新疆卡鲁安硬岩型锂矿床成矿流体性质:来自He—Ar同位素证据  

Characteristics of ore-forming fluids in Kalu’an hard-rock-type lithium deposit in Xinjiang Province,China: evidence from He—Ar isotopes

作　　者：刘涛 田世洪[2,1] 王登红 侯可军[2] 张玉洁[2,3] 李贤芳 杰肯·卡里木汗 张忠利 王永强 赵悦 秦燕[2] LIU Tao;TIAN Shihong;WANG Denghong;HOU Kejun;ZHANG Yujie;LI Xianfang;JIEKEN Kalimuhan;ZHANG Zhongli;WANG Yongqiang;ZHAO Yue;QIN Yan(State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang,330013;MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing,100037;School of Earth Science and Mineral Resources,China University of Geosciences,Beijing,100083;No.701 Geological Team,Bureau of Nonferrous Geo-exploration of Xinjiang Uygur Autonomous Region,Altar,836500)

机构地区：[1]核资源与环境国家重点实验室东华理工大学,南昌330013 [2]自然资源部成矿作用与资源评价重点实验室中国地质科学院矿产资源研究所,北京100037 [3]中国地质大学地球科学与资源学院,北京100083 [4]新疆维吾尔自治区有色地质勘查局七○六队,新疆阿勒泰836500

出　　处：《地质论评》2021年第6期1697-1708,共12页Geological Review

基　　金：国家重点研发计划课题(编号:2017YFC0602705);江西省双千计划和东华理工大学资助项目(编号:1410000874)的成果。

摘　　要：卡鲁安锂矿床位于新疆北部的阿尔泰造山带,是以锂辉石为主要矿石矿物的硬岩型锂矿床。前人对该矿床的岩石成因、成矿机制及构造背景已经有了初步的认识,但对该矿区内成矿流体的研究仍是空白,这将在一定程度上影响对矿床成因的认识。本文通过分析卡鲁安伟晶岩中锂辉石和石英流体包裹体He、Ar同位素组成,对成矿流体进行示踪研究。研究表明,含矿伟晶岩的n(^(3)He)/n(^(4)He)为0.25~3.19 Ra(平均0.97 Ra),无矿伟晶岩与外围伟晶岩n(^(3)He)/n(^(4)He)为0.13~5.32 Ra(平均1.13 Ra),均介于壳源与幔源He之间。根据成矿流体的壳幔二元混合模式进行计算:含矿伟晶岩中的地幔流体比例为3.55%~48.92%,平均值为14.67%,无矿伟晶岩与外围伟晶岩地幔流体占比为1.70%~81.79%,平均值为17.13%。含矿伟晶岩成矿流体的n(^(40)Ar)/n(,Ar)为552.50~13353.00,n(^(36)Ar,)相对含量为46.52%~97.79%,平均值为87.25%,大气的Ar贡献平均为12.75%。分析结果显示,成矿流体主要以壳源流体为主,部分幔源流体和改造型饱和大气水的混合流体,随着成矿作用的进行,地幔He与大气饱和水改造Ar皆有所减少。值得注意的是卡鲁安锂矿床成矿流体中幔源物质并非真的来自于地幔物质上侵,更有可能是来源于元古代的不成熟陆壳熔融。新疆卡鲁安锂矿床形成于陆—陆碰撞造山作用晚期的后碰撞造山阶段,造山后期的伸展导致含幔源物质的古老地壳与年轻地壳减压熔融,熔融所形成的岩浆流体随后经大气降水改造为成矿流体。Objectives: The Kalu’an lithium deposit is located in the Altay orogenic belt in northern Xinjiang,which is a hard rock type lithium deposit with spodumene as the main mineral. A lot of research on the petrology,mineralogy,petrochemistry,age and petrogenesis in the Kalu ’an lithium deposit,but few reports have been made on the Characteristics of ore-forming fluids.Methods: This paper reports He and Ar isotopic compositions of spodumene and quartz fluid inclusions in Kalu’an lithium ore.Results: The analytical results indicate that the n(;He)/n(;He) ratio of spodumene-bearing pegmatites is0. 25 ~ 3. 19 Ra( average 0. 97 Ra);and that of spodumene—barren pegmatites and outer pegmatites is 0. 13 ~8. 86 Ra( average 3. 10 Ra),which is between crust and mantle derived He. According to the crust mantle binary mixing model of ore-forming fluid,the proportion of mantle fluid in spodumene-bearing pegmatites is 3. 55% ~48. 92%,with an average of 14. 67%;the proportion of mantle fluid in spodumene—barren pegmatites and outer pegmatites is 1. 70% ~ 81. 79%,with an average of 17. 13%. The n(^(40)Ar)/n(^(36)Ar) of ore-forming fluid of spodumene-bearing pegmatites ranges from 552. 5 to 13353. 0,n(^(40)Ar) values range from 46. 52% to 97. 79%,with an average of 87. 25%,and the Ar contribution of atmosphere is 12. 75%.Conclusions: The results show that the ore-forming fluids are mainly crust derived fluids,and some mantle derived fluids is mixed with reformed saturated atmospheric water. With the progress of mineralization,mantle He and atmospheric saturated water reformed Ar decreases. It is worth noting that the mantle-derived fluid in the oreforming fluid of the Kalu’an lithium deposit does not really come from the mantle material invasion,but is more likely to come from the immature continental crust of the Proterozoic. The Kalu’an lithium deposit in Xinjiang was formed into the post-collisional orogenic stage in the late period of continental collisional orogeny. The extension of the late period of orogeny led to

关 键 词：He—Ar同位素 地壳流体 幔源物质 锂矿 新疆卡鲁安 

分 类 号：P618.71[天文地球—矿床学] P597[天文地球—地质学]