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INTRODUCTIONClays are the common product of weathering in all the tropicaland subtropical regions of world including India. Large claydeposits occur at Belgaum especially in Khanapurtaluk,

quite well known for bricks and ceramic industry. Studies on

GEOCHEMISTRY AND MINERALOGY OF CLAYS AROUND KHANAPUR,

BELGAUM DISTRICT, KARNATAKAS.M. Waghmare1, P.T. Hanamgond2, A. Sreenivas3, R. S. Munnolli1 and P. S. Shinde4

1Department of Civil Engg., KLSs VDRIT, Haliyal 581329. sagarwagh481@gmail.com2Departement of Geology, G.S.Sc. College, Tilakwadi, Belgaum 590 006. hanamgondpt@gmail.com

3Department of Studies in Geology, Karnatak University, Dharwad 580 003.1Department of Chemistry, KLSs VDRIT, Haliyal 581 329. rsmunnolli@gmail.com

4Department of Civil Engg., Jain College of Engineering, Belgaum 590 014. priyankashinde22@gmail.com

Abstract

Khanapur clay deposits are quite well known among Karnataka clay deposits that are used in ceramics, bricks and tiles industries.

These clay deposits contain mainly kaolinite. The chemical analysis shows high alumina and silica with low iron and titania.

These are in situ deposits formed by chemical weathering of Precambrian granites / gneisses under tropical climatic conditions.

Figure 1.Location map of the study area along with the sampling locations.

clay deposits of Belgaum and Khanapur have been reportedearlier by Geological Survey of India (2006); Annaiya andMuniswamaiah, (1972); Ahmed and Divakara Rao, (1986);and Devraju, et al., (1994). Khanapur clay was studied for its

mineralogy, geochemistry and grain size variation.

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The present study area forms a part of Khanapur taluk andcovers an area of about 1726 sq.km, lying between latitude

74 25 to 74 35N and longitude 15 35 to 15 45E, covering

the villages Desur, Nittur, Kuppatgiri, Toppinkatti, Idhalhond,Ganebail, Ramgurwadi, Nandihalli etc. Topographically arearepresents the rugged nature as the area forms a part of theWestern Ghats.

The area falls under tropical belt and receives significant

rainfall of about 250cm per annum. 80% of the rainfalloccurs between June to September. Summer is quite warmand the temperature varies between 8-400C, lowest beingobserved in winter and highest being observed summer.Such variable climate is quite favourable for the formationof clay deposits.

GEOLOGY OF THE AREAThe area under study entirely stand on granitic (mostly

granodiorite) basements belonging to Archeans located inthe western part of western Dharwar craton. These graniticrocks are dated as 3.4 to 2.5 Ga. (Devraju, et al 2007; Gupta,

et al 1988). These granites show coarse grained, moderatelyfoliated with orthoclase as phenocrysts. The granitic rocks tothe south grades into the tonalitic gneisses and migmatiticgneisses of Ramnagar (Devraju et al, 2007).

Most of the clay deposits of the study area are locatedoverlying granitic gneisses occurring due to extensive anddeep weathering (Plate 1A). These clays are used for bricksand ceramic materials (Plate 1B, D & E). At places, pegmatiteveins with graphic granite structures within the clay deposits(Plate 1C) and the altered bedrock are observed. The claydeposit here occurs as a blanket or cap deposit with varyingthickness of about 0.5 to 3.0 m. The lithology of the study

area is presented inTable 1.

Table 1.Lithology of the study area (After Devraju et al 2007)

lithounits Description

Soil cover/ lateritic capping0.5 to 3.0m thick. Mixed with corroded pebbles of quartz, ferroginous and pale tobrown in colour.

Zone of concretion/ variegated shaleLess than 1m thick made up of ferruginous concretion of 1 to 4cm in diameterembedded in clay matrix.

Clay(lithomarge)More than 10m thick, contains gritty clay and show preservation of rock structure

in the lower portion. White to yellowish brown in colour.

Altered Bedrock2 3m thick. Grit, commonly covered with a thin layer of loose mineral mattermade up of quartz, feldspar, clay.

Bedrock Granitic gneisses, mostly granodiorites.

Method of study: 12 representative samples were collectedfrom several villages around Khanapur taluk from theworking mine pits (Figure 1). All the samples representthe clay horizon. Five samples were subjected to chemicalanalysis (Table 2).

Further, all the samples were subjected to pipette analysis todetermine the percentage of sand silt and clay within the claydeposit (Table 3). Plotting this data on the triangular diagramusing USDA classification, the type of clay is determined.The sand fraction obtained by the pipette analysis, wassubjected to mechanical analysis using sieve shaker. Theresults of grain size parameters using Folk and Ward (1957)have been presented in Table 4. The parameters like mean,sorting, skewness, and kurtosis are calculated. Further, theclay fraction obtained from the pipette analysis is subjectedto the Infrared analysis to understand the mineralogicalcomposition (Table 5). The interpretation of the IR peaks wasdone using using Vander Marel and Beutle spacer (1976).

