Characteristics and geodynamic setting of the 2.7 Ga Yilgarn heterogeneous plume and its interaction with continental lithosphere: Evidence from komatiitic-basalt and basalt geochemistry of the Eastern Yilgarn Craton  

Authors / CoAuthors

Said, N. | Kerrich, R. | Cassidy, K. | Champion, D.C.

Abstract

A database of 1075 high-precision geochemical analyses of ultramafic-mafic units, predominantly flows, was compiled for the Eastern Yilgarn Craton. Samples are divided into a high-Mg population at MgO-10-24 wt.% and a basaltic population where 4-MgO<10 wt.%. There are 8 groups based on (La/Sm)N and Nb/Th ratios. Four magma series are identified. Uncontaminated komatiitic-basalts have MgO ~ 11-23 wt.% and Nb/Th-8, whereas contaminated counterparts have Nb/Th<8 corresponding to siliceous high-Mg basalts (SHMB). A distinct magma series with MgO ~ 5-18 wt.% MgO has a narrow range of Nb/Th at 0.5-?2 over a range of (La/Sm)N from 0.7-5.5, unlike contaminated suites where (La/Sm)N and Nb/Th are correlated; this series corresponds to the enriched-Paringa basalt of the Kalgoorlie Terrane. A third high-Mg magma series has a narrow range of MgO at ~13-16 wt.%, extends to elevated TiO2 and Ni relative to komatiitic-basalts at that MgO range, and features (La/Sm)N ?2. Prevalent, crustally uncontaminated, tholeiitic basalts all have Nb/Th?8, span Mg-rich to fractionated Fe-rich counterparts, and range from LREE-depleted to mildly LREE enriched. Contaminated equivalents have Nb/Th<8. Two additional uncontaminated tholeiitic basaltic groups are defined respectively by high-Nb to 20 ppm akin to alkaline ocean island basalts, and elevated total-REE relative to the other basaltic groups. Contamination of all groups was dominantly by interaction with continental mantle lithosphere with a minor crustal component.

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nonGeographicDataset

eCat Id

72925

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Keywords

• External Publication

( Theme )

• geochemistry

( Theme )

• plate tectonics

( Theme )

• geology

Australian and New Zealand Standard Research Classification (ANZSRC)

• Earth Sciences

• Published_Internal

Publication Date

2012-01-01T00:00:00

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Australian Government Security ClassificationSystem    

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Creative Commons Attribution 4.0 International Licence    

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unknown

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geoscientificInformation

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Unknown

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Extents

[-34.0, -24.0, 120.0, 126.0]

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