The metamorphic complexes of the Patagonian and Fuegian Andes

Abstract

The Patagonian and Fuegian Andes are made up in part by late Paleozoic to Mesozoic metamorphic complexes. The mostly low grade late Paleozoic Eastern Andes Metamorphic Complex (EAMC) crops out to the East of the Meso-Cenozoic South Patagonian batholith (SPB), which intruded the metamorphic complexes. The protholit of the EAMC was likely deposited in a passive margin setting and at the Puerto Eden area underwent Late Jurassic sillimanite grade and migmatite local metamorphic conditions. It is suspected, but not proven, that the Cordillera Darwin Metamorphic Complex is a higher grade metamorphic complex equivalent of the EAMC. West of the SPB, paleo subduction complexes occur and are represented by the allochtonous Madre de Dios terrane. This terrane is composed of the ocean floor lithologies of the Denaro Complex topped by the Tarlton limestones that represent a guyot assemblage. The low grade continent derived Duque de York complex was deposited down top of the ocean floor lithologies. Further west, the blueschist bearing Middle Jurassic Diego de Almagro Complex, with psammopelitic, mafic and siliceous volcanic rock protoliths, evolved deep in a subduction zone during the Cretaceous. The possibility that the Antarctic Peninsula was located west of the present margin of South America is discussed.