VULCANISMO BASÁLTICO Y MESOSILÍCICO DE LA SIERRA DE LOS CHACAYS.

BECHIS, F. ,; REMESAL, M.,; CERREDO, M. E.; SALANI, F. M.

Jujuy

Congreso; 9º Congreso de Mineralogía y Metalogenia; 2008

Asociación Argentina de Mineralogía

The mainly Oligocene Sierra de los Chacays Volcanic Complex (SCHVC) is characterized by its bimodal nature with a basaltic-trachytic association of alkaline character. This volcanic complex is stratigraphycally bracketed between the Early Oligocene Pilcaniyeu Basalts and the Early Miocene Plan Luan volcanic event The SCHVC volcanic sequence comprises an early basaltic event, followed by trachytic eruptions of varied textures and compositions and a posthumous basaltic stage. The basal basic lava flows are porphyritic with olivine and plagioclase phenocrysts. The most widespread facies within the SCHVC is represented by mesosiliceous rocks which were grouped into three petrographic types of trachytic lavas with characteristic alkaline mineral assemblages. The aphyric olivine-clinopyroxene-plagioclase ?bearing basaltic lavas represent the final stage of the SCHVC.