新疆库鲁克塔格新元古代花岗岩类年代学及成因研究

发布时间：2018-03-21 18:37

本文选题：库鲁克塔格　切入点：新元古代　出处：《新疆大学》2017年硕士论文　论文类型：学位论文

【摘要】：塔里木克拉通北缘库鲁克塔格地区,是塔里木克拉通前寒武地层出露最完整的地区之一,新元古代侵入岩极为发育,延续的时间长且具有明显的阶段性,岩石类型复杂,其中以花岗岩类分布最为广泛。本文选择库鲁克塔格西段花岗岩作为研究对象,进行系统的岩石地球化学、锆石U-Pb测年和锆石原位Hf同位素研究,并结合区域已有地质事实,讨论其形成时代、源区特征及成因。锆石U-Pb测年表明库鲁克塔格西段花岗岩类侵位于884Ma~735Ma,属新元古代。结合前人研究成果,将库鲁克塔格地区花岗岩类分为新元古代早期、中期、晚期及末期四个阶段,本文仅对前三期进行讨论。其中新元古代早期(~880Ma-~1000Ma)岩浆活动在库鲁克塔格记录较少,本文在研究区发现了两个~880Ma的花岗岩体,弥补了新元古代早期岩浆活动记录的空白。主要为石英二长闪长岩及英云闪长岩。该期花岗岩类为弱过铝质高钾钙碱性I型花岗岩,形成于流体参与下的古老基性下地壳的部分熔融。岩石具岛弧岩浆岩的特征,为塔里木北缘新元古代洋-陆俯冲作用早期的产物;新元古代中期(~840Ma-~780Ma)花岗质岩浆活动最为活跃,延续时间长且分布广泛,主要为英云闪长岩、二长花岗岩及花岗闪长岩,另外还有少量流纹岩,岩石同样具I型花岗岩特征,此外岩石强烈富集Sr、强烈亏损Y和Yb,以及高的Sr/Y和(La/Yb)N比值的特征与埃达克岩特征相似,岩石形成于加厚的古老基性下地壳在流体加入的条件下低温部分熔融,为塔里木北缘持续的洋陆俯冲-碰撞作用的产物;新元古代晚期(~740Ma-~730Ma)花岗质岩浆活动较弱,主要为正长花岗岩及流纹岩,岩石具A2型花岗岩的地球化学特征,形成于太古宙-古元古代古老结晶基底的部分熔融,为俯冲挤压向伸展构造转变期岩浆活动的产物,指示库鲁克塔格地区~735Ma开始进入减压伸展的环境。
[Abstract]:The Kuluktag area on the northern margin of the Tarim craton is one of the most complete areas in the Precambrian strata of the Tarim craton. The Neoproterozoic intrusive rocks are extremely developed, lasting for a long time, with obvious stages and complicated rock types. Granitic granites are the most widely distributed. In this paper, the granites in the western section of Kuluktag are selected as the research objects, and systematic geochemistry, zircon U-Pb dating and zircon in-situ HF isotopic studies are carried out, together with the geological facts in the region. The zircon U-Pb dating shows that the granitic transgressions in the western part of Kuluketagge are located at 884 Ma-735 Ma, belonging to the Neoproterozoic. Combined with the previous research results, the granitoids in the Kuruktag area are divided into early Neoproterozoic and middle Neoproterozoic. In the late and late stages, only the first three phases were discussed in this paper. In the early Neoproterozoic, the magmatic activity was less recorded in Kuluktag, and two granitic bodies of 880Ma were found in the study area. It is mainly composed of quartz diorite and dolomite. The granitoids of this period are weakly peraluminous high-potassium calc-alkaline I-type granites. Partial melting of the ancient basic lower crust formed with fluid participation. The rocks are characterized by island arc magma, which is the product of the early Neoproterozoic ocean-continental subduction in the northern margin of Tarim, and the most active magmatic activity is the granitic magma in the middle Neoproterozoic. It lasted for a long time and was widely distributed, mainly composed of quartz diorite, monzogranite and granodiorite, and a small amount of rhyolite, which was also characterized by I-type granite. In addition, the rocks are strongly enriched in Sr, strongly depleted in Y and Yb, and the characteristics of high ratios of Sr/Y and La / YbN are similar to those of the adakite, and the rocks formed in the thickened ancient basic lower crust are partially melted at low temperature under the condition of fluid addition. It is the product of continuous oceanic subduction and collision in the northern margin of Tarim, and the granitic magmatic activity of late Neoproterozoic is weak, mainly composed of syenite and rhyolite. The rocks have the geochemical characteristics of A2-type granite. The partial melting of the Archean-Paleoproterozoic ancient crystalline basement is the product of magmatic activity during the subduction and compression to extensional tectonic transition, indicating that the Kuluktag area began to enter a depressurized extensional environment at 735 Ma.
【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】：P588.121

【相似文献】