Geological and geochemical investigations on the eastern Trans-Mexican Volcanic Belt

Abstract

This paper reports upon geological and geochemical investigations of the easternmost extension of the Trans Mexican Volcanic Belt (T){VB). As a result of our work we prefer to consider that the TMVB terminates at the Gulf coast and not in ttie Altiplano area (e.g. Robín, 1981), with respect to a Pliocene-QuaterrÍary volcanic activity. During that time the volcanism is of calcalkaline and alkaline character. The older volcanic activíty, e.g. of Míocene times, produced alkaline-calcalkaline igneous rocks in the Massíf de Palma Sola and calcalkaline igneous rocks in the western part of Mexico due to the eastwest migration of the subductíon of the Palaeopacific plate (Robín, 1976). Our geochemícal results neíther deny nor favour one single geological model and do not even exclude the mícroplate versíon of Shurbet and Cebull (1984). However, the geochemícal data cannot be explained by direct derivation of the volcanics from the oceanic lithosphere (e.g. Robín, 1981, 1982). lrrespective of thís fact, the volcanísm of the TMVB suggests to be caused or induced by the subduction of the Rivera and Cocos plate assocíatíon.