El haz lineal filoniano granítico-adamellítico (riolítico), de dirección N120-130E asociado al batolito de los pedroches

Abstract

The late-Hercynian magmatic alignement of the Los Pedroches Batholith in South Central-Iberian Zone (Iberian Massif) exhibits a conspicuous dike swarm. Dikes are in chronological order: a) traquiandesite, b) dacite to rhyodacite, c) rhyolite, d) aplite, aplopegmatite and pegmatite, e) quartz, f) basic (diabase, lamprophyre). Rhyolite dikes (granite to adamellite) form a number of lineal swarms oriented N120-130E. The main group extends almost undisturbed from near Belalcázar (Córdoba) to the Guadalquivir fault (Jaén). This array, ca. 130 km length and 2-12 km thick, is usually composed of 3 to 50 dikes cutting across the main plutonic facies of the Batholith. Rhyolite dikes have the common granitic minerals, including zircon, apatite and ilmenite as accessories. According to their macroscopic features and petrography the dikes may be porphyritic microgranite, porphyritic rhyolite or porphyritic granophyre, whereas according to the mineral cheroistry the dikes range froro rhyolite-granite to alkali feldspar granite-rhyolite. The cheroical composition of studied rocks corresponds to peraluminous and calc-alkaline terms of a K-rich alumino-cafemic calc-alkaline association. The dike swarm cuts granite massifs of the Los Pedroches batholith intruded at ca. 300 ± 6 Ma (El Guijo pluton, Fernández et al., 1990), but the emplacement is poorly constrained as inferred by K-Ar mineral ages of ca. 315 ±15 Ma (Bellon et al, 1979) and Rb-Sr whole rockage of 295 ± 18 Ma (Defalque et al., 1992). The dike swarm would result of subvolcanic intrusions genetically related to the late-Hercynian igneous activity that originated the Los Pedroches Batholith.