The Guerrero suspect terrane (western Mexico) and coeval arc terranes (the Greater Antilles and the Western Cordillera of Colombia): a late Mesozoic intra-oceanic arc accreted to cratonal America during the Cretaceous

Abstract

The Guerrero suspect terrane, composed of Late Jurassic-Early Cretaceous sequences, extends from Baja California to Acapulco and is considered to be coeval with the late Mesozoic igneous and sedimentary arc sequences of the Greater Antilles, the West Indies, Venezuela and the Western Cordillera of Colombia. These sequences represent the remnants of an arc which accreted to the North American and northern South American cratons at the end of the Cretaceous. In western Mexico, the arc sequences built on continental crust consist of high-K calc-alkaline basalts, andesites and rhyolites enriched in LREE with abundant siliceous pyroclastic rocks interbedded either with Aptian-Albian reefal limestones or red beds. They do not show magmatic changes during the arc development. In contrast, the arc sequences built on oceanic crust show an evolution with time. Arc activity began with the development of depleted low K-tholeiitic mafic suite (Guanajuato igneous sequence), followed first by mature tholeiitic basalts and then by calc-alkaline olivine basalts interbedded with micritic limestones and radiolarian oozes of Early Cretaceous age. At the end of the arc growth, during Aptian-Albian times, calc-alkaline pillow basalts and and esites poured out in the volcanic front while shoshonitic olivine basalts extruded in the back arc. The tholeiitic and shoshonitic mafic rocks as well as the calc-alkaline lavas are mildly enriched in LREE, Y and Nb and show high ϵ Nd ratios, typical of oceanic arcs. In contrast, the calc-alkaline mafic suite enriched in LREE, Y and Nb exhibits lower ϵ Nd ratios suggesting that it was derived by the partial melting of a mantle source contaminated either by Paleozoic subducted sediments or old source enrichments (OIB). The Cretaceous arc rocks of the Greater Antilles, interbedded with and/or capped by Aptian-Albian limestones, the Cretaceous andesites of northern Colombia, the Cretaceous tholeiitic and calc-alkaline volcanic rocks of Venezuela, and the Cretaceous volcano-plutonic arc assemblage of Tobago share a similar magmatic evolution with the western Mexican oceanic arc. The tholeiitic plutono-volcanic assemblage of Tobago, depleted in LREE and characterized by high ϵ Nd values is similar to the Guanajuato volcano-plutonic sequence of Mexico, considered to represent the pristine stage of the arc. The mature tholeiitic sequences exposed in the proto-Caribbean arc show flat to moderately enriched LREE patterns like those of the Guerrero terrane. However, felsic plutonic and volcanic rocks prevail in the Caribbean. Calc-alkaline suites, accompanied locally by shoshonitic lavas, characterize the end of arc magmatic activity in both places. Thus, the geochemical features of the Late Jurassic-Cretaceous arc series of the Guerrero terrane and the proto-Caribbean are consistent with the following plate tectonic model. The Guerrero terrane and the proto-Caribbean probably belonged to the same intra-paleo-Pacific arc system the development of which was related to the subduction of oceanic basins fringing the North and northern South American cratons. This subduction zone was WSW dipping. While subduction was going on, these magmatic arcs drifted, moved closer to the North and South American cratons, and finally collided with the American borderlands at different periods during the Cretaceous. The late Mesozoic Guerrero and proto-Caribbean arc sequences show striking similarities with the Miocene calc-alkaline lavas dredged from the Banda Ridges, the North Marianas Seamount Province, and the Halmahera and Philippine arcs. We suggest that the diverse but mostly submarine segments of this late Mesozoic intra-Pacific arc rimmed the North and South American cratons as much as these Tertiary arcs rim Southeast Asia.