K-Ar and geologic data bearing on the age and evolution of the Trans- Mexican Volcanic Belt.

Abstract

New and published K-Ar dates and geologic mapping in the W and central parts of the Trans-Mexican Volcanic Belt (TMVB) provide a basis for examining the evolution of Late Cenozoic volcanism in Central Mexico. The modern volcanic arc, composed principally of calc-alkaline andesite and dacite, was formed during the Quaternary and its development is intimately connected with the contrasting subduction regimes of the Rivera and N Cocos plates. Major andesitic centers in the western TMVB that lie above the subducted portion of the Rivera plate began to evolve between 0.6 and 0.2 Ma. However, in the central and E parts of the arc where subduction of the Cocos plate is taking place, the construction of andesite-dacite cones started considerably earlier at approximately 1.7 Ma.-from Authors