The Study On Mineralization Mechanism Of The Baliersi Iron Deposit In The Southern Of Altay, Xinjiang

The South of Altay orogenic belt is important copper, iron, zinc-lead, nickel,gold and REE metallogenic belt in China. Baliersi iron deposit is located in MaiziBasin of the south margin of Altay orogenic belt. The orebodies are hosted in themetamorphosed volcaniclastic-sedimentary rocks of the Upper Silurian-LowerDevonian Kangbutiebao Formation. Abundant skarn minerals as garnet, diopside,amphibole, epitote, chlorite are widely distributed around the orebodies. This paperbased on detailed field study of Baliersi deposit, using some feasible methods such asEPMA, LA-ICP-MS zircon U-Pb dating, major and trace elements measuring, stableisotope measuring and inclusion homotemperature measuring, recognize its petrology,mineralogy, chronology and geochemistry characteristics. Some study results are asfollows:（1） The orebodies are hosted in the metamorphosed volcaniclastic-sedimentaryrocks of the Upper Silurian-Lower Devonian Kangbutiebao Formation. Theorebodies are largely concordant with the bedding of the strata, and the wall rocks areamphibolite, granulite and leptite.（2） Petrographic observation indicate three periods of metallogenic, includingskarns period, regional metamorphism period and supergene oxidation period. skarnsperiod experiences three stage, that is skarns, retrograde and quartz-sulfide.（3） Electron microprobe analyses show that the end number of garnet isAnd60.41⁸9.84Gro3.01³6.60Alm0.47¹1.56. The composition of clinopyroxene is Di50.38⁷5.43Hd22.99⁴7.02Jo1.38³.35.The amphiboles show insignificant compositional variation,mostly being ferrotschermakite. all of them show the characteristics of calcic skarn.The feature of major elements, trace elements and rare elements of magnetite isclosely related to the skarns.（4） The ore-forming fluids in skarn period is high-middle temperature,middle-low salinity and middle-low density, which is belong to H₂O-NaCl system;The ore-forming fluids in retrogressive metamorphism stage is middle temperature,middle-low salinity and middle-low density, which is belong to H₂O-NaCl system; The ore-forming fluids in regional metamorphism period is dominantly H₂O-NaCl–CO2system.（5） The ore-forming fluids in skarn period is magmatic water mixing of meteoricwater. The ore-forming fluids in regional metamorphism period is metamorphismhydrothermal and atmospheric precipitation.The sulfide and rare earth element dataof rocks and ores suggest that the ore-forming materials is mainly derived from theamphibolite.（6） LA-ICP-MS U-Pb zircon dating on the amphibolite in the district, yieldedconcordant ages of385±1.6Ma. which is earlier than the mineralization age.（7） The Baliersi iron deposit is belong to skarn type, and the mineralizationmechanism is Biotite-quartz-mica-diorite magmatic hydrothermal interacting withKangbutiebao Formation volcanic, the formation of magnetite is related to theretrogressive metamorphism of the skarns.