Temperature analysis is carried out using the Pc Bhati to

understand the melting point of the clay deposits (Table 6).

RESULTS AND DISCUSSION

Chemical weathering in the tropical climate is the important

process for the formation of clays. The major elements

identified by the chemical analysis are SiO2, Al2O3, Fe2O3,TiO

2, CaO, MgO, K

2O and Na

2O (Table 2). The chemical

analysis shows that they are rich in silica (SiO2), Aluminum

oxide (Al2O

3) and Iron Oxide (Fe

2O

3). This forms the major

constituents of these clays. Titanium Dioxide (TiO2), Lime

(CaO), Magnesia (MgO), Sodium oxide and potassium

oxide (Na2O and K

2O) are the minor constituents of these

clay deposits. Table 2 shows that aluminum has higher

concentration compared to iron which indicate that the clays

are more suitable for the ceramic and refractory industries,

as the presence of aluminum increases the melting

temperature of clay and adds to the refractory.

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Plate 1. Clay deposit (A), making up bricks (B) using the insitu clay; weathered pegmatite intrusionalong with the clay deposit (C); variety of ceramic toys (D); and Ceramic pipes prepared from clays.

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Table 2: Chemical analysis results of the clay sample

MineralChemical

composition

Soil cover Sample 3 Sample 6 Sample 9

Alumina Al2O

314.3 18.0 24.7 21.3

Silica SiO2

57.2 59.6 60.2 62.4

Iron Oxide Fe2O

310.7 6.9 2.8 21.3

Titanium Dioxide TiO2

1.8 1.0 0.5 4.4

Lime CaO 1.6 0.4 0.9 0.8

Magnesia MgO 1.3 0.1 0.3 0.7

Potassium and Sodium K2O and Na

2O 1.5 3.0 1.8 0.2

Loss on ignition Balanced

Pipette Analysis: The pipette analysis was performed following Folk (1974) and the percentage of sand, silt and clay for allthe samples is presented in Table 3 and Figure 2.

Table 3: Percentage of sand, silt and clay.

Sample No. Sand% Clay% Silt%

1 56.32 27.60 16.08

2 59.56 19.60 20.84

3 70.54 24.40 5.06

4 77.64 15.20 7.16

5 82.72 13.60 3.68

6 49.44 32.80 17.76

7 86.02 9.20 4.78

8 27.50 23.33 49.17

9 32.80 32.67 34.53

10 27.90 31.33 40.77

11 38.56 20.67 40.77

12 31.28 24.67 44.05

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In the ceramic industries the clay and silt are consideredtogether as clay. The data also shows that the clay and siltpercentage is more than 50% which infers its being suitableas the raw material for brick and tile industries. From thepipette analysis data triangular diagram (figure 2) for sand,silt and clay has been plotted and is used for classification ofthe type of clay using the USDA (United State Departmentof Agriculture) Classification. This shows that the samples1, 3 and 6 are of sandy clay loam type; samples 2, 4 and 5are of sandy loam type; sample 7 falls under loamy sand;samples 9 and 10 are of clay loam type; and samples 8, 11and 12 are of loam type.

Figure 2. Triangular plot of sand-silt-clay percent for classifying Khanapur clays

Sieve Analysis: The sand fraction obtained from the pipetteanalysis is subjected to sieve analysis to understand thegrain size variation. The textural analysis shows that theaverage mean size varies between 1.23 to 1.9 and theaverage sorting is between 1.06 to 1.31. This indicatesthat the grains are medium in size and poorly sorted innature. Majority of the samples show positively skewednature. The kurtosis values show that the grains are veryplatykurtic to platykurtic.

Table 3: Grain Size Parameters of the sand fraction

SampleNumber

Mean Sorting Skewness Kurtosis

1 1.834 1.276 0.236 0.722

2 1.709 1.261 0.309 0.650

3 1.725 1.223 0.190 0.653

4 1.813 1.231 0.047 0.584

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5 1.670 1.059 -0.031 0.794

6 1.229 1.104 0.737 0.867

7 1.338 1.126 0.579 0.787

8 1.814 1.307 0.264 0.597

9 1.330 1.161 0.688 0.782

10 1.699 1.207 0.232 0.632

11 1.894 1.287 0.093 0.586

12 1.572 1.151 0.258 0.682

Mineralogy: The mineralogical study of the clays is carriedout with the help of infrared spectroscopy. The obtained IRpeaks (Figure 3) shows that the Kaolin and the Smectiteare the major component in the clays,while the minerals

like Mica, Silica, Feldspar, Aluminous minerals (Gibbsite,Diaspore, Bohemite), Carbonate, Chlorite, Manganese arepresent as minor components.

Figure 3: Infrared Peaks of the clay samples of the study area.

Table 5. Infrared spectroscopy peak values of the clay fraction of the study area.

