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New Rb-Sr mineral ages temporally link plume events with accretion at the margin of Gondwana

M.J. Flowerdew·J.S. Daly·T.R. Riley
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Abstract

Five of six Rb-Sr muscovite mineral isochron ages from the Scotia Metamorphic Complex of the South Orkney Islands, West Antarctica, average 190 ± 4 Ma. The muscovite ages are interpreted to date foliation-formation and thus also accretion and subduction at the Gondwana margin. Coincident picrite and ferropicrite magmatism, indicative of melts from deep-seated depleted mantle, permits a causative link between accretion and the arrival of the Karoo – Ferrar – Chon Aike mantle plume in the Early Jurassic. Three biotite Rb-Sr mineral isochron ages are consistently younger and average 176 ± 5 Ma. The biotite ages may record post-metamorphic cooling or more likely retrogressive metamorphic effects during uplift.

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M.J. Flowerdew, J.S. Daly, T.R. Riley. 2007. New Rb-Sr mineral ages temporally link plume events with accretion at the margin of Gondwana. https://doi.org/10.3133/ofr20071047srp012

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