Low-grade metamorphism of Mesozoic and Cenozoic volcanic sequences of Patagonia, Chile (43-46°S)

Rocks belonging to various units from the Jurassic to the Neogene were studied in the Chilean Patagonian area between 43 and 46°S. All these rocks were affected by very low to low grade metamorphism in the zeolite, prehnite-pumpellyite and greenschist facies. Differences in grade are related to the age of the rock sequences with the youngest (Tertiary) metamorphosed in zeolite and the oldest (Jurassic) in greenschist facies. Temperatures for the metamorphic processes are in the range 120° to 340°C with P below 2kb. A thermal imprint of Cretaceous granitoids on the Jurassic rocks exists almost completely obliterating an earlier low-grade regional metamorphic pattern.