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 two metamorphic units. The metasedimentary unit is composed of metaquarzite, phyllite and banded schist exhibiting to the west a metamorphic prograde from low to medium metamorphic grade. Temperature calculated in banded schist range from 513 to 549 °C and from 431 to 529 °C (Ti-in-Biotite and Ti-in-Muscovite thermometry respectively) consistent with greenschist facies conditions. The mylonitic unit is composed of mylonites and ultramylonites derived from granites. Estimated metamorphic conditions during ductile deformation exceeded 450-500 °C. This ductile shear zone shows C planes that strike NNW and dip toward the W. The kinematic is reverse, with top to the NE displacements. The metasedimentary unit is correlated with the Ordovician La Cébila Metamorphic Complex and the mylonitic unit with others syn- to post-Ordovician ductile shear zones recognized in Sierra de Velasco. This suggests that the evolution of basement rocks of the northeastern region of the Sierra de Velasco was linked to the regional high temperature ? low pressure metamorphism and ductile deformation developed during the Famatinian Orogen.