METAMORPHIC AND IGNEOUS ROCKS FROM THE MEDELLIN-YARUMAL AND SANTA MARTA AREAS, COLOMBIA AND THEIR Rb-Sr AGES

Abstract

The Medellín-Yarumal area is located in the western side of the cordillera Central, which occupies the middle of the three Andean ranges (Fig. 1). The Santa Marta area is situated in the western part of an isolated block of the Santa Marta mountains (Fig. 1), which is considered as a morphostructural continuation from the cordillera Central because of many lithologic similarities (Mac-Donald, 1969). Metamorphic rocks of the Santa Marta area are of greenschist or amphibolite facies and their radiometric ages range from Cretaceous (128 Ma) to Tertiary (33 Ma) (Mac-Donald et al., 1971; Tschanz et al., 1969, 1974). The petrology and geochronology of the Medellín-Yarumal area are not yet developed. Samples described in this paper were collected during the Andes Scientific Expedition conducted in 1972 by Shizouka University. In this paper corundum-bearing pelitic schists are described by Fujiyoshi and Tokuyama, and the Rb-Sr ages of some igneous and metamorphic rocks in the Medellín-Yarumal area, and of quartz diorite in the Santa Marta Batholith are measured by Ishizaka and Hayase.