Ordovician syn-tectonic low-grade metamorphism in the La Cébila metamorphic complex: implications in the Famatinian retro-arc evolution within the proto-Andean margin of Argentina

VERDECCHIA, SEBASTIÁN; COLLO, GILDA; BALDO, EDGARDO

ANDEAN GEOLOGY

SERVICIO NACIONAL GEOLOGIA MINERVA

Año: 2011 vol. 38 p. 268 - 283

0718-7092

Two tectono-thermal metamorphic events, M1-D1 (S1, with associated white mica and chlorite: WM1-Chl1) and M2-D2 (S2, with development of WM2-Chl2), are established for low-grade units from the Ordovician metasedimentary successions of the La Cébila Metamorphic Complex (LCMC) in the Famatinian belt (Central Andes of Argentina). The thermobarometric characterization of the M1 main event was carried out in the Quebrada de La Cébila and Quebrada de Cantadero areas by means of clay-mineral analysis and crystallo-chemical parameter measurements. Epizonal conditions with temperatures between 300 and 400 ºC were obtained, with Kübler index values ranging from 0.23 to 0.17. The white mica b parameter values, between 9.004 and 9.022 Å (mean of 9.014 Å, n = 16), together with preliminary Si contents, suggest low-pressure conditions. The low-pressure M1-D1 event of the LCMC could be linked with a high-strain heating stage following the extension of the Famatinian back-arc basin.