西藏尼雄矿田日阿铜矿床矽卡岩矿物学特征及地质意义  

Mineralogical characteristics of skarn in Ri'a copper deposit of Nixiong orefield,Tibet,and their geological significance

作　　者：于玉帅 杨竹森[2] 刘英超[3] 田世洪[2] 赵灿 高原 纪现华[2,5] 胡为正 曹圣华 

机构地区：[1]武汉地质矿产研究所,湖北武汉430205 [2]中国地质科学院矿产资源研究所,北京100037 [3]中国地质科学院地质研究所,北京100037 [4]江西省地质调查院,江西南昌330201 [5]中国地质大学地球科学与资源学院,北京100083

出　　处：《矿床地质》2012年第4期775-790,共16页Mineral Deposits

基　　金："十一五"国家科技支撑计划项目(2006BAB01A04);国家重点基础研究发展计划973项目(2011CB403100;2009CB421007);地质调查计划项目(1212010918014)联合资助

摘　　要：尼雄矿田位于冈底斯成矿带西段中部隆格尔-南木林岩浆岩带的北侧。日阿铜矿床位于尼雄矿田的东南端,矿体产于晚白垩世侵入岩与下拉组灰岩接触带的矽卡岩或矽卡岩化大理岩中,主要矽卡岩矿物有石榴子石、透辉石、蛇纹石、金云母、绢云母、硅镁石、阳起石、透闪石、绿帘石、绿泥石等。电子探针分析表明,矿区石榴子石主要为钙铁榴石,次为钙铝榴石;辉石以透辉石为主;金云母明显富镁贫铁,且富含挥发分F;闪石类矿物属钙角闪石系列;绿泥石富镁贫铁。推断成矿流体大致经历了5个演化阶段:①干矽卡岩阶段,高温(>450℃)、低pH值、氧化-弱氧化;②湿矽卡岩阶段,温度降低,pH值和氧逸度逐渐升高;③氧化物阶段,温度进一步降低,pH值升高(碱性),氧逸度则呈降低趋势;④石英硫化物阶段,中等温度(200～300℃),高pH值(碱性),低氧逸度;⑤碳酸盐阶段,低温(160～203℃),低pH值,低氧逸度。此外,矿区还存在多金属矿化的可能。The Nixiong orefield is located in northern Longgeér-Nanmulin magmatic belt along the central part of western Gangdise metallogenic belt.The Ri＇a copper deposit is in southeast Nixiong ore field.The ore bodies mainly occur in the skarn and skarnized marble,which lie between the intrusive rock and Xiala Formation.The main skarn minerals are garnet,diopside,serpentine,phlogopite,actinolite,humite,tremolite,epidote,chlorite,sericite and so on.Electron microprobe analyses show that the garnet is composed mainly of grossularite（62.08%） and andradite（35.08%）.Almost all the pyroxenes belong to diopside.Phlogopites are rich in iron and poor in magnesium,also with features of high F.The amphiboles show characteristics of calc-amphibole.The chlorites are rich in magnesium and poor in iron.According to the above data,the authors infer that the ore-forming fluid might have experienced the following five evolutionary stages：① dry skarn stage of high temperature（450℃）,low pH,oxidation-weak oxidation;② wet skarn stage of lower temperature,with gradual increasing pH value and oxygen fugacity;③ oxide stage of further reducing temperature,increasing pH value（alkaline） and decreasing oxygen fugacity;④ quartz sulfide stage with temperature down to 200～300℃,high pH（alkaline）,low oxygen fugacity;⑤ carbonate stage of low temperature（160～203℃）,low pH and low oxygen fugacity.In addition,there probably exists more metal mineralization in the Ri＇a copper deposit.

关 键 词：地球化学 矽卡岩 矿物学 电子探针分析 日阿铜矿床 尼雄矿田 西藏 

分 类 号：P618.41[天文地球—矿床学]