THE PUERTA DEL SOL METAMORPHIC CORE COMPLEX: TRACE ELEMENT AND ISOTOPIC GEOCHEMISTRY, COMPARISON BETWEEN LARAMIDIC PLUTONS IN CENTRAL SONORA, MEXICO

In the state of Sonora in northwestern Mexico, there is a widely recognized orogenic phase that spans from late Cretaceous through early Tertiary known as the Laramide orogeny. This orogeny is characterized by a major magmatic event that generated, among other phenomena, the intrusion of several batholitic bodies that stretch along the western North American coast. The source of this huge flare of mainly calcalkaline magmatic intrusions is produced by the interaction between the Farallon oceanic plate and the North American continental plate. During the late Miocene the large scale exhumation of large deep-rooted plutonic rocks which were over-printed by a mylonitic deformation by means of low-angle normal faults are commonly known as metamorphic core complexes.

The footwall plutonic rocks of the Puerta del Sol core complex are made up of a Eocene and a Miocene magmatic pulse. Mid-Eocene intrusions consists of the calcalkaline Puerta del Sol granodiorite (49 Ma; U-Pb) and the peraluminous, two-mica and garnet bearing Oquimonis granite (42 Ma; U-Pb). The early Miocene intrusions consist of the gabbroic El Garamabullo pluton (20 Ma; U-Pb) and the Las Mayitas granodiorite (20 Ma; K-Ar in biotite), both of which are thought to be related to a great number of mafic dyke swarms that cross-cut the Sonoran Laramide batholiths.

We thus present in this work new geochemical data (Sr, Nd and Pb system isotopic geochemistry) from each pluton of the Puerta del Sol metamorphic core complex. Major and trace element composition of the Puerta del Sol footwall rocks indicate calc-alkaline differentiation trends pointing towards a continental magmatic arc tectonic setting, while isotopic geochemistry data suggest a contribution from continental crust. This data is compared to other major, trace-element and isotopic geochemical analyses from Sonoran Laramidic plutons presented in previous works to help understand how the magmatic activity along the Laramide magmatic arc in Sonora has evolved.