摘要
利用兰坪盆地内金顶矿床容矿围岩中的锆石,在SHRIMPⅡ上获得了一组1800～2000Ma的古元古代U-Pb年龄信息,认为它很可能来自扬子基底;由锆石的形态特征判断,它们未经强烈改造和长距离迁移,暗示该盆地形成和演化过程中有老物源物质的参与,为探讨三江造山带、兰坪盆地的大地构造演化及扬子原地台基底边界的划定、金顶超大型矿床成因的探讨提供了新的证据。
Jinding superlarge deposit located in the northern part of Lanping Basin, western Yunnan Province. It has been studied for more than 20 years, and a lot of genetic models were proposed such as stratabound type, synsedimentation-late reformation and mantle-crust compound mineralization. But some elementary geological problems such as some of the wall-rock ages and the structures that constrained orebodies have been suspended till now. These embarrassed the explanation of the genesis about Jinding deposit and the tectonic or crustal evolution of Three-River （Nujiang, Lancangjiang and Jinshajiang rivers） orogenic belt. For these reasons, this paper selected some zircons from the wall-rocks to discuss the tectonic setting. Based on crystal features and shapes of the zircons, which were different from the normal weathered zircons in sandstones, the wall-rocks must be not far where their source rocks formed According to the process of zircon dating, 4 group of isotopic ages were obtained by SHRIMP II in Beijing Ion Microprobe Center. They are 240Ma , 415Ma , 820Ma and 1800 -2000Ma. These suggested that the Pb-Zn metallization age was younger than 240Ma. Further more, a number of Plaeoprotozoic ages （1910Ma, 1867Ma, 2021Ma, 2487Ma） were more significance in geological studies. First, it indicated that the source rocks of Lanping basin contained some Precambrian ages. These implied that the Precambrian basement of Yangtze Plate could spread to Lancanjiang river. Second, these isotopic ages suggested that the evolution of Lanping-Simao basin must be related to early Precambrian basement. Third, it implied that the Central Fault （or Zhongzou Fault） zone , which is nearly relevant to the genesis of Jinding deposit, should be a multi-phased fractured faults.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2006年第4期1040-1048,共9页
Acta Petrologica Sinica
基金
国家重点基础研究发展规划项目(编号2002CB412607)资助成果。
