Las Cañas plutonic complex: Geodynamic implications during the Famatinian magmatism in northeast of Sierra de San Luis, Argentina

Abstract

Las Cañas Plutonic Complex (LCPC) is a small representative of the Famatinian Ordovician plutonism (470.4 ± 8.1 Ma) located in the northeastern sector of Sierra Grande de San Luis, Argentina. The LCPC was emplaced into a metasedimentary sequence, which reached their metamorphic climax under high-temperature/low-pressure conditions (∼680 ± 37 °C and 550 ± 120 MPa). The bodies of the LCPC are zoned by rocks of different compositions that represent ultrabasic, basic, intermediate and acidic trends (hornblendites, gabbros, tonalites, and granodiorites). Their petrological, mineralogical and geochemical characteristics indicate that multiple processes formed them, mainly crystal fractionation of magnesian, calc-alkaline and metaluminous magmas (typical of arc), but also different assimilation degrees of crustal melts from the fusion of metawackes involving AFC processes. Fieldwork (structural and petrological data), the geochemical characteristics of rocks [eg. Low Sr/Y and (Gd/Yb)C- N], and thermobarometric results, indicate a relatively shallow fractionalization for the LCPC, which is in line with a pre-collisional arc stage linked to an extensive retro-arc setting for the Famatinian orogeny in Sierra de San Luis.