新疆库鲁克塔格早元古代地壳深熔与地质演化

发布时间：2018-05-29 02:09

本文选题：库鲁克塔格 + 古元古代早期　；参考：《新疆大学》2017年硕士论文

【摘要】：库鲁克塔格地块西山口兴地塔格群下亚群浅粒岩组,普遍受到早元古代角闪岩相-麻粒岩相的变质作用。区域上浅粒岩组、片麻岩组、变质花岗质岩体,密切共生,被认为是古老地壳发生深熔作用的证据。本论文通过;1)深熔作用的野外宏观证据,2)浅粒岩组的原岩恢复,3)残余体与新生体的稀土元素对比,4)深熔作用的镜下特征,5)有关的锆石U-Pb年代学证据,6)相关变质作用的温压条件估算7)对变质花岗质岩体形成的构造背景探讨。结合这几点来对库鲁克塔格地区古元古代深熔作用进行时间上、程度上、阶段上的约束,对与此次深熔作用有关的造山带背景进行探讨。并在塔里木克拉通周边前寒武地块出露区域,进行同期的造山带对比。结合全球造山事件,推测库鲁克塔格地区深熔作用是1.9Ga哥伦比亚大陆聚合的响应。库鲁克塔格地块西山口兴地塔格群下亚群浅粒岩组,在地层中,尤其是褶皱端部等构造有利部位,广泛存在以透镜状、腊肠状、细脉状的浅色熔融新生体与变质闪长岩体。样品采自浅粒岩组中,岩性为二长浅粒岩、含石榴石斜长浅粒岩(两者被视为深熔残余体)、以及变质石英闪长岩(视为深熔新生溶体),浅粒岩组镜下可见变余层理以及在特定部位矿物颗粒明显增大与典型的熔融石英特征。二长浅粒岩变质矿物组合为Pl+Bi+Q,属低角闪岩相变质,含石榴石斜(钾)长浅粒岩峰期变质矿物组合为Pl+K+Gr+Q或Pl+Gr+Q为角闪岩相。两组样后期黑云母、石榴石等矿物被被绢云母等交代,显示为绿片岩相。综合显示该变质地层经过了低角闪岩相-角闪岩相-绿片岩相的顺时针Pt轨迹,这种轨迹符合碰撞造山的Pt轨迹。原岩的恢复显示,浅粒岩组原岩为一套杂砂岩组。其锆石普遍受到重熔,其核部年龄可视为深熔作用发生的时间(测得变质年龄1950±30Ma)。变质闪长岩锆石核部具有明显的岩浆锆石特征(测得岩体年龄1893±15Ma),对其形成的因素,在本人地球化学特征与前人Hf-O同位素工作的基础上,认为这期花岗岩在形成上涉及在地壳剧烈加厚过程中,新生基性下地壳与古老地壳两者熔融再造的混合,且混合可能发生在浅部地壳,其中黑云母脱水,对熔融作用的贡献较大。综合以上观点说明,与石英闪长岩(1893±15Ma)有关的岩浆事件,是以兴地塔格群杂砂岩组为深熔母岩,经过深熔作用的产物。且这次深熔作用的机制与古元古代晚期造山事件引起的地壳加厚有关。根据样品的变质程度,本人认为二长浅粒岩、含石榴石斜长浅粒岩分别代表了研究区深熔程度由低到高的变化,并结合该期花岗质岩体形成机制。推测与这次深熔作用有关的造山带类型,为碰撞造山带,原先沉积的地层,因板块碰撞,引起强烈的地壳加厚,在加厚升温的过程中发生初期的深熔作用,特征上以二长浅粒岩与浅色长英质脉体共生为特征,在变质作达到峰期时,形成含石榴石斜长浅粒岩与长英质透镜体,块体共生的特征,若溶体进一步聚集则形成原地或半原地的花岗闪长质岩体。同时,通过对这次造山事件与同期塔里木周边的造山事件的对比,本人认为这次造山事件与1.9Ga左右的Columbia超大陆汇聚有关,进而说明研究区,库鲁克塔格古元古代深熔事件,是Columbia超大陆集合的响应。
[Abstract]:The subgroup of subgroup in the lower subgroup of the Xishan estuary subgroup in the Xishan block of the quttg block is generally subjected to metamorphism of the early Proterozoic amphibolite facies and granulite facies. The regional superficial granulite group, the gneiss group and the metamorphic granitic rock mass are closely symbiotic, which are considered to be the evidence of the deep melting of the ancient crustal. 1) the field macroscopic view of the deep melting. Evidence, 2) the restoration of the primary rock in the shallow granulite group, 3) the contrast between the remnants and the rare earth elements, 4) the characteristics of the deep penetration, 5) the related zircon U-Pb chronological evidence, 6) the estimation of the temperature and pressure conditions of the related metamorphism 7) and the structural background of the metamorphic granitic rock formation. The deep melting process, in time, degree and stage constraints, discusses the orogenic belt background related to the deep melting, and the outcropping area of the Precambrian block around the Tarim Craton and contrasting the orogenic belt at the same period. Combined with the global orogenic event, the deep melting of the Kuru katG region is 1.9Ga Columbia continent. The response of the polymerization. The subgroup of the subgroup of the subgroup of the Xishan Dagg group in the Xishan block of the qutagg block, in the formation, especially in the end of the fold, is widely used as a lenticular, dachshund and fine vein light molten freshman and metamorphic diorite. The sample is collected from the shallow granulite group, and the lithology is two long light granulites, and the garnet is inclined. The long light granulites (both are regarded as deep melting remnants) and metamorphic quartz diorite (as deep melting new dissolved