【摘要】：西山灣羊場火山巖銀礦床位于內(nèi)蒙古中西部,大地構(gòu)造位置處于華北地臺(tái)西北部。銀礦體上盤圍巖為二疊紀(jì)黑云母二長花崗巖,下盤圍巖為寒武紀(jì)英云閃長巖,礦體呈透鏡狀或似層狀產(chǎn)出于下白堊統(tǒng)白女羊盤組及其與上下盤的接觸帶,賦礦巖石主要為具硅化、褐鐵礦化的碎裂流紋巖、流紋斑巖。礦石結(jié)構(gòu)主要有自形-半自形粒狀結(jié)構(gòu)、他形粒狀結(jié)構(gòu)、交代殘余結(jié)構(gòu)、碎裂結(jié)構(gòu)等;礦石構(gòu)造主要有角礫狀構(gòu)造、浸染狀構(gòu)造、脈狀構(gòu)造、塊狀構(gòu)造等。主要礦化現(xiàn)象為褐鐵礦化、黃鐵礦化、螢石礦化,局部見鉛鋅礦化。礦石礦物主要為黃鐵礦、輝銀礦、螺狀硫銀礦、閃鋅礦、方鉛礦等,礦物生成順序:黃鐵礦-閃鋅礦(黃銅礦)-方鉛礦-赤鐵礦-輝銀礦。根據(jù)礦物間的相互交代關(guān)系,將礦化過程分為早、中、晚三個(gè)階段,分別為石英-黃鐵礦、石英-多金屬硫化物和石英-碳酸鹽組合為標(biāo)志,特征性圍巖蝕變主要為褐鐵礦化、硅化、綠泥石化、碳酸鹽化等。脈石礦物主要有石英、蛋白石、玉髓、螢石、鉀長石及少量絹云母等。礦石的石英中主要可見氣液兩相水溶液包裹體,還可見少量含石鹽子晶三相包裹體,偶爾可見含硫化物子晶多相包裹體。早階段流體包裹體均一溫度大于330℃,鹽度0.35%~5.86%NaCleqv,主要發(fā)育氣液兩相的水溶液包裹體,為高溫、低鹽度流體特征;中階段流體包裹體均一溫度集中在250~330℃,鹽度為0.35%~31.90%NaCleqv,除水溶液包裹體外,還可見含石鹽子晶三相包裹體和含硫化物子晶多相包裹體,以低鹽度的水溶液包裹體和高鹽度的含子礦物多相包裹體并存為特征;晚階段流體包裹體均一溫度集中在169~250℃,鹽度0.71%~32.66%NaCleqv,除水溶液包裹體外,還可見含石鹽子晶三相包裹體,以低鹽度的水溶液包裹體和高鹽度的含石鹽子礦物包裹體并存為特征。中階段的含硫化物子礦物多相高鹽度流體包裹體是"巖漿二次沸騰"形成的,晚階段的含石鹽子礦物高鹽度流體包裹體是直接從結(jié)晶的熔體中出溶的,流體混合是該礦床的可能成礦機(jī)制,金屬沉淀主要是因含金屬高鹽度流體與冷的地下水在礦石沉淀部位混合而最終沉淀富集成礦。
[Abstract]:The Yanchang volcanic silver deposit in Xishan Bay is located in the central and western part of Inner Mongolia, and the tectonic position is in the northwest of North China platform. The upper wall rock of silver ore body is Permian biotite monzogranite, and the lower wall rock is Cambrian dolomite diorite. The orebody is lenticular or bedded in the lower Cretaceous Biniuyangpan formation and its contact zone with upper and lower plates. The ore-bearing rocks are mainly silicified, limonitization cataclastic rhyolite and ribbed porphyry. The ore structure mainly consists of automorphic-semi-automorphic granular structure, heteromorphic granular structure, metasomatic remnant structure, cataclastic structure and so on, while ore structure mainly includes breccia structure, disseminated structure, vein structure, block structure and so on. The main mineralization phenomena are limonite mineralization, pyrite mineralization, fluorite mineralization and local lead zinc mineralization. The ore minerals are mainly pyrite, pyroxene, snail sulfide, sphalerite, galena, etc. The order of mineral formation is: pyrite-sphalerite (chalcopyrite)-galena-hematite-pyroxene. According to the mutual metasomatism of minerals, the mineralization process is divided into three stages: quartz pyrite, quartz polymetallic sulphide and quartz carbonate assemblage. Silicification, green mud fossilization, carbonation, etc. Gangue minerals are mainly quartz, opal, chalcedony, fluorite, potassium feldspar and a small amount of sericite. There are mainly gas-liquid two-phase aqueous inclusions in quartz, a small amount of three-phase inclusions with rock salts, and polyphase inclusions containing sulphide crystals occasionally. The homogenization temperature of fluid inclusions in early stage is more than 330 鈩，

本文編號：2191041