Composición química (elementos mayores) de los magmas en el Cinturón Volcánico Mexicano

Abstract

A compilation is presented of 1797 major-element analyses of igneous rocks belonging to the Mexican Volcanic Belt (MVB). The geological si¡nificance of these geochemical data is inferred from a series of histograma and diqrams (bivariate and ternary) following a subdivision of this volcanic province into 10 morphological blocks. Although there has been a spectacular in crease in the number of major-element analyses since the fttst compilation by Pal et al. (1978) having that number increased from 330 to 1797 in the year 1985, it is evident that there still exists a great scarcity of su eh geochemical data in certain zones of the MVB (e.g: blocks V, VII and VIII). From the present compilation and analysis it is observed that both calc-alkaline and alkaline magmas have erupted in the westem and eastern extremes of the MVB, Whereas calc-alkaline products domina te in the central part of the Belt. Thus in contrast with the other circum-Pacific volcanic provinces the MVB does not show a lateral varlation in its volcanic products because a gradual increase in their alkali-contents is not observed as the distance between the magmatic arc and the subduction zone increases. On the other hand, the volcanic products of all the important strato-volcanoes show a somewhat similar evolution as judged from the various binary and temary diagrams, suggesting the existence of magmatic differentiation dominated mainly by fractional crystallization and accompanied by magma mixing at sorne stage of their evolution.