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The Somuncura Large Igneous Province in Patagonia: Interaction of a Transient Mantle Thermal Anomaly with a Subducting Slab |
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| Authors: | Kay S Mahlburg; Ardolino A A; Gorring M L; Ramos V A |
| Institution: | 1Earth and Atmospheric Sciences, Snee Hall, Cornell University, Ithaca, NY 14853, USA 2Dirección Nacional de Minería and Geología, Buenos Aires, Argentina 3Earth and Environmental Studies, Montclair State University, Upper Montclair, NJ 07043, USA 4Ciencias Exactas and Naturales, Ciudad Universitaria Pabellón II, 1428 Buenos Aires, Argentina |
| Abstract: | The Oligo-Miocene Somuncura province is the largest ( 55 000km2) back-arc mafic volcanic field in Patagonia, and one ofEarth's largest with no clear link to a hotspot or major extension.Major and trace element and Sr–Nd–Pb isotopic datasuggest involvement of a plume-like component in the mantlemagma source mixed with hydrous, but not high field strengthelement (HFSE)-depleted components, from a disintegrating subductingplate. Magmatism is attributed to mantle upwelling related todisturbances during plate reorganization, possibly at a timewhen the South America plate was nearly stationary over theunderlying mantle. Melting was enhanced by hydration of themantle during Paleogene subduction. Crustal contamination wasminimal in a refractory crust that had been extensively meltedin the Jurassic. Eruption began with low-volume intraplate alkalinemafic flows with depleted Nd–Sr isotopic signatures. Thesewere followed by voluminous 29–25 Ma tholeiitic maficflows with flat light and steep heavy rare earth element (REE)patterns, intraplate-like La/Ta ratios, arc-like Ba/La ratiosand enriched Sr–Nd isotopic signatures. Their source canbe explained by mixing EM1–Tristan da Cunha-like and depletedmantle components with subduction-related components. Post-plateau24–17 Ma alkaline flows with steep REE patterns, highincompatible element abundances, and depleted Sr–Nd isotopicsignatures mark the ebbing of the mantle upwelling. KEY WORDS: Somuncura plateau; slab interaction; Patagonia; large igneous province (LIP); plume-like upwelling |
| Keywords: | : Somuncura plateau slab interaction Patagonia large igneous province (LIP) plume-like upwelling |
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