
240
220
200
180
Datum
0 10
S
20 (m)
N
Expected mineralized zone
260
220
200
180
Datum240
Transverse section through bore hole BLD2 Transverse section through bore hole BLD3
RL-24062m
RL
(m)
BLD2
DD-13075m DD-16355m
640m840m
BLD3
RL
(m)
RL-24234m
Altered brecciated ultramafics
Ultramafics plusmn carbonatite Overburdenmine dumpRadioactive mineralizationKaolin zone
Quartz-magnetite-apatite rockQuartzite
Altered brecciated ultramafics
Ultramafics plusmn carbonatite
Figure 11 Transverse sections through bore holes BLD2 and BLD3 (after [7])
200m and 450m Apparent current density cross-sectiondepicts both of the structures between stations 150m and250m and 410m and 520m and shows that they are dippingstructures Radiometric data shows high radioactivity in thesouthern side of the profile compared to the northern sidewith peak value of total radiation and gamma activity (140counts100 sec and 28 120583Rh resp) found above the station250m
57 Profile 7 (P1700) Differing from all other profiles inprofile P1700 92mwest of P1600 (Figure 8) theVLF anomalycurves indicate a single wide conductive feature lying all overthe profile with centre at 350m Apparent current densitycross-section also shows a much wider conductive featurelying between 0m and 230m 250m and 370m and 390mand 500m ranging in current density values from 4 to10 4 to 12 and 4 to 8 respectively This shows that
12 International Journal of Geophysics
here the same conducting zone is wider than other locationsWhereas radiometric data suggests high radioactivity abovethe background level only between stations 70m and 210m
58 Profile 8 (P1800) Further 88m west of P1700 in profileP1800 (Figure 9) VLF anomaly curves indicate the presenceof two vertical conductors Current density contours alsoshow two conductive features between stations 160m and220m and 320m and 370m The first one is less conductiveas compared to the later one Radiometric data indicates highradioactivity in the southern part of the profile with threepeak regions around stations 50m 140m and 180m
6 Discussion
In the present study eight profiles were chosen on eitherside of the Beldih mine to investigate the uranium andorthorium mineralization by applying VLF-EM and radiomet-ric methods together Results show the presence of multipleisolated conductive features in the study area These con-ductive features appearing in the profile could be becauseof the presence of fractures filled with fluids hydrothermalalteration zones clay mineralization shearing and so forthThe conductive features are traced continuously well in allthe profiles showing a regular parallel trend except in profileP1400where the similar zone is identified in the southern sideof the profileThis implies that the conductive feature at P1400has shifted southward in this profile only This offset of thecurrent density anomaly (in profile P1400) could be due toeither strike slip fault or dip slip fault or subparallel faultingIn case of dip slip fault such offset can be observed only ifan inclined bed is cut by a vertical fault at right angles tothe strike and the slip is normal After erosion such an offsetcan be seen However the observed anomalies appear verticalin the current density profile and the offset or movementis lateral along the strike of the fault This happens in caseof strike-slip fault hence it appears to be the better reasonfor such lateral shift of the mineralized body This can befurther substantiated by successive structural mapping of thearea
The separation between the conductive bodies is notuniform along all the profilesThis further suggests that thesemineralized bodies have small strike length and lenticularshape This result together with the geology of the area indi-cates that the mode of mineralization may be hydrothermalalteration
Radiometric measurements indicate higher radiationsalong the profiles than the average or background radiationsobserved in the areaThe peak or elevated radiations indicatethe presence of uranium mineralization
Surface gamma activity superimposed over geologicalmap of the area of study (Figure 10) clearly depicts the coinci-dence of conductive zones and high radioactivity zones Thiscoincidence indicates the existence of alteration zones in thisarea These zones may contain radioactive mineralization asthey are also correlating with the radioactive bands identifiedby Katti et al [7] and with the bore hole data BLD2 and BLD3(Figures 10 and 11) All these identified mineralized zones are
