西藏冈底斯岩浆弧南缘晚白垩世早期石英二长闪长岩中锆石的成因矿物学研究  

A Genetic Mineralogical Study of Zircons from the Early Late-Cretaceous Quartz Monzodiorite in the Southern Margin of the Gangdise Magmatic Arc,Tibet,China

作　　者：梁贤 张聚全 王金贵 张鑫全 张立国 王硕 杨鑫朋 程洲 侯德华 陈圆圆 卢静 LIANG Xian;ZHANG Ju-quan;WANG Jin-gui;ZHANG Xin-quan;ZHANG Li-guo;WANG Shuo;YANG Xin-peng;CHENG Zhou;HOU De-hua;CHEN Yuan-yuan;LU Jing(Hebei Key Laboratory of Strategic Critical Mineral Resources,Hebei GEO University,Shijiazhuang,050031,China;College of Earth Sciences,Hebei GEO University y Shijiazhuang 050031,China;Regional Geological Survey Institute of Hebei Province,Langfang Hebei 065000,China)

机构地区：[1]河北省战略性关键矿产资源重点实验室,石家庄050031 [2]河北地质大学地球科学学院,石家庄050031 [3]河北省区域地质调查院,河北廊坊065000

出　　处：《矿物岩石地球化学通报》2021年第1期165-177,共13页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：中国地质调查局项目(DD20160015-09);河北地质大学青年项目(QN201708);河北地质大学博士科研启动基金(BQ201609);河北地质大学学生科技基金科研项目(KAZ201908);河北省在读研究生创新能力培养项目(CXZZSS2019110)。

摘　　要：锆石的形态标型和成分标型可用于反演岩浆的演化过程和构造环境。为探讨西藏桑耶地区晚白垩世的石英二长闪长岩的岩浆成因、演化过程及其物理化学条件,采用成因矿物学方法对石英二长闪长岩中的锆石的形态标型、成分标型及其构造环境进行了系统研究。结果表明,锆石的延长系数多集中于1.5∶1~3.0∶1,锆石群型多为S_(10)和P_(1)。锆石形态标型表明岩浆为壳幔混源成因,成分标型指示锆石的Ti饱和温度为802~896℃(均值为853℃)。氧逸度结果离散度较大,其lgf_(O_(2))为-15.37~-4.77(平均FMQ为0.41),属中等氧逸度。锆石的Th/U值(0.76~1.38)及其微量元素成因判别图解均显示其为岩浆锆石,构造-岩浆背景判别图指示石英二长闪长岩可能来源于岛弧岩浆环境,形成于大陆弧型的构造背景。The morphological and compositional typomorphic characteristics of zircons can be used to retrieve the evolution process and tectonic environment of magma.In order to explore the genesis,evolution process,and physico-chemical conditions of magma of the quartz monzodiorite in the Sangye area,Tibet,China,the morphological and compositional typomorphic characteristics and their tectonic environments of zircons in the early Late Cretaceous quartz monzodiorite have been studied systematically by means of genetic mineralogy in this paper.The results show that the zircon crystals have elongation coefficients varying mainly from 1.5∶1 to 3.0∶1,and zircon groups of mostly S_(10) and P_(1).The morphological typomorphic characteristics of zircons show that the magma is of crust-mantle mixed origin.The compositional typomorphic characteristics show that the Ti saturation temperatures of zircons vary from 802℃to 896℃,with an average of 853℃.The results of oxygen fugacity of zircons are largely dispersed within the lgfO2 values varying from-15.37 to 4.77.The average of FMQ values,converted from lgf_(O_(2)) values,is 0.41,which belongs to the category of moderate oxygen fugacity.The zircon Th/U ratios(0.76-1.38)and its trace element genetic discrimination diagrams show that the zircons are of magmatic origin.The tectonic-magmatic background discriminant diagram indicates that the quartz monzodiorite could be originated from the island arc magmatic environment but formed in the continental arc tectonic setting.

关 键 词：西藏 锆石 成因矿物学 形态标型 氧逸度 

分 类 号：P571[天文地球—矿物学] P572.1[天文地球—地质学]