Tellurium-Gold Mineralization Related to Cryptoexplosive Breccias within Volcanic Pipe in Zhuojiazhuang Gold Deposit,Shandong Province, China

Zhuojiazhuang gold deposit (ZGD) is the most enriched breccia pipe type gold deposit in East China, resulted from cryptoexplosion related to alkalinic magmatism and orebearing fluid filling. The ZGD is a small-sized mine with over 5 tons of gold reserves and grade of 156g/t in average and the highest 2 728 g/t as known. In addition, tellurium and silver are also valuable.The mineralized breccia pipe is cylinder-like in shape with 15 m long and 10 m wide and controlled by intersection ofNW and EW trend faults. Mining level has reached 170 m below the surface, but the whole pipe mineralization is still stable. Mineralization commonly occurs within the cements of breccias. Gold ores consist of hydrothermal breccia ore, shatteredbreccia ore and cataclastic ore. From the center of the ore body outwards, there is the transition from hydrothermal breccia toshattered breccia and then to cataclastic ores. According to composition and amount of the cements, the hydrothermal brecciaores can further be divided into three subtypes: sulfides cemented, hydrothermal mineral cemented and magma cemented.The content of gold is closely related to the types of the cements. The grade of the sulfide cemented breccia is the highestone, usually more than 1 000 g/t, and the known maximum grade is 2 728 g/t. The composition of the shattered breccia ismainly dioritic porphyrite and cemented by hydrothermal minerals, the grade ranges from ten to several tens g/t. The catsclastic ores are mainly composed of dioritic porphyrite, syenitic porphyry, as well as carbonate with mineralized veins, and the grade is only 35 g/t.Major ore minerals consist of pyrite, native tellurium, sphalerite, with minor calaverite, galena and altaite. Gangueminerals are composed of microcrystalline quartz, decktite and fluorite, with minor sericite and calcite. Brecciated and disseminited structures are main structures of ores. Four ore-forming stages are defined: microcrystalline quartz-pyrite stage,microcrystalline quartz-polymetal sulfides stage, quartz-adular stage and dickite stage. Wall rock alteration is characterized bysilicification, sericitization, adularization and fluoritization.The enrichment of tellurium may indicate that the ore-forming fluid was of a deep origin from upper mantle or lower crust. Mineral assemblage of microcrystalline quartz, fluorite, adularia and dickite suggest a relatively low-temperature forming condition. An extensive suite of elements, including Au, Ag, Te, Hg, Sb, As, Mo, F, Zn, and Tl, is significantly enriched in mineralized rocks. They can be geochemical indicators for exploration in the study area.Comprehensive studies show that the Zhuojiazhuang gold deposit is a type of sericite-adular gold deposit, belongs to epithermal gold deposits, or can be classified into alkali gold deposit series.