川西洛莫地区燕山早期花岗岩对稀有金属成矿的制约  

Distribution of early Yanshanian granite and its constraints on the mineralization of rare metals in Luomo area, western Sichuan

作　　者：谭洪旗[1,2] 朱志敏 罗林洪[3] 胡军亮 TAN Hongqi;ZHU Zhimin;LUO Linhong;HU Junliang(Institute of Multipurpose Utilization of Mineral Resources,Chinese Academy of Geological Sciences,Chengdu,Sichuan 610041,China;Technical Innovation Center of Rare Earth Resources,China Geological Survey,Chengdu,Sichuan 610041,China;No.108 Geological Team,Sichuan Geology and Mineral Bureau,Chengdu,Sichuan 611230,China;College of Earth Sciences,Chengdu university of technology,Chengdu,Sichuan 610059,China)

机构地区：[1]中国地质科学院矿产综合利用研究所,四川成都610041 [2]中国地质调查局稀土资源应用技术创新中心,四川成都610041 [3]四川省地质矿产勘查开发局一〇八地质队,四川成都611230 [4]成都理工大学地球科学学院,四川成都610059

出　　处：《地质学报》2023年第2期396-416,共21页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41603034,92262302);中国地质调查局项目(编号DD20190185,DD20221697,Gc20230222)联合资助的成果。

摘　　要：川西是我国重要的稀有金属产地之一,主要由甲基卡、可尔因、扎乌龙、九龙矿集区组成。甲基卡、可尔因矿集区已发现李家沟、党坝、甲基卡等超大型—大型锂铍矿床,而九龙地区仅发现打枪沟中型锂铍矿床。本文通过对九龙洛莫地区花岗岩开展岩石学、地球化学、锆石及独居石U-Pb年代学研究,以确定桥棚子及其周缘花岗岩的成因、构造背景和伟晶岩的时空联系,为九龙河流域及其周缘的稀有金属找矿勘探工作提供依据。结果显示,桥棚子及其周缘花岗岩具高的SiO_(2)(69.98%~76.80%)、Al2O3(13.72%~15.29%)、K_(2)O+Na_(2)O(6.71%~7.24%),为过铝质、钙碱性—高钾钙碱性系列,具低REE、Sr、δEu(0.35~1.02)和HFSE含量,高LREE/HREE、Yb和LILE含量及高分异指数(79.67~91.73),且花岗岩具有较高的Ga/Al比值(10000×Ga/Al=2.45~3.11)。锆石和独居石LA-ICP-MS U-Pb年龄显示,桥棚子岩体成岩年龄为(168.2±0.9) Ma,石梯子-烂碉岩株成岩年龄为157.1±1.6~152.5±0.5 Ma,这些岩体均遭受了晚期143.5±1.0 Ma的岩浆作用或构造热事件改造。石梯子-烂碉花岗岩浆温度为696~729℃,明显低于桥棚子花岗岩浆温度(766~804℃);桥棚子花岗岩中锆石的氧逸度(lg fO2=-18.71±1.84,ΔFMQ=-4.75±1.84)与烂碉花岗岩中锆石的氧逸度(lg fO2=-17.19±1.29,ΔFMQ=-1.87±1.29)均显示为低氧逸度条件。结合区域地质背景,170~140 Ma,松潘-甘孜地块南缘岩石圈处于伸展阶段,有三期岩浆活动或构造-热事件记录,早期(168 Ma)以桥棚子为主体的花岗岩浆活动,中期(157~152 Ma)以石梯子-烂碉为主的花岗岩浆活动,晚期(144 Ma)区内花岗岩遭受了岩浆作用或构造热事件的改造。打枪沟和洛莫锂铍等稀有金属成矿时代限制为167~157 Ma,在误差范围内与上述岩浆活动早期和中期时间基本一致,暗示了九龙地区存在燕山早期花岗岩与稀有金属成矿,在地球化学和年代学上不同于甲基卡、可尔因�Western Sichuan is one of the most important rare metal mining regions in China, composed mainly of Jiajika, Keryin, Shiqu and Jiulong deposit clusters. In the Jiajika and Keryin deposit clusters, lithium-beryllium deposits have been discovered in Lijiagou, Dangba and Jiajika, while only medium-sized lithium-beryllium deposits have been discovered in Daqianggou in the Jiulong deposit cluster. In this paper, petrological, geochemical and U-Pb chronological studies of zircon and monazite were conducted to determine the genesis and structural setting of Qiaopengzi and its peripheral granite, as well as its spatiotemporal relationship with pegmatite, providing a basis for the prospecting and exploration of rare metals in the Jiulong River Basin and its surrounding areas. The results show that Qiaopengzi granite, which is rich in SiO_(2)(69.98%~76.80%), Al2O3(13.72%~15.29%) and K_(2)O+Na_(2)O(6.71%~7.24%), is a peraluminous and calc-alkali-high-K calc-alkaline series that is low in REE, Sr, δEu and HFSE, but rich in LREE/HREE, Yb and LILE, boasts a high differentiation index(79.67~91.73) and high Ga/Al ratios(10000×Ga/Al=2.45~3.11). The diagenetic age of Qiaopengzi granite and Landiao-Shitizi granite are 168.2±0.9 Ma, 157.1±1.6~152.5±0.5 Ma, respectively. It underwent magmatic or tectonic thermal events at 143.5±1.0 Ma. The temperature of Landiao-Shitizi granite(696℃~729℃) is lower than that of Qiaopengzi granite 766~804℃. The oxygen fugacity parameter of zircon shows the Qiaopengzi granite(lgfO2=-18.71±1.84, ΔFMQ=-4.75±1.84) and the Landiao granite(lgfO2=-17.19±1.29, ΔFMQ=-1.87±1.29) are both low oxygen fugacity. Combined with the regional geological background, about 170 ~ 140 Ma, the lithosphere in the southern margin of Songpan Ganzi block is in the extension stage, with three stages of magmatic activity or tectonic thermal events recorded. The granite magma activity dominated in the early stage(168 Ma) by Qiaopengzi granite, and in the middle stage 157~152 Ma by Landiao-Shitizi granite, and in t

关 键 词：松潘-甘孜 川西 九龙 稀有金属 花岗岩 

分 类 号：P618.6[天文地球—矿床学]