bodies), the light granulites can be seen under the microscope, and the mineral particles in the specific parts are obviously enlarged and the typical fused silica features. The metamorphic minerals of the two long granites are composed of Pl+Bi+Q, low amphibolite facies metamorphism, and garnet oblique (potassium). The metamorphic mineral assemblages in the peak period of the long shallow kernels are Pl+K+Gr+Q or Pl+Gr+Q amphibolite facies. The two groups of anaphase anaphase, garnet and other minerals were metasomatism by sericite, which were shown as greenschist facies. The metamorphic strata showed that the metamorphic stratum passed the clockwise Pt locus of the amphibolite facies and greenschist facies of the amphibolite facies, which accorded with the collision orogenic Pt. The restoration of the original rock shows that the original rock of the shallow granulite group is a set of hetero sandstone group. Its zircon is generally remelted, the age of its nucleus can be seen as the time of deep melting (1950 + 30Ma). The zircon core of the metamorphic diorite has obvious characteristics of the magma zircon (the age of 1893 + 15Ma). On the basis of the geochemical characteristics of the human geochemistry and the previous work of Hf-O isotopes of the predecessors, it is believed that the granites are involved in the process of severe crustal thickening, and the mixture of the new basal lower crust and the ancient crust is mixed, and the mixture may occur in the shallow crust, in which the black cloud mother dehydrated and contributed greatly to the melting effect. It is pointed out that the magmatic events associated with quartz diorite (1893 + 15Ma) are the products of the deep melting parent rock in the Xingdi TGGE group complex sandstone group, which is related to the crustal thickening caused by the late Proterozoic orogeny. According to the metamorphic degree of the samples, I think two long granites, including pomegranates. It represents the change in the degree of deep melting from low to high and the formation mechanism of granitic rock mass in the study area. It is speculated that the type of orogenic belt, which is related to the deep melting, is the collision orogenic belt, the original sedimentary strata, the strong crust thickening caused by the collision of the plate, and the initial stage during the thickening of the heating process. The deep melting is characterized by the symbiosis between the two long granitoids and the light colored felsic veins. In the peak period of the metamorphic metamorphism, the granitoids with long granitoids and long angled lenticular bodies are formed, and the masses are symbiotic. If the dissolved body is further aggregated, the original or semi original granodiorite bodies are formed. In the same period of the comparison of orogenic events around the Tarim, I think the orogenic event is related to the Columbia supercontinent convergence around 1.9Ga, and then the study area, the Palaeoproterozoic Proterozoic deep melting event in the study area is the response of the Columbia supercontinent collection.
【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】：P542;P534.3

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