Termitaria sampling in uranium exploration: Refining an old technique

P Sinclair, I González-Álvarez, R Anand, A Stewart, W Salama, J Laird, T Pinchand

Cameco Australia & CSIRO

Termitaria sampling in uranium exploration: Refining an old technique

1 Cameco Australia

2 CSIRO

1

P. Sinclair1, I. González-Álvarez2, R. Anand2, A. Stewart2, W. Salama2, J. Laird2 and T. Pinchand2. Reference: I. González-Álvarez, R. Anand, A. Stewart, W. Salama, J. Laird and Pinchand, T., 2015. “Termitaria in Arnhem Land, Northern Territory, Australia: geochemical exploration for uranium”. In CSIRO, Mineral Resources Flagship Report, Western Australia, EP148115, 43.

Historic orientation surveys

2 AGES 2017

Koongarra Nabarlek Ranger 1 Aurari North Angularli

Conventional soils

Shallow regolith sampling

Vegetation Sampling

Metal depletion in soil

Cu, Pb ± U regolith horizons

U – Cu ± Ga ± Mo Seasonal variation

Mamadawerre Sandstone

Cretaceous sediment

Alluvium

Paleoprot. metasediment

Saprolite

UC

UC

UC

? ? ?

Aurari Termitaria Orientation Study

3 AGES 2017

0

1

2

3

4

5

6

7

8

0

0.5

1

1.5

2

2.5

3

3.5

133.2 133.202 133.204 133.206 133.208 133.21

As, Dy, U (ppm) Cu (ppm)

Cu

As U

Dy

Uranium mineralisation

● Fault hosted uranium mineralisation below 60 m cretaceous cover

● No surficial radiometric expression

Cretaceous marine sediment

Dolerite Felsic gneiss

Limit of weathering

Ferricrete

● U, As, Cu and HREE enrichment in termitaria samples over fault system

● 500 m wide low level dispersion anomaly

● Peak of anomaly displaced to east – shallower cover?

2014 Termitaria Research Study

4 AGES 2017

AIM: Optimise the termitaria sampling technique for uranium exploration in a sub-tropical weathering environment

B Br Cl I He Rn

Ca F Mg Na Co Cu Ni U V Zn

Al Si Ag Au Hg Sb REE

K As Mo Pb Be Bi

Fe Mn Ti W Zr Sn

B Br Cl I He Rn

F Na Mg Pd U V

Ca Ag Au As Cu Mo Ni Zn

K Li Mn Si Pb Hg Sb

Al Fe Ti W Pt Sn Th Zr

Oxidizing neutral to alkaline groundwater

Oxidizing acidic groundwater

Very high mobility

● Sub-tropical climate promotes leaching of soil and regolith

● Uranium is significantly more mobile than gold and most base metals

Very low mobility

Modified from Regolith Science (Scott & Pain, 2009)

Termites of the Top End

5 AGES 2017

Tumulitermes pastinator

Microcerotermes serratus

Coptotermes acinaciformis

Amitermes laurensis

Schedorhinotermes actuosus (?)

Nasutitermes

Speciation Study

6 AGES 2017

Seasonally flooded lowlands Grassland with sparse eucalypt Open eucalypt forest

Amitermes meridionalis Coptotermes acinaciformis Amitermes laurensis

Speciation Study

7 AGES 2017

Open Eucalypt Forest

Grassland with sparse eucalypt

Seasonally flooded

lowlands

Spot Imagery with termitaria sample points

Coptotermes

Amitermes Laur.

Sampling

8 AGES 2017

Zone of bioturbation

Internal structure of the above ground part of a Coptotermes nest

Clay carton

Organic-rich carton (food

storage)

50 cm

Clay carapace

Size Fraction Analysis

9 AGES 2017

● Highest uranium results consistently reported from the clay fraction

● Elevated uranium from coarse (> 2 mm) fragments

● Variable results from sand and silt sized fractions

0

1

2

3

4

5

6

7

8

9

10

Elevation relative to ground level 35 cm 15 cm 5 cm - 5 cm - 15 cm - 25 cm - 35 cm - 45 cm

Ura

nium

ppm

> 2 mm (Ferruginous gravel) 2 – 0.25 mm (Quartz sand) 0.25 – 0.053 mm (Fine sand & silt) < 0.053 mm (Clay)

Sur

face

Regolith Uranium Distribution

10 AGES 2017

Ferricrete

Sandy clay

Oxidised sandy soil

Organic carton

2 m

U ppm (< 53 µm fraction)

