Magmatismo, hiatus y tectonismo de Ia Sierra Madre Occidental y del Cinturón Volcánico Mexicano

Abstract

Space distribution of radiometric data - from 40 million years (Ma) to present - of rocks sampled in the Sierra Madre Occidental (SMO) and the Cintur6n Volcanico Mexicano (CVM: Mexican Volcanic Belt) provinces, allow to recognize three time intervals with distinctive lack of volcanic activity (volcanic hiatus): 28-25 Ma, 17-15 Ma and 7-5 Ma, approximately. The first seems to coincide with the end of a compressive phase of deformation before the Basin and Ranges deformation phase. The end of the second hiatus seems to point out the start of the basamental volcanism of the CVM and is related to the compressive phase from Middle-Upper Miocene. The last hiatus is noticeable only at the western and Eastern portions of the CVM; its end indicates the beginning of CVM typical volcanism, and it extends to about 3 Ma ago in the eastern portion. Configuration of radiometric age data also suggests the existence of a volcanic province which has an intermediate age between the SMO and the CVM; that volcanic province would be the basement of the CVM. In this context, the Taxco-Queretaro fault plays an important role as the eastern boundary of the SMO volcanism.