Geochemical Signals in Southern Puna Magmas for Crustal Thickening and Mantle Enrichment Related to Lithospheric Delamination and Forearc Subduction Erosion in the last 14 Ma

KAY, S.M., COIRA, B.

Foz do Iguazu

Congreso; The Meeting of the Americas; 2010

American Geophysical Union

New and published chemical analyses of 14-0 Ma southern Puna backarc magmatic rocks record the mantle and crustal evolution of the plateau. As the underlying subduction zone first shallowed and then steepened, the plateau uplifted and the mantle was enriched in crustal components by delamination of basal crust and lithosphere and intense forearc subduction erosion as the arc front moved eastward. Mid to late Miocene shallowing of the subduction zone is supported by widespread backarc 14 to 8 Ma volcanic centers. Cr (to 450 ppm) and Sr (450-700 ppm)-rich mafic (51-55% SiO2) lavas that erupted from these centers at 14 to 10 Ma have marked HFSE depletion (La/Ta=30-60), Ba/La