Anatectic Leucogranites of Molinos Range, Easthern Cordillera, NW Argentina: some issues concerning Nd-isotopic system

SOLA ALFONSO; RAUL BECCHIO; MARCIO PIMENTEL

Brasilia

Simposio; VII SSAGI South American Symposium on Isotope Geology. Phanerozoic isotope geology and crustal evolution.; 2010

Universidad de Brasilia

The isotopic data is consistent with all these rocks being genetically related, with the granitoids having been generated by anatexis of its high-grade host rocks and not as a result of a mixed source or mantle component. The various degrees of parent/daughter fractionations in the Sm–Nd isotopic systems could be consequence of several factors such as the non-modal nature of partial melting reactions, nature of source or protolith, H2O activity and the stability and equilibrium of the trace elements-bearing minerals entering the melt. During crustal anatexis these factors operating simultaneously would render melt products with distinct isotopic signatures, which could profoundly influence the products of subsequent mixing events. This is not only important for geochemical patterns of intracrustal differentiation, but also potentially important processes in generating crustal-scale as well as individual pluton-scale isotopic heterogeneities Zeng (2005c). Consequently, disequilibrium processes, as the mentioned, must be considered at the moment of interpreting the geological meaning of isotopic data of Famatinian granitic magmatism.