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

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SiO₂，贫Al₂O₃、TiO₂、MgO、P₂O₅，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。

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

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 SiO2, but poor in Al2O3, TiO2, MgO and P2O5, 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.