Nueva interpretación petrológica y tectónica de las anfibolitas pobres en calcio del antiforme de Arinteiro (NO del Macizo Ibérico). II: Estructura e implicaciones para la génesis de anfibolitas pobres en calcio

Abstract

The Arinteiro massif has a complex structure which includes shear zones, recumbent folds, thrusts and upright folds. Ca-poor amphibolites occur associated with the shear zones, although there is some controversy about the origin of such rocks. Shear zones could act as channel-ways for fluids during deformation, modifying the chemical composition of sheared rocks. Detailed field studies and fabric analysis show a close relationship between the impoverishment in calcium of the Arinteiro massif amphibolites and the ductile shear zones. A model to explain the evolution of Ca-poor amphibolites is proposed in which fluids are channelized by the shear zones, extracting calcium from the normal amphibolites. Moreover, calc-silicate rocks occur far from deformation zones and are considered to be metasomatic products of the interaction between Ca-rich fluids/common amphibolites