"Minerales del grupo del espinelo en metaperidotitas de la faja del Río de Las Tunas, Cordillera Frontal de Mendoza: su relación con el metamorfismo regional"

GARGIULO, M. FLORENCIA; BJERG, ERNESTO A.

San Juan

Congreso; 11º Congreso de Mineralogía y Metalogenia; 2013

Universidad Nacional de San Juan y Asociación Mineralógica Argentina

In the Río de Las Tunas belt, Frontal Cordillera of Mendoza province, Argentina, spinel group minerals occur in metaperidotites and reaction zones at the boundary between these ultramafic bodies and their country-rocks. In the metaperidotite studied samples, spinel group minerals comprise two types: i) Reddish-brown crystals with compositional zoning characterized by a ferritchromite core surrounded by an inner rim of Cr-magnetite and an outer rim of almost pure magnetite. ii) Green crystals chemically homogeneous with spinel (s.s.) and/or pleonaste compositions. The mineral paragenesis Fo+Srp+Cln+Tr+Fe-Chr and Fo+Cln+Tr+Tlc±Ath+Fe-Chr observed in the studied samples indicate lower and middle grade amphibolite facies metamorphic conditions. Nonetheless, the paragenesis (green)Spl+En+Fo±Di indicates that granulite facies conditions were also reached at few localities. Cr-magnetite and magnetite rims in zoned reddish-brown crystals and magnetite rims around green-spinel/pleonaste grains are attributed to a later serpentinization process during retrograde metamorphism. The mineral paragenesis in Río de Las Tunas metaperidotites together with the chemical characteristics of the spinel group minerals support a clockwise P-T path evolution for the ultramafic protoliths during the Paleozoic regional metamorphic cycle of this area.