Paleomagnetism and geochemistry of Upper Cretaceous Basalts of Patagonia

CLAUDIA BEATRIZ ZAFFARANA; SILVIA LEONOR LAGORIO; RUBÉN SOMOZA

Tandil

Congreso; Segunda Reunión Bienal de la Asociación Latinoamericana de Paleomagnetismo y Geomagnetismo (LATINMAG); 2011

Comité integrado por científicos de paises latinoamericanos

A paleomagnetic study on nine sites from lavas at the Upper Cretaceous Tres Picos Prieto locality (43º 50´S and 70º3´W), Patagonian Plateau Basaltic Province, revealed that a ca 300 m thick pile of basalts accumulated during three discrete (i.e. temporally separated) volcanic episodes. The chemistry of these lavas shows characteristics compatible with both intraplate and subduction-related magmatism, with the latter having a more important contribution in the younger lavas. Overall, we interpret these rocks to be transitional basalts in a supra-subduction environment. The Late Cretaceous to Cenozoic Patagonian Plateau Basaltic Province crop out from eastern Patagonia to the cordillera, and their genesis has been associated to different tectonic processes, even for spatially separated rocks of the same age. Since the development of the magmatic province is contemporary with the stage of fast westward drift of South America, we proposed that magma generation and upwelling due to rapidly shearing asthenosphere could have induced circulatory flow associated to asperities in the lithosphere-asthenosphere interface (shear-driven upwelling, Conrad et al., 2010). This geodynamic process should be evaluated as a possible contributing mechanism when exploring the genesis of most of these transitional magmas.