Gold occurrence at the Obichnik ore deposit, Eastern Rhodopes, Bulgaria

The epithermal Obichnik deposit is located in the Southeastern Rhodopes. It is a part of the Zvezdel-Pcheloyad ore field, which includes hydrothermal Pb-Zn and Au-Pb-Zn mineral occurrences and deposits associated with the Oligocene Zvezdel volcano. The ore mineralization is hosted by felsic, intermediate to mafic volcanic, volcano-sedimentary, and intrusive rocks. The gold presence in the area is known from many previous explorations. The most large-scale one has begun in 2019. So far, insufficient data on the mode of occurrence and composition of the gold in the deposit have been reported. This study reveals that gold associates with the minerals of quartz-sulphide stage of the mineralization. It mainly occurs as irregular grains and occasionally as isomorphic grains in fracture or cavity mainly in pyrite and marcasite, and rare in galena. The electron-microprobe analyses of gold detected only gold and silver and its fineness ranges from 870 to 915‰.