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    滇西弥渡—巍山地区富碱岩浆岩LA-ICP-MS 锆石U-Pb年龄及构造环境

    LA-ICP-MS ziron U-Pb isotopic age of alkali-rich magmatic rocks in the Midu-Weishan area,western Yunnan,and its tectonic setting

    • 摘要: 弥渡吉祥庄火山岩和巍山大莲花山岩体是金沙江富碱岩带的重要组成部分,两者总体呈近NW向展布,受哀牢山—金沙江断裂带控制。岩石学和LA-ICP-MS锆石U-Pb同位素年代学研究表明,弥渡吉祥庄火山岩为粗面岩,巍山大莲花山岩体为石英闪长斑岩; 吉祥庄火山岩LA-ICP-MS锆石U-Pb年龄为36.27 ±0.50 Ma,巍山大莲花山岩体LA-ICP-MS锆石U-Pb年龄为37.02 ±0.46 Ma。弥渡吉祥庄火山岩和巍山大莲花山岩体形成时代为喜马拉雅早期,两者形成于后碰撞构造背景。

       

      Abstract: The Jixiangzhuang volcanic rock at Midu and the Dalianhuashan pluton at Weishan are the major parts of the Jinshajiang alkali-rich magmatic rock belt, with both distributed along near north-west direction and controlled by the Ailaoshan—Jinshajiang fault zone. In this article, authors investigated petrology and LA-ICP-MS zircon U-Pb geochronology of the rock samples collected from the Jixiangzhuang volcanic rock and Dalianhuashan pluton. The petrographic characteristic shows that the Jixiangzhuang volcanic rock is trachyte and the Dalianhushan pluton is quartz-diorite-porphyry. The LA-ICP-MS zircon U-Pb dating yields a 206Pb/238U weighted average age of 36.27 ±0.50 Ma for the Jixiangzhuang volcanic rock and an age of 37.02 ±0.46 Ma for the Dalianhushan pluton. It can be concluded that the Jixiangzhuang volcanic rock and Dalianhuashan pluton formed in a post-collision tectonic background in Early Himalayan period.

       

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