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现代地质 ›› 2018, Vol. 32 ›› Issue (03): 438-452.DOI: 10.19657/j.geoscience.1000-8527.2018.03.03

• 矿床学与岩石学 • 上一篇    下一篇

滇西莲花山富碱斑岩体LA-ICP-MS锆石U-Pb年代学、地球化学特征及其地质意义

王涛1,2(), 张静1,2(), 佟子达1,2, 李腾建1,2   

  1. 1.中国地质大学(北京) 地质过程与矿产资源国家重点实验室,北京 100083
    2.中国地质大学(北京) 地球科学与资源学院,北京 100083
  • 收稿日期:2017-07-15 修回日期:2018-01-19 出版日期:2018-06-10 发布日期:2023-09-22
  • 通讯作者: 张静
  • 作者简介:张静,女,教授,博士生导师,1977年出生,矿物学、岩石学、矿床学专业,主要从事矿床学研究。Email:zhangjing@cugb.edu.cn
    王涛,男,硕士研究生,1990年出生,地质工程专业,主要从事矿床学及地球化学研究。Email:twang@cugb.edu.cn
  • 基金资助:
    国家“973”计划项目(2015CB452600)

LA-ICP-MS Zircon U-Pb Geochronology and Geochemistry Characteristics of the Lianhuashan Alkaline-rich Porphyry Intrusion in Western Yunnan Province

WANG Tao1,2(), ZHANG Jing1,2(), TONG Zida1,2, LI Tengjian1,2   

  1. 1. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China
    2. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China
  • Received:2017-07-15 Revised:2018-01-19 Online:2018-06-10 Published:2023-09-22
  • Contact: ZHANG Jing

摘要:

莲花山富碱斑岩体位于兰坪盆地东缘,是滇西富碱斑岩带的重要组成部分。该岩体主要由石英二长斑岩和角闪石英二长斑岩组成,对不同岩性中的锆石进行了LA-ICP-MS U-Pb同位素测年,获得其形成年龄为(35.6±0.5)~(35.7±0.5) Ma,表明该岩体的形成时代为始新世。其K2O/Na2O比值为0.97~1.42、K2O+Na2O含量为8.86%~9.59%,显示高钾富碱的特征,属于钾玄岩系列岩石;岩体具有轻稀土元素富集、重稀土元素亏损的特征,显示弱的Eu负异常。利用锆石Ti温度计,获得岩体中岩浆锆石样品的结晶温度较低,介于594~788 ℃,说明该岩体岩浆源区的形成与俯冲-碰撞作用有关。样品中存在有少量年龄为1 177~68 Ma的继承锆石,Nb/U比值为1.31~4.73,表明莲花山岩体的源区是由洋壳俯冲作用形成的交代富集地幔,在其上侵过程中受到壳源物质不同程度的混染;岩体侵位于印度板块—欧亚板块陆-陆碰撞的挤压环境向后碰撞伸展环境转换的构造背景下。

关键词: 锆石U-Pb定年, 富碱岩体, 莲花山岩体, 兰坪盆地

Abstract:

The Lianhuashan alkalic porphyry in the eastern Lanping basin is an important part of the alkalic porphyry belt in Western Yunnan. The porphyry is mainly composed of quartz monzonite porphyry and amphibole quartz monzonite porphyry. LA-ICP-MS zircon U-Pb dating reveals that the Lianhuashan porphyry was emplaced during the Eocene (from (35.6±0.5) Ma to (35.7±0.5) Ma). The K2O/Na2O values (0.97 to 1.42) and K2O+Na2O contents (8.86% to 9.59%) demonstrate high-K alkaline affinity. The study shows that all samples belong to the shoshonitic series and are LREE-enriched with weak negative Eu anomalies. Zircon Ti thermometry shows that all the analyzed magmatic zircons have relatively low crystallization temperatures (594 to 788 ℃), suggesting that the magma was originated from subduction and/or collision. Besides, inherited zircons of 1,177 to 68 Ma (Nb/U ratios=1.31 to 4.73) are found, which also reflect that the magma may have sourced from the mantle metasomatized by the oceanic subduction, with entrainment of crustal materials during its ascent. To conclude, the Lianhuashan alkalic porphyry was likely formed under a transitional tectonic setting from the India-Asia collisional compression to post-collisional extension.

Key words: zircon U-Pb dating, alkaline-rich porphyry, Lianhuashan intrusion, Lanping Basin

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