藏南浪卡子地区卡龙辉长岩的时代、成因及其大地构造意义  

Geochronology, petrogenesis and tectonic significance of the Kalong gabbro from Nagarze, South Tibet

作　　者：杨成业[1] 李玉彬[2,3] 张金树 张根[1] Yang Chengye;Li Yubin;Zhang Jinshu;Zhang Gen(College of Engineering,Tibet University,Lhasa 850000;College of Earth Science,Chengdu University of Technology,Chengdu 610059;Tibet Institute of Geological Survey,Lhasa 850000)

机构地区：[1]西藏大学工学院,拉萨850000 [2]成都理工大学地球科学学院,成都610059 [3]西藏自治区地质调查院,拉萨850000

出　　处：《地质科学》2022年第2期399-414,共16页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：青藏高原第二次科学考察项目(编号:2019 QZKK0806)资助。

摘　　要：早白垩世OIB(洋岛玄武岩)型基性岩在特提斯喜马拉雅带广泛分布,但对其形成构造背景的认识仍存在争议。本文基于浪卡子地区东北部卡龙辉长岩的锆石LA-ICP-MS U-Pb年代学、微量元素与同位素地球化学的新证据显示,该基性岩体年龄为136.6±1.4 Ma,形成于早白垩世的早期。地球化学显示出高的TiO;和Nb含量,低的MgO含量,弱的Nb、Ta正异常,以及轻稀土相对富集而重稀土亏损的特点。这些特征与OIB型基性岩的地球化学特征完全一致。而且卡龙辉长岩具有较低的Sr同位素初始值I;以及较高的ε;(t)值,也与特提斯喜马拉雅带上典型的OIB型基性岩的同位素组成一致。综合分析后认为,卡龙辉长岩应与措美大火成岩省中的OIB型基性岩成因一致,均代表了Kerguelen地幔柱作用下的产物。Early Cretaceous mafic rocks are widespread in the Tethyan Himalaya. However, there is still debate about the tectonic setting of these rocks. Based on detailed elemental and isotope geochemistry and zircon LA-ICP-MS U-Pb dating analyses, the Kalong gabbro in the northern margin of the eastern Tethyan Himalaya yields a crystallization age of 136.6±1.4 Ma, formed at the beginning of Cretaceous. Kalong gabbros have high TiO;and Nb contents, and show weakly positive Nb and Ta anomalies and enrichment of LREE, consistent with those of ocean island basalt(OIB). The isotopic compositions of Kalong gabbros are consistent with other OIB-type basic rocks in the Tethyan Himalaya, which exhibit relative low initial Sr isotopic ratios and high εNd(t)values. We suggest the Kalong gabbro also represents products from the Kerguelen mantle plume.

关 键 词：青藏高原 特提斯喜马拉雅带 OIB型基性岩 措美大火成岩省 Kerguelen地幔柱 

分 类 号：P541[天文地球—构造地质学] P588.12[天文地球—地质学]