Geological Characteristics And Genesis Of The Shuiyindong Gold Deposit, Guizhou, China

The Shuiyindong gold deposit is a typical large Carlin-type gold deposits concealed.Administrative division belongs to Xiaotun town, Zhenfeng county, Guizhou Province.Tectonic position is in site of the intersection between the south-west margin of Yangtze platform and the two tectonic units of gradeⅠof the South China fold line, which belongs to Youjiang fold line of South China fold belt. It locates in a "triangle" block, that is, Dianqiangui "Golden Triangle" area, which are surrounded by the north-east Mile-Shizong deep fault, the north-west Ziyun-Yadu deep fault and the near east-west Kaiyuan-Pingtang deep fault. By the impact and constraints of deep fault, construction lines are mainly east-west distribution, and the principal stress is of the north-south level extrusion. Structural features of different periods and different directions compositely superimposed. The characteristics of tectonic deformation of development and combination, affected by lithofacies and lithology, are obviously different in space. The output of orebody is controlled by huijiabao anticline and the near fault. Magmatic rocks in the mining area is not developed, being a small amount of alkaline ultrabasic rocks and Emeishan basalt.The strata drilled and exposed in Mining area are as follows: in the Permian Maokou EC, the EC Permian Longtan Formation, Changxing Group and Dalong Group, Lower Triassic Yelang EC group, the first paragraph of Yongning Town Group.Ore-bearing strata of Shuiyindong gold deposit are of Changxing Group, Longtan Group and the constructure-altered body(located in the unconformity interface between Maokou and Lungtan Group).Ore bodis are mainly lamellar bodies controlled by lithology, fault-type ore bodies as a supplement, as well as a small amount of layered like ore bodies. Ore-bearing rocks are mainly biogenic limestone, siltstone, and fault breccia. Ore minerals are: pyrite, arsenopyrite, hematite, stibnite (occasionally), cinnabar (occasionally), realgar (occasionally).Gangue minerals are: quartz, dolomite, calcite, water, mica, sericite, kaolinite, fluorite, glauconite, zeolite, organic carbon, asphalt deterioration. Pyrite is the main vehicle for gold. Gold-bearing pyrite, mainly in the size of 0.0005mm-0.05mm (0.5μm-50μm), the naked eye difficult to see, under the microscope was strawberry-like, spherical, Shell-like,ring band and so on. Ultrastructure showed mainly a state of disseminated non-uniform distribution in the belt loop of the hydrothermal arsenic pyrite. Arsenopyrite content is not high, not more than 1%, but are often closely linked with the high-grade ore. Clay minerals are also of a certain gold-bearing.Gold grade in ore changes from 1.06×10-6 to 48.40×10-6. Au has better correlation with As, Sb. Carbonate-type high-grade ore, with a mean of 21.82×10-6, the content is also relatively stable, changes in coefficient of 59.27%. Mudstone-type low-grade ore, with a mean of 6.73×10-6, the larger changes, changes in coefficient of 113.28%.The useful components of ore, Ag, Sb, Cu, Zn, Pb,and other useful elements,are of the value of non-utilization. Toxic and harmful elements such as Tl, Hg content is very low and so will not cause environmental problems. The average level of As is 0.40 percent, ore must to be dressed by high-temperature pre-oxidation process. Analysis of constant element shows that ore is with high silicon, magnesium, ferric iron, sulfur. Chemical composition analysis about sandstone shows that the tectonic setting of sandstone of Shuiyindong gold deposits may be active continental margin. Ore with a higher Ag, Mn, In, and elements of Li, Be, Sc, V, Cr, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Cd, Cs, Ba content is over low. The main ore-forming elements, Au between Cu, Zn, As, Sb, Tl, Bi, Sn, show a negative correlation,and linear correlation is not high. Relatively speaking, Au has closer relationship with As, Sb, Tl. TheΣREE, LREE, HREE and LREE/HREE of ore are lower than that of rock, that of limestone ore lower than sandstone ore. Eu negative anomaly of ore is weak, and Ce negative anomaly of it more pronounced. Under the structure of deposit, wall-rock alteration, the fabric of ore, the symbiotic composition and relationship of minerals, and so on, mineralization can be divided into two periods: period of sediment diagenesis and construction-hydrothermal period. construction-hydrothermal period can be divided into three phases: calcite-pyrite stage, quartz-dolomite-pyrite stage and realgar-cinnabar-quartz-calcite stage.In the late Permian, marine sedimentary basin margin prepared the lithology conditions for the gold deposits, that are ore-hosting rock (limestone or biological siltstone) and the favorable closure of rock (clay rocks). The tectonic movement from late Indosinian to early Yanshanian, accompanied by a deep fault and magmatic activity, provided channels for the ore-forming minerals from the deep.High paleotemperature anomaly provided the heat and thermal power conditions for the ore-forming hydrothermal. Ore-forming materials mainly come from the deep , shallow source material mixed. Ore-forming fluids show the epithermal characteristics; inclusion hydrogen and oxygen isotopes show that fluid may mainly derive from underground hot water coming from precipitation.Hydrothermal has LREE enrichment, and has a positive Eu anomaly relating to the deep feldspar-rich rock. Hydrothermal migrates upward along the deep fault, and penetrate the both sides of rock benefiting ore-forming. Secondary faults and the detachment surface of folds provided the mine-leading and ore-hosting structures for ore-forming minerals to reach favorable sites, forming orebodies along rock, fracture or the detachment surface of folds.