新疆西准噶尔地区古生代岩浆活动的年代学和地球化学研究

发布时间：2017-12-27 06:15

本文关键词：新疆西准噶尔地区古生代岩浆活动的年代学和地球化学研究　出处：《中国地质大学》2016年博士论文　论文类型：学位论文

【摘要】：西准噶尔地区经历了多期次、多阶段长期而复杂的构造地质演化,同时伴随着大量的花岗质岩浆活动。各期岩浆岩的成因、物源涉及西准噶尔造山带的形成,特别是各期次花岗岩浆活动的地球动力学过程与演化。本文选择西准噶尔地区古生代的岩浆岩(火山岩和侵入岩),重点对有代表性的岩体进行了岩石学、地球化学、锆石形态学、锆石LA-ICP-MS U-Pb年代学和锆石Hf同位素地球化学等分析等,厘定了各期构造事件的时限,划分了岩浆岩的活动期次,确定了岩浆岩成因,反演了西准噶尔造山带构造演化过程。运用锆石LA-ICP-MS U-Pb定年方法,对研究区内7个花岗岩体进行了精细的年代学研究,其中,苏根萨拉花岗岩体的年龄为415.6±1.1Ma,为晚志留世。玉什喀腊辉长岩体的年龄为364±1Ma,为晚泥盆世。黑子勒塔吾丁浩热石英二长闪长岩体的年龄为364.7±3.0Ma,为晚泥盆世。木斯岛山二长花岗岩体的年龄为335.9±0.9Ma,为早石炭世。加尔路阿甫花岗斑岩体的年龄为305±2Ma,为晚石炭世。阔依塔斯闪长岩体的年龄为297±2Ma,为晚石炭世。恰其海钾长花岗岩体的年龄为280.1±3.2Ma,为早二叠世。确认了各期次花岗岩的侵入时代,为认识西准噶尔构造岩浆演化提供了高精度的年代学依据。结合前人研究成果,将研究区内岩浆岩的期次划分为4个阶段：早志留世-早泥盆世(436-405Ma)、早石炭世(350-320Ma)、晚石炭世-早二叠世(318-270Ma)和中晚二叠世(270-263Ma)。岩浆岩在时空分布上具有明显的规律性,其形成时代具有南北老,中间新的变化规律。侵入岩的岩石地球化学研究表明,研究区各阶段岩体主要为A型和I型花岗岩。谢米斯台山西段花岗岩岩石类型为A2型花岗岩和碱性弱过铝质分异I型花岗岩。早石炭世花岗岩以I型为主,主要分布于萨吾尔地区,呈带状分布,可能形成于陆壳俯冲的构造背景下,晚石炭世-早二叠世花岗岩以A型为主,呈面状分布,具有碱性和准铝质特征,可能为俯冲有关的流体交代的产物,部分岩浆源区具有明显的弧岩浆活动特点,可能形成于碰撞后伸展环境中。晚泥盆世玉什喀腊辉长岩体为俯冲流体交代亏损的岩石圈地幔形成,岩浆在上升过程中没有遭受地壳物质的混染。早二叠世基性侵入岩的源区中既有俯冲消减的印迹,又有地幔组分的参与,可能是被俯冲板片或消减沉积物所释放的流体交代后的地幔橄榄岩部分熔融的产物。新获得了西准噶尔地区7个侵入岩锆石Hf同位素组成,结果表明,区内各时期侵入岩体具有相似的锆石Hf同位素,它们均具正的εHf(t)值,且正值较高,指示各期花岗岩主要为新生陆壳部分熔融的产物,反映在西准噶尔地区从中元古到早古生代的奥陶纪持续有新生陆壳形成。这与整个中亚造山带从新元古代以来持续形成新的陆壳和发生多起弧-陆碰撞拼贴、大陆增生是吻合的。在上述研究的基础之上,结合区域地质背景和西准噶尔造山带构造演化特征,讨论了古亚洲洋闭合的时限和后碰撞作用的时限。研究表明,该区为多次碰撞、多次消减,洋盆是形成一个、消减一个,再形成一个、再消减一个,相继出现,相继消减。古亚洲洋的范围很广,可能每个区域闭合的时间不尽相同。本文推断在西准噶尔北部地区(额尔齐斯缝合带附近),晚泥盆世洋陆俯冲事件已基本结束,古亚洲洋闭合的时间不早于364Ma。对于后碰撞作用的时限,结合区域地质资料,本文推测西准噶尔地区后碰撞深成岩浆活动是从早石炭世开始,于早二叠末期结束,即后碰撞深成岩浆活动发生在340-270Ma之间。通过对岩浆岩岩石成因、Hf同位素示踪与构造演化关系的研究,认为古生代特别是晚古生代是中亚造山带大陆地壳增生的重要时期。增生方式包括了与俯冲作用有关的侧向增生,还包括与幔源岩浆底侵有关的垂向增生,大陆地壳增生是一个多阶段多旋回的过程,贯穿于中亚造山带形成演化的整个过程。
[Abstract]:The western Junggar region has experienced a long and complicated tectonic and geological evolution with multiple stages and multiple stages, and accompanied by a large number of granitic magmatism. The genesis and source of the magmatic rocks in each period involve the formation of the western Junggar orogenic belt, especially the geodynamic process and evolution of the granitic magma activities of each period. This choice of Paleozoic in Western Junggar magmatite (volcano rock and intrusive rock), focusing on the petrology, geochemistry, zircon morphology, zircon LA-ICP-MS U-Pb geochronology and Hf isotope geochemistry analysis of representative rock bodies, determine the different tectonic events of the time, the division of magmatite activity second, to determine the origin of magmatite, West Junggar orogenic belt tectonic evolution inversion. Based on zircon LA-ICP-MS U-Pb dating method, 7 granitoids in the study area were studied in fine chronology. The age of the Sugang Sara granite is 415.6 + 1.1Ma, which is late Silurian. Jade Shenka wax gabbro age was 364 + 1Ma, late devonian. Wu Ding Hao Rotha sunspot two long hot quartz diorite age was 364.7 + 3.0Ma, late devonian. Jiamusi two long island mountain granite age was 335.9 + 0.9Ma, early carboniferous. Garr Road, Afu granitic porphyry, age 305 + 2Ma, the late carboniferous. The age of the Kuo TASI diorite body is 297 + 2Ma, which is late Carboniferous. The age of the pluton granite pluton in the Qitai sea is 280.1 + 3.2Ma, which is early Permian. The intrusive age of each period granite has been confirmed, which provides a high precise chronological basis for understanding the evolution of tectonic magma in Western Junggar. Combined with previous studies, the stages of magmatic rocks in the study area are divided into 4 stages: the Early Silurian Early Devonian (436-405Ma), the Early Carboniferous (350-320Ma), the Late Carboniferous Early Permian (318-270Ma) and the middle Late Permian (270-263Ma). The magmatic rocks have obvious regularity in the spatial and temporal distribution, and