| The Xiemisitai area is located in the northern part of western Junggar,Xinjiang,and is the eastern extension of the Boshchekul-Chingiz volcanic arcs in China.The area belongs to the Central Asia metallogenic region Balkhash-Jungar mineralization province Poshekul-Genghis-Xiemisitai-Shalbuti ore belt.Magmatic activity is developed in this area,and the development of porphyry copper?gold?mineralization associated with small porphyry and volcanic rocks formed in Silurian.Based on the previous studies,this paper selects the Shemisitai blatter porphyry copper mineralization,and systematically studies its geological characteristics,ore-forming physical and chemical conditions,ore-forming fluids,and sources of ore-forming materials.Metallogenic conditions and main controlling factors of porphyry copper deposits in this area,as well as the conditions for deposit preservation,discuss the metallogenic process,identify the target geological bodies for porphyry deposits,analyze the deep prospecting potential,and provide early Paleozoic plaques for the area Further prospecting of rock type copper deposits provides theoretical guidance.The paper has achieved the following main findings and results:?1?Through detailed field geological observations and indoor rock?mineral?facies studies,the geological characteristics of the Blatter porphyry copper mineralization were identified and the metallogenic periods were dividedBlatter porphyry copper mineralization occurs in Blatter mineralized subvolcanic rocks?Dacite porphyry and Rhyophytic porphyry,formed in the Early Silurian and Late Silurian,respectively?.The rock has developed strong chloridite and chlorite petrified surface alterations,as well as alterations such as silicification and carbonate formation,and localized muddying,developed of various metasomatic and filling veins,such as Quartz veins,quartz chloridite veins,chloridite veins,carbon Various veins.Porphyry copper mineralization is mainly developed in altered subvolcanic rocks and hydrothermal veins after the magmatic period,and the surface rocks are nearly full-rock mineralized.The primary sulfides are porphyry,chalcopyrite and pyrite,which occur strongly secondary oxidation,mainly malachite,chalcocite,etc.The ore structure is mainly semi-self-shaped-granular structure,metasomatic structure and typical Chalcopyrite-Bornite solid solution separation structure.The ore structure is mainly impregnated,fine veined and veined.The metallogenic period can be divided into the main metallogenic period?the hydrothermal period after the magmatic period?and the superficial metallogenic period?the secondary oxidation period?.The main metallogenic period can be divided into three stages according to different ore deposits:Copper mineralization,quartz-sulfide and chlorite-vein-sulfide phases in meta-porphyry.?2?Conducted geochemical studies on quartz fluid inclusion deposits and S,H-O,Si stable isotopes,and analyzed fluid sources and fluid evolution,the mineralization materialsStudies have shown that inclusion studies show that the ore-forming fluid belongs to the Na Cl-H2O system,and the ore-forming hydrothermal fluids from the early medium-high temperature,medium-low salinity,and medium-low density ore-forming fluids?uniform temperature is 475.3?194.3?,mainly concentrated at 430?290?,Salinity changes from6.0?23.66w B%Na Cleqv,density changes from 0.57?0.97g/cm3?to late medium medium and low salinity,medium and low density?uniform temperature is 242.2?154.2?,salinity changes from 0.7?17.4w B%Na Cleqv,density changes from 0.84?1.01g/cm3?,fluid mixing plays a leading role in fluid evolution.Copper mineralized sulfide?34S has a wide composition range,mainly distributed in three intervals:-20.2‰?-18.53‰,-13.7‰?-5.8‰,-1.3‰?0.62‰,concentrated in the vicinity of 0 And-8‰?-6‰,it shows that the ore-forming material has both magmatic and stratigraphic organic sulfur sources,but mainly deep-source magmatic sources;the?18O value of quartz is 4.3‰?13.0‰,and the?D value of the fluid is-96.5‰?-70.4‰,when the ore-forming fluid and quartz reach equilibrium,the value of?18OH2O is-8.2‰?7.6‰,indicating that the ore-forming fluid was a source of magma in the early ore-forming period,and atmospheric precipitation was gradually added with the ore-forming process.Significant oxygen drift occurred,and atmospheric precipitation was dominant in the late stage of mineralization;the distribution range of quartz?30Si was-0.5‰?0.2‰,and there was no significant difference in the?30Si composition of quartz at different mineralization stages,indicating that the source of Si O2 was basically the same and Originating from or closely related to magma.The above results show that the Blatter porphyry copper mineralization ore-forming fluids and ore-forming materials are multi-sources,but mainly magma sources.?3?Discuss the mineralization processIn Silurian,strong magmatic activity occurred in the area of Xiemisitai,which was formed in the continental margin arc environment under the background of subduction.It derived from partial melting of juvenile crust that is caused by basaltic magma upwelling from with a depleted asthenosphere mantle.The dacite and rhyolite magmas with high oxygen fugacity,with a difference of about 10 Ma,carried a large number of ore-forming elements upward to the near surface environment,During the rising process of magma,the temperature and pressure dropped significantly,which caused most of the volatiles in the magma to complex a large amount of ore-forming materials into the magma hydrothermal fluid.In the late stage of magmatic activity,the copper elements and fluids originating from the magma aggregated significantly.Under the effects of fluid mixing,the conditions of the physics-chemical equilibrium of the ore-forming fluid were destroyed,and finally a large amount of Cu was formed under suitable structural parts and lithological conditions.Unloading and enrichment,forming Blatter porphyry copper mine.?4?Analysis of metallogenic potential and prospecting direction of porphyry copper deposits in the Xiemisitai areaThe Xiemisitai area has favorable metallogenic geological background,tectonic environment and geological conditions for the porphyry copper deposits.The favorable ore-forming magmatic conditions,provenance conditions and fluid conditions should have good porphyry copper deposit formation.Mineral potential and prospecting.The overall uplift and erosion after the mineralization is not very strong in the Xiemisitai area,and the deposit conditions is good.Mineralization information of the Bulansala copper-gold deposits that have been found in the Silurian shallow intrusive rocks and the Blatter copper deposits that are present in the Silurian secondary volcanic rocks have shown that there is a good metallogenic potential of porphyry copper deposits in the area.The medium-acid small porphyry formed in the Middle Silurian in the XIemisitai area is the target geological for the porphyry copper-gold mineralization;the Silurian medium acidic subvolcanic rock is the target geology for the porphyry copper mineralization,In comparison,its deep part should have better prospecting potential for porphyry copper deposits.The porphyry copper?gold?mineralization related to the Early Paleozoic magmatic activity is the main type of mineralization in the subsequent prospecting breakthroughs in the Xiemisitai area. |
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