青海格尔木拉陵高里河上游花岗斑岩岩石成因及构造背景

发布时间：2018-05-11 23:18

  本文选题：花岗斑岩 + 锆石U-Pb年代学　； 参考：《中国地质大学(北京)》2017年硕士论文

【摘要】：本文以青海省格尔木拉陵高里河上游地区出露的花岗斑岩为研究对象,对花岗斑岩的地质学、岩相学、年代学和地球化学进行了研究,主要对上游地区花岗斑岩形成的时代和地球化学特征进行了测试分析,讨论了花岗斑岩的岩浆源区性质、岩石成因、岩石类型及其形成的大地构造背景,其结果对于揭示东昆仑拉陵高里河上游地区的大地构造演化具有一定意义。花岗斑岩的锆石LA-ICP-MS U-Pb年龄跨度较大(215Ma-230Ma),主要集中在227.2±1.7Ma和218.7±1.2Ma两个年龄群,其中218.7±1.2 Ma代表了拉陵高里河地区花岗斑岩岩浆最后固结的年龄。表明拉陵高里河上游地区花岗斑岩主要形成于印支晚期。拉陵高里河上游地区花岗斑岩具有较高的SiO2、K2O含量和分异指数,显示高钾钙碱性的弱过铝质特征,为高分异的S型花岗岩。微量元素分析结果显示,拉陵高里河上游花岗斑岩显示中等的稀土元素总量(∑REE=121.52×10-6~145.23×10-6),重稀土元素(HREE)亏损,轻稀土元素(LREE)富集,LREE/HREE为11.08~12.72,轻重稀土分馏现象相对明显,σEu介于0.48~0.63之间,均小于1,具有中等Eu负异常。σCe介于0.82~0.90之间,为轻微的负异常或无异常。样品中普遍表现出富集K、Rb、Th、U等元素,亏损Nb、Ta、P、Ti等元素,表现出与壳源相一致的特征。岩石的Al_2O_3/TiO_2比值为37~53,Rb/Sr介于0.87~1.20之间,岩浆源区表现为下地壳变质杂砂岩特征。在花岗岩主量元素和微量元素显示有后碰撞S型花岗岩特征。同时代东昆仑地区花岗岩特征、区域构造背景和构造环境判别图解均表明研究区中花岗斑岩的形成主要与东昆仑造山带的造山作用以及造山晚期的伸展作用有关。印支早期区域上古特提斯洋发生闭合,从而进入到陆陆碰撞阶段,由于持续的挤压作用使得上覆岩石圈增厚,到印支晚期由挤压作用转化为伸展作用,使得增厚的下地壳发生拆沉,因此可造成地幔岩浆上涌从而发生底侵作用,形成流体运移的通道,由于高温流体的进入,提供相对较高的温度,使下地壳杂砂岩发生重熔形成了本区花岗斑岩。
[Abstract]:In this paper, the granitic porphyry in the upper reaches of Gali River in Golmud Laling, Qinghai Province is taken as the research object, and the geology, petrography, geochronology and geochemistry of the granitic porphyry are studied. The age and geochemical characteristics of granitic porphyry formation in the upper reaches are analyzed, and the magmatic origin, petrogenesis, rock types and tectonic setting of the granitic porphyry are discussed. The results are of significance for revealing the tectonic evolution of the upper reaches of the Gali River in Laling, East Kunlun. The zircon LA-ICP-MS U-Pb age span of granitic porphyry is larger than 215Ma-230 Ma, mainly in two age groups of 227.2 卤1.7Ma and 218.7 卤1.2Ma, of which 218.7 卤1.2Ma represents the final consolidation age of granitic porphyry magma in Laling Golihe area. This indicates that granitic porphyry was mainly formed in the upper reaches of the Laling Golihe River during the late Indosinian period. The granitic porphyry in the upper reaches of Laling Gaolihe has high SiO2K2O content and differentiation index, which shows the weak peraluminous character of high potassium calc-alkaline, and it is a S-type granite with high differentiation. The results of trace element analysis show that the granitic porphyry in the upper reaches of Lalinggaoli River shows that the total amount of rare earth elements (鈭，

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