The Paleozoic Central Patagonian Igneous Metamorphic Belt: its geodynamic and tectonic interpretation based on paleogeographic reconstructions

Abstract

On the southwestern margin of the North Patagonian Massif (Argentina), there is a NW–SE trending belt consisting of igneous and metamorphic rocks that is named the Central Patagonian Igneous Metamorphic Belt. It defines the boundary between the mentioned massif and southern Patagonia (including the Deseado Massif). It is debatable whether this belt belongs to an orogen generated by accretion or collision and whether it was created in a single event or over the course of several events. Paleogeographic reconstructions were conducted to answer this query, confirming that there are tectonic processes involved in two events: the Chanic (Devonian) and the Gondwanan (late Carboniferous–early Permian) events. They show a movement of South America toward the SW during which an accretionary orogen was built during the Chanic event between ca. 400 Ma and ca. 360 Ma. Later, the paleogeographic reconstructions show an abrupt change in the movement of South America; it is proposed that due to this movement, the previously built orogen collapsed between ca. 360 Ma and ca. 330 Ma. During the Gondwanan event, the subduction surrounding Pangea in the Patagonian belt caused plutonic emplacement in the already-existing orogen structures and paleogeographic reconstructions depict South America with a movement toward the northeast, which involves a displacement due to a slab pull from the northern Paleotethys Ocean boundary. It is further supported that lateral displacement between Gondwana domains brought forth by this slab pull is what led to the assembly between the North Patagonian Massif and southern Patagonia.