Magmatic and seismic evidence for neogene crustal and mantle evolution under the Puna plateau of the Central Andes.

KAY, S.M.; COIRA, B.L.

Honolulu, Hawai

Congreso; 2017 GSA Cordilleran Section 113th Annual Meeting; 2017

The Geological Society of America

Crustal and mantle lithospheric delamination along with forearcsubduction erosion have become popular mechanisms for explaining processes operating along continental margin orogenic belts and have raised questions of the balance of creation and destruction of continental crust at active subduction margins. Evidence for changes in subduction zone geometry and crustal loss though delamination of thickened dense lower crust beneath the Central Andean Puna plateau comes from petrologic and geochemical studies of 1350°C at ~2 GPa followed by fractionation and mixing with melts of garnet-pyroxene bearing crust to produce the andesites and dacites. In accord, these lavas along with the Cerro Galan ignimbrites lie above a region where receiver functions indicate a lithosphere-asthenosphere boundary at ~60-80 km that lies below a regionally thin 45-55 km thick crust with a low Vp/Vs (< 1.70) ratio.