Register      Login
Exploration Geophysics Exploration Geophysics Society
Journal of the Australian Society of Exploration Geophysicists
RESEARCH ARTICLE

Ground resistivity method and DCIP2D forward and inversion modelling to identify alteration at the Midwest uranium deposit, northern Saskatchewan, Canada

Samuel R. M. Long 1 3 Richard S. Smith 1 Robert B. Hearst 2
+ Author Affiliations
- Author Affiliations

1 Department of Earth Sciences, Laurentian University, 935 Ramsey Lake Road, Sudbury, Ontario, Canada, P3E 2C6.

2 Areva Resources Canada Inc., PO Box 9204, Saskatoon, Saskatchewan, Canada, S7K 3X5.

3 Corresponding author. Email: sam.long68@gmail.com

Exploration Geophysics 48(4) 383-393 https://doi.org/10.1071/EG15059
Submitted: 3 August 2015  Accepted: 22 April 2016   Published: 3 June 2016

Abstract

Resistivity methods are commonly used in mineral exploration to map lithology, structure, sulphides and alteration. In the Athabasca Basin, resistivity methods are used to detect alteration associated with uranium. At the Midwest deposit, there is an alteration zone in the Athabasca sandstones that is above a uraniferous conductive graphitic fault in the basement and below a conductive lake at surface. Previous geophysical work in this area has yielded resistivity sections that we feel are ambiguous in the area where the alteration is expected. Resolve® and TEMPEST sections yield an indistinct alteration zone, while two-dimensional (2D) inversions of the ground resistivity data show an equivocal smeared conductive feature in the expected location between the conductive graphite and the conductive lake. Forward modelling alone cannot identify features in the pseudosections that are clearly associated with alteration, as the section is dominated by the feature associated with the near-surface conductive lake; inverse modelling alone produces sections that are smeared and equivocal. We advocate an approach that uses a combination of forward and inverse modelling. We generate a forward model from a synthetic geoelectric section; this forward data is then inverse modelled and compared with the inverse model generated from the field data using the same inversion parameters. The synthetic geoelectric section is then adjusted until the synthetic inverse model closely matches the field inverse model. We found that this modelling process required a conductive alteration zone in the sandstone above the graphite, as removing the alteration zone from the sandstone created an inverse section very dissimilar to the inverse section derived from the field data. We therefore conclude that the resistivity method is able to identify conductive alteration at Midwest even though it is below a conductive lake and above a conductive graphitic fault. We also concluded that resistivity inversions suggest a conductive paleoweathering surface on the top of the basement rocks at the basin/basement unconformity.

Key words: 2D inversion, alteration, pole-pole, resistivity, Saskatchewan, sensitivity, uranium.


References

Alexandre, P., Kyser, K., Jiricka, D., and Witt, G., 2012, Formation and evolution of the Centennial unconformity-related uranium deposit in the south-central Athabasca Basin, Canada: Economic Geology and the Bulletin of the Society of Economic Geologists, 107, 385–400
Formation and evolution of the Centennial unconformity-related uranium deposit in the south-central Athabasca Basin, Canada:Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC38XlslamtLk%3D&md5=c2b0be691ef2756387cb8eb44f1fc585CAS |

Areva Resources Canada, Inc., 2008, Activities and results, 2008 Geophysics Program: Mineral Claims, Government of Saskatchewan.

CGG Corporation, 2016, HFEM minerals. Available at: http://www.cgg.com/en/What-We-Do/Multi-Physics/Minerals/HFEM-Minerals

Grenthe, I., Buck, E. C., Drozdynski, J., Fujino, T., Albrecht-Schmitt, T., and Wolf, S. F., 2006, Uranium, in L. R. Moss, N. Edelstein, J. Fuger, and J. J. Katz, eds., The chemistry of the actinide and transactinide elements, 3rd edition: Springer, 253–639.

Hoeve, J., 1984, Host rock alteration and its application as an ore guide at the Midwest Lake uranium deposit, northern Saskatchewan: CIM Bulletin, 77, 63–72
| 1:CAS:528:DyaL2cXlsFGisbs%3D&md5=2ac80827f69a42a39d54848d9a7dda7cCAS |

Hoeve, J., and Quirt, D., 1984, Mineralization and host rock alteration in relation to clay mineral diagenesis and evolution of the middle-Proterozoic Athabasca Basin, northern Saskatchewan, Canada: Saskatchewan Research Council, Technical Report, 187.

IAEA, 2009, World distribution of uranium deposits (UDEPO) with uranium deposit classification: International Atomic Energy Agency, IAEA-TECDOC-1629.

Jefferson, C. W., Thomas, D., Quirt, D., Mwenifumbo, C. J., and Brisbin, D., 2007, Empirical models for Canadian unconformity-associated uranium deposits, in B. Milkereit, ed., Proceedings of Exploration 07: Fifth Decennial International Conference on Mineral Exploration, 741–769.

