Geochemistry and Sr-Nd-Pb isotopic constraints on the petrogenesis of Cenozoic lavas from the Pali Aike and Morro Chico area (52°S), southern Patagonia, South America

Abstract

Geochemical and isotopic analyses (Sr-Nd-Pb) of late Miocene to Quaternary plateau lavas from the Pali Aike and Morro Chico areas (52°S) were undertaken to constrain the melting processes and mantle sources that contributed to magma generation and the geodynamic evolution of southernmost Patagonia, South America. The Pali Aike and Morro Chico lavas are alkaline (Pali Aike, 45？49 wt.% SiO2;4.3？5.9 wt.% Na2O+K2O) and subalkaline (Morro Chico, 50.5？50.8 wt.% SiO2;4.0？4.4 wt.% Na2O+K2O), relatively primitive (Pali Aike, 9.5？13.7 wt.% MgO;Morro Chico, 7.6？8.8 wt.% MgO) mafic volcanic rocks that have typical intraplate ocean island basalt-like signatures. Incompatible trace element ratios and isotopic ratios of the Pali Aike and Morro Chico lavas differ from those of the majority of Neogene southern Patagonian slab window lavas in showing more enriched characteristics and are similar to HIMU-like basalts.On the basis of geochemical and isotope data and the available geological and geotectonic reconstructions, a link between the HIMU asthenospheric mantle domain beneath southernmost Patagonia and the HIMU mega-province of the southwestern Pacific Ocean is proposed.neration and the geodynamic evolution of southernmost Patagonia, South America. The Pali Aike and Morro Chico lavas are alkaline (Pali Aike, 45？49 wt.% SiO2;4.3？5.9 wt.% Na2O+K2O) and subalkaline (Morro Chico, 50.5？50.8 wt.% SiO2;4.0？4.4 wt.% Na2O+K2O), relatively primitive (Pali Aike, 9.5？13.7 wt.% MgO;Morro Chico, 7.6？8.8 wt.% MgO) mafic volcanic rocks that have typical intraplate ocean island basalt-like signatures. Incompatible trace element ratios and isotopic ratios of the Pali Aike and Morro Chico lavas differ from those of the majority of Neogene southern Patagonian slab window lavas in showing more enriched characteristics and are similar to HIMU-like basalts.On the basis of geochemical an