西藏斯弄多地区晚白垩世埃达克岩:岩石成因及成矿潜力指示  

Late Cretaceous Adakite in Sinongduo Area, Tibet:Implications for Petrogenesis and Mineralization

作　　者：杨昕 唐菊兴[2] 杨宗耀 谢富伟 郝金月 吴鑫 宋壮壮 Yang Xin;Tang Juxing;Yang Zongyao;Xie Fuwei;Hao Jinyue;Wu Xin;Song Zhuangzhuang(School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Science,Beijing 100037,China;Faculty of Geosciences and Environmental Engineering,Southwest Jiaotong University,Chengdu 611756,China;College of Earth Science,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]中国地质科学院矿产资源研究所自然资源部成矿作用与资源评价重点实验室,北京100037 [3]西南交通大学地球科学与环境工程学院,四川成都611756 [4]成都理工大学地球科学学院,四川成都610059

出　　处：《地球科学》2021年第5期1597-1612,共16页Earth Science

基　　金：国家自然科学基金项目(No.41772075);国家重点研发计划项目(No.2018YFC0604105)。

摘　　要：西藏冈底斯带广泛分布晚白垩世埃达克质岩,其岩石成因一直存在争论,并且对于成矿潜力的研究也十分有限.为此对谢通门县斯弄多-加多捕地区具铜矿化的黑云母二长花岗岩开展了锆石U-Pb定年、全岩地球化学以及锆石微量元素地球化学特征的研究,以探明岩石成因及成矿潜力.结果表明黑云母二长花岗岩侵位时间为晚白垩世(83.1±1.6 Ma).岩石具有相对高的Si O2含量(60.21%~62.54%)、Mg O(2.19%~3.02%)、Mg#(41.25~50.73)值.较低含量的Y(15.9×10^(-6)~17.8×10^(-6))、Yb(1.46×10^(-6)~1.73×10^(-6))及较高的Sr/Y(35.0~47.6)、La/Yb(29.6~38.6)比值,表现出高硅型埃达克质岩亲和性.岩石属高钾钙碱性、准铝质系列(A/CNK值为0.84~0.92),富集LREE、大离子亲石元素(LILE)、亏损高场强元素(HFSE),如Nb、Ta等.锆石微量元素具较高的V/Sc、Ce/Ce*、10 000×(Eu/Eu*)和Eu/Eu*比值.通过对比冈底斯带晚白垩世典型的埃达克岩,认为斯弄多黑云母二长花岗岩是新特提斯洋俯冲洋壳部分熔融的产物,岩浆氧逸度较高,显示出斯弄多黑云母二长花岗岩具有良好的Cu-Au成矿潜力.The genesis of the Late Cretaceous adakite in the Gangdese belt,Tibet,has been debated for decades,and research on the productivity of these intrusions is limited.To provide a further understanding of this issue,it presents zircon U-Pb data,geochemical and zircon trace element data of the biotite monzogranite from Sinongduo-Jiaduobu area,Xietongmen County,Tibet.New age data indicate that the biotite monzogranite emplaced in the Late Cretaceous (83.1±1.6 Ma).These rocks arecharacterized by relatively high contents of Si O2(60.21%-62.54%),Mg O (2.19%-3.02%),Mg#(41.25-50.73),low contents of Y (15.9×10^(-6)-17.8×10^(-6)),Yb (1.46×10^(-6)-1.73×10^(-6)) and high Sr/Y (35.0-47.6),La/Yb (29.6-38.6) ratios,showing high-Si O2adakitic rock affinity.These rocks belong to high-K calc-alkaline and metaluminous series (A/CNK=0.84-0.92),and enriched in LREE,LILE (large ion lithophile element) and depleted in HREE,HFSE (high field strength element),such as Nb and Ta.The zircon trace element data show high V/Sc,Ce/Ce*,10 000×(Eu/Eu*),and moderate Eu/Eu*ratios.By comparing with typical adakitic rocks from the Gangdese belt,it is proposed that these rocks with high oxygen fugacity were derived from the partial melting of subducted Neo-Tethyan slab,and have good potential for Cu-Au mineralization.

关 键 词：冈底斯带 斯弄多 埃达克岩 岩石成因 成矿潜力 矿床地质 

分 类 号：P611[天文地球—矿床学]