【作者】 王雁飞；

【导师】 杨家喜；

【作者基本信息】 长安大学 ， 矿物学、岩石学、矿床学， 2011， 硕士

【摘要】 研究区处于阿尔泰山脉东段南缘,位于西伯利亚板块西南边缘、准噶尔板块的东北边缘,是西伯利亚板块和准噶尔板块斜向碰撞对接的构造部位。本文以新疆青河卫东乡变质基性岩为研究对象,通过详细野外路线调查、重点剖面测制和室内镜下薄片分析,对该变质基性岩野外分布情况、延伸方向、规模和产状及岩石组合特征、岩相学特征进行了认真研究。同时,对样品进行了岩石地球化学分析测试和同位素年代学测试,从地球化学和同位素地质年代学方面探讨该变质基性岩的形成构造环境和形成时代,取得了以下初步认识：通过实测剖面分析卫东乡姜巴斯套组沉积环境应为深海—次深海—浅海。卫东乡姜巴斯套组变质英安岩LA-ICP-MS锆石U-Pb同位素年龄为(359.3±2.5)Ma (MSWD=0.09),表明其形成时代为晚泥盆世—早石炭世(D3—C1)。地球化学特征分析显示,卫东乡变质基性火山岩具有贫碱、尤其是贫钾,低Ti02的特征,应为低钾拉斑玄武岩。其稀土分配模式为LREE弱富集型,具有较高的∑REE。MORB标准化的微量元素蛛网图呈现出大离子亲石元素(K, Sr, Rb, Ba)富集,亏损高场强元素,具Nb、Ta和Hf的负异常。这些地球化学特征表明卫东乡变质基性火山岩形成于弧后盆地环境。阿勒泰地区在晚泥盆世—早石炭世末为沟-弧-盆体系演化阶段,从晚泥盆世开始,由于准噶尔洋在向北面的大陆之下俯冲,形成了沿额尔齐斯—乌伦古湖俯冲带、喀拉通克岛弧带、阿舍勒—克兰弧后盆地带。因此研究区在晚泥盆—早石炭世的形成环境与整体区域上的构造环境应该是相对应的。更多还原

【Abstract】 Researched area is located at the south margin of the east section of Altai mountain,the southwest margin of Siberia plate,northeast margin of Junggar plate,where is the oblique collision and jointing position of the two plates.Metabasites of Weidong,Qinghe,Xinjiang is selected as the research object of the study.After detailed wild-field geological survey, key section measuring and indoor microscope study, the wild-field distribution, scale, occurrence and assemblage and petrology of the rocks are ascertained.Meanwhile, the petrogeochemistry analysis and isotopic dating of rock samples were tested. So we can discuss the tectonic environment and formation age of metabasites via geochemistry and isotope geochronology. Main cognitions are acquired as follows:The sedimentary environment of Jiangbasitao formation in Weidong Country should be from deep-sea,sub-deep sea to epeiric sea by analysis of the measured profile.The LA-ICP-MS zircon U-Pb isotope age of metadacite of Jiangbasitao formation in Weidong Country.It shows that the formation age of Jiangbasitao is from late devonian to early carboniferous(D3-C1).The geochemical analysis showed that the metabasites have the characteristics with poor alkali, especially poor potassium and low TiO2.So they should be low potassium tholeiite.The distribution model of rare-earth elements is weak LREE enrichment and high∑REE type.The spiderweb figure of trace elements with MORB standardization shows that large ion lithophile elements (K, Sr, Rb, Ba) are enriched,high field strength elements are lossed and Nb, Ta and Hf with negative anomaly. The geochemical characteristics show that the tectonic environment of metabasites is retroarc basin.Altay region is the trench-arc-basin system evolution stage from Late Devonian to the end of Early Carboniferous.Starting from the Late Devonian,due to Junggar ocean subduction under the northern continent,along Eerqisi-Wulungu lake subduction zone,Kalatongke island arc belt and Ashele-Crane retroarc basin belt are formed.Therefore,the formation environment of research area during the late Devonian-Early Carboniferous and the overall regional tectonic environment should be corresponding.更多还原