THE DYKE SWARMS ASSOCIATED WITH THE LOS PEDROCHES BATHOLITH (IBERIAN MASSIF): THEIR RELATIONSHIP TO THE LATEST VARISCAN STRESS FIELD VARIATIONS

摘要

The Los Pedroches batholith (Iberian massif, SW Spain) is composed of a large biotite ± amphibole granodiorite pluton and several, smaller variably porphyritic, biotite ±cordierite monzogranite intrusions. The batholith is cross cut by a dyke complex composed essentially of trachyandesite, dacite and rhyolite dykes. Dacite dykes and the rocks of the granodioritic pluton are cogenetic and, probably, comagmatic. A similar conclusion may be deduced for the rhyolites dykes and monzogranitic plutons. Older trachyandesite dykes, showing locally syn-plutonic relationships to the granodiorite, might be cogenetic with mafic microgranular enclaves scattered through the granodiorite unit. Emplacement of the batholith and dyke swarms was controlled by a transtensional shear zone at a crustal seale developed around 300 Ma ago. The whole set of plutonic and subvolcanic rocks define a K-rich, calc-alkaline alumino-cafemic association. This type of magmatism was related to the transition from a late orogenic compressional regime to an extensional tectonic setting during the period of relaxation and uplift following the Variscan collision.