【作者】 杨宝凯；

【导师】 李永军；

【作者基本信息】 长安大学 ， 构造地质学， 2011， 硕士

【摘要】 本文以西准噶尔唐巴勒蛇绿岩为研究对象,从岩石组合、岩石学、岩石地球化学、构造环境、及大地构造意义等方面对该岩带作了比较系统的研究。(1)唐巴勒蛇绿岩位于哈萨克斯坦—准噶尔板块唐巴勒—卡拉麦里古生代复合沟弧带内的准噶尔盆地西南部,出露宽度约4km～8km,由大小不等的多个超基性岩块组成,表现为组分齐全的蛇绿岩。(2)空间位置关系上,蛇纹岩作为基质分布于岩带的最下部,辉长岩、辉石岩及玄武岩堆积于蛇纹岩之上,硅质岩覆盖在玄武岩之上。各单元之间由于后期构造破坏,均为断层接触。(3)蛇绿岩中的辉长岩LA-ICP-MS锆石U—Pb测年结果显示,年龄分散且年轻(240-320Ma),代表热事件或者变质年龄,并不代表辉长岩形成的真实年龄。为此综合前人的年代学研究资料,认为唐巴勒蛇绿岩的年龄为447-531Ma,时代属于寒武纪—奥陶纪。(4)唐巴勒蛇绿岩中玄武岩具有拉斑玄武岩特征,富集大离子亲石元素,亏损高场强元素和显示弱的或没有Eu异常,普遍具有Nb,Ta相对亏损。地球化学特征表明,其形成于弧后盆地环境。(5)通过对抗蚀变元素Zr,Nb和Y分析,揭示唐巴勒蛇绿岩的岩浆来源于亏损地幔。(6)综合前人资料及本次研究,西准噶尔地区寒武纪—奥陶纪曾经发生过一次北西向的洋内俯冲事件。更多还原

【Abstract】 This dissertation is object on Tangbale ophiolitic in Western Junggar, Xinjiang. Systemic researching the character of ophiolitic of rock combination, petrology, formtive age、petrochemistry, geochemistry, tectonic setting, tectonic significance and so on.(1)Tangbale ophiolitic distribute the southwest of Junggar basin, kazakhstan-Junggar plate Tangbale-Kalamaili Paleozoic complex trench arc zone, the width is about 4 to 8km, consist of kind of ultrabasicrock, has a complete sequence of ophiolite.(2)The position of serpentinite is lowest as matrix, gabbro、diabase and basalt accumulate on the serpentinite, and siliceousrock cover with basalt. contact relation between each sequence was fault because of structural demolished.(3)The gabbro, a sequence of ophiolitic, LA-ICP-MS zircon U-Pb dating shows that ages are disperse and young, stand for tectothermal event or metamorphic age, which can’t stand the gabbro’s true formation age. so synthesize former formation data, consider that Tangbale ophiolitic was formed about 447Ma-531Ma, belong to Cambrian-Ordovician.(4)The basalts from the Tangbale ophiolitic display tholeiitic in composition with enrichment in LILEs (e.g., Rb, K and Ba), depletion in HFSEs (e.g., Nb, Ti, Zr and Hf) and weak or no Eu anomalies, depletion Nb, Ta generally, geochemistry character show Tangbale ophiolitic formed in back-arc basin setting。(5)Insusceptible elements, such as Zr, Nb and Y, are employed to discriminate the nature of magma source of depleted mantle.(6)This study and previous work constrains north westward subduction model in the West Junggar for the Cambrian-Ordovician.更多还原