藏东丁青蛇绿岩中堆晶辉长岩锆石SIMS U-Pb定年及其意义  

Zircon SIMS U-Pb dating and its significance of cumulate gabbro from Dengqen ophiolite,eastern Tibet, China

作　　者：强巴扎西 谢尧武 吴彦旺[2] 解超明[2] 李秋立[3] 邱军强[1,4] 

机构地区：[1]西藏地勘局区域地质调查大队,西藏堆龙德庆851400 [2]吉林大学地球科学学院,吉林长春130061 [3]中科院地质与地球物理研究所/岩石圈演化国家重点实验室,北京100029 [4]安徽省地质调查院,安徽合肥230001

出　　处：《地质通报》2009年第9期1253-1258,共6页Geological Bulletin of China

基　　金：国家自然科学基金项目(编号:40872146;40672147);中国地质调查局项目(编号:1212010510214)资助

摘　　要：丁青蛇绿岩位于班公湖-怒江缝合带东段,蛇绿岩的各端元组分出露齐全。纳永拉堆晶辉长岩作为蛇绿岩的端元组分之一,地球化学特征反映可能形成于MOR环境。纳永拉堆晶辉长岩获得SIMS锆石U-Pb年龄为217.8Ma±1.6Ma。CL照相和测试数据表明,锆石为典型岩浆成因的锆石。锆石定年确定纳永拉堆晶辉长岩形成于晚三叠世,为丁青段班公湖-怒江洋盆的打开时间提供了准确的时间约束。Dengqen ophiolite is located in the eastern of Bangong Co-Nujiang suture zone,and is composed of ultra-mafic rocks, mafic dykes, cumulate gabbro, pillow basalt and siliceous rocks. The geochemical data suggest that the Nayongla cumulate gabbros from Dengqen ophiolite maybe formed under the setting of MOR. Zircons from the cumulate gabbro are all magmatic origin according to their CL images and analytic data. SIMS U-Pb zircon age of 217.8 ± 1.6 Ma is obtained, which suggest that the Nayongla cumulate gabbro formed in Late Triassic. The age of Nayongla cumulate gabbro provides the exact time for the opening of Bangong Co-Nujiang ocean in Dengqen area.

关 键 词：班公湖-怒江缝合带 藏东丁青地区 纳永拉堆晶辉长岩 SIMS锆石U-Pb定年 

分 类 号：P588.124[天文地球—岩石学] P597.3[天文地球—地质学]