Mexican Volcanic Belt: an intraplate transform?

Abstract

Temporal and "geometric" evidence suggests that several regional tectonic events were especially important contributors during the evolution of the Mexican Volcanic Belt (MVB). These include (1) development of a tectonic zone of weakness in the area of the present MVB, followed in Cenozoic time by (2) tectonic activity in the Caribbean region that includes sea-floor spreading in the Cayman Trough, (3) progressive southward cessation of subduction along the west coast of North and Central America, and (4) development of the proto-Gulf, Gulf of California, and basin-and-range (extensional) faulting north of the MVB. The zone of weakness fixed the location and orientation of the MVB. Subsequently, in response to cessation of subduction along the coast of North America, extensional tectonics developed to the north of the zone. To the south, where subduction of Chilean-type prevailed, extensional tectonism was inhibited. Thus, the zone of weakness became a belt of tectonic accomodation, perhaps associated with internal extension, between regions of contrasting structural kinematics. In short, it became an (leaky) intraplate tr-ansform (in the sense of Davis, 1980) along which the volcanism was both permitted and localized. Paradoxically, this interpretation implies that volcanism along the MVB is more closely allied to the cessation of subduction north of the MVB than to ongoing subduction to the south. It further implies that the MVB is fundamentally unlike the typical volcanic arcs of the Pacific rim.