The North American Cordillera is composed of exotic blocks accreted to nuclear America during the Paleozoic and Mesozoic times. The Guerrero terrane forms most of western Mexico and consists of Late Jurassic-Early Cretaceous arc sequences which are considered as developed in an active continental margin, linked to the subduction of the paleo-Pacific under the North American craton. The volcano-plutonic assemblages are predominantly mafic in composition and emplaced in pelagic, neritic or subaerial environments. The igneous rocks belong to tholeiitic, calc-alkaline and shoshonitic suites, and show high eNd ratios. These features indicate that these arc sequences developed in an intra-oceanic environment. The incompatible trace elements and Nd isotopic compositions of the basalts indicate that they probably derived from the partial melting of a N-MORB source, enriched or not by an OIB component, and more or less contaminated by pelagic or terrigeneous sediments. The intra-oceanic features of the Guerrero arc rocks and the absence of volcanic rocks interbedded within the Lower Cretaceous platform carbonates exposed in eastern Mexico suggest that an oceanic domain was located betwwen the Guerrero arc and the north of American craton.Remnants of this oceanic domain are presently exposed along the major thrust ENE verging where the Guerrero terrane tectonically overlap nuclear Mexico. They consist of pillow-basalts interbedded with Early Cretaceous pelagic sediments.Thus, the Guerrero arc growth is likely linked to the subduction of this oceanic domain, labelled Arperos basin, under the paleo-Pacific. Petrological and geochemical data on the Arperos basalts suggest that they derived from mixtures of OIB and N-MORB sources and developped in an assseismic ridge located near a spreading center.
