Zhongliang Wang

Hydrothermal Alteration and Gold Mineralization in the Jiaojia Gold Deposit, Jiaodong Peninsula, China

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.

Sulfur Isotope Geochemistry of the Xincheng Gold Deposit, Jiaodong: Constraints on the Material Source and Ore-forming Environment

The Xincheng gold deposit, located at the Jiaodong peninsula currently the China’s most important gold producer in Southeast of the North China Craton (Deng et al., 2008, 2011; Yang et al., 2009, 2014), is hosted in the Early Cretaceous Guojialing granodiorite which was generated by partial melting of the metamorphosed basement rocks of the Jiaodong group (Wang et al., 2014a). Besides the Guojialing granodiorite, the granulite, which is one kind of metamorphic rocks of Jiaodong group, and felsic dikes were also developed in the deposit. Although the gold deposit is one of the typical altered-type gold deposits, not only disseminated-stockwork but also quartz vein styles of mineralization was developed. The disseminated-stockwork orebodies, constituted the bulk of gold of the deposit, are controlled by the Jiaojia fault, while the quartz vein orebodies, which are less common ore type, are controlled by the subsidiary faults of the Jiaojia fault. Based on the crosscutting relationships and mineral paragenesis, four mineralization stages in Xincheng gold deposit were identified, which contained pyrite-quartz-sericite stage (stage I), quartz-pyrite stage (stage II), quartz-polysulfide stage (stage III) and quartzcarbonate stage (stage IV) (Wang et al., 2014b).

REE and Trace Elements of Auriferous Pyrite from the Taishang Gold Deposit, Jiaodong, China: Implication for ore Fluid Evolution

The Jiaodong peninsula is the largest gold province in China, its proven gold reserve occupies 25% of the countrys (Deng et al., 2006), the proven gold reserve in north-western Jiaodong peninsula occupies 90% of that of Jiaodong peninsula (Yang et al., 2014a). Zhaoping fault belt is the largest fault belt in north-western Jiaodong peninsula, within which the proven gold reserve is more than 1500t (Yang et al., 2014b). Taishang gold deposit is an important Jiaojia-type gold deposit in the northern part of Zhaoping fault belt, whose proven gold reserve is more than 100t. The Potouqing fault is the main ore-controlling fault, the hanging wall mainly consists of Linglong monzogranite and the footwall mainly consists of Luanjiahe monzogranite. The orebodies are controlled by Potouqing fault and its secondary faults. There are 9 main orebodies abut upon the fracture surface and the secondary orebodies are away from the fracture surface. Alteration type includes potash-feldspathization, sericitization, silication and carbonatation. Mineralization type includes fractured belt-alteration rock type and vein type. Pyrite, chalcopyrite, galena and sphalerite are the most common metallic minerals. The pyrites are euhedralsubhedral granular, mainly occur as mineral aggregation and veinlet type. The chalcopyrites are allotype granular, often coexist with pyrites. Pyrites and chalcopyrites mainly occur in the phyllic alteration rocks, silicified rocks, potash-feldspathization granites, quartz veins and the interface of quartz veins and wallrocks. Galenas coexist with other metallic minerals and occur as granule mineral aggregation. Sphalerites are mostly observed microscopically. According to the characteristics of alteration and mineralization in the field, hand specimen, petrography and ore microscopy observation, the mineralization stages are divided into the pyrite-quartz-sericite stage (I), the quartz-pyrite stage (II), the quartz-polysulfide stage (III) and the quartz-carbonate stage (IV). Stage I is the early mineralization stage. Quartz, sericite and pyrite are the common minerals. In this stage, pyrites are small in quantity, often shattered into pieces and disseminated in the milky white quartz and scaly sericites. Stage II is the main mineralization stage. Pyrites are subhedral cubic and become larger in quantity, often occur as vein-type aggregation. Stage III is the main mineralization stage. Pyrites, chalcopyrites, galenas and sphalerites coexist with each other and occur as the quartz sulphide vein. Stage IV is the late mineralization stage. The quartz is ash grey and irregular shape. Calcite is the main carbonate mineral and cuts through the earlier stage quartz. Pyrites are small in quantity and often occur in the calcite vein.

