青海拉脊山东段峡门蛇绿混杂岩带的物质确定及其构造意义  

DETERMINATION OF THE XIAMEN OPHIOLITE MELANGE IN THE EASTERN SECTION OF LAJI MOUNTAIN,QINGHAI PROVINCE:Tectonic Implication

作　　者：曹锦山 王伟[1] 李五福[1] 张新远[1] 缑明亮[1] CAO Jin-shan;WANG Wei;LI Wu-fu;ZHANG Xin-yuan;GOU Ming-liang(Key Laboratory of Geological Process and Mineral Resources in Northern Qinghai-Tibet Plateau/Qinghai Institute of Geological Survey,Xining 810012,China)

机构地区：[1]青海省青藏高原北部地质过程与矿产资源重点实验室/青海省地质调查院,青海西宁810012

出　　处：《地质与资源》2022年第6期716-728,共13页Geology and Resources

基　　金：中国地质调查局项目“青海区域地质调查片区总结与服务产品开发”(12120114079701);“青海省民和县西沟地区三幅1∶5万区域地质矿产调查”(12120114041301).

摘　　要：在拉脊山东段青海省民和县峡门镇以南地区新识别出一条蛇绿混杂岩带,其物质组成复杂,构造岩块主要由蛇绿岩岩块、外来岩块、火山岩岩块以及变沉积岩岩块组成.基性火山熔岩和辉绿岩具轻稀土富集的“右倾”配分模式,大离子亲石元素Ba、Th、Sr相对富集,高场强元素P、Ti、Nb相对亏损,总体岩石地球化学特征与岛弧拉斑玄武岩类似.岩石学、岩石地球化学、同位素年代学特征及区域资料综合研究认为,峡门蛇绿岩属与俯冲有关的SSZ型蛇绿岩,很可能是早古生代原特提斯洋俯冲消减的弧后小洋盆,属于弧后盆地扩张型蛇绿岩.An ophiolite melange belt with complex material compositions is newly identified in Xiamen Town in the eastern section of Laji Mountain,Qinghai Province.The tectonic blocks are mainly composed of ophiolites,exotic blocks,volcanic rocks and meta-sedimentary rocks.The basic volcanic lava and diabase are characterized by right-dipping LREE enrichment patterns,enrichment of LILEs(Ba,Th and Sr),and depletion of HFSEs(P,Ti and Nb),with the general petrogeochemistry similar to that of island-arc tholeiite.The comprehensive study of petrology,petrogeochemistry,isotope chronology and regional geology show that the Xiamen ophiolite is of supra-subduction zone(SSZ)type,which is probably a back-arc small ocean basin formed by Early Paleozoic Proto-Tethyan Ocean subduction,belonging to back-arc basin spreading ophiolite.

关 键 词：拉脊山 蛇绿混杂岩 岩石地球化学 SSZ型蛇绿岩 构造环境 青海省 

分 类 号：P542[天文地球—构造地质学] P597[天文地球—地质学]