New U-Pb LA–ICPMS geochronological evidences of a Neoproterozoic arc along the easternmost Pampean ranges sequences

LISANDRO GASTÓN RODRIGUEZ; MONICA P ESCAYOLA; RAMOS V.; MIGUEL BASEI

Santiago de Chile

Simposio; XII SSAGI; 2022

Sociedad Geológica de Chile

One of the leading models proposed for the geotectonic evolution of the eastern Sierras Pampeanas [1], proposes a magmatic arc collision against the Rio de La Plata Craton (RPC) during the Neoproterozoic, followed by a change of subduction polarity [2] and acretion of the Pampia terrane. We sampled and dated zircons by U-Pb ages from the easternmost metacarbonate rich sequences association, which constitute the first outcrops to the west of the RPC. Studied rocks are metacarbonates and amphibolites never dated before, which could be interpreted either as: (i) remaining sequences of the cratonic passive margin, (ii) part of the Neoproterozoic arc proximal deposits [2], or (iii) the Pampia terrane passive platform. Outcrops south of the Sierra Chica, located 5 km west of San Agustin village, shows interfingered silicate-rich and metacarbonate deposits that could be interpreted as arc related tuffs preserved in the island shelf deposits, linked to phases III and IV of Oceanic Arc Depositional Systems (OADS) [3]. Determinations on zircon (n=50) yielded maximum depositional ages of 569 Ma, and metamorphic events during the Cambrian and Ordovician