Petrología, estructura y geocronología de los granitoides del batolito de Gredos (sistema central español)

Abstract

This paper describes in detail an example of a calc-alkaline batholith, located in the Gredos massif (Spanish Central system batholith, Iberian Variscan massif), intruded into pelitic metasediments at shallow crustal levels. The field relations, geochemical data, geochemical trends and laboratory experiments strongly suggest a process of bulk assimilation of the host metasediments by the intruding Bt granodiorites to generate the Crd monzogranites. This work studies the emplacement mechanism of several tabular bodies of granodiorite and monzongranite magmas along large-scale shear zones active during the D3 phase of Variscan deformation of the Central Iberian Zone (Iberian Massif). A new model of syn-tectonic, sequential emplacement of magma batches accounts for the complex spatial variation of magmatic and solid-state fabrics. This work also adds information about the characteristics of the last stages of the Variscan orogeny in the Iberian Massif, associated with the tightening of the Ibero-Armorican Arc. According to geochronological data, the first intrusive batch is the Circo Bt granodiorite (floor layer), followed by the Barbellido-Plataforma Bt-granodiorite (roof layer) and the Pozas Crd monzogranite, which intruded between previously emplaced layers. There's a 4-5 Ma delay between the successive magmatic batches. Therefore, the general structure is that of a layered intrusive complex, with distinct magma batches successively intruding a heterogeneous crust, which suffered a renewed episode of partial melted by the heat influx coming from magmatic batches.