OVERVIEW OF MESOZOIC SUBDUCTION-RELATED MAGMATIC EVENTS OF MEXICO AND THEIR RELATIONSHIP TO THE REST OF THE CORDILLERA

Four major Mesozoic tectonomagmatic events have been identified. During Permo-Triassic time a linear belt of granitoids in eastern Mexico suggest that a short span continental arc developed around 260-240 Ma. In contrast with the Cordillera, continental arc magmatism was not active during Carnian-Norian time. Instead, a passive margin seems to have developed along the western margin of continental Mexico. Norian pillow lavas, interbeded with volcaniclastic and siliciclastic rocks, and chert indicate that an oceanic arc/back-arc system developed in western Mexico. Recent detailed mapping in central and western Mexico allowed to record a major angular unconformity that places Callovian to Neocomian rocks on deformed and metamorphosed Triassic units. This suggests a major compressional between 208 and 158 Ma that might be related to the accretion of the Triassic oceanic island arc/back arc of western Mexico. This is contemporaneous to thrusting that formed the J-O angular unconformity in Southwestern US. A third magmatic event developed along North-Central Mexico during Callovian time. Subaereal volcanic and volcaniclastics rests unconformably on the Triassic allochthon, and are interpreted as a Jurassic continental arc. These units are transitionally overlain by limestone of Kimmerigdian to Campanian age. Stratigraphic and geochemical data suggest that magmatism might have migrated westward during Late Jurassic to Early Cretaceous, forming the arc(s) system of Guerrero and Alisitos terranes. Both are in part floored by Early Mesozoic deformed rocks of oceanic affinity, and are characterized by large volumes of Late Jurassic-Cretaceous submarine subaereal volcanism of arc affinity. Subduction accretionary prisms are found at the western side of the terranes, suggesting that subduction was dipping toward the east. At least the Guerrero terrane was a marginal oceanic arc (Japan type) during Tithonian-Early Albian time. This arc was thrusted eastward and was placed against nuclear Mexico between 105 to 90 Ma. Large granitoids that cut the deformed volcanic Cretaceous arc suggest that subduction related volcanism was re-established during Late Cretaceous-Cenozoic time.