本文選題：塔里木北緣 + 南天山�。� 參考：《中國地質(zhì)大學(北京)》2017年博士論文

【摘要】：塔里木北緣-南天山地區(qū)位于塔里木克拉通與中亞造山帶過渡地帶,構(gòu)造位置十分關(guān)鍵。但就南天山洋俯沖極性、閉合時代以及地殼深部物質(zhì)組成等關(guān)鍵問題上還存在爭議。本文以塔里木北緣-南天山東部地區(qū)若干古生代侵入體為研究對象,在詳細的野外地質(zhì)調(diào)查基礎(chǔ)上,以巖相學、礦物學、巖石地球化學及鋯石U-Pb年齡、Hf同位素為主要研究手段,對巖體成因、構(gòu)造演化及地殼深部物質(zhì)組成進行了綜合研究,取得以下認識:1、初步厘定了塔里木北緣-南天山地區(qū)古生代巖漿活動期次依據(jù)新獲得的鋯石U-Pb年齡和前人研究成果統(tǒng)計分析,古生代巖漿活動主要作用在晚奧陶世、中志留世至中泥盆世和晚石炭世至中二疊世三個時間段。其中,晚奧陶世的巖漿活動相對較弱,侵入體分布規(guī)模較小,而中志留世-中泥盆世(峰期年齡420 Ma)和晚石炭世-中二疊世(峰期年齡284 Ma)兩期巖漿活動規(guī)模相對較大,以花崗質(zhì)侵入巖為主,構(gòu)成塔里木北緣-南天山地區(qū)古生代巖漿活動的主體。2、探討了塔里木北緣-南天山地區(qū)東段古生代侵入巖成因及構(gòu)造背景古生代中期巖石類型包括輝長巖、閃長巖和花崗巖。輝長巖體形成時代為晚志留世到早泥盆世(424±4 Ma和416±4 Ma),具有相對高的MgO和Mg#值(49-53),以及正的εHf(t)值(+4.0~+11.4),富集大離子親石元素,虧損高場強元素,暗示其母巖漿源自俯沖板片流體改造的虧損地幔楔部分熔融;閃長巖體侵位時代為早泥盆世(415±2Ma),具有與輝長巖類似的地球化學特征及正的εHf(t)值(+3.0~+9.4),表明其源于虧損地幔的玄武質(zhì)巖漿的分離結(jié)晶作用;花崗巖體形成于早泥盆世到中泥盆世(408~385Ma),均屬于高鉀鈣堿性弱過鋁質(zhì)I型花崗巖,物質(zhì)來源主要為年輕物質(zhì),或者不同程度新老物質(zhì)的混合物源。不同類型的巖石,在區(qū)域上均表現(xiàn)出類似于安第斯型大陸弧巖石的地球化學特征,說明在古生代中期塔里木北緣為活動大陸邊緣。古生代晚期巖體主要為花崗質(zhì)巖體,巖體成因類型上具有A型,I型和S型花崗巖共存的特征。庫爾楚II號花崗巖體(311±4 Ma),具有A型花崗巖特征,明顯不同于俯沖帶上形成的花崗巖,指示了其形成于后碰撞環(huán)境。從時間上來看,從庫爾楚II號巖體、七個星晚期侵入體到盲起蘇巖體(311~302Ma),源區(qū)形成深度不斷增加(如Sr從91.9→192.8→592.5ppm),地殼逐漸加厚。之后形成的花崗巖(300~290 Ma)則具有低Sr(58.6~67.4ppm)和高Y(15.9~19.4ppm)的特征,暗示后碰撞階段拆沉作用的發(fā)生,巖石圈發(fā)生了一定程度的減薄。隨后,巖石圈—軟流圈界面上移至地殼底部,使花崗質(zhì)巖漿在地殼淺部處于較高的溫度環(huán)境,巖漿緩慢冷卻和充分分離結(jié)晶形成含石榴石花崗巖(~283Ma)。3、通過古生代花崗巖類Hf同位素特征揭示地殼深部物質(zhì)組成,限定中亞造山帶南界塔里木北緣-南天山地區(qū)地殼深部物質(zhì)組成主要以前寒武紀古老地殼為主,兼并含有少量新生地殼(如虎拉山地區(qū))。虎拉山地區(qū)花崗巖類明顯具有高和正的εHf(t)值(-8.68~+13.2)以及年輕的Hf模式年齡(543~1854 Ma),其以幸格爾斷裂為界與塔里木克拉通北緣的庫魯克塔格地區(qū)(εHf(t)=-23.4~+2.5,TDM2=1244~2845 Ma)具有明顯不同的地殼深部物質(zhì)組成,因此,將幸格爾斷裂認定為中亞造山帶和塔里木克拉通的界線。4、結(jié)合前人研究成果,提出新的構(gòu)造演化模式460~430 Ma南天山洋發(fā)生向南俯沖并產(chǎn)生了活動大陸邊緣,并促使微陸塊(如虎拉山地塊)沿幸格爾斷裂碰撞增生在塔里木克拉通;隨后,430~370 Ma,產(chǎn)生新的弧系統(tǒng)(塔里木克拉通+增生體),輝長巖、閃長巖和花崗巖體即為俯沖產(chǎn)物。370~320 Ma,南天山洋向南俯沖終止,為單一的北向俯沖,并發(fā)生陸陸碰撞。320~270 Ma,本次研究的晚期花崗質(zhì)侵入體以及南天山西段的花崗質(zhì)侵入體形成于古南天山洋最終閉合之后的后碰撞環(huán)境中,并且?guī)r體年齡呈現(xiàn)從東到西逐漸減小的趨勢,暗示剪刀式閉合方式。
[Abstract]:The northern Tarim South Tianshan area is located in the Tarim Craton and the Central Asian orogenic belt, and the tectonic position is very critical. However, there are still disputes on the key problems of the South Tianshan ocean subduction polarity, the closed age and the deep crust material composition. This paper is a study of some Paleozoic intrusions in the northern Tarim North Shandong region. On the basis of detailed field geological survey, taking petrography, mineralogy, petrography, geochemistry and zircon U-Pb age and Hf isotopes as the main research means, a comprehensive study of rock formation, tectonic evolution and deep crustal mass composition has been carried out to obtain the following understanding: 1, the Paleozoic rocks of the northern Tarim North edge of the South Tianshan area were preliminarily determined. According to the statistical analysis of the newly acquired zircon U-Pb age and previous research results, the Palaeozoic magmatic activity mainly acts in the late Ordovician, middle Silurian to Middle Devonian and Late Carboniferous to Middle Permian, of which the late Ordovician magmatic activity is relatively weak and the intrusive body is smaller, and middle Silurian - middle three. Devonian (peak age 420 Ma) and Late Carboniferous to Middle Permian (peak age 284 Ma) have relatively large scale of magmatism, mainly granitic intrusive rocks, which constitute the main.2 of Paleozoic magmatism in the northern margin of Tarim and South Tianshan area, and discussed the origin and tectonic setting of the Paleozoic intrusive rocks in the eastern part of the northern Tarim South Tianshan region. The Middle Paleozoic rock types include gabbro, diorite and granite. The age of gabbro is formed from late Silurian to early Devonian (424 + 4 Ma and 416 + 4 Ma), with relatively high MgO and Mg# value (49-53), and positive epsilon (T) value (+4.0~+11.4), enriching large ion stone elements and losing