almost parallel and have a collective strike oriented along E-W direction which is in agreement with the strike of SPSZ
7 Conclusions
VLF-EM and radiometric methods were applied togetherin this region to study the correlation between these twomethods as well as to utilize their integrated results for theexploration of uranium Results indicate good correlationbetween VLF data and radiometric dataThis is because theseradiometric signals are associated with shallow uraniummineralization which is associated with altered mineralsthat gives conductivity contrast with the neighboring rocksCoincidence of high radioactivity over conductive zonesand their correlation with radioactive bands observed inthe area confirms the presence of uranium mineralizationThus the study also suggests that these two methods can beintegrated to explore uraniumandor thoriummineralizationeffectively at low cost with the advantage of being quick andnondestructive compared to other routine methods used forsuch purposesThe study also reveals the presence of a strike-slip fault in the eastern side of the Beldih mine proving theability and advantage of this integrated approach in detectingsuch planner structures and correlating the lithology bothvertically and laterally Since these methods are quick andcost effective they can be utilized to search for shallowuranium mineralization along the SPSZ and other suchregions quickly VLF observations are sometimes affected bypower lines in such areas Gradient Resistivity Profiling andgravity and magnetic methods can be applied to aid in theinterpretation of subsurface structures
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors would like to thank the editor and anonymousreviewers for their valuable comments and suggestions toimprove the quality of the paper
References
[1] B K Bhaumik T Bhattacharya A A P S R AcharyuluD Srinivas and M K Sandilya Principles of Radiometry inRadioactive Metal Exploration Physics Lab AMD ComplexJamshedpur India 2004
[2] V Tuncer M J Unsworth W Siripunvaraporn and J ACraven ldquoExploration for unconformity-type uranium depos-its with audiomagnetotelluric data a case study from theMcArthur River mine Saskatchewan Canadardquo Geophysics vol71 no 6 pp B201ndashB209 2006
[3] J M Legault D Carriere and L Petrie ldquoSynthetic modeltesting and distributed acquisition dc resistivity results overan unconformity uranium target from the Athabasca Basinnorthern SaskatchewanrdquoTheLeading Edge vol 27 no 1 pp 46ndash51 2008
International Journal of Geophysics 13
[4] G Nimeck and R Koch ldquoA progressive geophysical explorationstrategy at the Shea Creek uranium depositrdquoThe Leading Edgevol 27 no 1 pp 52ndash63 2008
[5] A Mandal A Biswas S Mittal et al ldquoGeophysical anomaliesassociated with uranium mineralization from Beldih mineSouth Purulia Shear Zone Indiardquo Journal of the GeologicalSociety of India vol 82 no 6 pp 601ndash606 2013
[6] S P Sharma A Biswas and S Mittal ldquoDelineation of extensionof uranium mineralization zone using resistivity and VLFsur-veys around South Purulia Shear Zone Indiardquo Journal of theGeological Society of India In press
[7] V J Katti J Sen andAK Bhatt ldquoUraniumpotentiality of SouthPurulia Shear Zone in Eastern Indian Shieldrdquo in Proceedings ofthe Technical Meeting on Low Grade Uranium Ore pp 29ndash31International Atomic Energy Agency Vienna Austria 2010
[8] A Acharyya S Ray B K Chaudhuri S K Basu S K Bhaduriand A K Sanyal ldquoProterozoic rock suites along South PuruliaShear Zone eastern India evidence for rift-related settingrdquoJournal of the Geological Society of India vol 68 no 6 pp 1069ndash1086 2006
[9] Y Vapnik S Bushmin A Chattopadhyay and D Dolivo-Dobrovolsky ldquoFluid inclusion and mineralogical study of vein-type apatite ores in shear zones from the Singhbhum metallo-genetic provinceWest Bengal IndiardquoOre Geology Reviews vol32 no 1-2 pp 412ndash430 2007
[10] T K Baidya ldquoApatite-magnetite deposit in the chhotanagpurgneissic complex Panrkidih area Purulia District West Ben-galrdquo Indian Journal of Geology vol 64 pp 88ndash95 1992
