A Grenvillian granulite belt in the Colombian Andes and its relation to the Guiana Shield

Abstract

Precambrian high-grade metamorphic rocks emplaced tectonically in the Central and Eastern Cordillera of Colombia define a granulite belt which is lithologically, petrologically and geochronologically distinct from the adjacent part of the Guiana Shield. This Garzón-Santa Marta Granulite Belt was formed at the western border of the Early to Mid Proterozoic nucleus of the Shield by an orogenic event around 1.2-1.4 Ga. The Nickerie Metamorphic Episode, characterized in the whole western part of the Guiana Shield by mica age resetting around 1.2 Ga, extensive mylonitization along prominent ENE-WSW shear zones, and low-grade metamorphism, is brought into relation with this orogenic event. A continental collision model and a relationship with the Grenville Orogeny are suggested for this orogeny.