Boletín de Ciencias de la Tierra
versión impresa ISSN 0120-3630
DUQUE TRUJILLO, JOSÉ FERNANDO; TORO VILLEGAS, GLORIA ELENA; CARDONA MOLINA, AGUSTÍN y CALVACHE VELAZCO, MARTA. GEOLOGY, GEOCHRONOLOGY AND GEOCHEMISTRY OF MORASURCO VOLCANO, PASTO, COLOMBIA. Bol. cienc. tierra [online]. 2010, n.27, pp. 25-36. ISSN 0120-3630.
A field study of the Morasurco volcano in southern Colombia allows the understanding of volcanic geoforms and to identify five lava flows and three pyroclastic flows from its major volcanic activity. Furthermore, the existence of two eruptive stages was stablished, the first, an effusive stage with eruption of large amounts of basaltic lavas, and a second stage with partial destruction of the volcanic edifice and the emission of large amounts of pyroclastic material that cover a large portion of the studied area. The first stage has a composition which varies between two pyroxene basaltic fenoandesite and hornblendic fenoandesite of the calcalkaline series of medium K2O. The petrography as well as other disequilibrium textures, indicate magma mingling within the magmatic chamber. Zircon fission tracks and K-Arages of 2.02±0.27 Ma, 1.95±0.52 Ma and 1.94 0.28 Ma were obtained for the effusive activity and an age of 1.94±0.13 Ma was obtained for the explosive event that destroyed the volcanic cone. Major and trace elements from five samples show constant geochemical characteristics along the volcanic evolution. The constant geochemical composition and the similarities seen when compared with published results from the Galeras Volcano suggest that these two volcanic centers may belong to the same magmatic system.
Palabras llave : Volcanism; Pliocene; geochemistry; Galeras volcano; Morasurco; Pasto; Colombia.