藏西班公湖斑岩铜矿带的形成时代与成矿构造环境  

Ages and tectonic environment of the Bangong Co porphyry copper belt in western Tibet, China

作　　者：曲晓明[1] 辛洪波[1] 

机构地区：[1]中国地质科学院矿产资源研究所,北京100037

出　　处：《地质通报》2006年第7期792-799,共8页Geological Bulletin of China

基　　金：国家"十一五"科技攻关项目(编号:2003BA612A-1);"973"项目<印度与亚洲大陆主碰撞带成矿作用>(2002CB412605)资助。

摘　　要：通过对藏西班公湖斑岩铜矿带多不杂和尕尔穷2个大、中型斑岩铜矿床含矿斑岩的研究,初步查明了该铜矿带的形成时代、含矿斑岩性质及成矿构造环境。锆石SHRIMPU-Pb定年结果给出2个铜矿床含矿斑岩的时代分别为127.8Ma±2.6Ma和112.0Ma±2.3Ma,处于造山带演化的碰撞后阶段(班公湖-怒江洋盆的闭合时间为145Ma)。岩石地球化学分析表明,该铜矿带的含矿斑岩属钾玄岩-高钾钙碱性岩系,以富集Rb、K、Sr、Pb等大离子不相容元素和亏损Nb、Ta、Ti等高场强元素为特点,与冈底斯斑岩铜矿带的含矿斑岩相似。所不同的是,班公湖斑岩铜矿带含矿岩浆生成深度较浅,构造环境上处于碰撞后地壳隆升阶段,而冈底斯斑岩铜矿带则处于地壳上升到最大高度后的伸展塌陷阶段。The ages, natures and tectonic environments of the Bangong Co porphyry copper belt have been preliminarily determined through a study of ore-bearing porphyries in the Dobuzha and Garqiong porphyry copper deposits in the porphyry copper belt. Zircon SHRIMP U-Pb dating yielded ages of 127.8±2.6 and 112.0±2.3 Ma for the two deposits respectively and indicates that the two deposits formed in a post-coUisional stage of the orogen evolution （the Bangong Co-Nujiang ocean basin closed at 145 Ma）. Geochemical analysis demonstrates that the ore-bearing porphyries of the copper belt belong to the shoshonite-high-K calc-alkaline rock series and are characterized by enrichment of large ion lithophile elements （LILE） such as Rb, K, Sr and Pb and depletion of high field strength elements （HFSE） such as Nb, Ta and Ti. These features are similar to those of the ore-bearing porphyries of the Gangdise porphyry copper belt. Differences between them lie in that the ore-bearing magma of the Bangong Co copper belt was generated at a shallower depth in a post-collisional crustal uplift stage, whereas the ore-bearing magma of the Gangdise porphyry copper belt in a stage of post-coUisional crustal extensional collapse when the crust rose to the maximum height.

关 键 词：斑岩铜矿 含矿斑岩 锆石SHRIMP U—Pb年龄 成矿构造环境 班公湖-怒江缝合带 西藏 

分 类 号：P618.41[天文地球—矿床学]