INTRAOCEANIC SETTINGS OF THE WESTERN MEXICO LATE JURASSIC-EARLY CRETACEOUS ARC SEQUENCES - IMPLICATIONS FOR THE PACIFIC-TETHYS GEODYNAMIC RELATIONSHIPS DURING THE CRETACEOUS

The Guerrero suspect terrane composed of Late Jurassic-Early Cretaccou s sequences, extends from Baja California up to Acapulco and is consid ered to be coeval with the Late Mesozoic igneous and sedimentary arc s equences of the Greater Antilles, Venezuela and Western Cordillera of Colombia. New geological, petrological and geochemical data from centr al and southern Mexico, led us to propose a new model for the building of the Alisitos-Teloloapan arc. This arc, partly built on the Pacific oceanic lithosphere and partly on continental fragments, could be rel ated to the subduction of an oceanic basin - the Arperos basin - under the Paleo-Pacific plate. This subduction was dipping southwest. At th e beginning of the magmatic activity of the oceanic segment of this ar c, depleted tholeiitic basalts were emitted in a submarine environment below the CCD. While subduction was going on, the arc magmas evolved from LREE depleted tholeiites to slightly LREE enriched tholeiites and then, to calc-alkaline basalts and andesites enriched in LREE and HFS E. Concurrently, the arc sedimentary environment changed from deep oce anic to neritic with the deposition of Aptian-Albian reefal limestones , at the end of the arc building. In the continent-based segment, the arc magmas are exclusively differentiated calc-alkaline suites deplete d in HREE and Y, formed of predominantly siliceous lavas and pyroclast ic rocks, emitted in a sub-aerial or shallow marine environment. Thus, taking into account this above mentioned model, the Cretaccous volcan ic series, accreted to the margins of cratonal America, in Colombia, V enezucla, Greater Antilles and Mexico, could be related to the same we st-south-west dipping subduction of oceanic basins, fringing the North and South American continental cratons and connected directly with th e inter-American Tethys. While the subduction was proceeding, this mag matic arc drifted towards the North and South American cratons and fin ally, collided with the continental margins at different periods durin g the Cretaceous.