新疆库鲁克塔格地区高级变质岩复杂锆石成因

发布时间：2018-04-08 11:40

本文选题：兴地塔格岩群　切入点：锆石U-Pb年龄　出处：《新疆大学》2017年硕士论文

【摘要】：本研究在新疆兴地塔格阿訇口地区1:5万区域地质调查项目的基础上,对库鲁克塔格地区古元古界兴地塔格岩群岩石样品的岩相学、锆石U-Pb年龄分析、锆石成因分析及变质相分析,确定样品的岩性、锆石的年龄特征、锆石的稀土元素特征、锆石的成因及样品变质程度,为库鲁克塔格地区古元古界兴地塔格岩群研究提供证据。为我们对塔里木克拉通年代学的研究,也有着十分重要的意义。岩相学研究表明,样品为含石墨石榴长石石英岩,为角闪岩相变质成因。对80个锆石U-Pb年龄点进行测年及CL图像分析,发现样品中最古老的锆石年龄为2666±10Ma,最年轻的锆石为1838±21Ma。绝大多数锆石都为变质成因,内部结构多数呈弱分带特征,能识别出核部和变质增生边。部分变质锆石为典型的角闪岩相,发育岩浆岩内核及变质增生边。变质成因的年龄分布在2100~1800Ma之间,变质作用主峰值期为1910Ma,反映出研究区受到2.0~1.8Ga变质作用影响。对64组锆石元素地球化学数据进行分析,在球粒陨石标准化图中,样品均呈轻稀土(LREE)亏损,重稀土(HREE)总体富集、明显Ce正异常和Eu负异常的特征。锆石稀土总量较高(260.6ppm-11915.6ppm,平均3719.7ppm),变化范围较大,具有两分的特征,260.7-996.1ppm和1536.3-11915.6ppm两组,重稀土元素含量也呈现两分特征,部分样品具有重稀土亏损的现象。(Pr/Gd)CN-(Gd/Yb)CN图解中,显示也存在明显的两分特征。呈重稀土(HREE)亏损的特征的测点锆石,与麻粒岩相变质条件具有一致性,而另一部分测点锆石则呈重稀土(HREE)富集的特征,与角闪岩相变质条件具有一致性。综合分析认为锆石核部具有角闪岩相和麻粒岩相变质条件双重特征,而变质增生部分锆石是在角闪岩相变质条件形成的。
[Abstract]:On the basis of the 1: 50 000 regional geological survey project in Xinjiang Xingdi Taag Akunkou area, the lithofacies and zircon U-Pb age of the paleoproterozoic Xingdi tag rock group in Kuluktag area were analyzed.The genetic analysis and metamorphic facies analysis of zircon determine the lithology of the sample, the age characteristics of zircon, the characteristics of rare earth elements of zircon, the origin of zircon and the degree of metamorphism of the sample, which provide evidence for the study of paleoproterozoic Xingdi tag rock group in Kuluktag area.It is also of great significance for us to study the Tarim craton chronology.The petrographic study shows that the samples are graphite-bearing garnet feldspar quartzite and amphibolite facies metamorphic origin.The dating of 80 zircon U-Pb sites and CL image analysis show that the oldest zircon age is 2666 卤10 Ma and the youngest zircon is 1838 卤21 Ma.Most zircons are metamorphic, and most of the internal structures are weakly zoned, which can identify the nuclear part and the metamorphic accretive edge.Some metamorphic zircons are typical amphibolite facies, with magmatic core and metamorphic accretive edge.The age distribution of metamorphic origin is between 2100~1800Ma and the main peak period of metamorphism is 1910 Ma, which indicates that the study area is affected by 2.0~1.8Ga metamorphism.Based on the analysis of 64 sets of zircon element geochemistry data, it is found that in the chondrites standardized map, the samples are characterized by LREE (light rare earth) depletion, HREE (heavy rare earth) enrichment, and ce positive anomaly and negative EU anomaly.The display also has obvious dichotomous features.The zircon, which is characterized by HREE (heavy rare earth) depletion, is consistent with the granulite metamorphic condition, while the other part of the zircon is enriched by the heavy rare earth HREE), which is consistent with the amphibolite metamorphic condition.It is considered that the zircon core is characterized by amphibolite facies and granulite facies metamorphism while the metamorphic accretive part of zircon is formed under the amphibolite metamorphic condition.
【学位授予单位】：新疆大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P588.3

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