THE PUERTA DEL SOL PLUTONIC SUITE, A RECORD OF EOCENE TO MIOCENE PLUTONISM IN CENTRAL SONORA

The Puerta del Sol plutonic suite (PSPS) consists of mid-Eocene subduction-related granodioritic to granitic intrusions of the Sonoran Laramide Batholitic belt (SBB), and early Miocene gabbroic to granitic intrusions which are believed to be related to Basin and Range Metamorphic core complex (MCC) extension. Mid-Eocene intrusions consist of the calcalkaline, amphibole-bearing Puerta del Sol granodiorite (49 Ma; U-Pb) and the peraluminous, two mica-bearing Oquimonis granite (42 Ma; U-Pb). These plutons are typical and widespread in the SBB. The early Miocene intrusions consist of the gabbroic El Garambullo pluton (22 Ma; U-Pb) and the Las Mayitas granite, both of which are thought to be the source of a great number of dyke swarms that cut the SBB. Several relevant structural features in the PSPS which are related to Basin and Range extension include the MCC detachment fault in the western part of the area where PSPS is the footwall plate of this detachment. Also, along the contact of the two mid-Eocene intrusions, a mylonitic shear zone with an E-W trend was developed. The relation of this mylonitic gneiss with the detachment fault is still uncertain but it is believed to be also associated with the MCC. Studies in further structural, geochemical, and geochronologic features are still taking place to provide a better understanding of this area.