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Hydrothermal Alteration and Gold Mineralization in the Jiaojia Gold Deposit, Jiaodong Peninsula, China
Author(s) -
ZHANG Binglin,
YANG Liqiang,
WANG Zhongliang,
LIU Yue,
ZHAO Rongxin
Publication year - 2014
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/1755-6724.12375_76
Subject(s) - beijing , china , mineral resource classification , geology , mining engineering , geological survey , mineralization (soil science) , geochemistry , chinese academy of sciences , geography , archaeology , geophysics , soil science , soil water
province in China with proved gold reserves of as much as 4000 tonnes (Deng et al., 2006; Yang et al.,2006, 2014a). Disseminatedand stockwork-style gold deposit is the most important deposit type which accounts for more than 90% of the proved gold reserves in the Jiaodong Peninsula (Deng et al., 2000; Yang et al., 2014b). The Jiaojia gold deposit, a typical disseminatedand stockwork-style gold deposit, is the one of the large gold deposits with a proven reserve of >200 t. Sericite-quartz and potassic alteration are well developed in the deposit with the width of 20-200 m and 50-300 m respectively. The disseminatedand stockwork-style ores, located in the footwall of the Jiaojia fault, are strictly controlled by the Jiaojia fault (Yang et al., 2009). The bulk of gold orebodies in the deposit occur in the intensely altered zone of sericite-quartz alteration (Deng et al., 2010). The spatial distribution of the alteration in the Jiaojia gold deposit is controlled by Jiaojia fault, showing obvious zoning. In the footwall of the Jiaojia fault, pyrite-sericite-quartz, sericite-quartz and potassic alteration zones are distributed successively from the fault plane to outside. A small quantity of breccia of potassic granite are residual in the pyrite-sericite-quartz and sericite-quartz altered rock, which demonstrates that the potassic alteration occurred before the gold mineralization and sericite-quartz alteration. Compared with the fresh biotite granite, rocks from each alteration zone show high contents of K2O and low contents of Al2O3, CaO and Na2O, while elements such as Si, Fe and Mg have different characteristics. K2O are enriched in potassic granite, while both sericite-quartz and pyritesericite-quartz altered rocks are characterized by high contents of MgO and Fe2O3. Based on the mass balance calculations (Gresens, 1967; Zhang and Yang, 2002), during the process of potassic alteration, the contents of SiO2 and K2O rose, indicating that the ore-forming fluids are characterized by silicon-rich, alkaline and oxidation. And this kind of fluids extracted gold with high valence from wall rocks thorough the metasomatism in the process. To be precise, dispersed reduced gold (Au) was activated to be oxidized (Au, Au), and migrated with the fluids in the form of AuH3SiO4. Then, in the process of alteration from potassic granite to pyrite-sericite-quartz altered rock, the Fe2O3 increased obviously, which may result from the decomposement of biotite and other femic minerals. Meanwhile, the contents of sulfophilic elements such as Au, Ag, As, Pb and Zn also increased obviously, especially for the Au. The deposition and enrichment of gold may be induced by the descent of the content of SiO2 which lead to the decomposement of AuH3SiO4 and the consumption of Fe and Fe to form the pyrites.