地学前缘 ›› 2019, Vol. 26 ›› Issue (2): 137-156.DOI: 10.13745/j.esf.sf.2019.2.7

• 陆缘构造–岩浆与成矿作用 • 上一篇    下一篇

滇西北休瓦促晚白垩世岩浆成矿作用动力学机制探讨

江小均, 陈政宇 李文昌, 余海军, 李超, 张向飞, 王忠强, 严清高   

  1. 1. 昆明理工大学 国土资源工程学院地球科学系, 云南 昆明 650093
    2. 中国地质调查局 成都地质调查中心, 四川 成都 610081
    3. 云南地质调查局 自然资源部三江成矿作用及资源勘查利用重点实验室, 云南 昆明 650051
    4. 国家地质实验测试中心, 北京 100037
  • 收稿日期:2018-10-20 修回日期:2019-02-20 出版日期:2019-03-30 发布日期:2019-03-30
  • 通讯作者: 李文昌(1962—)，男，博士，教授级高级工程师，主要从事找矿勘探和矿床地质研究。
  • 作者简介:江小均(1985—)，男，博士，讲师，主要从事区域成矿与大地构造学研究。E-mail:cagsjiang@126.com
  • 基金资助:
    国家自然科学基金项目(41673060；41762009)；国家重点基础研究发展计划“973”项目(2015CB452605)；云南省应用基础研究计划青年项目(2016DF031)

Discussion on the dynamic mechanism of the Late Cretaceous magmatism-metallogenesis in Xiuwacu, northwestern Yunnan Province. 

JIANG Xiaojun, CHEN Zhengyu, LI Wenchang, YU Haijun, LI Chao, ZHANG Xiangfei, WANG Zhongqiang, YAN Qinggao   

  1. 1. Department of Earth Sciences, Faculty of Land Resource Engineering, Kunming University of Science and Technology, Kunming 650093, China
    2. Chengdu Geological Survey Center, China Geological Survey, Chengdu 610081, China
    3. MNR Key Laboratory of Sanjiang Metallogeny and Resource Exploration-Utilization, Yunnan Geological Survey, Kunming 650051, China
    4. National Research Center for Geoanalysis, Chinese Academy of Geological Sciences, Beijing 100037, China
  • Received:2018-10-20 Revised:2019-02-20 Online:2019-03-30 Published:2019-03-30
  • Supported by:
     

PDF (PC)

290

摘要： 休瓦促W-Mo矿床位于滇西北义敦—格咱岛弧中部，为一中大型斑岩岩浆热液矿床。由于自然环境恶劣，对该区晚白垩世构造岩浆活动的研究工作起步较晚，且主要集中于富碱岩浆成岩成矿年代学、岩石成因、动力学背景、流体特征和成矿物质来源研究等方面，但对岩浆成矿作用构造应力场和动力学机制的研究还比较薄弱。文中对休瓦促W-Mo矿床东、西矿区重点坑道和剖面开展构造岩相蚀变特征解析研究，并结合锆石U-Pb、Lu-Hf和O同位素特征，认为休瓦促花岗岩体为一个两期复式岩体，以近S-N向F4断层为界可分为东、西矿区。东矿区以晚三叠世(212~201 Ma)似斑状黑云母花岗岩为主；西矿区以晚白垩世(85.6~84.4 Ma)似斑状石英二长花岗岩和二长花岗斑岩为主。西矿区W-Mo矿床寄主石英二长花岗岩锆石原位U-Pb、Lu-Hf和O同位素显示其形成时代为(80.18±0.80) Ma (LA-ICP-MC U-Pb)，εHf(t)和δ18O值分别为-4.49~-8.07和5.98‰~7.45‰，Hf同位素TDM2模式年龄分别为1 432~1 239 Ma，结合前人地球化学特征资料，推知晚白垩世石英二长花岗岩物质来源于加厚下地壳部分融熔作用。对矿区135个晚白垩世石英二长花岗岩岩脉和白钨矿辉钼矿石英脉产状数据进行区域构造解析研究，可判断义敦—格咱地区晚白垩世区域构造应力场特征为NE-SW向伸展。综上所述，义敦—格咱地区晚白垩世花岗岩可能形成于NW-SE向延伸的新特提斯洋盆俯冲作用致使先存古特提斯—中特提斯碰撞造山加厚下地壳减压部分熔融的动力学背景。

 

关键词: 滇西北, 休瓦促W-Mo矿床, 锆石U-Pb、Hf和O同位素, 区域构造解析, 动力学机制

Abstract: The Xiuwacu W-Mo deposit is a middle-large porphyry magmatic hydrothermal deposit located at the central section of the Yidun-Geza orogenic belt in northwestern Yunnan Province. Adverse natural environment in this region has delayed studies on Late Cretaceous tectono-magmatic activities in Late Yanshan, with focuses mainly on geochronology, petrogenesis, geodynamic background, fluid characteristics and source of ore-forming materials related to the Late Cretaceous alkali-rich granite, etc. However, discussion on structural stress field and dynamic mechanism is still rare. In this paper, we investigated in detail the structures and alteration-lithofacies of key sections and gallery in the east and west districts, Xiuwacu W-Mo deposits. Taking into account the zircon U-Pb, Lu-Hf and O isotopic characteristics, we believe that the Xiuwacu granitic pluton is a two phase complex pluton divided into east and west ore districts with a near S-N F4 fault as the boundary. The east district is dominated by Late Triassic (212201 Ma) porphyritic biotite granite, while mainly Late Cretaceou porphyritic quartz monzogranite and monzogranitic porphyry are in the west district. The situ-zircon U-Pb, Lu-Hf and O isotopic analysis on the porphyritic quartz monzogranite suggests that the monzogranite formation age is 80.18±0.80 Ma (LA-ICP-MC U-Pb) (negative zircon εHf(t)=-4.49-8.07, variable δ18O ranged 5.98‰7.45‰). Hf isotopic TDM2 model age is 14321239 Ma. Together with known geochemical characteristics, they show that the magmatic-mineralization material source of Late Cretaceous porphyritic quartz monzogranite was derived from the partial melting of thickened lower crust. Furthermore, Late Cretaceous regional tectonic stress field is characterized by NE-SW extension in the Yidun-Geza Area by regional structural analysis on 135 typical Late Cretaceous quartz monzogranite dykes and scheelite-molybdenite quartz veins. In summary, we believe that Late Cretaceous magmatic metallogenesis in this region is formed by the NW-SE extension of Neo-Tethys oceanic subduction resulting in partial melting of pre-existing thickened crust decompression.

Key words: Northwestern Yunnan Province, Xiuwacu W-Mo deposit, zircon U-Pb, Lu-Hf and O isotopes, regional structural analysis, dynamic mechanism

中图分类号: