CHLORITE MICROTEXTURE AND ALTERATION PATTERN AS INDICATOR OF THE DEFORMATION DEGREE OF PULL-APART BASINS ASSOCIATED TO THE PORTO-TOMAR-FERREIRA SHEAR ZONE (W PORTUGAL)

摘要

We have carried out HRTEM studies of chlorite from black shales of very low to low-grade metamorphism from Middle/late Devonian and early Carboniferous basins created in either traspressional or transtensional areas associated to the dextral strike-slip shear zone of Porto-Tomar-Ferreira (Ossa-Morena Zone, Portuguese Iberian Variscan Massif). These black shales are overhanged and then imbricated in an upper Proterozoic metamorphic substratum and could have been affected by the strengths associated to the shear zone. We have observed important differences between HRTEM features of chlorite from both basins.