[11] S K Basu ldquoAlkaline-carbonatite complex in Precambrian ofSouth Purulia Shear Zone eastern India its characteristics andmineral potentialitiesrdquo Indian Minerals vol 47 no 3 pp 179ndash194 1993
[12] A K G Roy and P R Sengupta ldquoAlkalic-carbonatitic magma-tism and associated mineralisation along the Porapahar-Tamarlineament in the Proterozoics of Purulia District West BengalrdquoIndian Journal of Earth Sciences vol 20 no 3-4 pp 193ndash2001993
[13] T K Pyne ldquoThe Proterozoic fold belt and the chhotanagpurgneissic complex in the eastern Indian Shieldmdasha tectono-metamorphic appraisalrdquo Indian Minerals vol 46 no 1 pp 25ndash34 1992
[14] S Bhattacharya ldquoDuctile shear Zone in Purulia West BengalrdquoIndian Journal of Geology vol 61 pp 172ndash178 1989
[15] B D Smith and S H Ward ldquoOn the computation of polariza-tion ellipse parametersrdquo Geophysics vol 39 pp 867ndash869 1974
[16] N R Paterson and V Ronka ldquoFive years of surveying with thevery low frequency-electromagnetics methodrdquoGeoexplorationvol 9 no 1 pp 7ndash26 1971
[17] M Karous and S E Hjelt ldquoLinear filtering of VLF dip-anglemeasurementsrdquo Geophysical Prospecting vol 31 no 5 pp 782ndash794 1983
[18] A T Ramli S Sahrone and H Wagiran ldquoTerrestrial gammaradiation dose study to determine the baseline for environ-mental radiological health practices in Melaka state MalaysiardquoJournal of Radiological Protection vol 25 no 4 pp 435ndash4502005
here the same conducting zone is wider than other locationsWhereas radiometric data suggests high radioactivity abovethe background level only between stations 70m and 210m
58 Profile 8 (P1800) Further 88m west of P1700 in profileP1800 (Figure 9) VLF anomaly curves indicate the presenceof two vertical conductors Current density contours alsoshow two conductive features between stations 160m and220m and 320m and 370m The first one is less conductiveas compared to the later one Radiometric data indicates highradioactivity in the southern part of the profile with threepeak regions around stations 50m 140m and 180m
6 Discussion
In the present study eight profiles were chosen on eitherside of the Beldih mine to investigate the uranium andorthorium mineralization by applying VLF-EM and radiomet-ric methods together Results show the presence of multipleisolated conductive features in the study area These con-ductive features appearing in the profile could be becauseof the presence of fractures filled with fluids hydrothermalalteration zones clay mineralization shearing and so forthThe conductive features are traced continuously well in allthe profiles showing a regular parallel trend except in profileP1400where the similar zone is identified in the southern sideof the profileThis implies that the conductive feature at P1400has shifted southward in this profile only This offset of thecurrent density anomaly (in profile P1400) could be due toeither strike slip fault or dip slip fault or subparallel faultingIn case of dip slip fault such offset can be observed only ifan inclined bed is cut by a vertical fault at right angles tothe strike and the slip is normal After erosion such an offsetcan be seen However the observed anomalies appear verticalin the current density profile and the offset or movementis lateral along the strike of the fault This happens in caseof strike-slip fault hence it appears to be the better reasonfor such lateral shift of the mineralized body This can befurther substantiated by successive structural mapping of thearea
The separation between the conductive bodies is notuniform along all the profilesThis further suggests that thesemineralized bodies have small strike length and lenticularshape This result together with the geology of the area indi-cates that the mode of mineralization may be hydrothermalalteration
Radiometric measurements indicate higher radiationsalong the profiles than the average or background radiationsobserved in the areaThe peak or elevated radiations indicatethe presence of uranium mineralization
Surface gamma activity superimposed over geologicalmap of the area of study (Figure 10) clearly depicts the coinci-dence of conductive zones and high radioactivity zones Thiscoincidence indicates the existence of alteration zones in thisarea These zones may contain radioactive mineralization asthey are also correlating with the radioactive bands identifiedby Katti et al [7] and with the bore hole data BLD2 and BLD3(Figures 10 and 11) All these identified mineralized zones are