MineralInfrared Spectroscopy Peaks

(Wavelength in cm-1)Sample Number

Kaolin429 to 430, 471 to 472, 537 to 538, 693 to 694,

753 to 754, 798.8, 793.1, 913 to 914,1030 to 1035, 1008.2,

1118.9, 1032.3, 1007.9,1031.5, 3620 to 3699

All 12 samples

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Smectite 467 to 470, 792, 914.6, 1030 to 1033, 1107 to 1109, 1012.2 All 12 samples

Mica

534.5, 752.9, 912 to 913, 1033.0, 1012.2,

1030.4, 1000.9, 3663.0, 3620.8 3, 4, 5, 6, 7, 8, 10, 11

Silica 694 to 695, 798.8. 2, 4, 7, 8, 10, 11.

Interstratified 914.0, 427.6, 536 to 538 2, 4, 6, 7, 9

Feldspar 641.5, 751.9 4, 6, 7

Aluminous minerals 912 to 913 7, 8, 10, 11

Carbonate 1110.9, 2921 to 2922,3651.8 2, 5, 7, 8, 9, 10

Chlorite 752.9, 1045.9, 3440.2 3, 5, 6

Manganese 536.3, 695 to 696, 1113.3 1, 3, 12

Temperature Analysis: Temperature resistance is theone of theimportant property of the ceramic minerals andthus of the clay, which determines the quality of the ceramic

product. Temperature analysis is carried out with the help ofPc Bhatti, the results of which are given in Table 6.

Table 6.Temperature analysis of the clays of the study area.

Sample No. Temperature Sample Number Temperature

1 1670C 7 1633C

2 1600C 8 1050C

3 1543C 9 1060C

4 1636C 10 1642C

5 1050C 11 1530C

6 1650C 12 1622C

CONCLUSIONThe Khanapur clay deposits are studied to investigate thechemical, mineralogical, grain size and melting point of theclay deposits. Mineralogical study shows that the these clayscontain high quantity of the Kaolin and smectite along withsome of the minerals like Mica, Silica, Feldspar, Aluminous

minerals, Carbonate, Chlorite, Manganese. These clayshave high melting point which varies between 1600-1700C.The clays of these area are used extensively because ofthe higher content of alumina and less iron content whichindicate these clays are very well suitable for ceramicindustries and refractory industries. The study confirms theuse of Khanapur clay for ceramic industries like bricks, Tiles,Ceramic Products like Fire bricks, Ceramic pipes, ceramicMoulds etc.

Acknowledgement

The authors are thankful to Shri.V.A.Joshi (MEAI LM),

Ceramic Industries, Khanapur, for his help and guidance.

REFERENCES

1. Ahemad S.M and Divakar Rao, 1986.Physico chemical

and mineralogical studies on some of the clay mineral

deposits of Karnataka, India. Jour. Geol. Soc. India. V.

27(3), pp 298 302.

2. Annaiya and Muniswamaiah, 1972. Fire-clay deposits

in the Mining Lease Block (no. 467) of M/s Mysore

Stoneware Pipes and Potteries (P) Ltd. in Kadlegudda-

Bhimasamudra area, Chitradurga District, TN104.M9 A27

no. 54.

3. Devraju T.C., Ali Khoshroo and Ugarkar A.G., 1994.Mineralogy, geochemistry, and genesis of clay deposits inBelgaum, Dharwad and Chitradurga District, Karnataka.Jour. Geol. Soc. India. V.44, pp 157 - 165.

4. Devaraju T. C., Alapieti T. T., Kaukonen R. J., SudhakaraT. L. and Anathamurthy K. S. 2007. Geochemistry of thePGE mineralized petrological units of the Hanumalapursegment of the Channagiri mafic-ultramafic complex,

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WestrernDharwarCraton, South India, Jour. Geol. Soc.India. V.70, pp 535-556.

5. Doeglas D.J., 1946. Interpretation of the results of

mechanical analysis, Jour. Sed. Petro V.16, pp 1940.

6. Folk, R. L., 1974. Petrology of Sedimentary rocks. Pub:Hemphill Publishing Company, Austin Texas, 185p.

7. Geological Survey of India, Geology and mineral resourcesof the states of India. Misc. Pub. No.30, 61p.

8. Griffiths, J. C. 1951. Scientific method in analysis ofsediments; McGraw Hill book co. Inc, New York, p508.

9. Gupta, J.N., Pandey, B.K., Prasad, P.N., Yadav, G.S.,Ramesh Kumar, K. and Rao, S.S., 1988. Rb-Srgeochemistry of some granitic rocks around Arbail.

10. Haydn H. Murray, 2007. Applied Clay Mineralogy -Occurrences, Processing and Application of Kaolins,

Bentonites, Palygorskite-Sepiolite, and Common Clays(Elsevier Publication), 188p.

11. Van der Marel H. W and Beutlespacher H, 1976. Atlasof Infrared spectroscopy of clay minerals and theiradmixtures, (Elsevier Science Ltd) 396 pp.

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