LAS ROCAS TRAQUITICAS DEL COMPLEJO VOLCANICO BARRIL NIYEU

SALANI, FLAVIA M.; REMESAL, MARCELA B.; CERREDO, MARÍA E.

Buenos Aires

Congreso; VIII Congreso de Mineralogía y Metalogenia 2006; 2006

Asociación Mineralógica Argentina

The Neogene Barril Niyeu Volcanic Complex is a postshield eruptive assemblage located at the SW of the Oligocene basaltic Somún Curá plateau of the northern Extrandean Patagonia. The complex is made up of pyroclastic and lava facies which span from basaltic through trachyte to minor rhyolite compositions. Petrography and geochemistry outline of the trachyte rocks is reported in this contribution. Trachyte rocks mostly occur as thick lava flows; rocks are porphyric, with sanidine and aegirine, aegirine/augite phenocrysts set in a trachytic groundmass. The domes within the four cauldrons of the complex are composed either of comendites or quartz-trachytes. All the distinguished trachyte groups share a peralkaline character, as is common in other Neogene postshield complexes of the Somún Curá area.