Auriferous sulfides from Hired gold mineralization, South Birjand, Lut block, Iran

Abstract

The Hired gold mineralization is located in the Lut Block, eastern Iran. Reduced intrusion of subvolcanic granodiorite to quartz diorite stock with porphyry texture of the post Eocene age intruded into the Eocene volcanics and pyroclastic units led to alteration and gold mineralization. Mineralization occurred as three separate parts: instrusion-hosted, proximal and distal. The Hired gold mineralization can be considered as gold mineralization related to reduced granitoid intrusions. Free gold has not been observed in the form of native gols during microscopic studies. Therefore, it appears that gold probably occurs as invisible or submicrometer-sized inclusions in sulfide minerals. Electron probe microanalysis (EPMA) confirmed the existence of sulfide minerals such as pyrrhotite, galena, pyrite and arsenopyrite having the highest gold content; however, because of the relative abundance of pyrite and arsenopyrite, a high gold concentration corresponds to the presence of these sulfides. Considering the paragenetic sequences, gold mineralization occurred as invisible gold in the early and late hydrothermal stages.