藏北卡易错地区晚侏罗世花岗闪长岩形成时代、地球化学特征及其地质意义  

Formation Age,Petrogenesis and Geological Significance of Late Jurassic Granodiorites in Kayico Area,Northern Tibet

作　　者：李昊 杜文强 张超 李智楠 韦代硬 吴浩 LI Hao;DU Wenqiang;ZHANG Chao;LI Zhinan;WEI Daiying;WU Hao(Collaborative Innovation Center for Exploration of Nonferrous Metal Deposits and Efficient Utilization of Resources in Guangxi&Guangxi Key Laboratory of Hidden Metallia Ore Deposits Exploration,Guilin University of Technology,Guilin 541004,Guangxi,China;North Geological Survey Fourth Geological Brigade,Qinhuangdao 066000,Hebei,China)

机构地区：[1]有色金属矿产勘查与资源高效利用省部共建协同创新中心&广西隐伏金属矿产勘查重点实验室,桂林理工大学,广西桂林541004 [2]华北地质勘查局第四地质大队,河北秦皇岛066000

出　　处：《西北地质》2025年第1期81-92,共12页Northwestern Geology

基　　金：广西中青年教师基础能力提升项目“藏北多龙矿集区成矿期高硅流纹岩成因及其构造意义”(2021KY0249);桂林理工大学人才引进科研启动项目(RD2000002384);中国地质调查项目“藏西北铜多金属资源基地综合调查评价”(DD20190167)联合资助。

摘　　要：南羌塘地块南缘在中—晚侏罗世爆发了大规模、多样性的岩浆作用,是认识班公湖–怒江缝合带构造演化过程的理想研究对象。笔者对卡易错地区出露的花岗闪长岩进行了锆石U-Pb定年、全岩地球化学以及锆石Lu-Hf同位素测试分析和研究工作。测年结果表明,卡易错花岗闪长岩形成于158 Ma,与区域上中—晚侏罗世岩浆活动时代相一致,其地球化学组成显示高SiO_(2)和全碱含量(Na_(2)O+K_(2)O)、低MgO和TiO_(2)的含量,并显示Eu、Sr、Ba的负异常,具有钙碱性Ⅰ型花岗岩的特征。结合区域现有研究资料,研究认为卡易错花岗闪长岩是古老变火成岩下地壳部分熔融、并经历结晶分异作用的产物,是班公湖–怒江特提斯洋洋壳北向俯冲在南羌塘地块南缘引发的弧型岩浆活动。结合区域研究资料,卡易错地区同时发育钙碱性Ⅰ型和高分异型两类花岗岩,分别代表着熔体在浅层岩浆房内经历矿物结晶作用后不同端元冷凝的产物。The widely distributed Middle-Late Jurassic magmatic rocks in south margin of Southern Qiangtang block display complex geochemical compositions,providing an ideal research object for the tectonic evolution of Bangong-Nujiang Suture Zone. In this paper, zircon U-Pb dating, whole rock geochemistry and zircon Lu-Hf isotopes of Kayico granodiorites were analyzed. The investigated granodiorites yielded zircon ages of 158 Ma, coeval with the regional Middle-Late Jurassic magmatic rocks. Geochemically, the granodiorites were character-ized by high SiO_(2) and total alkalis (Na_(2)O+K_(2)O) contents, but low MgO and TiO_(2) contents, with depletion in Eu、 Sr、 Ba, suggesting a geochemical affinity with calc alkaline I-type granites. Combined with the regional research data, it is thus concluded that these granodiorites were derived by partial melting of the ancient metaigneous lower crust, followed by vary degree of crystallization differentiation. Our research favor that the Middle- Late Jurassic magmatic rocks in Southern Qiangtang block were generated in an arc setting during the north-ward subduction of Bangong-Nujiang oceanic lithosphere. Furthermore, considering the preexisting geochemical data, the granitic rocks of Kayico area can be divided into two groups of calc-alkaline I-type granites and highly fractionated granites, which were derived by the different end-members of the crystal mush process with-in the shallow crust.

关 键 词：青藏高原 晚侏罗世 班公湖–怒江缝合带 岩石成因 洋壳俯冲 

分 类 号：P597.3[天文地球—地球化学]