Modelización P-T del metamorfismo Famatiniano en el sureste de la Sierra de Pie de Palo, Sierras Pampeanas Occidentales, Argentina

RAMACCIOTTI, C.; BALDO, E.G.; VERDECCHIA, S.; CASQUET, C.

Congreso; XX Congreso Geológico Argentino; 2017

The Sierra de Pie de Palo is one of the westernmost Sierras Pampeanas of Argentina. It consists of a polymetamorphic Mesoproterozoic basement and a monometamorphic Ediacaran to Cambrian metasedimentary cover, i.e., the Difunta Correa Metasedimentary Sequence. The latter underwent metamorphism in the Famatinian orogeny in the early Ordovician. P-T pseudosections were obtained for one staurolite-schist from this sequence from the southeasternmost part of the range. A starting point on the P-T path yielded ca. 520 ºC and ca 3.1 kbar. Metamorphic peak was attained at ca. 640 ºC and ca. 9.2 kbar implying medium-to high- P/T gradient. Petrographic evidence along with mineral equilibria modeling suggests that two texturally different garnets (Grt1 and Grt2) grew during prograde metamorphism with a growth interruption between them. The latter probably resulted from bulk composition fractionation. Grt2 grew at higher pressures, which resulted in an increase of the grossular content (Grs = 0.16).