Origin and Evolution of Ore Fluid in the Wang'ershan Gold Deposit, Jiaodong, China

The Jiaodong peninsula is situated in the southeastern of the north China craton, and it defines Chinas largest gold province (Deng et al., 2006; Yang et al., 2014). The Wang’ershan gold deposit, occuring in the largest goldfield of the peninsula, is hosted by the Late Jurassic Linglong type biotite granite. As Jiaodong’s largest proven gold deposit which is controlled by second order Wang’ershan fault belt, it develops both disseminatedstockwork and and quartz vein styles of mineralization. The four main gold orebodies locate in the silicatized or sericited granite, No.1 and No.5 orebodies are controled by the faults F1 and F5, respectively, No.3 and No.23 orebodies are controled by the secondary fractures of F1 and F5. Four mineralization stages have been identified on the basis of characteristics of alteration and mineralization, and crosscutting relationships observed in the field, and structure, texture and mineral assemblages by petrography and ore microscopy observation. They include a pyritequartzsericite stage (I), a quartz-pyrite stage (II), a quartzpolysulfide stage (III) and a quartz-carbonate stage (IV).

Jiaodong Gold System in China: Is it Unique?

The Jiaodong peninsula contains the most important concentration of gold deposits in China, with more than 150 known deposits and the proven gold reserves of as much as 4000 tonnes (Yang et al., 2014). The Jiaodong hydrothermal gold deposits are hosted by Precambrian basement and ultra-high pressure (UHP) metamorphic rock terranes. The terranes were overprinted by Mesozoic tectonism and magmatic events, with gold formation at about 130 to 110 Ma and thus 2 billion years later than the regional high-grade metamorphism (Deng et al., 2006). . The gold deposits cluster mainly along regional NE-NNE detachment faults between Precambrian metamorphic rocks and Mesozoic granites. The mineralization types mainly include disseminated ore in altered granites and breccias, sulphide-bearing quartz veins, and deposits with both styles of mineralization. Metallic minerals mainly include pyrite, chalcopyrite, galena, and sphalerite; nonmetallic minerals mainly include quartz, sericite, Kfeldspar and calcite. Gold minerals mainly include the electrum, free gold and minor küstelite, which mainly occur in fractures in pyrite and in quartz, with some as inclusions in sulfides. Hydrothermal alteration is mainly pyritization, silicification, sericitization, and carbonatization. The ore-forming fluids came from both the crust and mantle, with mainly a crustal source of metamorphic fluids (Yang et al., 2009). Metals were derived from the Precambrian metamorphic basement rocks that were remobilized in the Mesozoic, mingling with a small amount of material from the shallow crust and mantle (Wang et al., 2014a). The consistency of regional metallogenic characteristics indicates that the Early Cretaceous large-scale gold metallogenesis in the Jiaodong gold province is controlled by uniform geological event, and the gold deposits belong to an epigenetic mesozonal-epizonal hydrothermal metallogenic system.

Isotope Geochemistry of the Dayingezhuang Gold Deposit, Jiaodong Peninsula, China: Insights for Gold Mineralization

The Jiaodong Peninsula defines the Chinas largest gold province with more than 150 known gold deposits and 4000t proved gold reserves (Goldfarb and Santosh, 2014; Yang et al., 2014a). The disseminatedand stockworkstyle gold deposit, whose giant source of gold is a striking and key scientific issues, accounts for 90% of the proved gold reserves in the Peninsula. The Dayingezhuang gold deposit, a typical a disseminatedand stockwork-style gold deposit, whose proved reserves were about 125 t Au, located in the central part of Zhaoping metallogenic belt, the largest faultmetallogenic belt in the Jiaodong Peninsula (Deng et al., 2011) with proved gold reserves exceed 1500 t. The main ore-controlling structures are made up of NNEtrending Zhaoping and NNWtrending Dayingezhuang faults. The Zhaoping fault, which controls the occurrence of the gold orebodies in the gold deposit, separates two units: the Precambrian metamorphic rocks in the hangingwall and the Mesozoic Linglong granite in the footwall. The Linglong granite underwent pyritesericitequartz alteration and hosts most part of the gold orebodies. The metamorphic rocks in the haningwall comprise biotiteplagioclasegranulite, carbonate schist and amphibolite of Archaean Jiaodong Group, and garnetsillimanitebiotite schist and biotite schist of Paleoproterozoic Jingshan Group. The gold mineralization is closely related to sericitization, pyritization and silication. The gold orebodies occur in the pyrite-sericitequartz altered rock and cataclasite in footwall of Zhaoping fault. The main metallic minerals are consist of pyrite, galena, sphalerite and chalcopyrite. The No. I and II orebodies, which account for 85% of the proved gold reserves in the gold deposit, are located in the footwall and hangingwall of the Dayingezhuang Fault respectively. More galena, sphalerite and silver minerals are developed in the No. I orebody than the No. II orebody and the orebodies in any other deposits in Jiaodong Peninsula. According to ore mineral assemblages, the mineralization can be divided into pyrite-quartz, gold-quartz-pyrite, goldpolymetallic sulfide, silver-polymetallic sulfide, and quartz-carbonate five metallogenic stages.

