Estrutura, “petrofabric” e paragénese do índice tungsteno-aurífero de Ruivos - rede de cisalhamentos intra-graníticos de Ponte da Barca

Abstract

In Ponte da Barca region, inner-granite, the intersections of multistage shear zones, N0°-7°E / N70°E, are the main focus of hydrothermal Au + As mineralization, especially when a third set of ruptures (~N30°E), reticulates the adjacent volume of massif. The detailed study of the Boivão – Ruivos shear junction showed that the more varied are the strikes and deeps of the ruptures that affect a granite compartment, the greater is the diversity of mineralizations, which may include, early scheelite associated with microcline and albite and later gold ± silver ± bismuth, tellurides and selenides, associated with adularia. The petrofabric analysis allowed to determine successive stages of gold liberation from arsenopyrite related to progressive deformation.