Geology and mineralization of the Dongping supergiant alkalic-hosted Au-Te deposit (>100 t Au) in Northern Hebei Province, China: A review

The Dongping deposit is the largest alkalic-hosted gold deposit in China containing >100 t of Au. This paper presents a new understanding for Dongping ore system, based on the previous studies. The mineralization originally occurred at 400–380 Ma, simultaneous with emplacement of the Shuiquangou alkaline complex, and was overprinted by the hydrothermal activity in the Yanshanian. Isotope compositions of ores indicate metals of the deposit are mainly provided by the Shuiquangou complex. Ore-forming fluids are characterized by increasing oxygen fugacity and decreasing sulfur fugacity, while tellurium fugacity increased in the Stage II-2 and decreased in Stage II-3. These systematic changes are closely related to the processes of mineral precipitation and fluid evolution. Sulfide precipitation from Stage I to Stage II was triggered by fluid boiling, which leads to the precipitation of Pb-Bi-Te, due to decrement of sulfur fugacity. Condensation of gas phase containing high concentration of H₂Te leads to precipitation of Te-Au-Ag minerals and native tellurium. Based on these hypotheses, this paper present a polyphase metallogenic model as follow. During the Devonian, fluids were released from alkaline magmas, which carried ore-forming materials form the surrounding rocks and precipitate the early ores. During the Jurassic-Cretaceous, fluorine-rich fluids exsolved from highly factionated Shangshuiquan granite, which extracted and concentrated Au from the Shuiquangou complex and the Sanggan Group metamorphic rocks, and finally formed the Dongping gold deposit.