Metamorfismo y deformación del sector nor-oriental de la Sierra de Velasco, La Rioja

VILA TELLO, MARIANELA; LARROVERE, MARIANO A.; ROCHER, SEBASTIÁN; MORENO, GABRIEL G.; ALASINO, PABLO H.

San Miguel de Tucumán

Congreso; XX Congreso Geológico Argentino; 2017

The basement of the northeastern region of the Sierra de Velasco comprises metasedimentary and mylonitic units. The metasedimentary unit is composed of metaquarzite, phyllite and naded schist exhibiting to the west a metamorphic prograde from low to medium metamorphic grade. Temperature calculated in banded schist range from 513 to 548°C and from 431 to 519° (Ti-in-Biotite and Ti-in.Muscovite thermometry respectively) consitent with greenschist facies conditions. The mylonitic unit is composed of mylonites and ultramylonites derived from granites. Based on microstructures, estimated metamorphic conditions suggest that temperature during ductile deformation exeeded 450-500°. This ductile shear zone shows C planaes that strikes NNW and dip to the W. The kinematic is reverse, with top to the NE displacements. The metasedimentary unit could be correlated with the Ordovician La Cébila Metamorphic Complex whereas the mylonitic unit with others syn- to post-Ordovician ductile shear zones recognized in Sierra de Velasco. This suggest that the evolution of the metasedimentary succesion from northeastern Sierra de Velasco would be linked to the regional high temperature - low preassure metamorphism and ductile deformation developed durin the Famatinian Orogen.