Abstract

A temporal and tectonic framework for the initiation of the Andean magmatism at its earliest stages is presented in this work, based on the current geological, geochemical, and geochronological information available in northern Chile between 20º and 30º S. This information has been collected from Triassic and Jurassic plutonic, volcanic, and volcanosedimentary units cropping out at the Coastal, Domeyko, Frontal Cordilleras, and the Precordillera, as two roughly parallel belts that extend for more than 1,000 km in the Chilean territory. Petrological and geochemical data suggest that the magmatism during the Triassic and Jurassic was dominantly intermediate in composition and had arc or subduction affinities. Even though magma sources should have had a clear mantle component, a crustal influence was more important during the Triassic. Geochronological information shows a significant magmatic lull near the Triassic–Jurassic boundary, associated with the retraction of the arc to the present-day Coastal Cordillera. Based on these data, the early stages of the Andean magmatism can be tracked backup to the Triassic igneous units in northern Chile.