| This paper takes the Lower Cambrian black rock series nickel-molybdenum polymetallic deposit in Zhangjiajie area of Hunan Province as the research object.Based on the detailed collection and consolidation of previous research results,the paper combines the field geological survey and sample collection work,combined with indoor flake identification,E-probe analysis,SEM observation,and main trace elements and other modern analysis and testing techniques for the deposit characteristics of the Lower Cambrian black rock nickel-molybdenum polymetallic ore deposits in Zhangjiajie area of Hunan Province,the occurrence patterns of major minerals,and mineralogy the symbiosis between features and minerals,the micromorphology of various minerals,and the geochemical characteristics of major and trace elements have been studied.The genesis of the deposit has been explored and the following findings have been achieved:1.The mineral composition is complex,which the metallic minerals mainly include Pyrite,Molybdenum mineral,Millerite,Gersdorffite,Sphalerite,Chalcopyrite,Arsenic,Copper,Arsenic,Antimony,Copper,etc.Non-metallic minerals include Colloidal phosphate,Apatite,Calcite,Barite,Quartz,Clay minerals and so on.2.The form of molybdenum is given priority to with MoSC,its morphology can be divided into other forms and ellipsoidal aggregates shapes,while in scanning electron microscope secondary electron images is mainly bamboo-like and main colloidal aggregation.The main forms of nickel are Millerite and Gersdorffite.Among them,the form of Millerite can be divided into disseminated and veins.Under the scanning electron microscope,the Millerite is very irregular in shape,mainly in veins.The Gersdorffite is respectively shaped(colloidal assemblage)and zonal structure.It was observed under scanning electron microscopy that the Gersdorffite is mainly responsible for the presence of other minerals on the surface,so the morphology is various.Pyrite is widely distributed in the ore and surrounding rock strata;Among them,the pyrite in the surrounding rocks is usually distributed in sporadic spots,and the form of pyrite in the ore can be divided into three types:(1)Shape,semi-automorphism and other forms of aggregates;(2)gel-like,ribbon-like forms;(3)mildew-like forms.3.The order of formation of minerals is: Clay minerals,Phosphate minerals,and self-shaped Pyrite are first formed;Molybdenum minerals are formed secondarily;Nickel minerals may form again,and Nickel minerals may be formed;Finally,Calcite,Quartz,Barite,etc.;Pyrite may accompany the whole process of mineralization,and the specific form of pyrite formation needs further detailed study.According to the above analysis,the metallogenic stage may exist in the following stages: sedimentary stage--hydrothermal stage.The sedimentary period mainly produces Molybdenum minerals;The hydrothermal stage is mainly Nickel sulfide.4.It is known through elemental geochemical characteristics that the ore-bearing rock series is formed in a reduced(oxic)environment,and that the phosphorus rock,nickel-molybdenum ore suffers hydrothermal influence,while the black shale minerals are derived from terrigenous materials.5.Based on mineral characteristics and elemental geochemical analysis results,it is believed that the deposit formed in shallow water(mainly on continental slopes and marginal seas)and the sea phase is blocked by a water-reducing(anoxic)environment,and the seafloor hot water(liquid)provides abundant material sources.The deposits are mainly due to seawater deposition under the participation of seabed hydrothermal fluids.The ore-forming material molybdenum may come from seawater,and nickel mainly comes from the seabed hydrothermal fluid. |
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