摘要
为了探讨北祁连玉石沟地区蛇绿混杂岩带的形成时代及环境,对玉石沟蛇绿混杂岩带中的堆晶辉长岩岩石地球化学和U-Pb年龄样测年进行了分析。结果表明:玉石沟堆晶辉长岩Al_2O_3(7. 36～15. 69%)、MgO(6. 24%～13. 27%)、FeO(5. 13%～8. 20%)较为富集,SiO_2含量为45. 61%～52. 63%,属于大洋中脊玄武岩(MORB);岩石中(La/Yb)N介于6. 04～9. 77之间,(La/Sm)N介于3. 84～4. 35之间,LREE/HREE=5. 67～8. 79之间,表明轻稀土富集,重稀土亏损,其有明显的富集型洋脊玄武岩(E-MORB)特征;利用LA-ICP-MS锆石U-Pb定年方法测年,获得502. 0 Ma±4. 3 Ma,表明在晚寒武世北祁连玉石沟地区有一次伸展事件发生。结合本区已有的研究成果,表明北祁连确实存在古生代洋盆事件,至少在晚寒武世北祁连洋盆已极具规模。
In order to investigate the formation age and environment of the ophiolitic melange belt in Yushigou area of North Qilian, we have made a research of the geochemical and U-Pb age measurements of the piled gabbro in Yushigou ophiolitic melange belt. The results show that the Jupiter ditch crystal gabbro Al2O3 （7.36 -15.69% ） ,MgO（6.24% - 13.27%）, FeO（5.13% - 8.20% ） are enriched. The SiO2 content is 45.61% - 52.63%, belonging to the ocean. Middle ridge basalt（MORB） and （La/Yb） N in rock is between 6.04 and 9.77. （La/Sm） N is between 3. 84 and 4. 35, and LREE/HREE is between 5. 67 and 8. 79, indicating light rare earth Enrichment, heavy rare earth loss. It has obvious characteristics of enriched oceanic basalt （E-MORB） by using LA-ICP-MS zircon U-Pb dating method to measure 502.0 Ma ± 4.3 Ma. There was a stretching event in Yushigou area of northem Qilian. Combined with the existing research results in this area, it is indicated that there are indeed Paleozoic ocean basin events in Beiqilian, at least in the Late Cambrian North Qilian Ocean Basin.
作者
吴少锋
何存发
张海青
袁桂林
陈礼标
钱玉山
WU Shaofeng;HE Cunfa;ZHANG Haiqing;YUAN Guilin;CHEN Libiao;QIAN Yushan(The Fourth Qinghai Institute of Geology and Mineral Exploration,Xining,Qinghai 810029,China)
出处
《中国锰业》
2018年第5期137-140,150,共5页
China Manganese Industry
基金
中国地质调查局"祁连成矿带肃南-大柴旦地区地质矿产调查"(DD20160012)