the age of its formation has a new law of change in the north and the South and in the middle. The rock geochemical study of intrusive rocks shows that the rock mass in each stage of the study area is mainly A and I type granite. The granite rock types in the western section of Semis Taishan are type A2 granite and alkaline weak peraluminous I type granite. Early Carboniferous granite is dominated by I, mainly distributed in the Sawuer region, zonal distribution, tectonic background may be formed in the continental subduction, the Late Carboniferous and Early Permian granites are mainly of A type, a planar distribution, are basic and metaluminous characteristics, may have related products of subduction fluid metasomatism the arc magmatism has the obvious characteristics of some magmatic source, probably formed in a post collisional extensional environment. The middle Late Devonian formation of jade Shenka wax gabbro in the subduction metasomatism depleted lithospheric mantle, magma has not been contaminated by crustal materials during ascending. Both subduction imprint source area as early as two fold mafic intrusive rocks, and mantle components involved, may be a product of mantle peridotite partial melting fluid metasomatism released by the subducting slab or subducted sediments after the. To get the new West Junggar area 7 intrusive rocks zircon Hf isotopic composition, the results show that the zircon Hf isotopic has similar intrusions in each period in the region, they are epsilon Hf positive (T) value, and when higher, indicating the granite is mainly a product of partial melting of continental crust new, reflected in the West Junggar area from Middle Proterozoic to early Paleozoic Ordovician continuous new continental crust formation. This is in accordance with the whole Central Asian orogenic belt, which has been formed from the Neoproterozoic Era to the new continental crust and many arc - land collision collages and continental hyperplasia. On the basis of the above research, combined with the regional geological background and the structural evolution characteristics of the West Junggar orogenic belt, the time limit for the closure of the Asian Asian Ocean and the time limit for post collisional action are discussed. Study shows that this area is many collisions and multiple cuts, is the formation of a basin, a cut, and then form a cut, one appeared one after another, have been cut. The ancient Asian Ocean has a wide range, and it may be different for each area to close. This paper concluded that in the northern region of Western Junggar (near Eerqisi suture), Late Devonian oceanic subduction event has been completed, the closure of the paleo Asian Ocean time not earlier than 364Ma. For the time limit of post collisional interaction, combined with regional geological data, we conclude that the post collisional deep plutonic activity in the western Junggar area started from the Early Carboniferous and ended at the early two stage. That is, post collisional deep magmatic activity occurs between 340-270Ma. Based on the study of petrogenesis, Hf isotope tracing and tectonic evolution of magmatic rocks, it is considered that Palaeozoic, especially late Paleozoic, is an important period of continental crustal accretion in the Central Asian orogenic belt. The way of proliferation includes lateral proliferation related to subduction, and vertical hyperplasia related to mantle derived magma underplating. Continental crust proliferation is a multi stage and multi cycle process, which runs through the whole process of the formation and evolution of the Central Asian orogenic belt.
【学位授予单位】：中国地质大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P597.3;P588.11

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