Lane, R., Green, A., Golding, C., Owers, M., Pik, P., Plunkett, D., Sattel, D., and Thorn, B., 2000, An example of 3D conductivity mapping using the TEMPEST airborne electromagnetic system: Exploration Geophysics, 32, 162–172

Loke, M. H., and Barker, R. D., 1996, Rapid least-squares inversion of apparent resistivity pseudosection by a quasi-Newton method: Geophysical Prospecting, 44, 131–152
Rapid least-squares inversion of apparent resistivity pseudosection by a quasi-Newton method:Crossref | GoogleScholarGoogle Scholar |

Matthews, R., Koch, R., and Leppin, M., 1997, Advances in integrated exploration for unconformity uranium deposits in western Canada, in A. G. Gubins, ed., Proceedings of Exploration 97: Fourth Decennial International Conference on Mineral Exploration, 993–1024.

McMullan, S. R., Matthews, R. B., and Robertshaw, P., 1989, Exploration geophysics for Athabasca uranium deposits, in G. D. Garland, ed., Proceedings of Exploration ’87: Third Decennial International Conference on Geophysical and Geochemical Exploration for Minerals and Groundwater: Ontario Geological Survey, Special Volume 3, 547–566.

Morrison, F., and Gasperikova, E., 2012, DC resistivity and IP field systems, data processing and interpretation. The Berkeley course in applied geophysics. Available at: http://appliedgeophysics.berkeley.edu/ (accessed 23 March 2014).

Mwenifumbo, C. J., Elliot, B. E., Jefferson, C. W., Bernius, G. R., and Pflug, K. A., 2004, Physical properties from the Athabasca Group: designing exploration models for uranium deposits: Journal of Applied Geophysics, 55, 117–135
Physical properties from the Athabasca Group: designing exploration models for uranium deposits:Crossref | GoogleScholarGoogle Scholar |

Nimeck, G., and Koch, R., 2008, A progressive geophysical exploration strategy at the Shea Creek uranium deposit: The Leading Edge, 27, 52–63
A progressive geophysical exploration strategy at the Shea Creek uranium deposit:Crossref | GoogleScholarGoogle Scholar |

Oldenburg, D. W., and Li, Y., 1994, Inversion of induced polarization data: Geophysics, 59, 1327–1341
Inversion of induced polarization data:Crossref | GoogleScholarGoogle Scholar |

Oldenburg, D. W., and Li, Y., 2005, Inversion for applied geophysics: A tutorial, in D. K. Butler, ed., Near-surface geophysics: Society of Exploration Geophysicists, Geophysics Series, no. 13, 89–150.

Quirt, D. H., 1989, Host-rock alteration at Eagle Point South: Saskatchewan Research Council, Publication No. R-855–1-E-89.

Quirt, D. H., 2003, Athabasca unconformity-type uranium deposits: one deposit type with many variations, in M. Cuney, ed., Uranium Geochemistry: Proceedings of the International Conference on Uranium Geochemistry, 309–312.

Raffensperger, J. P., and Garven, G., 1995a, The formation of unconformity-type uranium ore deposits; 1, Coupled groundwater flow and heat transport modeling: American Journal of Science, 295, 581–636
The formation of unconformity-type uranium ore deposits; 1, Coupled groundwater flow and heat transport modeling:Crossref | GoogleScholarGoogle Scholar |

Raffensperger, J. P., and Garven, G., 1995b, The formation of unconformity-type uranium ore deposits; 2, Coupled hydrochemical modeling: American Journal of Science, 295, 639–696
The formation of unconformity-type uranium ore deposits; 2, Coupled hydrochemical modeling:Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK2MXnsFKkt78%3D&md5=289ad046f04a94ede068de06b7db9442CAS |

Smith, R. S., and Koch, R., 2006, Airborne EM measurements over the Shea Creek uranium project, Saskatchewan, Canada: SEG Technical Program, Expanded Abstracts, 1263–1267.

Smith, R. S., Wood, G. R., and Powell, B., 2010, Detection of alteration at the Millennium uranium deposit in the Athabasca Basin: a comparison of data from two airborne electromagnetic systems with ground resistivity data: Geophysical Prospecting, 58, 1147–1158
Detection of alteration at the Millennium uranium deposit in the Athabasca Basin: a comparison of data from two airborne electromagnetic systems with ground resistivity data:Crossref | GoogleScholarGoogle Scholar |

Smith, R. S., Koch, R., Hodges, G., and Lemieux, J., 2011, A comparison of airborne electromagnetic data with ground resistivity data over the Midwest deposit in the Athabasca basin: Near Surface Geophysics, 9, 319–330
A comparison of airborne electromagnetic data with ground resistivity data over the Midwest deposit in the Athabasca basin:Crossref | GoogleScholarGoogle Scholar |

Telford, W. M., Geldart, L. P., and Sheriff, R. E., 1990, Applied geophysics (2nd edition): Cambridge University Press.

Wray, E. M., Ayres, D. E., and Ibrahim, H., 1985, Geology of the Midwest uranium deposit, northern Saskatchewan, in T. I. Sibbald, and W. Petruk, eds., Geology of uranium deposits: Canadian Institute of Mining and Metallurgy, Special Volume 32, 54–66.