Abstract

LOPEZ C., ADRIANA ; SIERRA L., GLORIA M.  and  RAMIREZ S., DIEGO A.. NEOGENE VULCANISM IN SOUTHWEST ANTIOQUEÑO AND ITS TECTONIC IMPLICATIONS. Bol. cienc. tierra [online]. 2006, n.19, pp.27-42. ISSN 0120-3630.

The Combia Formation outcrops in northweat colombiano, end of the w:st="on"> Cauca Basin which lies between the Central and Western Cordillera, approximately 6 °N, 75° W as corresponds to a volcano sedimentary sequence originated by several volcanic-magmatic pulses recorded between 10 and 6 Ma and deposited under fluvial and lacustrine conditions. It appears that these magmatic events occurred under a transpresional regime associated with the accretion of oceanic material (The Choco Block) in the northwester margin of South America and the development of pull-apart or backarc basins related to pre-existing structures associated with the Romeral System Fault that acted as channels through which magmas ascended and emplaced. The presence of garnet crystals of pyrope type along with some piroclastic flows and the  tholeitic affinity suggests a mantle origin for the first pulses of this volcanism. As magma evolved and basins closed, the magma underwent crustal contamination and volcanism turned calc-alkaline in affinity and explosive, as a result, several volcanic cones formed along the Cauca basin.

Keywords : Combia Formation; Neogene Volcanism; Pyrope Garnet; Southwest of Antioquia; Fisural Volcanism.

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