1887
Volume 26, Issue 2-3
  • ISSN: 0812-3985
  • E-ISSN: 1834-7533

Abstract

Hill 50 Gold Mine is located at Mt Magnet, 560 km NNE of Perth, in the Murchison Province of the Yilgarn Craton. The Mt Magnet greenstone belt consists of a sequence of mafic, ultramafic and felsic volcanic rocks, with interbedded vol-canogenic sediments, predominantly banded iron formations (BIFs). The belt has been deformed into a principal structure, known as the Boogardie Synform. Major NNE - NE striking faults, superimposed on the synform, are referred to as Boogardie Breaks and exhibit important control over many of the ore deposits. Historically, most of the gold production in the Mt Magnet district has come from BIF - hosted deposits (e.g. Hill 50 and Boomer - styles).

Hill 50 - style deposits are hosted by BIF "bars" of the Sirdar Formation, having a width generally greater than 20 m, and being structurally controlled by the Boogardie Breaks. Gold mineralisation is closely associated with pyrrhotite and to a lesser degree, pyrite. Hillcrest South and Brown Hill West prospects are currently being explored using a Hill 50 model. Petrophysical measurements carried out on samples from these areas demonstrate that pyrrhotite - rich BIFs are characterised by lower magnetic susceptibilities and higher Koenigsberger Ratios, conductivities and densities. Use of downhole EM in locating the pyrrhotite - rich BIF has been highly successful.

Boomer - style deposits are hosted by multiple NW - trending BIF units, and breccias, and are distinguished by the close association of gold mineralisation with pyrite. Petrophysical testing on samples from the Boomer pit showed that the pyrite - rich rocks are characterised by higher densities and magnetic susceptibilities than their pyrite - poor counterparts. Although the conductivities are also slightly higher, Boomer -style deposits are not detectable using downhole EM.

The differing conductivities observed in unmineralised BIFs and BIFs with significant pyrite and/or pyrrhotite can be explained by varying textural and mineralogical characteristics of the metallic lustre minerals involved.

© 1995 ASEG
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1995-06-01
2026-01-22

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References

  1. Baker, C.J., 1990, Hydrothermal alteration associated with the Boomer gold deposit, Mt Magnet, Murchison Province, WA: MSc thesis, Queens University, Ontario, (unpublished).
  2. Emerson, D.W., 1994, Electrical properties of magnetite rich ores and rocks: Quarterly Report P416, AMIRA (unpublished).
  3. Emerson, D.W., 1995, Hill 50 Gold Mine exploration areas: Petrophysics data - Preliminary results from October 1994 site visit and laboratory measurements: Company Report, Systems Exploration (NSW) Pty. Ltd. (unpublished).
  4. Goodgame, V.R., 1992, The geology and associated gold mineralisation of the Hill 50 shaft area: Company Report, WMC (unpublished).
  5. Goodgame, V.R., 1993, Geology of the Boomer breccias: Company Report, WMC (unpublished).
  6. Hodges, D.G., and Crone, J.D., A new multiple component downhole pulse EM probe for directional interpretation: in Proceedings of the 4th International MGLS/KEGS Symposium on Borehole Geophysics for Minerals, Geotechnical and Groundwater Applications: Toronto, 18-22 August 1991.
  7. Kelly, P., 1994, Nature, genesis and controls on the Hill 50, Boomer and Hesperus Archaean gold deposits, Mt Magnet - with emphasis on structure and alteration: PhD thesis (quarterly report), University of Western Australia, Perth (unpublished).
  8. McQuitty, B., 1988, Hillcrest: Company Report, Brunswick (unpublished).
  9. Perriam, R.P.A., 1992, Summary of the geology of the Mt Magnet goldfield: Company Report, WMC (unpublished).
  10. Perriam, R.P.A., 1994, Exploration target areas: Hill 50 leases: Company Report, WMC (unpublished).
  11. Thompson, M.J., Watchorn, R.B., Bonwick, CM., Frewin, M.O, Goodgame, V.R., Pyle, M.J., and McGeehan, P.J., 1988, The gold deposits of Hill 50 Gold Mine NL, Mt Magnet, WA: AUSIMM, Monograph 53.
  12. Watkins, K.P., and Hickman, A.H., 1990, Geological evolution and mineralisation of the Murchison Province, Western Australia: Geological Survey of Western Australia, Bulletin 137, 267 pp.
  13. Western Mining Corporation, 1993, Annual Report, 30 June 1993. Western Mining Corporation.
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  • Article Type: Research Article
Keyword(s): aeromagnetics; Archaean banded iron formation - hosted gold; downhole EM; Kirkalocka SH50-3; Murchison Province; petro-physics

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