Jimblebar, Wheelarra Hill (McCameys Monster), Hashimoto, Jimblebar South

Western Australia, WA, Australia

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The Jimblebar iron ore operation is located on the eastern end of the Ophthalmia Range, some 48 km east of the centre of the Mount Whaleback pit. It comprises the Wheelarra Hill (McCamey's Monster) W1 to W6 and Hashimoto H1 to H4 groups of Brockman Iron Formation deposits to the west and east respectively, and the Jimblebar South string of Marra Mamba deposits, 1 to 2 km to the south of the Brockman deposits (#Location: 23° 22' 46"N, 120° 07' 46"E).

See the Hamersley Basin Iron Province record for the regional setting and stratigraphy.

These deposits are distributed over a total, east-west oriented strike length of ~18 km, and represents the far eastern end of the Ophthalmia Range. This section of the range is bounded to the west, and offset from the sequence to the west, by the major low angle, dextral, NE-SW trending, normal Wheelara Fault. Brockman mineralisation continues east from the Hashimoto deposts for a further 7 km in the East Jimblebar zone.

The sequence to the east of the Wheelara Fault has been subjected to strong deformation. Bedding dips at around 10° to the north, with overturned to recumbent F2 folds that have shallow south dipping axial surfaces and a series of south-dipping thrusts which have stacked the stratigraphy. These have been refolded by an F3 event. The main structures are the result of the 2.3 to 2.2 Ga Ophthalmia Orogeny (Harmsworth et al., 1990).

The structurally stacked stratigraphy from south to north, comprises:
Archaean basement of the Sylvania Dome, that has been overthrust to the north over the;
Fortescue Group basaltic volcanic, and clastic sedimentary rocks. These are overlain by the;
Marra Mamba Iron Formation and Wittenoom Dolomite of the Hamersley Group folded into a tight syncline, before beng thrust obliquely northward over the;
Brockman Iron Formation, with the McCrae Shale and Mount Sylvia Formations exposed on the northern fringe of the thrust to the east, in the Hashimoto deposits area, and a narrow thrust sliver of Dales Gorge Member iron formation to the west corresponding to the Wheelarra Hill string of deposits. These exposures are followed progressively to the north by the Dales Gorge and Joffre Members, Weeli Wolli Formation, Woongarra Volcanics and Boolgeeda Iron Formation (Miller and Dransfield, 2011).

The lower thrust sheet containing the bulk of the Brockman sequence has been strongly faulted, with the majority of structures trending NE-SW, sub-parallel to parallel to the Wheelara Fault, with a lesser set of NNW-SSE structures. These strutures have influenced the distribution of higher grade ore.

Ore is a mixture of low P martite-microplaty hematite and medium- to high-P martite-goethite ore within the Joffre Member of the Brockman Iron Formationand medium to high P martite-goethite ore from the underlying Dales Gorge Member.

The reserve in 2001 was stated at 95 Mt at a grade of 62.6% Fe, 4.7% SiO2, 2.5% Al2O3, 0.060% P, 2.8% LOI,
    with an additional 25 Mt of lower grade blending ore.

High grade lump detrital ore has been mined with a grade of 61.2% Fe, 5.8% SiO
2, 3.5% Al2O3, 0.073% P, 2.6% LOI.

Resources and reserves at Jimblebar at 30 June 2012 (BHP Billiton, 2012) were:
    Measured + indicated + inferred Brockman resources - 2.157 Gt @ 60.3% Fe, 0.13% P, 4.9% SiO
2, 3.1% Al2O3, 5.2% LOI;
    Measured + indicated + inferred Mara Mamba resources - 485 Mt @ 59.6% Fe, 0.08% P, 4.5% SiO
2, 2.5% Al2O3, 6.9% LOI;
    Proved + probable Brockman reserves - 499 Mt @ 62.4% Fe, 0.11% P, 3.4% SiO
2, 2.4% Al2O3, 4.3% LOI;
    Proved + probable Mara Mamba reserves - 92 Mt @ 61.3% Fe, 0.08% P, 3.2% SiO
2, 2.2% Al2O3, 6.2% LOI.

The most recent source geological information used to prepare this summary was dated: 2011.     Record last updated: 22/5/2013
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.

  References & Additional Information
 References to this deposit in the PGC Literature Collection:
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 FE (Ed.), 1990 Geology of the Mineral Deposits of Australia & Papua New Guinea The AusIMM, Melbourne   v1 pp 617-642
Kerr, T.L., O’Sullivan, A.P., Podmore, D.C., Turner, R. and Waters, P.,  1994 - IRON: Geophysics and iron ore exploration: examples from the Jimblebar and Shay Gap-Yarrie regions, Western Australia: in Dentith, M.C., Frankcombe, K.F., Ho, S.E., Shepherd, D.I. and Trench, A., (Eds.),  Geophysical Signatures of Western Australian Mineral Deposits, Australian Society of Exploration Geophysicists, Special Publications,   v.7 pp. 355-368
Miller, R. and Dransfield, M.,  2011 - Airborne Gravity Gradiometry and Magnetics in the Search for Economic Iron Ore Deposits: in   Proceedings, Iron Ore 2011 Conference, 11-13 July 2011, Perth, Western Australia, The Australasian Institute of Mining and Metallurgy, Melbourne,    pp. 109-116
Ward D F, Coles I G, Carr W M B  1975 - Jimblebar and Western Ridge Iron Ore Deposits, Hamersley Iron Province: in Knight CL (Ed.), 1975 Economic Geology of Australia & Papua New Guinea, Monograph 5 The AusIMM, Melbourne   v1 - Metals pp 916-924

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