almost parallel and have a collective strike oriented along E-W direction which is in agreement with the strike of SPSZ
7 Conclusions
VLF-EM and radiometric methods were applied togetherin this region to study the correlation between these twomethods as well as to utilize their integrated results for theexploration of uranium Results indicate good correlationbetween VLF data and radiometric dataThis is because theseradiometric signals are associated with shallow uraniummineralization which is associated with altered mineralsthat gives conductivity contrast with the neighboring rocksCoincidence of high radioactivity over conductive zonesand their correlation with radioactive bands observed inthe area confirms the presence of uranium mineralizationThus the study also suggests that these two methods can beintegrated to explore uraniumandor thoriummineralizationeffectively at low cost with the advantage of being quick andnondestructive compared to other routine methods used forsuch purposesThe study also reveals the presence of a strike-slip fault in the eastern side of the Beldih mine proving theability and advantage of this integrated approach in detectingsuch planner structures and correlating the lithology bothvertically and laterally Since these methods are quick andcost effective they can be utilized to search for shallowuranium mineralization along the SPSZ and other suchregions quickly VLF observations are sometimes affected bypower lines in such areas Gradient Resistivity Profiling andgravity and magnetic methods can be applied to aid in theinterpretation of subsurface structures
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors would like to thank the editor and anonymousreviewers for their valuable comments and suggestions toimprove the quality of the paper
References
[1] B K Bhaumik T Bhattacharya A A P S R AcharyuluD Srinivas and M K Sandilya Principles of Radiometry inRadioactive Metal Exploration Physics Lab AMD ComplexJamshedpur India 2004
[2] V Tuncer M J Unsworth W Siripunvaraporn and J ACraven ldquoExploration for unconformity-type uranium depos-its with audiomagnetotelluric data a case study from theMcArthur River mine Saskatchewan Canadardquo Geophysics vol71 no 6 pp B201ndashB209 2006
[3] J M Legault D Carriere and L Petrie ldquoSynthetic modeltesting and distributed acquisition dc resistivity results overan unconformity uranium target from the Athabasca Basinnorthern SaskatchewanrdquoTheLeading Edge vol 27 no 1 pp 46ndash51 2008
International Journal of Geophysics 13
[4] G Nimeck and R Koch ldquoA progressive geophysical explorationstrategy at the Shea Creek uranium depositrdquoThe Leading Edgevol 27 no 1 pp 52ndash63 2008
[5] A Mandal A Biswas S Mittal et al ldquoGeophysical anomaliesassociated with uranium mineralization from Beldih mineSouth Purulia Shear Zone Indiardquo Journal of the GeologicalSociety of India vol 82 no 6 pp 601ndash606 2013
[6] S P Sharma A Biswas and S Mittal ldquoDelineation of extensionof uranium mineralization zone using resistivity and VLFsur-veys around South Purulia Shear Zone Indiardquo Journal of theGeological Society of India In press
[7] V J Katti J Sen andAK Bhatt ldquoUraniumpotentiality of SouthPurulia Shear Zone in Eastern Indian Shieldrdquo in Proceedings ofthe Technical Meeting on Low Grade Uranium Ore pp 29ndash31International Atomic Energy Agency Vienna Austria 2010
[8] A Acharyya S Ray B K Chaudhuri S K Basu S K Bhaduriand A K Sanyal ldquoProterozoic rock suites along South PuruliaShear Zone eastern India evidence for rift-related settingrdquoJournal of the Geological Society of India vol 68 no 6 pp 1069ndash1086 2006
[9] Y Vapnik S Bushmin A Chattopadhyay and D Dolivo-Dobrovolsky ldquoFluid inclusion and mineralogical study of vein-type apatite ores in shear zones from the Singhbhum metallo-genetic provinceWest Bengal IndiardquoOre Geology Reviews vol32 no 1-2 pp 412ndash430 2007
[10] T K Baidya ldquoApatite-magnetite deposit in the chhotanagpurgneissic complex Panrkidih area Purulia District West Ben-galrdquo Indian Journal of Geology vol 64 pp 88ndash95 1992
[11] S K Basu ldquoAlkaline-carbonatite complex in Precambrian ofSouth Purulia Shear Zone eastern India its characteristics andmineral potentialitiesrdquo Indian Minerals vol 47 no 3 pp 179ndash194 1993
