A post-collisional batholith from Southern Iberia rooted in the Earth’s mantle: Los Pedroches batholith

Abstract

The Los Pedroches batholith (SW Spain) is one of the most salient igneous alignments of the Iberian massif. The batholith is considered one of the best examples of post-collisional batholiths of Iberia and is dominated by a biotite granodiorite that was emplaced in the shallow crust postdating the main deformation phases of the Variscan orogeny. In the Quintana de la Serena area, to the northwest of the batholith, granodiorites were partially emplaced into dacites characterized by the presence of abundant orthopyroxene. The quality of outcrops and abundant quarries in the area, together whit the near absence of local crustal contamination, make this zone an ideal location for petrogenetic studies about the origin of granodiorite magmas and their related microgranular enclaves. We present in this paper new SRHRIMPII-based zircon geochronology data that indicate orthopyroxene-bearing subvolcanic rocks emplaced and cooled at the age of 310 ± 2 Ma, slightly earlier than the intrusion and cooling of the massive granodiorites (307 ± 1 Ma and 306.6 ± 0.7 Ma) and their related mafic microgranular enclaves (307.8 ± 0.8 Ma). Whole rock geochemistry demonstrates that the three groups of rocks, dacites, granodiorites and mafic microgranular enclaves, define a coherent geochemical trend indicating that they are cogenetic and related by fractionation of a common parental magma. This study proves the role played by intermediate magmas of sanukitoid affinity in the generation of the most abundant and massive granodiorite rocks that form large post-collisional batholiths in Iberia.