MINERALOGY OF THE GAIRA SCHISTS: AN EXAMPLE OF METAMORPHIC ROCKS FROM THE SIERRA NEVADA DE SANTA MARTA, COLOMBIA

The Sierra Nevada de Santa Marta, Colombian Caribbean, groups the highest coastal mountains in the world. This mountain system is located north of the South American Andes and contains a great variety of igneous and metamorphic rocks with wide compositional variations. The area has been subjected to complex tectonic and orogenic processes due to the interaction of the Caribbean and South American plates, especially during the last 35 million years.

The Gaira schists, proposed as possible allochthonous fragments probably accreted during the Meso-Cenozoic (Tschanz et al., 1969, 1974; Doolan, 1970, Cardona-Molina et al., 2006), are a group of rocks with evidence of dynamic and regional metamorphism that is believed to have affected nearshore marine sediments. The mineralogical composition of numerous surface samples has been analyzed to test this hypothesis.

Our results suggest that sediments accumulated in shallow seafloors underwent burial and low to medium-grade metamorphism due to the activity of the Santa Marta - Bucaramanga fault. The subsequent rapid exhumation was accompanied by the emplacement of igneous intrusions of mafic composition.