Geología del sector oriental del Complejo plutónico volcánico Curaco (Triásico Superior), Río Negro

Abstract

The Curaco plutonic-volcanic Complex (Upper Triassic), is located at the NE of El Cuy town, Río Negro, and its eastern sector is formed by monzogranites, minor granodiorite and mafic to felsic dikes, and a less amount of syenite, monzonite, and diorite. The monzogranites are biotitic with porphyric, equigranular, and granophyric-graphic textures, and exhibit sub-volcanic intrusion features. These three monzogranite facies show tectonic contacts through brittle-ductile shear zones, although a single transitional contact between porphyric and equigranular facies has been mapped. The granodiorite is represented by sharp contacts xenoliths within the monzogranite facies. Synmagmatic aplitic-pegmatitic dikes are consanguineous of the porphyric monzogranite. The QAP analysis suggests a monzogranitic evolution progressively enriched by quartz towards the consanguineous dikes, and a granodioritic one that parallel evolutes. The Curaco Complex is cut by the Brusain ductile shear zone oriented NW-SE, composed by mylonitized granites at the centre, and medium grade mylonites and ultramylonites at both edges. Synorogenic granite dikes intrude concordantly to the shear. One 192 Ma. Rb-Sr age indicates that ductile shear occurred at Lower Jurassic. Mafic dikes intrude the monzogranite, whereas rhyolitic dikes are post orogenic with respect to the ductile shear and contain mafic dikes xenoliths. Finally, E-W oriented dextral strike-slip faults cut the whole Complex. Petrologic and structural features of the Curaco Complex indicate a probable correlation with the Calvo Granite of the Dos Lomas plutonic-volcanic Complex.