Magma hybridization, mingling, and recycling in the Manzanillo plutonic complex, Mexican Cordillera

Abstract

ABSTRACT The Manzanillo Plutonic Complex (MPC) forms part of the Mexican Cordilleran plutonic belt at ~ 19°N. A special feature of the MPC is more than 125 km2 outcrops of gabbroic rocks, thus constituting the largest body of this lithology along the belt. The overall MPC composition is heterogeneous including gabbros and granitoids with or without hybridization structures and minor alkali-rich granites. In contrast to other Cordilleran plutons, MPC intrusives are often strongly deformed and foliated heterogeneous structures with evidence of magma mingling and mixing. U-Pb emplacement and Rb-Sr and K-Ar cooling ages are between 59 and 73 Ma. Four U-Pb gabbro ages from 63 to 65 Ma define the peak of the hybridization event. Although geochemical analyses display considerable differences within MPC members, their Sr-Nd isotopic signatures are highly homogeneous with magmatic primitive εNd parameters between +5 and +6 and low 87Sr/86Sr around 0.7035. Geothermobarometric data provide information for a hot environment for the gabbroic pulse at 3.4–4.9 Kb and >900°C, indicative for depths ~15 km. On the other hand, granitoids show typical Cordilleran characteristics with lower temperatures and shallow emplacement conditions. The MPC shows a unique petrogenetic evolution in the Cordilleran arc; there is no evidence for a relation to other events such as the Early Cretaceous Alisitos arc.