新疆康西瓦伟晶岩的成矿潜力判断:来自锆石U-Pb年代学、地球化学与Hf同位素证据  

Judgment of metallogenic potential of Kangxiwa pegmatite in Xinjiang:Evidence from zircon U-Pb geochronology,geochemistry and Lu-Hf isotope

作　　者：陈谋 王核[1] 张晓宇 闫庆贺 高昊 CHEN Mou;WANG He;ZHANG XiaoYu;YAN QingHe;GAO Hao(CAS Key Laboratory of Mineralogy and Metallogeny,Guangzhou Institute of Geochemisty,Chinese Academy of Sciences,Guangzhou 510640,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院广州地球化学研究所矿物学与成矿学重点实验室,广州510640 [2]中国科学院大学,北京100049

出　　处：《岩石学报》2022年第7期2095-2112,共18页Acta Petrologica Sinica

基　　金：第二次青藏高原综合科学考察(2019QZKK0802);国家自然科学基金项目(91962215,41972088);新疆维吾尔自治区科技重大专项、重点研发专项(2019B00011、2020A03005);国家重点研发计划项目(2019YFC0605201)联合资助.

摘　　要：稀有金属作为战略性关键金属矿产对我国国家安全和经济健康可持续发展具有重要的意义。它们是不可再生的,并具有独特的物理化学性质。新疆西昆仑地区通过多年的基础地质调查和找矿勘查,在大红柳滩-白龙山一带的稀有金属找矿取得重大突破。本文对大红柳滩西的康西瓦铅银矿区中的无矿伟晶岩进行了岩石学、元素和同位素地球化学及同位素年代学综合研究。无矿伟晶岩富SiO_(2),贫Al_(2)O_(3)、TiO_(2)、MgO、P_(2)O_(5),主体属于高钾钙碱型系列岩石;无矿伟晶岩中的锆石是岩浆锆石,LA-ICPMS U-Pb年龄为208±5.5Ma~210.3±2.3Ma。稀土总量低(∑REE 4.21×10^(-6)~26.98×10^(-6)),亏损重稀土元素,Eu负异常明显(δEu为0.04~0.61),富集Rb、U和K,亏损Nb、La和Zr,严重亏损Ba、Ti和Sr。研究表明,康西瓦无矿伟晶岩与其东侧的大红柳滩岩体形成于同一时期,Hf同位素特征相似。根据大红柳滩稀有金属矿床成矿特征,预测康西瓦含绿柱石白云母伟晶岩脉带以北喀拉喀什河第四系覆盖区及康西瓦一带海拔更高的地段是下一步锂矿找矿取得突破的有利区段。Rare metals,as the strategic key metal minerals,are of great significance to the national security,economic health and sustainable development of our country.They are non-renewable and have unique physical and chemical properties.Through years of basic geological survey and prospecting in West Kunlun region in Xinjiang,a major breakthrough has been made in rare metal prospecting in the Dahongliutan-Bailongshan.In this paper,we conducted a combined study on detailed ziron U-Pb geochronology,Hf isotope,whole-rock major and trace elements in the Kangxiwa non-mineral pegmatites.These pegmatites are rich in SiO_(2),but poor in Al_(2)O_(3),TiO_(2),MgO and P_(2)O_(5),and mainly belong to high-potassium calcium-alkali type series rocks.Zircons from the pegmatites are of magmatic origin,with LA-ICP-MS U-Pb ages of 208±5.5Ma to 210.3±2.3Ma,which are consistent with the age of Dahongliutan pluton,indicating that they are the products of the same tectonic event.Furthermore,these pegmatites are characterized by low REE contents(∑REE=4.21×10^(-6)~26.98×10^(-6))with HREE loss,obvious negative Eu anomaly(δEu=0.04~0.61),enrichment of Rb,U and K,considerably loss of Nb,La and Zr,and serious loss of Ba,Ti and Sr.The research demonstrates that the Kangxiwa non-mineral pegmatites and the Dahongliutan pluton were formed in the same period,with similar Hf isotope characteristics.According to the metallogenic characteristics of Dahongliutan rare metal deposit,it is predicted that the Quaternary cover area of Kalakashi River north of Kangxiwa beryl-muscovite pegmatite dike zone and the section with higher elevation in Kangxiwa area are favorable areas for further lithium ore prospecting breakthrough.

关 键 词：锆石U-Pb年龄 HF同位素 晚三叠世 康西瓦 西昆仑造山带 

分 类 号：P588.131[天文地球—岩石学] P597.3[天文地球—地质学] P618.71