新疆波孜果尔超大型稀有-稀土金属矿床的成矿时代和成矿动力学背景:来自独居石U-Th-Pb定年和石墨激光拉曼光谱的指示  

Metallogenic age and metallogenic dynamic setting of the Boziguoer super-large rare-rare earth metal deposit in Xinjiang:Insights from monazite U-Th-Pb dating and graphite Laser Raman spectroscopy

作　　者：谢明材 韩春明[1] 范宏瑞[1] 杨奎锋[1] 李兴辉 佘海东 梁改忠 XIE MingCai;HAN ChunMing;FAN HongRui;YANG KuiFeng;LI XingHui;SHE HaiDong;LIANG GaiZhong(Key Laboratory of Mineral Resources,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院地质与地球物理研究所,矿产资源研究重点实验室,北京100029 [2]中国科学院大学地球与行星科学学院,北京100049

出　　处：《岩石学报》2023年第10期2927-2950,共24页Acta Petrologica Sinica

基　　金：国家重点研发战略性矿产资源开发利用项目(2021YFC2901704);青藏高原科学考察任务八子专题(2019QZKK0806)联合资助.

摘　　要：波孜果尔碱性岩型Nb-Ta-Rb-Zr-REE矿床位于塔里木克拉通北缘与南天山造山带的接合地段,是近年来在塔里木北缘碱性岩带中发现的规模最大的稀有-稀土综合性矿床。本文通过对含矿岩体中的独居石和晶质石墨包体开展成矿年代学和岩浆形成条件研究,结合含矿碱性岩全岩成分,揭示波孜果尔碱性岩型稀有-稀土金属矿床的岩石地球化学特征、晶质石墨对成岩/成矿的指示、稀土成矿时代和成矿动力学背景,并进一步总结区域成矿指示意义。研究发现,波孜果尔碱性岩以富含碱性暗色矿物(钠铁闪石和霓石)为特征,岩性以正长岩为主,有较高的稀土总量,富集轻稀土元素和高场强元素(Nb、Ta、Zr、Hf、Th、U等),亏损重稀土元素和Ba、Sr等大离子亲石元素,显示强烈的负Eu异常。通过对晶质石墨的研究发现,不同岩相组中石墨的拉曼谱峰相似,显示具有较高的结晶程度,岩浆演化从细晶到伟晶阶段,石墨的无序度增大,可能与烧绿石和锆石等含放射性元素矿物增多使得辐射加强的影响有关。估算石墨的结晶温度介于700~800℃之间,其形成早于碱性岩浆,指示碱性岩浆早期为还原环境,晚期趋于氧化。独居石LA-ICP-MS U-Th-Pb结果显示波孜果尔稀土矿化时代约为280Ma,结合前人已获得的锆石U-Pb年龄,表明波孜果尔碱性岩浆活动时间从~290Ma到280Ma,持续了至少10Myr。进一步研究发现,从时间和空间上,波孜果尔含矿碱性岩所在的碱性岩带形成与塔里木地幔柱有关。地幔柱就位诱发被先前俯冲物质交代富集稀有-稀土元素和挥发性成分的岩石圈地幔低程度部分熔融形成富成矿元素的碱性岩母岩浆,随后在岩浆演化晚期富集成矿。The Boziguoer alkaline rock-type Nb-Ta-Rb-Zr-REE deposit is located in the junction area of the northern margin of the Tarim Craton and the Southern Tianshan Orogenic Belt.It is the largest alkaline rock-type rare metal-rare earth element composite deposit discovered in the alkaline rock belt on the northern margin of Tarim in recent years.In this paper,studies on the mineralization age of monazite and magmatic formation conditions of crystalline graphite inclusions in ore-bearing rock bodies,together with the whole rock composition of ore-bearing alkaline rocks,are conducted to reveal the petrogeochemical characteristics,crystalline graphite indications for rock/mineral formation,rare earth element mineralization age and mineralization dynamics background of the Boziguoer alkaline rock-type rare metal-rare earth element deposit,and further to summarize the regional mineralization indication significance.The results show that the Boziguoer alkaline rocks are characterized by rich alkaline dark minerals(arfvedsonite and aegirine),mainly syenite in lithology,with high total rare earth content,enriched LREEs and HFSEs(Nb,Ta,Zr,Hf,Th,U),depleted HREEs and LILEs such as Ba and Sr,showing a strong negative Eu anomaly.Through the study of crystalline graphite,it was found that the Raman spectrum peaks of graphite in different lithofacies groups are similar,showing a high degree of crystallization.However,as magmatic evolution progresses from fine-grained to coarse-grained/pegmatite stages,the disorder of graphite increases,which may be related to the increase in radiation due to the increase in radioactive element-containing minerals such as pyrochlore and zircon.The estimated formation temperature of graphite is between 700~800℃,and its formation age is earlier than that of its alkaline magma,indicating that the early stage of alkaline magma was reduced and later tended to oxidize.Monazite LA-ICP-MS U-Th-Pb results show that the age of the Boziguoer rare earth elements mineralization is about 280Ma.Combined with prev

关 键 词：波孜果尔 碱性岩 独居石U-Th-Pb定年 石墨拉曼光谱 地幔柱 塔里木北缘 

分 类 号：P597.3[天文地球—地球化学] P618.7[天文地球—地质学]