| Balugou Polymetallic Deposits is located geotectonically at the north edge ofMiddle East Kunlun in Dulan County, Qinghai Province. The deposits lies in thenortheast of Wulonggou ore concentration area. As the important mineral base ofQinghai Province, it has a good geological condition of Mineralzation and also is richin mineral resources.Most of the exposed strata in this area are the Lower Proterozoic Baishaheformation in Jinshuikou Group. Rocks are composed of biotite plagioclase gneiss,amphibole plagiogneiss, quartzose schist, biotite plagioclase schist, plagioclasitehornblende schist with lentoid marble. The strata is striked by NW-SN, dipping NE.The faults are well-developed, and the NW-striked faults mainly control and hold themineralized rocks in the deposits. Intrusive rocks are mostly alkali feldspar granite,which cotrolled skarn-type mineralization. The granite zircon U-Pb age is244Ma,which belongs to the Middle Triassic epoch.The mine district can be divided into three polymetallic ore belts, i.e. the Ⅱ belt,Ⅴ belt and Ⅷ belt. There are40ore bodies, which all lie in the contact betweenmarble lenses and acid intrusive rocks. The ore bodies are controlled by the NW-strikedfaults.The metallic minerals in ores are mainly composed of chalcopyrite, pyrite, galena,sphalerite, pyrrhotite, native bismuth and so on. The gangue minerals consist mainly ofquartz, feldspar, calcite and so on. Major textures of ores are characterized by cataclastic, sosoloid-separation, metasomatic relict, euhedral-subhedral and poikilitictextures etc. The structures of ores are comoposed of massive, disseminated and veinstructures. The country rock alterations are mainly composed of skarnization, and withminor baratization, carbonatization, chloritization.The granite related to the mineralization of Balugou Polymetallic Deposits contain64.89%75.34%of Sio2,12.46%14.84%of Al2O3,3.93%6.54%of K2O,2.51%3.91%of Na2O,0.33%0.52%of MgO,1.28%3.59%of CaO and0.02%0.08%of P2O5. The rock belongs to the group of high-K calc-alkali series and also hasthe aluminous-peraluminous characteristics. The REE pattern shows that the rockenriches in LREE, lacks HREE and has Eu negative anomaly at the same time. Therock is rich in large ion lithophile element e.g. Rb, Ba, K etc. and active incompatibleelements e.g. Th, U, Pb etc. and deplet in high field intensity elements e.g.Nb, Ta, La,Ce, P, Ti etc. Granite gentic type is I type. The forming geotectonic setting of Balugougranite is characterized by not only volcanic arc but also syc-collision to post-collisiongranites. Sr-Nd isotope shows that the material source comes from the mantle with themixture of the earth’s crust. Hf isotope of zircon shows that the granite resulting fromthe partial melting of juvenile mantled-derived mafic lower crust, and the Pb isotope ofpotassium feldspar shows the characteristics of enriched mantle and also the features oforogenic belt granite. According these facts, we argue that the juvenile mantled-derivedmafic lower crust formed from the partial melting of mantle in Mesoproterozoic, thenthis juvenile lower crust generate the Balugou granite through partial melting in MiddleTriassic epoch.Microthemometer of fluid inclusion in Balugou Polymetallic Depositsdemonstrate that the peak homogenization temperatures of quartz-sulphide periodranges from160℃to280℃, the peak value of fluid salinity is410%NaCl, the peakvalue of the fluid density is0.840.96g/cm3.Totally speaking, the fluid put up thefeatures of medium-high temperature, low salinity and low-density.The range of the result of δ34SV-CDTvaries from-2.1‰to2.8‰, xmax-xmin is4.9‰, mean value is0.07‰. δ34SV-CDTspread around the zero line, shows Sulfur comes from magma. Lead isotope result of metallic mineral in ore shows that206Pb/204Pbrange from18.3647to18.4287,207Pb/204Pbrange from45.6332to15.6415,208Pb/204Pbrange from38.4555to38.4961.The results indicate that lead comes from mantle, and italso show that the lead in ore and that in the potassium feldspar are same orgin. Finallyit was considered that metallogenic materials of Balugou deposits comes from thegranite in this ore district. And the metallogenic age is later than the granite. Balugoudeposits is the production of Middle Triassic epoch metallogenesis in East Kunlun.After the comprehensive research of Balugou deposits, such as, regional geology,geology in ore district, geological features of ore deposits, physical-chemicalconditions and the origin of metallogenic material, we confirm that the genesis of theBalugou deposits is skarn-type polymetallic deposits formed in Middle Triassic epoch.On the basis of the metallogenic genesis, a metallogenic model was established. |
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