西藏当雄县九子拉蛇绿混杂岩中超基性岩地球化学特征及地质意义

樊洪富; 马义波; 白培荣; 廖铸敏

樊洪富,马义波,白培荣,廖铸敏.西藏当雄县九子拉蛇绿混杂岩中超基性岩地球化学特征及地质意义[J].贵州地质,2024,(3):241-248

西藏当雄县九子拉蛇绿混杂岩中超基性岩地球化学特征及地质意义

Geochemical Characteristics and Geological Significance of Ultrabasic Rocks in Jiuzila Ophiolitic Mellitic Rocks in Dangxiong County, Xizang

投稿时间：2024-03-11

DOI：

中文关键词: 超基性岩蛇绿岩弧间盆地九子拉区域冈底斯-喜马拉雅造山系

英文关键词:Ultrabasic rocks Ophiolite Interarc basin Jiuzila region Gangdise-Himalayan orogenic system

基金项目:西藏1∶5万九子拉地区四幅区域地质调查项目(编号:1212011121230)和西藏1∶5万恐弄拉地区四幅区域地质调查项目(编号:12120114062301)项目联合资助

作者	单位
樊洪富	贵州省地质调查院，贵州贵阳550081
马义波	贵州省地质调查院，贵州贵阳550081
白培荣	贵州省地质调查院，贵州贵阳550081
廖铸敏	贵州省地质调查院，贵州贵阳550081

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中文摘要:

通过对九子拉区域出露的蛇绿混杂岩中超基性岩进行了岩石学、岩相学、地球化学特征等方面的研究，结果表明:九子拉地区超基性的岩石类型为辉橄岩，岩石具强烈蛇纹石化。主量元素方面表现出高Mg(MgO=4327%4546%)、高Si(SiO₂=4393%4652%)、贫Al(Al2O3 =052%086%)、低铁Fe(FeOT=833%884%)的特征，经球粒陨石标准化的稀土元素配分模式表现为从轻稀土略富集趋势向右缓倾的特征，其(La/Yb)N为32942，具较轻铕负异常(Eu/Eu=015199)和较轻正铈异常(Ce/Ce=071114)。微量元素明显富集大离子亲石元素K、Rb、P，相对富集Rb、Ta等元素，贫Hf、Sm、Yb元素，属典型的镁铁质超基性岩。样品中LA-ICP-MS锆石U-Pb最小年龄为119 Ma。结合区域构造背景，认为九子拉地区中部可能是一个早侏罗世开始俯冲、早白垩世闭合的具有独立演化历程的局限性洋盆，代表了特提斯洋向南俯冲诱导出的一系列藕断丝连的中生代弧间及弧后扩张盆地。

英文摘要:

By study the petrological and geochemical characteristics of the ultrabasic rocks in the ophiolite complex in Jiuzhaila area，the results show that the ultrabasic rocks in Jiuzhaila area are gabbro，with strong serpentinizationThe major elements show high Mg (MgO=4551%4642%)，high Si (SiO₂=4393%4652%)，poor Al (Al2O3 =052%086%) and low Fe (FeOT=833%884%)The REE distribution model normalized by chondrite shows a trend of slightly enriched light rare earth to the right，with (La/Yb) N ranging from 032942，with a relatively light negative Eu anomaly (Eu/Eu=015199) and a relatively light positive Ce anomaly (Ce/Ce=071114)The trace elements are obviously enriched in large ion lithophile elements K，Rb，P，relatively enriched in Rb，Ta，poor in Hf，Sm，Yb，belonging to a typical mafic ultrabasic rockThe minimum age of LA-ICP-MS zircon U-Pb in the sample is 119 MaCombined with the regional tectonic setting，the Tethys Ocean represented by the ophiolite in Shiquanhe area may be a local ocean basin with an independent evolutionary process，which began to subduct in the Early Jurassic and closed in the Early Cretaceous，and represents a series of interarc and backarc basin induced by the southward subduction of the Tethys Ocean

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