Authors / CoAuthors
Sheraton, J.W. | Sun, S.S.
Abstract
Several petrographically and geochemically distinct suites of mafic dykes crop out in the Mesoproterozoic Musgrave Block. Intergranular dolerites (group A), as well as the voluminous Giles Complex layered mafic-ultramafic intrusions and Tollu Group basaltic volcanics, were formed by large-scale melting of heterogeneous enriched subcontinental lithospheric mantle about 1080 Ma ago, more than 100 m.y. after the 1200-Ma regional high-grade metamorphism of the Musgrave Block country rocks. The coeval Kulgera (eastern Musgrave Block) and Stuart (Arunta Block) dyke swarms are chemically and isotopically similar. Slightly younger (-1000 Ma), particularly heterogeneous olivine dolerites (group C) were also derived from a similarly enriched source. Mantle heterogeneity was apparently both lateral (as group C dolerites show significant geographical variations) and vertical (because chemically distinct dyke suites of similar age crop out in the same area). Microgabbro dykes and sills associated with troctolitic intrusions of the Giles Complex are compositionally similar to both gabbronorite intrusions of the Giles Complex and to group A dolerite dykes therein. The least fractionated microgabbros are probably representative of an evolved magma that was parental to the major gabbroic intrusions of the Giles Complex, and underwent some degree of high-pressure pyroxene ± olivine fractionation. They cannot be directly parental to the leucotroctolite cumulates. which reflect much more extensive high-pressure fractionation before they were emplaced. Quartz dolerites emplaced 800 Ma ago (group B) were derived by higher-pressure partial melting of a much less enriched (-Nd +2.8 to +3.8), homogeneous asthenospheric mantle source, probably related to mantle-plume activity. They are virtually identical chemically and isotopically with dykes, including the Amata (eastern Musgrave Block) and Gairdner (Gawler Craton) dyke swarms, that crop out over a distance of more than 1000 km.
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document
eCat Id
81466
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Keywords
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- GA PublicationJournal
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- NTSAWA
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_External
Publication Date
1997-01-01T00:00:00
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geoscientificInformation
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AGSO Journal of Australian Geology and Geophysics 16:5:621-636
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Unknown
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[-35.46, -18.72, 125.26, 137.92]
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