摘要
为厘定拉孜县彭措林石英闪长斑岩的形成时代,探讨其成因和形成的构造背景,对其进行了锆石LA-ICP-MS U-Pb定年和锆石原位Hf同位素、全岩地球化学分析。结果表明,石英闪长斑岩的结晶年龄为(171.8±2)Ma,代表中侏罗世的岩浆活动;锆石的εHf(t)值为12.88~15.26,显示出新生地壳的特点。在全岩地球化学组成上,石英闪长斑岩具有高SiO2(64.99%~67.51%)、K2O(1.84%~3.22%),低MgO(0.67%~0.93%)特点,微量元素地球化学特征显示岩石相对富集大离子亲石元素(如Rb、Sr和K)和轻稀土元素,亏损高场强元素(如Nb、Ta和Ti)和重稀土元素。结合前人资料,认为岩石产于与新特提斯洋向北俯冲相关的火山弧环境。此外,岩石具有相对高的Sr、Ba含量、无Eu负异常,表明源区无斜长石的明显残留;且较低的Mg^#值,低的Cr、Ni含量和较低的εHf(t)值,均表明其主要形成于下地壳的部分熔融。
In order to constrain the age,petrogenesis and tectonic setting of the quartz diorite porphyry from Pengcuolin in the Lhaze terrane,Tibet,zircon U-Pb and Hf isotopes and whole rocks elemental geochemistry have been conducted in this study.The quartz diorite porphyry has zircon U-Pb ages of (171.8±2)Ma,indicating that it was formed in middle Jurassic.The rocks have high Si02(64.99%-67.51%),K20(1.84%-3.22%)and low MgO (0.67%-0.93%)and are characterized by enrichment of LILEs (such as Rb,Sr and K)and LREEs and depletion of HFSEs (such as Nb,Ta and Ti)and HREEs.We thus conclude that the quartz diorite porphyry was formed in the volcanic arc related to northward subduction of the Neo-Tethys oceanic slab.Relatively high Sr and Ba,and the absence of Eu anomaly indicate plagioclasewas not remained in the source as residual phases.Positive εHf(t)values of zircons (12.88to 15.26)and low Mg^# values,Cr and Ni contents,suggesting that the parental magmas were derived from the partial melting of juvenile lower crust.
作者
邓煜霖
郎兴海
杨宗耀
谢富伟
王旭辉
尹青
张忠
张金树
DENG Yu-lin;LANG Xing-hai;YANG Zong-yao;XIE Fu-wei;WANG Xu-hui;YIN Qing;ZHANG Zhong;ZHANG Jin-shu(College of Earth Science and MLR Key Laboratory of Tectonic Controls on Mineralization and Hydrocarbon Accumulation Chengdu University of Technology,Chengdu 510059,China;Faculty of Geoseiences and Environmental Engineering,Southwest Jiaotong University,Chengdu 611755,China;Institute of Mineral Resources,CA GS ,Beijing100037,China;Tibet Tianyuan Minerals Exploration Co.,Ltd,Rikaze Tibet 857000,China;College of Engineering,Tibet University,Lhasa 850012,China)
出处
《矿物岩石地球化学通报》
CAS
CSCD
北大核心
2018年第5期953-966,共14页
Bulletin of Mineralogy, Petrology and Geochemistry
基金
国家自然科学基金项目(41502079)
国土资源部公益性行业专项(201511022-02)
四川省教育厅自然科学重点项目(15ZA0073)
四川省青年基金项目(2014JQ0047)
中国地质调查局地质调查项目(DD20160346)
关键词
拉萨地体南缘
闪长岩
晚三叠世-中侏罗世
新特提斯洋
the southern margin of the Lhasa terrane
diorite
Late Triassic-Middle Jurassic
the Neo-Tethys ocean
作者简介
邓煜霖(1993-),男,硕士研究生,研究方向:岩石学及矿床学.E-mail:dengyulin93@126.com;通讯作者:郎兴海(1982-),男,教授,研究方向:岩石学及矿床学.E-mail:langxinghai@126.com.
