Possible sources for monogenetic Pliocene–Quaternary basaltic volcanism in northern Patagonia

Abstract

The Pliocene- Quaternary times in Extra-Andean Patagonia are characterized by the effusion of intraplate basalts. This work is focused on those basalts outcropping between 40° and 46°S. The age of this volcanism varies between 0.23 and 5 Ma. Based on the general geochemical characteristics, geographic distribution, and structural framework of the region, we propose that the basalts originated in response to the back arc extension that caused the thinning, doming and fracturing of the lithosphere, and extrusion of mafic magmas with a relatively primitive nature and OIB-like compositions. The geochemical characteristics allow to distinguish three types of basalts: basanites, alkaline basalts and tholeiitic basalts, each one representing different sources and percentages of partial melt and implying a heterogeneous source. A source with these characteristics could be the lithospheric mantle.