0 2 4 6 8 10 12

Clay carapace ● Background uranium concentrations

4 to 5 metres from nest

● Above background values within buried laterite and throughout nest

● Highest uranium in clay carapace

Clay carton

Uranium Deportment

11 AGES 2017

● Uranium is finely distributed at low levels

● Pb, Cu and As finely disseminated and as < 0.5 mm grains

● Poor correlation between uranium and iron

Fe Pb

Cu

U

Ca

Al As

XRF Mapping

25 mm

15 mm

FOV

Fe Uranium 0.5 mm 0.5 mm

PIXE Mapping

Uranium Deportment

12 AGES 2017

● < 53 µm samples prepared with a Na4P2O7 leach

● Targets highly soluble organics (humic and fulvic acid)

● Indicates a portion of the uranium occurs within organic material in the clay fraction

0

5

10

15

20

25

30

0 20 40 60 80 100

Total digest (HF) vs Tetra sodium pyrophosphate digest

U ppm (total digest)

U p

pm (N

a 4P

2O7 l

each

)

Clay carton composed of alluvium bound together by organic material

Uranium dispersion mechanisms

13 AGES 2017

Biogenic physical transport access

saturated soil below the water table U

< 1.5 ppm

1.5 – 3 ppm

3 – 5 ppm

5 – 8 ppm

> 8 ppm

Uranium concentration

Weathering ore system at depth

Uranium dispersion mechanisms

14 AGES 2017

Biogenic physical transport of enriched particles from regolith horizons

U

< 1.5 ppm

1.5 – 3 ppm

3 – 5 ppm

5 – 8 ppm

> 8 ppm

Uranium concentration

Weathering ore system at depth

Uranium dispersion mechanisms

15 AGES 2017

Biogenic consumption of uranium enriched wood, roots & leaves

Tree roots draw from water table

U

U U

< 1.5 ppm

1.5 – 3 ppm

3 – 5 ppm

5 – 8 ppm

> 8 ppm

Uranium concentration

Weathering ore system at depth

Termites excrete U-enriched organic material to bind mound

Leaching of soil/regolith

profile

Impermeable clay cap prevents U leaching

U U

Conclusion

16 AGES 2017

AIM: Optimise the termitaria sampling technique for uranium exploration in a sub-tropical weathering environment

● No evidence to suggest that any particular mound building termite species provides better sampling media

● Apical cemented clay-rich portion of mounds is the optimal sample media

● Tenor of uranium anomalism can be improved by only analysing the < 53 µm size fraction

● Partial leach technique (i.e. Aqua regia) should be sufficient to liberate uranium from sample

Termitaria sampling technique

References

17 AGES 2017

● Cruickshank, B. I and Pyke, J.G., 1986. Biogeochemistry and soil geochemistry of the Ranger One, Number 3 orebody, Australia. Uranium, U: 1-26.

● Eupene, G.S. and Williams, B.T., 1980. Ranger One U deposits, Pine Creek Block, N.T. In C.R.M. Butt and R. E. Smith (editors), Conceptual Models in Exploration Geochemistry, 4: Australia. Journal of Geochemical Exploration 12: 230-233.

● Giblin, A.M. and Snelling, A.A., 1983. Applications of hydrogeochemistry to uranium exploration in the Pine Creek Geosyncline, Northern Territory, Australia. Journal of Geochemical Exploration 19: 33-55.

● Gilblin, A. M. 2004. Alligator Rivers uranium deposits (Koongarra, Nabarlek and Ranger One). In C.R.M Butt, I.D.M. Roberston, K.M. Scott and M. Cornelius (editors), Regolith expression of Australian ore systems, CRC LEME: 411-414.

● González-Álvarez, I., Stewart, A., Anand, R., Sinclair, P., Salama, W., Laird, J., Ibrahimi, T., Pinchand, T., 2015. Termitaria Geochemistry for Uranium Exploration in Arnhem Land, Northern Territory, Australia. Society of Economic Geology Annual Meeting, September 2015 Hobart, Tasmania, Australia, P218.

● González-Álvarez, I., Stewart, A., Anand, R.R., Salama, W., Laird, J., Ibrahimi, T., Pinchand, T., 2014. Termitaria in Arnhem Land, Northern Territory, Australia: geochemical exploration for uranium. CSIRO, Mineral Resources Flagship Report, Western Australia, EP148115, 43.

● Snelling, A.A., 1984. A soil geochemistry orientation survey for uranium at Koongarra, Northern Territory. In Journal of Geochemical Exploration, 22: 83-99.

● Watters, R.A., 1988. Biogeochemistry and soil geochemistry of the Ranger One, Number 3 Orebody, Australia – Comments. Uranium, 4: 415-418.

CSIRO entomologist, Dr Aaron Stewart, collecting soldier termites, 2014.