Abstract
The Numão gold deposit in the northern part of the Iberian Variscan belt is close to the regional first-order Vilariça-Manteigas fault system. The second and third-order structures controlled the gold mineralized bodies. These bodies consist of disseminated sulfides, arsenopyrite-quartz veins, and sulfides-scheelite-quartz veins. The scheelite occurrence predates the gold mineral assemblage and is lithologically controlled by host rocks with calc-silicate minerals. The ore mineral assemblage comprises scheelite, arsenopyrite, chalcopyrite, bismuth, and Au-Ag mineral phases, with minor pyrite, pyrrhotite, sphalerite, and galena. The hypogene gold minerals at Numão deposit are hosted by arsenopyrite, chalcopyrite, and silicate matrix in minor amounts. Chemically, gold fineness ranges from 663 to 841. The thermal evolution of the mineralization was estimated based on arsenopyrite (381° to 502 °C) and chlorite geothermometers (264° to 341 °C). The multi-element and principal component analysis information was used to better identify geochemical patterns and trends in hydrothermal alteration. The gold-metal association (Au-As-W-Bi) was found to be similar to other gold deposits in the European Variscan belt.
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