Plio-Quaternary tectonics of the Central Mexican Volcanic Belt and some constraints on its rifting mode

Abstract

Stratigraphy and structure of the central sector of the Mexican Volcanic Belt and adjoining areas were investigated in order to evaluate its Plio-Quaternary tectonic evolution, the stress directions, and their relative values. Three main periods, characterized by different mechanisms of deformation limited to the MVB area, may be grouped in a single deformation cycle. The Late Pliocene period was characterized by strike-slip faulting induced by a horizontal ENE-WSW maximum principal stress (d) and NNW-SSE least principal stress (r3). In Early-Middle Pleistocene left-lateral normal faulting occurred with the same r3 and a ENE-WSW intermediate principal stress (r2). During Late Pleistocene-Holocene, normal faulting with a slight clockwise rotation of r3 developed. These structures correspond to the surface expression of E-W left-lateral wrenching which was initially parallel and later divergent. The kinematics and the uniformity of the stress trajectories during Plio-Quaternary times suggest plate tectonic control and a passive mode of rifting. In this framework the large amount of magma extruded is believed to be produced by a thermal anomaly induced by the rifting and affecting also the subducted slab.