P-T Conditions and Mechanisms for Precipitation of Gold in the Xincheng Deposit, Jiaodong Peninsula, China

China with reserves of 2300 t gold, is located in southeast North China Craton (Deng et al., 2009, Wang et al., 2014a). Gold deposits in the area occur as disseminatedand stockwork-style mineralization (“Jiaojia-type”), mainly consisting of disseminatedand stockwork-style pyrite-sericite-quartz-altered ores that are controlled by major regional-scale faults such as the Sanshandao, Jjiaojia and Xincheng faults (Yang et al., 2014), as well as auriferous quartz-veins (“Linglong-type”) (Deng et al., 2000, 2006; Li et al., 2006), composed of single or multiple quartz veins and occur along the secondor thirdorder faults that cut the Mesozoic granitoids (Deng et al., 2008, 2011; Wang et al., 2014b; Yang et al., 2007a). Fluid inclusion studies show that the ore-forming fluids through the Jiaodong province are H2O-CO2 ±CH4-bearing fluids with low-medium salinity (1.2-13.6 wt.% equiv. NaCl) (Fan et al., 2003; Yang et al., 2008, 2009). Minimum mineralizing P-T conditions were regarded as being 170377°C and 500-3,160 bars (Hu et al., 2007; Yang et al., 2007b). However, few studies reported more than the homogenization temperature, salinity and / or pressure for the fluid inclusions, with little discussion about the goldbearing fluids’ composition and the physico-chemical constraints, as well as the precipitation mechanisms of gold mineralization. The Xincheng gold deposit, located along the Jiaojia fault zone in west Jiaodong Peninsula, is a representative lode gold deposit hosted in the granitoids in Jiaodong. It has been exploited since 1979 by the Xincheng Gold Company and has a proven reserve of >200 t gold. However, so far, no information on the gold-bearing fluids and gold deposition of the deposit has been published in English. Our recent fluid inclusion work at the Xincheng deposit showed the quartz-pyrite and quartz-sulphide veins contain H2O-CO2, aqueous, and CO2 inclusions, and they often occur within the same growth plane. This provides a good chance to investigate whether fluid immiscibility took place at the deposits in the Jiaodong province, and to reveal the ore fluids P-T-X conditions of Mesozoic granitoid-hosted gold deposits. Four paragenetic stages: pyrite-quartz-sericite (stage 1), quartz-pyrite (stage 2), quartz-polysulfide (stage 3) and quartz-carbonate (stage 4), were identified at Xincheng deposit based on the crosscutting relationships and mineral paragenesis. Gold was deposited during the quartz-pyrite and quartz-polysulfide stages. With careful petrography, microthermometry, and Raman spectroscopy, we identified three types of fluid inclusions trapped in goldbearing quartz veins that are related to the ore forming even: (1) type 1 H2O-CO2 inclusions that show high temperatures (ca. 260 °C), low salinities (2.4-8.9 wt.% equiv. NaCl) and variable XCO2 (0.03 to 0.20), (2) type 2 aqueous inclusions with medium temperatures (ca. 220 ° C) and low to moderate salinities (3.1-13.3 wt.% equiv. NaCl); (3) type 3 pure CO2 inclusions with a carbonic phase density of 0.712±0.03 g/cm. Types 1 and 2 inclusions appear in the same growth phase of the quartz grains from the breccias and tensile auriferous veins. These coexisting inclusions are likely formed by fluid immiscibility due to unmixing from a single homogeneous H2O-CO2 parent fluid at trapping P-T conditions of 221 to 304 °C and 780 to 2,080 bars. The fluid immiscibility was likely initiated by fluid pressure reduction at about 300 °C. The ore-fluid P-T conditions of the Xincheng gold deposit are consistent with those of the mesothermal lodeWANG Zhongliang, YANG Liqiang, GUO Linnan, LIU Yue, ZHANG Chao, LI Ruihong, ZHANG Liang, ZHENG Xiaoli, ZHAO Rongxin, 2014. P-T Conditions and Mechanisms for Precipitation of Gold in the Xincheng Deposit, Jiaodong Peninsula, China. Acta Geologica Sinica (English Edition), 88(supp. 2): 1167-1168.