东昆仑造山带巴隆地区羊粪沟中酸性岩脉成因及其地质意义  

Petrogenesis and Geological Implications of the Yangfengou Intermediate-Felsic Dykes in the Balong Area Within the Eastern Kunlun Orogen

作　　者：徐晓波 王连训[1] 马昌前[1,2] 朱煜翔 王珂 XU Xiao-bo;WANG Lian-xun;MA Chang-qian;ZHU Yu-xiang;WANG Ke(School of Earth Science,China University of Geosciences(Wuhan),Wuhan 430074,China;State Key Laboratory of Geological Processes and Mineral Resources,Wuhan 430074,China)

机构地区：[1]中国地质大学(武汉)地球科学学院,武汉430074 [2]地质过程与矿产资源国家重点实验室,武汉430074

出　　处：《矿物岩石地球化学通报》2021年第3期653-676,共24页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家自然科学基金项目(41502046,41972066);中国地质调查局地质调查项目(DD20160123-01,DD20160030)。

摘　　要：为探讨东昆仑东段巴隆羊粪沟地区中酸性岩脉的成因和演化,对采自该区的样品进行了LA-ICP-MS锆石定年和主、微量元素测定。结果显示,花岗闪长岩、正长花岗岩脉和闪长玢岩脉分别形成于(239.5±1.2)、(239.0±1.8)和(236.4±2.5)Ma,均为中三叠世岩浆活动产物。其中正长花岗岩脉富硅(SiO2平均值为76.06%)、富碱,K_(2)O/Na_(2)O为1.67,分异指数高(平均93.4);闪长玢岩脉相对贫碱,其K_(2)O/Na_(2)O为0.63,Mg#值较高(平均49)。岩石成因研究表明,正长花岗岩脉为高钾钙碱性高分异I型花岗岩,是古老下地壳物质部分熔融产生的岩浆分异演化作用的产物;闪长玢岩脉是由下地壳角闪岩类部分熔融产生的岩浆与幔源岩浆发生均匀混合形成。结合区域资料分析认为,阿尼玛卿洋在中三叠世晚期已经闭合,暗示东昆仑东段已进入造山后伸展阶段。In order to explore the genesis and evolution of the Yangfengou intermediate-felsic dykes in the Balong area of the eastern Kunlun orogen, LA-ICP-MS zircon U-Pb dating and analysis of major and trace elements of samples from those dykes have been undertaken in this study. Zircon U-Pb dating results reveal that the granodiorite intrusion, and syenogranite and diorite porphyry dykes were formed at(239.5±1.2),(239.0±1.8), and(236.4±2.5) Ma, respectively, indicating that they were products of Middle Triassic magmatic activities. Syenogranite dyke is rich in Si(average SiO_(2) of 76.06%) and alkalinity(average K_(2)O/Na_(2)O value of 1.67), with high differentiation index(average of 93.4). In contrast, diorite porphyry dyke is characterized with relatively poor alkalinity(average K_(2)O/Na_(2)O value of 0.63) but high Mg# value(average of 49). The syenogranite dyke belongs to the high K calcic-alkaline and highly fractionated I-type granite, likely generated from the highly differentiated magma which was originally derived from the partial melting of the ancient lower crust. However, the diorite porphyry dyke could be resulted from the relatively homogeneous mixing of the magma produced by partial melting of the lower crust amphibolite and the mantle-derived magma. Combined with regional data, it is believed that the A’nemaqen ocean could be closed in the Late stage of the middle Triassic, indicating that the eastern part of the eastern Kunlun orogen was changed to a post-collision extensional setting at that time.

关 键 词：东昆仑造山带 巴隆地区 中酸性岩脉 中三叠世 碰撞后伸展 

分 类 号：P588.12[天文地球—岩石学]