Gravity modelling of regional and upper mantle structure of the Guerrero terrane - 1. Colima graben and southern Sierra Madre Occidental, western Mexico

Abstract

Crustal thickness increases from the Pacific ocean margin towards the continental interior, presenting higher value beneath the plateaus of the Trans-Mexican volcanic belt (TMVB) and the Sierra Madre Occidental (SMO). The region appears to be under regional isostatic equilibrium. Results of the gravity study suggest a crust of continental (or transitional), character, with a thick lower crust of metamorphic or igneous nature. Two-dimensional crustal models are compatible with the occurrence of a low- to intermediate-density layer at the base of the crust which has been proposed as reponsible for the uplift mechanism of the volcanic plateaus. Geotherms constructed from travel time analysis of surface Raleigh and Love waves for central Mexico indicate a high thermal regime with partial molten material at the base of the crust. -from Authors