[12] A K G Roy and P R Sengupta ldquoAlkalic-carbonatitic magma-tism and associated mineralisation along the Porapahar-Tamarlineament in the Proterozoics of Purulia District West BengalrdquoIndian Journal of Earth Sciences vol 20 no 3-4 pp 193ndash2001993
[13] T K Pyne ldquoThe Proterozoic fold belt and the chhotanagpurgneissic complex in the eastern Indian Shieldmdasha tectono-metamorphic appraisalrdquo Indian Minerals vol 46 no 1 pp 25ndash34 1992
[14] S Bhattacharya ldquoDuctile shear Zone in Purulia West BengalrdquoIndian Journal of Geology vol 61 pp 172ndash178 1989
[15] B D Smith and S H Ward ldquoOn the computation of polariza-tion ellipse parametersrdquo Geophysics vol 39 pp 867ndash869 1974
[16] N R Paterson and V Ronka ldquoFive years of surveying with thevery low frequency-electromagnetics methodrdquoGeoexplorationvol 9 no 1 pp 7ndash26 1971
[17] M Karous and S E Hjelt ldquoLinear filtering of VLF dip-anglemeasurementsrdquo Geophysical Prospecting vol 31 no 5 pp 782ndash794 1983
[18] A T Ramli S Sahrone and H Wagiran ldquoTerrestrial gammaradiation dose study to determine the baseline for environ-mental radiological health practices in Melaka state MalaysiardquoJournal of Radiological Protection vol 25 no 4 pp 435ndash4502005
[4] G Nimeck and R Koch ldquoA progressive geophysical explorationstrategy at the Shea Creek uranium depositrdquoThe Leading Edgevol 27 no 1 pp 52ndash63 2008
[5] A Mandal A Biswas S Mittal et al ldquoGeophysical anomaliesassociated with uranium mineralization from Beldih mineSouth Purulia Shear Zone Indiardquo Journal of the GeologicalSociety of India vol 82 no 6 pp 601ndash606 2013
[6] S P Sharma A Biswas and S Mittal ldquoDelineation of extensionof uranium mineralization zone using resistivity and VLFsur-veys around South Purulia Shear Zone Indiardquo Journal of theGeological Society of India In press
[7] V J Katti J Sen andAK Bhatt ldquoUraniumpotentiality of SouthPurulia Shear Zone in Eastern Indian Shieldrdquo in Proceedings ofthe Technical Meeting on Low Grade Uranium Ore pp 29ndash31International Atomic Energy Agency Vienna Austria 2010
[8] A Acharyya S Ray B K Chaudhuri S K Basu S K Bhaduriand A K Sanyal ldquoProterozoic rock suites along South PuruliaShear Zone eastern India evidence for rift-related settingrdquoJournal of the Geological Society of India vol 68 no 6 pp 1069ndash1086 2006
[9] Y Vapnik S Bushmin A Chattopadhyay and D Dolivo-Dobrovolsky ldquoFluid inclusion and mineralogical study of vein-type apatite ores in shear zones from the Singhbhum metallo-genetic provinceWest Bengal IndiardquoOre Geology Reviews vol32 no 1-2 pp 412ndash430 2007
[10] T K Baidya ldquoApatite-magnetite deposit in the chhotanagpurgneissic complex Panrkidih area Purulia District West Ben-galrdquo Indian Journal of Geology vol 64 pp 88ndash95 1992
[11] S K Basu ldquoAlkaline-carbonatite complex in Precambrian ofSouth Purulia Shear Zone eastern India its characteristics andmineral potentialitiesrdquo Indian Minerals vol 47 no 3 pp 179ndash194 1993
[12] A K G Roy and P R Sengupta ldquoAlkalic-carbonatitic magma-tism and associated mineralisation along the Porapahar-Tamarlineament in the Proterozoics of Purulia District West BengalrdquoIndian Journal of Earth Sciences vol 20 no 3-4 pp 193ndash2001993
[13] T K Pyne ldquoThe Proterozoic fold belt and the chhotanagpurgneissic complex in the eastern Indian Shieldmdasha tectono-metamorphic appraisalrdquo Indian Minerals vol 46 no 1 pp 25ndash34 1992
[14] S Bhattacharya ldquoDuctile shear Zone in Purulia West BengalrdquoIndian Journal of Geology vol 61 pp 172ndash178 1989
[15] B D Smith and S H Ward ldquoOn the computation of polariza-tion ellipse parametersrdquo Geophysics vol 39 pp 867ndash869 1974
[16] N R Paterson and V Ronka ldquoFive years of surveying with thevery low frequency-electromagnetics methodrdquoGeoexplorationvol 9 no 1 pp 7ndash26 1971
[17] M Karous and S E Hjelt ldquoLinear filtering of VLF dip-anglemeasurementsrdquo Geophysical Prospecting vol 31 no 5 pp 782ndash794 1983
[18] A T Ramli S Sahrone and H Wagiran ldquoTerrestrial gammaradiation dose study to determine the baseline for environ-mental radiological health practices in Melaka state MalaysiardquoJournal of Radiological Protection vol 25 no 4 pp 435ndash4502005
