阿尔金西段库木塔什萤石矿床成因:磷灰石U-Pb年龄、原位Sr-Nd同位素、地球化学约束
Genesis of Kumutashi Fluorite Deposit in the West Altyn-Tagh Orogen,NW China:Constraints from Apatite In-Situ U-Pb Dating,Sr-Nd Isotope and Chemistry
高永宝 1陈康 2王亮 1赵辛敏 3李艳广 3刘明 1张龙 4王元伟 1张毅 4刘基1
作者信息
- 1. 中国地质调查局金矿勘查技术创新中心,陕西 西安 710100;中国地质调查局西安矿产资源调查中心,陕西 西安 710100
- 2. 中国地质调查局金矿勘查技术创新中心,陕西 西安 710100;中国地质调查局西安矿产资源调查中心,陕西 西安 710100;西北大学 地质学系大陆动力学国家重点实验室,陕西 西安 710069
- 3. 中国地质调查局西安地质调查中心,陕西 西安 710119
- 4. 中国地质调查局金矿勘查技术创新中心,陕西 西安 710100;中国地质调查局西安矿产资源调查中心,陕西 西安 710100;长安大学地球科学与资源学院,陕西 西安 710054
- 折叠
摘要
近年来,阿尔金西段取得萤石找矿重大突破,相继发现卡尔恰尔和库木塔什等矿床,但成矿时代和成矿机制研究薄弱.笔者选取库木塔什矿床与萤石密切共生磷灰石为研究对象,开展原位U-Pb定年、Sr-Nd同位素及地球化学分析,以探讨萤石矿成矿时代及矿床成因.磷灰石常呈自形-半自形结构,表面均匀,单偏光下近乎透明,主要与萤石、方解石、带云母、氟碳铈矿等矿物共生.结果显示,磷灰石U-Pb同位素年龄为(448±27)Ma,成矿作用与碱长花岗岩侵入活动密切相关,均为晚奥陶世构造-岩浆活动产物.磷灰石中F含量为4.20%～5.12%,Cl含量小于0.02%,极低的Cl含量表明出溶的流体Cl含量较低.磷灰石稀土元素含量较高(908×10-6～2 164×10-6),稀土配分曲线显示强烈Eu负异常和Ce正异常,且与萤石、方解石、碱长花岗岩有明显的一致性,推测与岩浆-热液阶段大量流体出溶密切相关.磷灰石的 87Sr/86Sr值为 0.709 13～0.710 47,143Nd/144Nd值为 0.511 38～0.511 53,εNd(t)值为-13.3～-10.3,表明成矿物质具有壳幔混合特征.综合研究表明,阿尔金西段萤石成矿时代为奥陶纪,与同期碱长花岗岩密切相关,形成于后碰撞伸展阶段,成矿流体来源于碱长花岗岩的熔体-流体演化,为岩浆热液充填型矿床.
Abstract
In recent years,significant breakthroughs in fluorite prospecting have been made in the western Al-tyn-Tagh Terrane,and Kaerqiaer,Kumutashi and other deposits have been discovered successively,however,the research on metallogenic epoch and ore-forming processes are still unclear.In this paper,the closely symbi-otic apatite with fluorite were selected as the research object to carry out the main microanalysis of apatite,U-Pb dating and in situ Sr-Nd isotopic test analysis,so as to explore the metallogenic epoch and the genesis of deposit.The apatite often has a self-semi-automorphic structure with uniform surface and nearly transparent under monopolarized light,mainly symbiotic with fluorite,calcite,tainiolite,bastnaesite and other minerals.The study shows that the U-Pb isotope age of apatite microregion is(448±27)Ma,and the fluorite mineralization is close-ly related to the invasive activity of alkali feldspar granite,all of which are the products of the late Ordovician tectonic-magmatic activity.The F content of apatite is 4.20%to 5.12%;the Cl content is less than 0.02%,and the very low Cl content indicates a low dissolved fluid Cl content.The content of rare earth elements is high(908×10-6～2 164×10-6),and the partition curve of rare earth shows strong Eu negative anomaly and positive Ce negative anomaly.This anomaly is obviously consistent with its associated fluorite,calcite and alkali feldspar granite,which may be closely related to the dissolution of massive fluid in the magma-hydrothermal stage.The ratio of 87Sr/86Sr of apatite is from 0.709 13 to 0.710 47,the ratio of 143Nd/144Nd is from 0.511 38 to 0.511 53,and εNd(t)is from-13.27 to-10.26,reflecting that the ore-forming materials have the characteristics of crust-man-tle mixing.Comprehensive studies show that the ore-forming age of fluorite in the western Altyn-Tagh Terrane is Ordovician,closely related to the same period alkali feldspar granite,formed in the post-collision extension stage,the ore-forming fluid may be derived from the melt-fluid evolution of alkali feldspar granite,and it is a magmatic hydrothermal filling type deposit.
关键词
地球化学特征/磷灰石/萤石矿床/库木塔什/阿尔金西段Key words
geochemical characteristics/apatite/fluorite deposit/the Kumutashi deposit/West Altyn-Tagh Orogen引用本文复制引用
基金项目
陕西省自然科学基础研究计划项目(2023-JC-YB-241)
中国地质调查局自然资源综合调查指挥中心科技创新基金项目(KC20230011)
中国地质调查局项目(DD20190143)
&&(DD20243309)
&&(DD20211551)
出版年
2024
国家科技期刊平台
NSTL
万方数据