Geochemical Characteristics And Genesis Of Gold-antimony Orefield In Jiangdongwan, Western Hunan

Jiang Dongwan located in China’s Hunan Province, gold-antimony deposits in gold-antimony arsenic Xupu Dragon King River Gold belt, there are two NE assigned to rising regional fault kidnapped anticlinorium secondary structural fracture zone. Based on the full collection of information and understanding and summarizing the previous research results, from major and trace elements and carbon, hydrogen isotope geochemistry to investigate the origin of minerals and ore-forming fluid nature and sources of arsenic and antimony Jiang Dongwan gold deposits. And explore the genesis, metallogenic model, metallogenic mechanism and prospecting mark of the deposit. Obtain the following understanding:(1) In the altered rocks with normal rock, K2 O percentages are greater than the percentage of Na2 O and potassic general; K2 O / Na2 O ratio was significantly increased by the alteration before this change process described alteration of K+ content increased, indicating potassic favor mineralization. Ca O / Mg O did not change significantly before and after the alteration, description, ore rock substance occurred components into and out of, that is, after the hydrothermal metamorphism. Si O2 content and the increase is small, indicating that the hydrothermal mineralization process, basically no foreign Si O2 increases, only the structure of the rock composition further configured to display sedimentary- hydrothermal deposits filling type features.(2) Respectively Banxi group Sb, As, Au, higher than average levels of the average of the upper continental crust 93.5,14.9 times and 2.9 times. Overburden Sinian a Cambrian Sb, Au and other elements were 1.2 times lower than Banxi group and 1.7-2.6 times. Explain the existence of Sb, Au and other elements of the initial enrichment. Near ore formation Wuqiangxi group profile Sb, As, Au trace element content of less than 9.1 times the area Banxi group, 14.6 times and 1.5 times, a marked loss phenomenon, described as minerals may result from regional Proterozoic boundary formation, the presence of mining ore source layers.(3) There must Sb Au, Au was not necessarily Sb, Au but at As certain high. As changes in the profile of Au is very similar to the strong positive correlation; Au and Sb change and change in the profile of the performance of a weak positive correlation. Description Au is enriched with As and enrichment. Ore Sb, Au concentration is significantly higher than the surrounding rock alteration occurred in Sb, Au concentration an order of magnitude. This fully shows that the main ore-forming elements from the formation, the formation of hydrothermal mineralization in mineralization the rock leaching occurs. Gold mineralization has inherited the characteristics of the construction of a combination of elements.(4) The main carrier of minerals gold is arsenopyrite and pyrite, but the distribution is uneven, arsenopyrite the Au content of 2 to 5 times higher than the symbiotic Au pyrite content, indicating that Au generally preferred enriched in arsenopyrite in. Au atom is a higher ionization potential atoms, and has a high oxidation reduction potential, is a strong oxidizing agent, readily available electrons native gold. Au and Fe ion radius big difference, but limited pyrite and arsenopyrite lattice space, Au atoms enough to be accommodated, so it is difficult to Au isomorphous way into pyrite, but in machinery Sulfur is present in the mix(arsenic) of the composition.(5) Ore(La/Yb)N value is much greater than 1, LREE/HREE values 1.05-15.85; alteration rock(La/Yb)N value of 7.11, much larger than 1, ΣREE range 37.63-43.65 and both REE patterns were generally figure was skewed to the right, indicating that is a light rare earth enrichment, HREE and gradually becoming flat features. Wall rock alteration in relation to the total content of rare earth ore more stable. Judging from the distribution patterns of each ore between Eu anomalies are very similar, δEu value focused, and the overall change slightly, weakly negative Eu anomaly, altered wall rock δEu value of 0.32, weakly negative Eu anomaly; alteration δCe value close to a rock and mine, indicating no obvious abnormalities or negative Ce anomalies. Reflecting the relatively low oxygen fugacity metallogenic environment restored.(6) Gold ore samples REE curve and area Banxi group Wuqiangxi group unaltered slate and slate REE pattern is very similar and also very close to the total rare earth. Basically similar alteration rock REE curve Lengjiaxi regional groups and ore formation horse bottom group unaltered release slate of REE curves. Clastic sedimentary strata into direct display of minerals from the area close to the Proterozoic.(7) Arsenopyrite, pyrite and stibnite tower in δ34S values overall were distributed, of which nearly a smaller negative number to zero-based, from the difference of only 2.2, sulfur source may mainly from a higher degree of homogenization The deep crust or lower crust, during or biological or organic sulfur participation. δ34S values descending from pyrite to arsenopyrite to stibnite averages, indicating that in the process of mineralization of S isotope fractionation occurred to some extent. Au and gold-sulfur(arsenic) of having a close relationship between the causes and time. Formation(arsenic) compounds simultaneously or later when the time of its symbiotic relationship between the performance of Au gold contained sulfur.(8) Slate wall rock samples δ13C, δ18O values are negative; range quartz vein samples δ13C changes:-9.12 ‰ to-7.95 ‰, with an average of:-8.42 ‰, δ18O value distribution range:-15.02 ‰ to-14.99 ‰, with an average of: 15.3 ‰. Description ore from carbon or deep mantle degassing magma source.(9) Mineralization process of evolution, the temperature gradually decreased mineralization, ore fluid salinity increases, and underground water with approximate values, indicating mixing of metallogenic fluid had occurred. The various stages of mineralization were higher SO42- content reflects fluid rich in sulfur and chlorine is relatively poor, high CO2 content showing metamorphic water features. At the same time, part of the sample ω(Na +) / ω(K +)> 2, ω(F-) / ω(Cl-)> l, and in mineralization in the late stages of Ca2+ content was significantly increased, showing hydrothermal with mixed the characteristics of the fluid. So the source of ore-forming fluids Jiang Dongwan gold arsenic and antimony deposits more complicated. Both metamorphic water features, but also has the characteristics of underground water, so that the metallogenic fluid is mainly metamorphic and hydrothermal fluids underground hot water mixed incorporation.(10) Before the proterozoic crustal melting over a long period differentiation, the formation of a mixture of Sb-rich magma, magma mixing in the basement faults and ridges along with increased migration, extraction formation mineralization components on Located in the uplift of land and increased pressure, compound fracture of a closed environment, in order to fill metasomatism antimony lode gold deposits.