Estudio petrográfico y geoquímico del volcán Cotacachi – provincia de Imbabura

Abstract

The Cotacachi Volcano is located to the north of Western Cordillera of Ecuador. Comprised three litho-stratigraphic major units. Central Volcano: COTACACHI I (Base and Top) and COTACACHI II (Central Vent and Domes), Caldera: COTACACHI III-CUICOCHA (Pre-caldera dome, Pyroclastic Deposits and Post-caldera domes). It has been hit by at least two catastrophic events that destroyed the initial configuration of your building, and associated deposits are distributed to the northwest and northeast of the volcano. Petrography is represented by: COTACACHI I (basaltic andesites and andesites, 56-62 SiO2% wt), COTACACHI II (andesites, dacites; 60-62% SiO2 wt) and COTACACHI III-CUICOCHA (andesites, dacites, 61-63 SiO2% wt). They are typical rocks of continental arc with calc-alkaline affinity, the Cotacachi - Cuicocha rocks are the result of fractional crystallization, the trend about the rocks of Cuicocha is the result of different conditions of stability of magma in the chamber and/or reservoir. Magnesian rocks are in the tholeiitic limit of AFM diagram. Stratigraphically, northeastern debris avalanche is overlying the avalanche of Chachimbiro (Huanguillaro) and underlying the Imbabura volcano avalanche, positioning the occurrence of this event during the evolution of COTACACHI II-VENTO CENTRAL unit. Radiometric data reflect the Middle Pleistocene or earlier age for Cotacachi volcano.