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现代地质 ›› 2018, Vol. 32 ›› Issue (06): 1263-1271.DOI: 10.19657/j.geoscience.1000-8527.2018.06.14

• 岩石学 • 上一篇    下一篇

滇西凤庆三岔河晚三叠世火山岩年代学、地球化学特征及其地质意义

李国昌(), 王巍, 杨立刚, 田应贵, 费志斌, 李维忠   

  1. 云南省地质矿产勘查院,云南 昆明 650051
  • 收稿日期:2018-03-19 修回日期:2018-07-28 出版日期:2018-12-10 发布日期:2018-12-20
  • 作者简介:李国昌,男,高级工程师,1963年出生,地质矿产勘查专业,长期从事地质矿产勘查、区域地质调查工作。Email:1277969229@.
  • 基金资助:
    中国地质调查局地质调查工作项目(12120113048700)

Zircon U-Pb Age and Lithogeochemical Characteristics of Late Triassic Dacite in Sanchahe Area, Fengqing County, Western Yunnan Province

LI Guochang(), WANG Wei, YANG Ligang, TIAN Yinggui, FEI Zhibin, LI Weizhong   

  1. Yunnan Exploration Institute of Geology & Mineral Resources,Kunming,Yunnan 650051,China
  • Received:2018-03-19 Revised:2018-07-28 Online:2018-12-10 Published:2018-12-20

摘要:

滇西凤庆三岔河地区火山岩岩性主要为英安岩,火山活动以宁静式喷溢为主。锆石LA-ICP-MS U-Pb年代学结果表明,英安岩的形成时代为209.7~218.8 Ma,锆石中含有大量不同时期的继承锆石核,指示其具有丰富的物质来源。全岩主量、微量元素分析结果显示,英安岩具有富硅、富铝的高钾钙碱性—钙碱性系列岩石特征,中等负Eu异常,轻、重稀土均强烈分馏,轻稀土分馏较重稀土明显,亏损Ta、Ba、Nb、Sr,而富集Rb、Th。地球化学特征显示,该套英安岩可能由古老地壳物质(富含长石的碎屑岩为主)在温度较高的环境中重熔形成,是晚三叠世古特提斯洋盆闭合后的陆内应力调整阶段的岩浆记录。

关键词: 昌宁—孟连带, 古特提斯洋, 英安岩, 锆石U-Pb定年, 地球化学

Abstract:

Volcanic rocks in Sanchahe area are mainly composed of dacite. LA-ICP-MS zircon U-Pb dating indicates that the dacite was formed in 209.7-218.8 Ma. Many inherited zircon cores of different periods were found, suggesting that the dacite have had complex magma source. The dacite contains high Si and Al contents, and belongs to high-K calc-alkaline series. The rocks show strongly fractionated REE pattern, medium negative Eu anomalies, depletions of Ta, Ba, Nb and Sr and enrichments of Rb and Th. This suggests that the dacitic magma was originated from the anatexis of crustal source. Integrating geochemical and geochronological results, we propose that the Sanchahe dacite formed in a post-collision extensional setting after the Paleo-Tethys closure.

Key words: Changning-Menglian suture zone, paleo-Tethys, dacite, zircon U-Pb dating, geochemistry

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