MINERALOGY AND VERTICAL ZONING OF GOLD MINERALIZATION AT THE BALAZHAL DEPOSIT, EASTERN KAZAKHSTAN

Abstract

The Balazhal gold deposit is located in the West Kalba gold belt of Eastern Kazakhstan and is hosted mainly by a differentiated gabbro-diorite–diorite intrusion. This study examines the relationships between hydrothermal alteration, ore mineralogy, native gold occurrence, and the structural position of mineralization. The study is based on geological observations, petrographic and ore microscopy, and SEM–EDS investigations. Two main styles of gold mineralization are distinguished: quartz-vein mineralization and veinlet–disseminated gold–sulfide mineralization hosted by beresitized intrusive rocks. Pyrite and arsenopyrite are the dominant sulfide minerals. Fine-grained gold is mainly associated with pyrite and arsenopyrite in beresitized rocks, whereas coarser native gold occurs predominantly in quartz veins and late quartz–carbonate assemblages. Four successive hydrothermal stages are recognized, from early beresitic alteration and pyrite–arsenopyrite mineralization to quartz–polymetallic and late quartz–carbonate mineralization. The distribution of the ore types also changes with structural level: quartz veins predominate in the upper part of the deposit, whereas broader zones of veinlet–disseminated pyrite–arsenopyrite mineralization become more important at depth. These features should be considered in exploration of the deeper parts of the Balazhal deposit.