川西九龙白台花岗岩地球化学特征、锆石U-Pb年龄和Hf同位素组成及其稀有金属成矿意义  

Geochemical characteristics,zircon U-Pb ages and Hf isotopic compositons of Baitai granite in Jiulong area,western Sichuan,and their significance for rear metals mineralization

作　　者：胡军亮 谭洪旗[2,3] 倪志耀 周家云[2,4] 朱志敏[2,4] 周雄 骆志红[5] 岳相元 牛腾[1] 徐力 黄驰轩 HU Juniang;TAN Hongqi;NI Zhiyao;ZHOU Jiayun;ZHU Zhimin;ZHOU Xiong;LUO Zhihong;YUE Xiangyuan;NIU Teng;XU Li;HUANG Chixuan(College of Earth and Planetary Sciences,Chengdu University of Technology,Chengdu610059;Institute of Multipurpose Utilization of Mineral Resources,Chinese Academy ofGeological Sciences,Chengdu610041;Sichuan Geological and Mineral Resources Group Co.,Ltd,Chengdu610016;Technical Innovation Center of Rare Earth Resources,China Geological Survey,Chengdu610041;The 3rd Geological Brigade of Sichuan,Chengdu611230)

机构地区：[1]成都理工大学地球与行星科学学院,成都610059 [2]中国地质科学院矿产综合利用研究所,成都610041 [3]四川省地质矿产(集团)有限公司,成都610016 [4]中国地质调查局稀土资源应用技术创新中心,成都610041 [5]四川省第三地质大队,成都611230

出　　处：《地质论评》2024年第2期449-475,共27页Geological Review

基　　金：中国地质调查局项目(编号:DD20221697、DD20230039、DD20230341);国家自然科学基金资助项目(编号:92262302)的成果。

摘　　要：为揭示川西九龙白台花岗岩成因及其与稀有金属成矿的关系,笔者等对白台花岗岩开展了岩相学、岩石地球化学、LA-ICP-MS锆石U-Pb年代学、锆石微量元素地球化学、Hf同位素地球化学测试。结果显示,白台黑云母二长花岗岩具高SiO_(2)(69.01%~70.55%)、高K_(2)O(3.86%~4.99%)、高碱(K_(2)O+Na_(2)O=7.41%~8.18%),低CaO(1.49%~2.2%)、低MgO(0.44%~0.57%)等特征,里特曼指数σ=2.03~2.43,A/CNK=1.07~1.14,为弱过铝质的高钾钙碱性系列岩石;微量元素特征显示相对富集Rb、K等大离子亲石元素,相对亏损Nb、P、Hf等高场强元素;球粒陨石标准化的稀土元素配分模式为明显的轻稀土富集和重稀土亏损的右倾型。白台黑云母二长花岗岩锆石U-Pb年龄为(213~212)Ma,ε_(Hf)(t)值为-7.4~-1.1,Hf同位素二阶模式年龄T_(DM2)为(1.6~1.2)Ga。研究结果表明,白台花岗岩形成于后碰撞伸展背景,是在松潘—甘孜地块遭受挤压碰撞后,增厚的岩石圈地幔拆沉,软流圈地幔物质上涌后发生减压熔融形成的晚三叠世I型花岗岩。同时,笔者等认为白台伟晶岩型铍矿床与白台花岗岩密切相关,是该花岗岩体残余岩浆热液分异的产物。To reveal the petrogenesis of Baitai granite in Jiulong area and its relationship with rare metal mineralization,petrographic,whole-rock geochemistry,LA-ICP-MS zircon U-Pb geochronology,zircon trace element geochemistry and Hf isotope geochemistry were studied in this paper.Samples from the Baitai biotite monzonitic granite are characterized by high SiO_(2 )contents(69.01%~70.55%),high K_(2)O(3.86%~4.99%),high alkali(K_(2)O+Na_(2)O=7.41%~8.18%),low CaO(1.49%~2.2%),low MgO(0.44%~0.57%),withσof 2.03~2.43,and A/CNK of 1.07~1.14.These granite samples could be ascribed to peraluminous—weak high-K calc-alkaline series,with the characterics of enriched in large ionic lithophile elements(K and Rb),and depleted in high field strength elements(Nb,P and Hf).In chondrite normalized rare-earth element pattern,they show obvious right deviation type characterized by enrichment of light rare earth elements and depleted in heavy rare earth elements.The biotite monzonitic granite was formed at 213~212 Ma,and the zirconε_(Hf)(t)values ranges from-7.4 to-1.1,with the T_(DM2) age of 1.6~1.2 Ga.In conclusion,we propose that the Baitai I-type granite developed in a postcollisional extensional regime in the Late Triassic,and that it was related to an induced mantle upwelling after the delamination of thickened lithosphere following the final compression collision of the Songpan—Garze terrane.At the same time,the Baitai pegmatite-type beryllium deposits are closely related to the Baitai granite,which are derived from the residual crystallization products of the Baitai granite.

关 键 词：岩石成因 岩石地球化学 锆石U-PB年代学 HF同位素 花岗岩 松潘—甘孜地块 

分 类 号：P618.6[天文地球—矿床学]