New Rb-Sr mineral ages temporally link plume events with accretion at the margin of Gondwana.
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.
Authors: Flowerdew, M.J., Daly, J. S., Riley, T.R. ORCID record for T.R. Riley
In: Cooper, A.K., Raymond, C.R., ISAES Editorial Team, . (eds.). Antarctica: a keystone in a changing world. Online proceedings of the 10th International Symposium on Antarctic Earth Sciences, Santa Barbara, California, August 26 - September 1, 2007, U.S. Geological Survey and National Academies Press, 4 pp.