Holocene eruption history and magmatic evolution of the colima volcanic complex

Abstract

The Colima Volcanic Complex (CVC) erupts in both highly explosive and effusive fashion. Detailed radiocarbon dating of tephra fallout deposits exposed in road-cuts on the flanks of Nevado de Colima reveal at least 25 major Plinian eruptions occurred during the last 30,000 years. Deposits from these eruptions are basaltic to andesitic in composition showing an arc affinity in their immobile trace element abundance patterns. Detailed studies of the mineralogy, major and trace element and isotope chemistry reveal two distinct magma types erupted at the CVC during the Holocene. Group I, which comprise the bulk of eruption deposits, are calc-alkaline basaltic-andesites to andesites, while Group II magmas show strong petrological and geochemical similarities to alkaline lamprophyric magmas that formed monogenetic cinder cones to the east and west of the northern CVC. The presence of alkaline and calc-alkaline magmas at the CVC has allowed us to investigate the nature between these magma types in an arc setting. Data presented here reveal that the Group II magmas formed from pulses of alkaline melts intercepting the magmatic storage region of the CVC stratovolcanoes, mixing with the calc-alkaline Group I magmas. These pulses appear to have recurrence rates on the timescales of a few thousand years.