|Earth and Environmental Sciences
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Volcanics from cinder cones and lava flows collected in the Barrancas region of northern Patagonia were analyzed for major and trace element concentrations, and for Sr, Nd, and Pb isotopic ratios. The analyses revealed that both an arc-like and intraplate-like geochemical signature occurs within this narrow geographic area, a 15km wide transect parallel to the Chile Trench. Several samples reflect the typical, yet muted characteristics of arc-type rocks displaying Nb-Ta negative anomalies, LILE enrichments and HFSE depletions. This manifestation suggests subduction flux transfer to a region of the mantle normally beyond the spatial extent of subduction related volcanism sometime within the last 3.5 Ma. Depletions of HREEs in other Barrancas rocks indicate that a component of deeper mantle plume material is also available for volcanics of this region. The analysis of geologic features across the Andes at 35-39°S in conjunction with geochemical profiles of regional centers allows to be presented here, a plausible mechanism for transport of both the IAB and OIB components to the mantle region below Barrancas.