Volcanismo riolitico en el Eje Neo volcanico Mexicano

Abstract

The Mexican Neovolcanic Belt is a plio-quaternary volcanic belt, of east-west orientation, that bisects central Mexico. It is formed by large andesitic stratovolcanoes, silicic volcanic centers, and extensive basaltic and an: desitic cinder cone fields. Five silicic volcanic centers have been recognized to date in the Neovolcanic Belt: La Primavera, Jal., Los Azufres, Mich., Amealco, Qro., Huichapan, Hgo., and Los Humeros, Pue .. These centers are located along the northern portion of the Belt, "behind" the front of the active andesitic stratovolcanoes. Toe volumes of rhyolitic and rhyodacitic magmas erupted in each one of these centers range from 10 to 150 km 3. In most of these centers sorne of the individual eruptive units are strongly zoned in composition, and in sorne instances span the range rhyolite to andesite. An exception is La Primavera, where only high-silica rhyolitic magma was erupted. In addition to these five centers, there are numerous other occurrences of rhyolitic volcanism throughout the Neovolcanic Belt; sorne of them might be related to large but as yet unrecognized volcanic centers, but others seem to represent isolated events. Toe silicic volcanism of the Neovolcanic Belt has two important economic implications: volcanic risk and geothermal energy. Among the known silicic centers, La Primavera represents the major potential hazard on account of its youth and proximity to the city of Guadalajara. With respect to geothermal energy, Los Azufres is a geothermal field currently under production, and La Primavera and Los Humeros are prospects currently under exploration. In ali three cases the reservoirs are located in zones of secondary permeability within the local volcanic basement.