| The genesis of nickel-molybdenum sulfide ore deposit was analysised based on its geological characteristics and its geochemical characteristics in the light of the theory of the Tectonometallogeny, Metallogeny and Geochemistry. Six results are obtained as follows: (1) Many basic rocks and ultrabasic rocks were found in mesoproterozoic, which was formed by continental and submarine volcanic activities. Then, tuffaceous flysch clastic rock was deposited during 850Ma-800Ma. After then, gravel sand mudstone of Liantuo was firstly deposited, and then was Nantuo's moraine rock. Phosphoric dolomite and carbonaceous shale of the Later Sinian was lying above Nantuo's moraine rock, and a set of dolomite with great thickness of Dengying Formation was lying above. Black series was deposited in Lower Cambrian. (2) The occurrence of ore layer was mainly layered and resembling layered with disseminated structure and clastic-banding structure. The sulfide ore texture included clastic, semi-euhedral, unformal, including, colloidal and so on, and resembling metasomatic texture was also found here. The mineral assemblages are composed of nickel-sulfide, molybdenum mineral aggregate and some transparency minerals. The nickel-sulfide such as millerite and gersdorffite were imbedded in MoSC phase (with the approximate composition ((Mo, Fe, Ni)(S, As)2C7), which seem to be metasomatic pyrite. (3) Pyrites from different samples that was intergrowth with Ni-sulfide was analysis by electrical microprobe with energy spectrum, and the ratio of its n(S)/n(Fe) was less than 2 (2 is a theory ratio of sedimentary genesis of pyrite). (4) The Ni element content of section of black series in Sancha (Zhangjiajie) ranges from 0.0082% to 0.36%, and Ni content in the ore layer is 0.36%; Mo is from 0.033% to 0.67%, and the content of ore layer is far higher than mining content; V is from 0.019% to 0.19%, and still the content of ore layer is far higher than mining content; the content of P2O5 ranges from 0.03% to 23%. Compare to the black series as well as the underlying dolomite of Dengying Formation around, element content abounded in the ore is obviously higher. (5) The assemble style of element between ore and black series was quite different. For example, the trace element geochemical characteristics of the ore layer was highly enrichments in Ni , Mo , V , U , Cu , Pb , Zn , Cd , Tl and Ba, while high field strength elements (HFSE) and lithophile elements such as Nb , Ta , Zr , Hf , Li , Be , Rb , Cs , Th were scare remarkably in ore layer, but higher in the upper unit and lower parts in the lower Niutitang Formation. (6) Rare earth element characteristic of ores standardized by chondrite shows that Eu/Eu*=1.24 ~1.69>1,Ce/Ce*=0.53-2.75,0.5-0.7 mainly, Y/Ho ratio varies from 48.5-58.77 and∑REE 3.63-251.81, and the rare earth element characteristic of phosphorite of the same strata show that LREE/HREE=4.48~6.95, Eu/Eu*=0.73 ~1.59, Ce/Ce*=0.32~0.60 and Y/Ho is from 46.40 to 54.41, the content of∑REE is 156.69-273.85×10-6, by contrast, the shale's Eu/Eu*=0.03~0.34, Ce/Ce*=1.51~2.75, Y/Ho is from 22.16 to 35.60 and the∑REE is from 75.86×10-6 to 212.95×10-6.Based on the results above and previous researchers, the following conclusions can be obtained: (1) According to previous study on Lithology and Stratigraphic sequence and the related data of age determination, it is concluded that the background evolution from Mesoproterozoic to early Paleozoic in Hunan area is from island arc or marginal basin to continental rift and lastly evolving to passive continental margin. The Ni-Mo ore and phosphate ore hosted in black rock series which were deposited at early Cambrian are formed in passive continental margin. Moreover, the combination of following conditions, such as passive continental margin that may generate contemporaneous fault, the event of magmatic activity is found at southeast margin of Yangzi platform such as Guizhou, and ancient basic basement also can be the source of ore-forming elements, which provide the possibility of hydrothermal mineralization at early Cambrian. (2) Based on the relationship between minerals, the mineralization period can be divided into three stages: sedimentary stage, hydrothermal stage and reformation stage. Pyrite, phosphate, and Mo hosted phosphate are the main products of the first stage. Millerite, gersdorffite, vaesite,"MoCS", sphalerite and chalcopyrite are the primary products of hydrothermal stage. Quartz and calcite is the product of the third stage. (3) The results of Electron microprobe analysis shows that the symbiotic phosphate and molybdenum bearing minerals may have the similar enrichment mechanism. The relationship between phosphate and molybdenum bearing minerals is a new discovery in the research. It helps the study of their genesis. (4) The ratio of n(S)/n(Fe) of most of pyrites that intergrowth with Ni-sulfide is less than 2, which -reflects that Ni-Mo sulfide ores has hydrothermal genesis. (5) The geochemical character of ores with the ratio of Eu/Eu*>1and the low content of REE is also similar to the modern hydrothermal vent's. (6) In conclusion, the metal deposition model was supposed as follow: the elements such as phosphor which comes from continent were in poured into basin on the side of passive continental margin. The basin is getting closed because side-mountain-range still be existed with continental drawing at the early Cambrian, then the biology blooms in that closed basin, and phosphorite and molybdenum bearing minerals sediment at the same time. The iron, nickel and molybdenum that come from Proterozoic along contemporaneous fault combine with sulfur which deoxidize by bacteria in the closed basin, then leads to appearance of pyrite and Ni- sulfide which is supposed as particles. Those particles'round faces is enwrapping by molybdenum mineral aggregation in biologic or chemical reaction. The emergence of large scale black series throughout southeastern China may be because of the same background environment and geological condition.
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