| 羌塘盆地东部那益雄组玄武岩地球化学特征及构造意义 |
| |
| 引用本文： | 李学仁,王剑,万友利,付修根.羌塘盆地东部那益雄组玄武岩地球化学特征及构造意义[J].地球科学,2018,43(2):401-416. |
| |
| 作者姓名： | 李学仁 王剑 万友利 付修根 |
| |
| 作者单位： | 1.中国地质科学院, 北京 100037 |
| |
| 基金项目： | 中国地质调查局项目121201010000161110国家青年科学基金项目41502112中国地质调查局项目DD20160159国家青年科学基金项目41702119 |
| |
| 摘 要： | 羌塘盆地东部那益雄组玄武岩作为裂谷演化最后阶段的喷发产物，其成岩年龄和地球化学特征为裂谷的关闭时间和二叠纪构造演化提供了重要约束.在剖面地质调查基础上，对那益雄组玄武岩进行了LA-ICP-MS锆石U-Pb测年及全岩分析测试，结果显示:那益雄组玄武岩锆石U-Pb年龄为257.2±2.9 Ma，形成于晚二叠世；该玄武岩属于大陆拉斑玄武岩系列，轻微富集Ta元素而轻微亏损Nb元素，是软流圈地幔物质上涌与岩石圈地幔相互作用的产物，形成于裂谷关闭碰撞后的伸展背景.羌塘地块东部二叠纪玄武岩的地球化学数据显示，早二叠世-晚二叠世玄武岩具有由OIB型玄武岩向火山弧型玄武岩过渡的演化趋势，表明羌塘地块东部板内裂谷在早二叠世打开，中二叠世进入裂谷演化阶段，于晚二叠世关闭.
|
| 关 键 词： | 羌塘盆地 那益雄组 玄武岩 U-Pb定年 构造意义 地球化学 地质年代学 |
| 收稿时间： | 2017-10-07 |
Geochemical Characteristics and Tectonic Implications of Nayixiong Formation Basalts in Eastern Qiangtang Basin,Tibet |
| |
| Abstract: | The Nayixiong Formation basalts in the eastern Qiangtang basin were the eruption products of the last stage of rift evolution, and their diagenetic age and geochemical characteristics provided important constraints for the closure time of the rift and the tectonic evolution of the Permian. Based on the profile geological survey, LA-ICP-MS zircon U-Pb dating and whole rock analysis of the Nayixiong Formation basalts were carried out in this study. Nayixiong Formation basalt samples yield the concordant age with a weighted mean 206Pb/238U age of 257.2±2.9 Ma. The geochemical characteristics of the basalts show a tholeiitic basalt affinity, with slight enrichment of Ta and slight negative Nb anomalies, as well as exhibiting no Eu-anomalies. The Nayixiong Formation basalts were likely resulted from the interaction between the upwelling asthenosphere and the lithospheric mantle that formed by the predated underplating. we propose that the basalts formed in an extensional setting after the closure of the Permian rift. All of the Permian basalts geochemical data show a transitional trend that the Early Permian-Late Permian basalts gradually evolved from OIB continental basalt to volcanic arc basalt, demonstating that the Permian rift undergoing the opening, rifting and closing from Early Permian to Late Permian in eastern Qiangtang terrane. The Nayixiong Formation basalts formed in an extensional setting after the amalgamation of intra-plate rift, confirming that the Qiangtang terrane was a tectonic transitional phase experiencing extension and closure of intra-plate rift (limited ocean) in the Late Permian. |
| |
| Keywords: | |
| 本文献已被 CNKI 等数据库收录！ |
| 点击此处可从《地球科学》浏览原始摘要信息 |
| 点击此处可从《地球科学》下载免费的PDF全文 |
|
