Devonian magmatism in the Coastal Ranges of the Chilean Lake district: The Zarao Metatrachyte

Abstract

The Zarao metatrachyte is a small and isolated Early-Middle Devonian felsic subvolcanic intrusion spatially associated with mafic schists. It was initially included in the ‘Metabasitas de Estaquilla’, a sub-unit of the Permian to Triassic Bahia Mansa Metamorphic Complex (Duhart et al., 2001) although no contact relationships can be seen in the field. It is located on the eastern slope of the Coastal Ranges of the Lake District (c. 41º30’S), around 50 km west of Los Muermos (Fig 1). Between 39º and 43ºS, Devonian magmatism is interpreted as forming two discontinuous belts of granitoids, one located near the western edge of the North Patagonian Massif and the other in the western slope of the main Andes – the latter along the strike of the Liquiñe-Ofqui Fault Zone (Fig. 1). Both were generated in a supra-subduction zone environment (Quezada et al., 2015) and zircon O-Hf isotope data indicate that continental crust contributions to the magmas are significant in granitoids of the NPM but absent in the plutonic rocks of the Chilean Andes (Hervé et al., 2016).