阿尔金卡尔恰尔超大型萤石矿带成因:来自年代学、稀土元素和Sr-Nd同位素的约束  

Genesis of Kalqiaer Super-large Fluorite Zone in Altyn Tagh Area:Chronology,Rare Earth Elements and Sr-Nd Isotopes Constraints

作　　者：赵辛敏 高永宝[1,2] 燕洲泉 张江伟[1] 王博[3] 金谋顺[1] ZHAO Xinmin;GAO Yongbao;YAN Zhouquan;ZHANG Jiangwei;WANG Bo;JIN Moushun(Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits,MNR,Xi’an Center of China Geological Survey,Xi’an 710054,Shaanxi,China;Xi’an Center of Mineral Resources Survey,China Geological Survey,Xi’an 710100,Shaanxi,China;Geology Institute of China Chemical Geology and Mine Bureau,Beijing 100101,China)

机构地区：[1]自然资源部岩浆作用成矿与找矿重点实验室,中国地质调查局西安地质调查中心,陕西西安710054 [2]中国地质调查局西安矿产资源调查中心,陕西西安710100 [3]中化地质矿山总局地质研究院,北京100101

出　　处：《西北地质》2023年第1期31-47,共17页Northwestern Geology

基　　金：陕西省自然科学基础研究计划项目“阿尔金西段吐格曼伟晶岩型稀有金属矿床成矿机制研究”(2022JQ-268);国家重点研发计划课题“西部锂、铍等战略性金属矿产资源成矿规律与预测评价”(2019YFC0605201);中国地质调查局项目“西北地区铜镍稀有金属等矿产地质调查”(DD20221691)联合资助。

摘　　要：阿尔金卡尔恰尔一带近年来萤石找矿取得重大突破,新发现卡尔恰尔、小白河沟、库木塔什、拉依旦北、盖吉克等多处萤石矿,形成超大型萤石矿带。矿带内萤石矿与肉红色碱长花岗岩关系密切,矿化主要赋存于岩体内外接触带附近,赋矿围岩主要为阿尔金岩群中的黑云斜长片麻岩、碳酸盐岩等富钙质岩系,矿体明显受北东向断裂构造控制,矿石类型主要有脉状、角砾状、块状、条带状矿石,矿物组成主要是萤石、方解石,矿床成因类型属于热液充填型。LA-ICP-MS锆石U-Pb测试结果表明,卡尔恰尔超大型萤石矿区与成矿有关的碱长花岗岩成岩年龄为(455.8±2)Ma,结合区域成岩成矿年代学研究,认为该萤石矿带形成于加里东期中—晚奥陶世,为挤压造山转变成伸展构造背景下岩浆活动的产物。矿区片麻状钾长花岗岩锆石U-Pb年龄为(914.5±4.1)Ma,形成于新元古代早期,与Rodinia超大陆汇聚事件有关。稀土元素特征显示,卡尔恰尔、小白河沟、库木塔什3个矿床的萤石、方解石稀土元素配分模式均为右倾的LREE富集型,具有明显的负Eu异常,与成矿岩体、围岩地层十分相似,表明萤石、方解石的稀土可能继承了岩体、地层的稀土配分模式。各矿床萤石均为热液成因,表现出同源同期成矿流体的特征,成矿环境为还原条件下的中低温环境。各矿区萤石Sr-Nd同位素组成显示成矿物质来源于地壳,结合成矿特征初步认为Ca可能主要来源于岩浆热液对地层的淋滤萃取,而F可能主要来源于成矿岩体碱长花岗岩。In recent years,great breakthroughs have been made in fluorite prospecting of Altyn-Tagh which new discovery of the super-large fluorite ore belt in the Kalqiaer area.The typical fluorite ore deposits such as Kalqiaer,Xiaobaihegou,Kumutashi,Layidan and Gaijike are closely related to and mainly distributed in the outer contact zones of the flesh red alkali feldspar granite.The host rocks are mainly biotite plagioclinal gneiss and carbonate rocks in Altyn rock group.Their orebodies obviously controlled by NE direction fault structure and the main ore types are veined,brecciated,massive and banded ore which major minerals are fluorite and calcite.The genesis of the deposit belongs to hydrothermal filling deposit.Zircon LA-ICP-MS dating yields concordant ages of 455.8±2 Ma for the alkali feldspar granite in the Kalqiaer super-large fluorite deposit which indicating it was formed in the Middle to late Ordovician and was the product of magmatic activity in the transitional tectonic setting from the compressional to extensional segimes.Gneissic potassium feldspar granite obtains the concordant age of 914.5±4.1 Ma respectively indicating it was formed in the early Neoproterozoic and related to the convergence event of the Rodinia supercontinent.The rare earth element characteristics show that the distribution pattern of rare earth in fluorite and calcite was a rightward light rare earth enrichment type,with negative Eu anomalies.The REE patterns of fluorite and calcite are similar to the ore-forming rock and ore-hosting strata,indicating a genetic relationship.Fluorite deposits in Kalqiaer area are hydrothermal origin,showing the characteristics of homologous and homochronous ore-forming fluids,and the ore-forming environment is medium-low temperature under reducing conditions.The Sr-Nd isotopic composition of fluorite in Kalqiaer area shows that the ore-forming materials are all derived from the crust.It is suggested that Ca may be mainly derived from the leaching extraction of the strata by magmatic hydrothermal,whil

关 键 词：萤石矿床 锆石U-PB年龄 稀土元素 SR-ND同位素 卡尔恰尔 阿尔金 

分 类 号：P595[天文地球—地球化学] P611[天文地球—地质学]