Basaltos de San Pablo: un bloque de un arco de islas en el norte de la cordillera Central de Colombia. Caracterización petrográfica y química

Abstract

The San Pablo Basalts constitute an exotic block of volcanic rocks that crop out next to marine sediments, located in the Northern part of Colombia ́s Central Cordillera, between metamorphic blocks of the Cajamarca Complex and intruded by the Antioquia Batholith, Upper Cretaceous in age. The San Pablo Basalts are composed of basalts (spilitic diabases), with intergranular to phiticsubophitic and occasionally porphyritic and variolitic-subophitic textures, similar to the oceanic crust rocks of the Quebradagrande Complex and the San Jose de Urama Diabases. The higher oxides results suggest that the rocks correspond to calc-alkaline, basalts and basaltic andesites, with SiO2 contents between 43.13% and 55.36%, MgO concentration ranges between 5.85% and 9.45% and TiO2 values between 1% and 2%. Multi-element diagrams of rare earth elements and trace elements show a negative Nb anomaly and positive anomalies of Cs, Ba, K and Pb, which suggests an arc environment with an REE trend similar to MORB-type oceanic crust basalts in the less differentiated rocks, but with higher Th values, which relates them to an island arc environment.