Geochronology and geochemistry of the Puerto Vallarta igneous and metamorphic complex and its relation to Cordilleran arc magmatism in northwestern Mexico

Abstract

New field, geochemical, Sr-Nd-O isotopic, and U-Pb geochronological data constrain the lithological diversity and geologic history of the Puerto Vallarta Batholith (PVB), which is one of the largest calc-alkaline intrusives along the Mexican Pacific coast. I-type granitoids were emplaced during the Late Cretaceous between 80 and 85 Ma in multiple magmatic pulses, confirmed by U-Pb and Rb-Sr geochronological data. PVB igneous rocks intrude paragneiss, schist, and orthogneiss of a recently discovered ∼400 km2 poly-lithological metamorphic unit which we named Yelapa-Chimo Metamorphic Complex (YCMC), located at the northern PVB coastline. 128–136 Ma zircon ages from western YCMC orthogneiss and amphibolite samples suggest the existence of an Early Cretaceous arc with a nearly contemporaneously accreted and collided component of M-type granites. These rocks can be regarded as the roots of an oceanic island arc in front of today’s southern Baja California and Jalisco. We called it Chimo Arc and it reveals an apparent resemblance to the Early Cretaceous (∼110 Ma) Alisitos arc in Baja California and the intruding plutons further to the northwest. Another PVB wall rock unit is represented by ∼160 Ma two-mica granites from the eastern part of the PVB, which are considered as part of a widespread, magmatically more evolved, Late Jurassic arc in western Mexico. These granites intruded a Late Triassic volcanosedimentary greenschist sequence, similar to that from the Arteaga Complex, which is the oldest lithological unit in the Zihuatanejo subterrane of the Guerrero tectonostratigraphic terrane. When comparing the vast PVB geochemical and isotopic dataset with those of the neighboring Late Cretaceous intrusive rocks, there is strong evidence for the PVB as being part of a southeast extended Peninsular Ranges Batholith. Our new geochemical and geochronological results contribute to a better understanding of the arc magmatism in northwestern Mexico.