Temporal and Spatial Geochemical Variations in Patagonian Plateau Basalts: Implications for the Evolution of the Continental Lithosphere

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Continental back-arcs and within-plate basaltic volcanic provinces provide a view into the evolution of the mantle and lower crust beneath continents and the mass flux of materials that are subducted, but not extracted by arc volcanism. One of the largest of these continental basaltic provinces is the Patagonian basalt field in southern South America which extends discontinuously for 1800 km. east of the Andes and in places almost reaches the Atlantic coast. Basaltic volcanism ranges continuously in age from late Paleocene to Recent with activity concentrated in different places at different times. The geographical distribution of the basalts, their spectrum of ages, and their variable basement make the Patagonian plateau an excellent place to examine the cause and effect of varying tectonic conditions on the evolution of the basalts and more indirectly, the crust and mantle. An understanding of the source region of both arc and back-arc rocks is dependant on understanding which components change due to variable tectonic conditions and which are the result of long term mantle and crustal heterogeneities. This project is to examine temporal geochemical variation (using major and trace element chemistry; Nd, Sr and Pb isotopes; and some mineral chemistry) in two regions of the plateau. It complements the detailed studies being done in the Andean arc and the more limited studies of the late-Pliocene to Recent evolution of the plateau. ***//