| Located in the northern margin of Xilamulun River deep fracture,southeast of the CentralAsian Orogenic Belt，Binding site of Siberian Plate and North China Plate with favorableregional metallogenic geological conditions, Bianjiadayuan Pb-Zn-Ag deposit was discoveredbefore a short time, and is now in the stage of exploration and exploitation. The main work ofthe past was geological exploration work,and the research degree in genetic mechanism is stillvery low,therefore, systematic study of the genesis mechanism has important significanwce toguide prospecting and summarize regional metallogenic regularity.Through geological fieldwork, It is observed that the ore of the deposit is mainly veins,obviously controlled by faults,there is a close temporal relationship between the miningoutcropping diorite and monzonite granite rock and ore, Sturgis middle group and diorite rockare the ore-bearing rock, ore-bearing rock alteration is weak, it shows that metasomatism isnot the main reason of ore-forming elements precipitation, there is a large number ofboulangerite in the ore, suggesting that late Ore-forming hydrothermal has higher sulfurfugacity, the main reason for mineral deposits is sulfur reduction.Geochemical studies have shown that, diorite and monzonite granite rock ofBianjiadayuan Pb-Zn-Ag deposit should have the same source and been the same sequence ofmantle magma evolution, diorite was K calc-alkaline series peraluminous rock, adamellitewas alkaline series peraluminous granites, and the a-type granites, indicating the formation ofextensional environment, differentiation was obvious in Light rare earthsboth and not obviousin heavy rare earths,REE patterns are different parts of the light rare earths obvious, REEpatterns were both right-wing type, elements of enrichment and losses were similar on traceelement distribution patterns with varying degrees of loss of Nb,P,Ti and Enrichment of U,Pb,from the tectonic discrimination diagrams adamellite was formed in Yanshan in plate insideextensional environment caused by squeezing.inclusions of the main mineralization stage in quartz of oreclosely associated withOre-forming substance in Bianjiadayuan Pb-Zn-Ag deposit test shows that the fluid inclusionswere dominated by gas and fluid phases, with gas/fluid ratios mainly between10%and55%,and were all homogenization to the liquid phase, homogenization temperature ranged of326.2~377.6℃, belonging to the high-temperature hydrothermal deposits range. Accordingquartz inclusions calculation, salinity salinity ranged of10.24~17.87wt%NaCl, mineralization pressure ranged of31~45MPa, mineralization depth ranged of3.1~5.2km,belonging to the shallow range. Inclusions salinity-homogenization temperature diagramshows that the evolution of forming fluids of the main mineralization stage were mixedeffects from atmospheric precipitation the fluid with low temperature, low salinity early, andwere a slow cooling process latterly, the main reason for mineral deposits is slowcooling,indeed of metasomatism and boiling.Sulfur isotope tests show galena δ34SV-CDT is0.4‰~1‰, mean of0.78‰, poor as0.6‰, sphalerite δ34SV-CDT ranges between2.4‰~2.9‰, with an average of2.7‰, therange of0.5‰, showed a more single source of mineral material, and is derived from thedeep magmatic hydrothermal of the lower crust or upper mantle,metallogenic elementabundances were more enriched in diorite and adamellite trace elements, but also to prove thispoint,and the final concentration of ore-forming elements should occur relating withadamellite formation.In summary,Bianjiadayuan Pb-Zn-Ag deposits is Yanshan caused by extensionalenvironment shallow high-medium-temperature magmatic hydrothermal vein-type lead-zincdeposits. |
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