Comparison of Archean dunites and komatiites associated with nickel mineralisation in Western Australia: Implications for dunite genesis |
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| Authors: | M J Donaldson C M Lesher D I Groves J J Gresham |
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| Institution: | (1) Kambalda Nickel Operations, Western Mining Corporation Limited, 6442 Kambalda, Western Australia;(2) Department of Geology, University of Western Australia, 6009 Nedlands, Western Australia;(3) Present address: Western Mining Corporation Ltd., P.O. Box 71, 6430 Kalgoorlie, Western Australia;(4) Present address: Department of Geology, University of Alabama, 35486-1945 University, Alabama, USA;(5) Present address: Western Mining Corporation Ltd., 168 Greenhill Road, 5063 Parkside, South Australia, Australia |
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| Abstract: | The two important classes of Archean Fe-Ni-Cu sulphide deposits in Western Australia are those hosted by (1) coarse-grained adcumulate dunites (e.g. Agnew, Mount Keith) and (2) komatiitic lavas (e.g. Kambalda). Close similarities in compositions of relict olivine, pyroxene, and chromite from dunitic and komatiitic host rocks and compositional and textural similarities between chilled margins of some dunites and some komatiites indicate origins from similar komatiitic liquids which contained 20%–32% MgO. As field relations suggest that the dunites are probably lateral stratigraphic equivalents of spinifextextured komatiites, they are interpreted as the slowcooled end member of a continuum from spinifex-textured komatiites (former liquids) through cumulate komatiites (40%–90% olivine) to adcumulate komatiitic dunite (>90% olivine). Previous classification of these Ni deposits as  intrusive - and volcanic-related deposits now appears unwarranted, and the terms komatiitic dunite-hosted and komatiite-hosted deposits are preferred. |
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