1887
Geophysical Signatures of West Australian Mineral Deposits
  • ISSN: 2202-0586
  • E-ISSN:

Abstract

Aeromagnetic and downhole logging data have been acquired for iron ore deposits at Jimblebar and Shay Gap-Yarrie in the Pilbara region of Western Australia. The Jimblebar deposits are from the Archaean-Early Proterozoic Hamersley Group and the Shay Gap-Yarrie deposits are from the Archaean Gorge Creek Megasequence.

Aeromagnetic data are used to assist in regional mapping and generation of exploration targets. In structurally complex areas, a very close line-spacing may be necessary to provide data of sufficient resolution. Careful processing is necessary to reduce the large dynamic range of the data, caused by highly magnetic banded iron-formation (BIF), so that subtle features may be seen. Deposits display both structural and stratigraphic controls which may be evident in aeromagnetic data. In addition, the iron enrichment process alters magnetite within the parent BIF to haematite, which may give rise to subdued responses in aeromagnetic data. The application of the aeromagnetic technique to exploration at Yarrie was an integral part of the discovery of the Y2 deposit.

Downhole natural gamma logging is used as an in-hole stratigraphic mapping tool. In the Jimblebar area, the stratigraphy, comprising interbedded oxide BIF and silicate iron formation (shale) macrobands, is very regular. As a result, it is generally possible for gamma ray logging to identify the strata intersected in drillholes to within a several metres, even where they are complexly deformed. Hence natural gamma logging can play an important role in resolving complex structural problems. At Shay Gap-Yarrie, gamma logging does not show the stratigraphic discrimination seen in the Jimblebar area, because the stratigraphy in the Shay Gap region is not as laterally consistent. However, gamma logging is still useful for general delineation of rock types.

Density logging is used for a variety of applications, including confirmation of ore grades, bulk density estimates for resource calculation, and geotechnical studies. At Shay Gap-Yarrie, back-scattered gamma density logging is used downhole to determine the density of iron ore, an important parameter in resource calculations. Frequent calibration of the probe with known reference samples is critical.

© ASEG 1994
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1994-12-01
2026-01-17

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References

  1. FORREST J., 1875. Journal of proceedings of the Western Australian exploring expedition through the centre of Australia, from Champion Bay, on the west coast, to the overland telegraph line between Adelaide and Port Darwin. Parliamentary Paper No, 1, 167 pp. Western Australian Parliament, Perth.
  2. HARMSWORTH R.A., KNEESHAW M., MORRIS R.C., ROBINSON C.J. & SHRIVASTAVA P.K., 1990. BIF-derived iron ores of the Hamersley Province. In Hughes F.E. (ed.), Geology of the Mineral Deposits of Australia and Papua New Guinea, pp. 617-642. Australasian Institute of Mining and Metallurgy, Melbourne.
  3. HICKMAN A.H., 1983. Geology of the Pilbara Block and its environs. Geological Survey of Western Australia, Bulletin127, 268 pp.
  4. HICKMAN A.H., CHIN R.J. & GIBSON D.L, 1983. Yarrie, Western Australia. Geological Survey of Western Australia 1:250,000 Geological Series Explanatory Notes. Geological Survey of West-em Australia, Perth, 33 pp.
  5. HORWITZ R.C., 1990. The Archaean unconformity at Shay Gap, northeastern Pilbara Craton. Australian CSIRO, Division of Exploration Geoscience, Restricted Report123R, 11 pp.
  6. JONES H., WALRAVEN F. & KNOTT G.G., 1973. Natural gamma logging as an aid to iron ore exploration in the Pilbara Region of Western Australia. In Western Australian Conference 1973, pp. 53-60. Australasian Institute of Mining and Metallurgy, Melbourne.
  7. KNEESHAW M., 1984. Pilbara iron ore classification � a proposal for a common classification for BIF-derived supergene iron ore. Australasian Institute of Mining and Metallurgy, Proceedings289, 157-162.
  8. KRAPEZ B., 1993. Sequence stratigraphy of the Archean supracrustal belts of the Pilbara Block, Western Australia. Precambrian Research60, 1 -47.
  9. MORRIS R.C., 1985. Genesis of iron ore in banded iron-formation by supergene and supergene-metamorphic processes - a conceptual model. In Wolf K. (ed.), Handbook of Strata-Bound and Stratiform Ore Deposits, Volume 13, pp. 73-235. Elsevier, Amsterdam. TRENDALL A.F., 1983. The Hamersley Basin. In Trendall A.F. & Morris R.C. (eds), Iron Formations � Facts and Problems, pp. 69-129. Elsevier, Amsterdam.
  10. TYLER I.M., 1991. The geology of the Sylvania Inlier and southeast Hamersley Basin. Geological Survey of Western Australia, Bulletin138, 108 pp.
  11. WARD D.F., COLES I.G. & CARR W.M.B., 1975. Jimblebar and Western Ridge iron ore deposits, Hamersley Iron Ore Province. In Knight C.L. (ed.), Economic Geology of Australia and Papua New Guinea, pp. 916-923. Australasian Institute of Mining and Metallurgy, Melbourne.
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  • Article Type: Research Article
Keyword(s): Banded iron-formation; downhole logging; magnetics; Pilbara Craton; Robertson SF51-13; supergene enriched iron ore; Yarrie SF51-1

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