Fábrica magmática y relaciones de contacto de los granitoides intrusivos en el Prado de las Pozas, zona central del macizo de Gredos, batolito del Sistema Central, España

Abstract

In its central area, the Gredos massif is comprised of three intrusive granodioritic to monzogranitic sheets separated by tabular to lensoidal metasediment bodies with varying metamorphic grades. At the mesoscopic scale, intrusive granitoids cut part of the complex migmatitic structures found in the Prado de las Pozas migmatitic hornfelses, but are also affected by late shears and folds together with the migmatític layering, which suggests that the emplacement of intrusive magmas occurs during a intense deformational process and the main anatectic episode in the host metasediments. This deformational process mainly occurs under magmatic conditions, as indicated by the magmatic foliation and structures marked by the ubiquitous Kfs-megacrysts present in the granitoids. Magmatic fabric might be the result of the complex interaction between internal (flow) and external (tectonic) stresses during ascent, emplacement and crystallization of magmas. The large crystal size, the euhedral shape and the inclusion alignment are some of the features that point to a magmatic origin for the Kfs-megacrysts, which may result from the increase of K2O in the granodioritic liquids originated during the Ms and Bt dehydration melting in metasedimentary host rocks.