本文關(guān)鍵詞：新疆西準(zhǔn)噶爾地區(qū)古生代巖漿活動(dòng)的年代學(xué)和地球化學(xué)研究　出處：《中國(guó)地質(zhì)大學(xué)》2016年博士論文　論文類(lèi)型：學(xué)位論文

  更多相關(guān)文章： 西準(zhǔn)噶爾 古生代 巖漿巖 年代學(xué) 地球化學(xué) LA-ICP-MS 鋯石U-Pb測(cè)年 Hf同位素

【摘要】：西準(zhǔn)噶爾地區(qū)經(jīng)歷了多期次、多階段長(zhǎng)期而復(fù)雜的構(gòu)造地質(zhì)演化,同時(shí)伴隨著大量的花崗質(zhì)巖漿活動(dòng)。各期巖漿巖的成因、物源涉及西準(zhǔn)噶爾造山帶的形成,特別是各期次花崗巖漿活動(dòng)的地球動(dòng)力學(xué)過(guò)程與演化。本文選擇西準(zhǔn)噶爾地區(qū)古生代的巖漿巖(火山巖和侵入巖),重點(diǎn)對(duì)有代表性的巖體進(jìn)行了巖石學(xué)、地球化學(xué)、鋯石形態(tài)學(xué)、鋯石LA-ICP-MS U-Pb年代學(xué)和鋯石Hf同位素地球化學(xué)等分析等,厘定了各期構(gòu)造事件的時(shí)限,劃分了巖漿巖的活動(dòng)期次,確定了巖漿巖成因,反演了西準(zhǔn)噶爾造山帶構(gòu)造演化過(guò)程。運(yùn)用鋯石LA-ICP-MS U-Pb定年方法,對(duì)研究區(qū)內(nèi)7個(gè)花崗巖體進(jìn)行了精細(xì)的年代學(xué)研究,其中,蘇根薩拉花崗巖體的年齡為415.6±1.1Ma,為晚志留世。玉什喀臘輝長(zhǎng)巖體的年齡為364±1Ma,為晚泥盆世。黑子勒塔吾丁浩熱石英二長(zhǎng)閃長(zhǎng)巖體的年齡為364.7±3.0Ma,為晚泥盆世。木斯島山二長(zhǎng)花崗巖體的年齡為335.9±0.9Ma,為早石炭世。加爾路阿甫花崗斑巖體的年齡為305±2Ma,為晚石炭世。闊依塔斯閃長(zhǎng)巖體的年齡為297±2Ma,為晚石炭世。恰其海鉀長(zhǎng)花崗巖體的年齡為280.1±3.2Ma,為早二疊世。確認(rèn)了各期次花崗巖的侵入時(shí)代,為認(rèn)識(shí)西準(zhǔn)噶爾構(gòu)造巖漿演化提供了高精度的年代學(xué)依據(jù)。結(jié)合前人研究成果,將研究區(qū)內(nèi)巖漿巖的期次劃分為4個(gè)階段：早志留世-早泥盆世(436-405Ma)、早石炭世(350-320Ma)、晚石炭世-早二疊世(318-270Ma)和中晚二疊世(270-263Ma)。巖漿巖在時(shí)空分布上具有明顯的規(guī)律性,其形成時(shí)代具有南北老,中間新的變化規(guī)律。侵入巖的巖石地球化學(xué)研究表明,研究區(qū)各階段巖體主要為A型和I型花崗巖。謝米斯臺(tái)山西段花崗巖巖石類(lèi)型為A2型花崗巖和堿性弱過(guò)鋁質(zhì)分異I型花崗巖。早石炭世花崗巖以I型為主,主要分布于薩吾爾地區(qū),呈帶狀分布,可能形成于陸殼俯沖的構(gòu)造背景下,晚石炭世-早二疊世花崗巖以A型為主,呈面狀分布,具有堿性和準(zhǔn)鋁質(zhì)特征,可能為俯沖有關(guān)的流體交代的產(chǎn)物,部分巖漿源區(qū)具有明顯的弧巖漿活動(dòng)特點(diǎn),可能形成于碰撞后伸展環(huán)境中。晚泥盆世玉什喀臘輝長(zhǎng)巖體為俯沖流體交代虧損的巖石圈地幔形成,巖漿在上升過(guò)程中沒(méi)有遭受地殼物質(zhì)的混染。早二疊世基性侵入巖的源區(qū)中既有俯沖消減的印跡,又有地幔組分的參與,可能是被俯沖板片或消減沉積物所釋放的流體交代后的地幔橄欖巖部分熔融的產(chǎn)物。新獲得了西準(zhǔn)噶爾地區(qū)7個(gè)侵入巖鋯石Hf同位素組成,結(jié)果表明,區(qū)內(nèi)各時(shí)期侵入巖體具有相似的鋯石Hf同位素,它們均具正的εHf(t)值,且正值較高,指示各期花崗巖主要為新生陸殼部分熔融的產(chǎn)物,反映在西準(zhǔn)噶爾地區(qū)從中元古到早古生代的奧陶紀(jì)持續(xù)有新生陸殼形成。這與整個(gè)中亞造山帶從新元古代以來(lái)持續(xù)形成新的陸殼和發(fā)生多起弧-陸碰撞拼貼、大陸增生是吻合的。在上述研究的基礎(chǔ)之上,結(jié)合區(qū)域地質(zhì)背景和西準(zhǔn)噶爾造山帶構(gòu)造演化特征,討論了古亞洲洋閉合的時(shí)限和后碰撞作用的時(shí)限。研究表明,該區(qū)為多次碰撞、多次消減,洋盆是形成一個(gè)、消減一個(gè),再形成一個(gè)、再消減一個(gè),相繼出現(xiàn),相繼消減。古亞洲洋的范圍很廣,可能每個(gè)區(qū)域閉合的時(shí)間不盡相同。本文推斷在西準(zhǔn)噶爾北部地區(qū)(額爾齊斯縫合帶附近),晚泥盆世洋陸俯沖事件已基本結(jié)束,古亞洲洋閉合的時(shí)間不早于364Ma。對(duì)于后碰撞作用的時(shí)限,結(jié)合區(qū)域地質(zhì)資料,本文推測(cè)西準(zhǔn)噶爾地區(qū)后碰撞深成巖漿活動(dòng)是從早石炭世開(kāi)始,于早二疊末期結(jié)束,即后碰撞深成巖漿活動(dòng)發(fā)生在340-270Ma之間。通過(guò)對(duì)巖漿巖巖石成因、Hf同位素示蹤與構(gòu)造演化關(guān)系的研究,認(rèn)為古生代特別是晚古生代是中亞造山帶大陸地殼增生的重要時(shí)期。增生方式包括了與俯沖作用有關(guān)的側(cè)向增生,還包括與幔源巖漿底侵有關(guān)的垂向增生,大陸地殼增生是一個(gè)多階段多旋回的過(guò)程,貫穿于中亞造山帶形成演化的整個(gè)過(guò)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.
【學(xué)位授予單位】：中國(guó)地質(zhì)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：P597.3;P588.11

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