西藏狮泉河早白垩世中基性火山岩对中特提斯洋西段闭合时限的制约  

Constraints on the closure timing of the western segment of the Meso-Tethys Ocean from Early Cretaceous intermediate-basic volcanic rocks in Shiquanhe,Tibet

作　　者：黄玉 马菁宇 赵志丹[2] 朱弟成[2] HUANG Yu;MA JingYu;ZHAO ZhiDan;ZHU DiCheng(MOE Key Laboratory of Western China's Mineral Resources and Geological Engineering,School of Earth Science and Resources,Chang'an University,Xi'an 710054,China;State Key Laboratory of Geological Processes and Mineral Resources,School of Earth Science and Mineral Resources,China University of Geosciences(Beijing),Beijing 100083,China)

机构地区：[1]西部矿产资源与地质工程教育部重点实验室,长安大学地球科学与资源学院,西安710054 [2]中国地质大学(北京)地质过程与矿产资源国家重点实验室,地球科学与资源学院,北京100083

出　　处：《岩石学报》2025年第5期1740-1758,共19页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41702044);陕西省自然科学基金项目(2023-JC-QN-0339);中央高校基本科研业务费项目(300102270101)联合资助详细信息。

摘　　要：中、北拉萨地体广泛分布的早白垩世岩浆作用对研究拉萨地体的构造背景、壳-幔相互作用过程以及特提斯洋壳俯冲-消减等科学问题具有重要意义。本文针对中拉萨地体西段狮泉河地区的玄武岩-玄武安山岩-安山岩开展了系统的锆石U-Pb年代学、全岩主微量元素地球化学、Sr-Nd-Pb同位素及锆石Hf同位素分析工作。安山岩中的锆石U-Pb年龄为102.6±0.9Ma, 狮泉河原典中组中基性火山岩形成于早白垩世末期。岩石地球化学结果表明, 玄武岩-玄武安山岩-安山岩富集大离子亲石元素、亏损高场强元素且富集Pb同位素, 其中玄武岩-玄武安山岩Sr-Nd同位素组成略亏损, 而安山岩的Sr-Nd同位素组成较为富集且具有宽泛的锆石εHf(t)值范围(-0.5~+10.0)。综合岩石学、地球化学和区域构造背景研究, 本文认为狮泉河中基性火山岩的源区为受俯冲沉积物交代的富集岩石圈地幔, 可能形成于以班公湖-怒江洋为代表的中特提斯洋岩石圈南向俯冲相关的陆缘弧环境。本文的研究成果表明, 直至早白垩世末期中特提斯洋盆在狮泉河地区仍未完全闭合, 为理解中特提斯洋自东向西逐渐闭合的过程提供了重要证据。The widespread Early Cretaceous magmatism in the central and northern Lhasa subterranes is of significant importance for studying scientific issues such as the tectonic background of the Lhasa Terrane, crust-mantle interaction process, and the subduction of the Tethyan oceanic crust. This paper presents systematic analyses of zircon U-Pb chronology, whole-rock major and trace element geochemistry, Sr-Nd-Pb isotopes, and zircon Hf isotopes on basalts-basaltic andesites-andesites from the Shiquanhe area in the western part of the central Lhasa subterrane. The zircon U-Pb ages of the andesite are 102.6±0.9Ma, indicating that these intermediate-basic volcanic rocks formed at the end of the Early Cretaceous. Geochemical analyses reveal that these rocks are characterized by enriched large ion lithophile elements (LILEs), depleted high field strength elements (HFSEs) and enriched Pb isotopic compositions. The Sr-Nd isotopic compositions of the basalt-basaltic andesite are slightly depleted, while those of the andesite are more enriched, showing a wide range of zircon εHf(t) values (-0.5 to +10.0). Based on petrological, geochemical, and regional tectonic studies, this paper proposes that the source region for the Shiquhe intermediate-basic volcanic rocks is an enriched lithospheric mantle modified by subduction sediments, likely formed in a continental margin arc environment associated with the southward subduction of the Meso-Tethyan Ocean. These findings suggest that the Meso-Tethyan Ocean basin had not fully closed in the Shiquhe area at the end of the Early Cretaceous, offering critical evidence for understanding the progressive westward closure of the Meso-Tethyan Ocean from east to west.

关 键 词：早白垩世 中特提斯洋 闭合时限 拉萨地体 火山岩 

分 类 号：P588.14[天文地球—岩石学] P597.3[天文地球—地质学]