high field strength elements, suggesting that the mother magma originated from the subduction plate. The depleted mantle wedge partially melted by the slice fluid, and the diorite intrusive age was early Devonian (415 + 2Ma), with the geochemical characteristics of the gabbro and the positive epsilon Hf (T) value (+3.0~+9.4), indicating that it originated from the separation and crystallization of the basaltic magma from the depleted mantle, and the granite body formed from the early Devonian to the Middle Devonian (408~385Ma). All of them belong to high potassium calcium alkaline weakly peraluminous I type granite, which are mainly derived from young material or mixture of new and old materials. Different types of rocks show geochemical characteristics similar to the Andean continental arc rocks in the region, indicating that the northern margin of the Palaeozoic was the active continental margin in the middle Paleozoic. The late Cenozoic rock mass is mainly granitic rock mass. The genetic type of the rock mass is characterized by A type and I type and S type granite. The kurchu II granite body (311 + 4 Ma) has the characteristics of A type granite, which is obviously different from the granite formed on the subduction zone, indicating its formation in the post collision environment. From the time point of view, from the kurchu II rock. Body, seven late intrusive bodies to the blind Suzhou pluton (311~302Ma), the formation depth of the source region is increasing (e.g., Sr from 91.9 to 192.8 to 592.5ppm), and the crust gradually thickens. After that, the granite (300~290 Ma) has the characteristics of low Sr (58.6~67.4ppm) and high Y (15.9~19.4ppm), suggesting the occurrence of delamination in the post collision stage, and the lithosphere occurred. A certain degree of thinning. Then, the lithosphere - asthenosphere interface is moved to the bottom of the crust, and the granitic magma is in a high temperature environment in the shallow crust of the crust. The magma slowly cooled and fully separated and crystallized to form a garnet granite (~283Ma).3. Through the Hf isotopic characteristics of the Palaeozoic granitoids, the deep crustal composition was revealed and limited. The main crustal crust in the northern margin of Tarim south of the southern orogenic belt of the Central Asian orogenic belt is the main crustal crust of the former Cambrian, with a small amount of new crust (such as the hula mountain area). The granitoids in the mountain area of the hiraman area have obvious high and positive epsilon Hf (T) values (-8.68~+13.2) and the young Hf model age (543~1854 Ma). The fault is divided into the kuukatg area (Hf (T) =-23.4~+2.5, TDM2=1244~2845 Ma) in the northern margin of the Tarim craton, which has a distinct crust deep material composition. Therefore, the luckel fault is identified as the boundary between the Central Asian orogenic belt and the Tarim craton.4, and a new tectonic evolution model, 460~430 Ma south, is proposed in combination with the former research results. The Tianshan ocean dives southward and produces the active continental margin, and causes the micro block (such as the hula Mountain Block) to proliferate along the Tarim craton, and then the 430~370 Ma produces a new arc system (the Tarim cratonic + hyperplastic body), the gabbro, diorite and granite body is the subduction product.370~320 Ma, and the South Tianshan ocean direction The southern subduction is terminated by a single North subduction and a continental collision.320~270 Ma. The late granitic intrusive body and the granitic intrusive body of the South Tianshan Shanxi section were formed in the post collision environment after the final closure of the ancient South Tianshan ocean, and the age of the rock mass decreased gradually from east to West, suggesting the scissors closure. Way.

【學位授予單位】：中國地質(zhì)大學(北京)
【學位級別】：博士
【學位授予年份】：2017
【分類號】：P588.12;P542
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本文編號：1833616