本文選題：花崗巖 + 暗色微粒包體　； 參考：《南京大學(xué)》2015年博士論文

【摘要】：西昆侖造山帶位于位于青藏高原西北緣,是古亞洲構(gòu)造域與特提斯構(gòu)造域結(jié)合、轉(zhuǎn)換地帶,北以烏依塔克-庫地縫合帶與塔里木地塊相接,南以麻扎-康西瓦縫合帶為界與甜水海地體拼接。目前可以接受的觀點是西昆侖造山帶經(jīng)歷了多期造山作用,但有關(guān)其具體構(gòu)造演化過程還存在很大的爭論。此外,西昆侖造山史還關(guān)系到對歐亞大陸與羌塘地塊碰撞并最終焊接歷史的認(rèn)識。西昆侖造山帶發(fā)育兩條醒目的中-酸性深成巖帶,即西昆侖北巖帶和西昆侖南巖帶。其中北巖帶分布于烏依塔克-庫地縫合帶南側(cè),形成于古生代(以早古生代為主),而南巖帶分布于麻扎-康西瓦縫合帶北側(cè),形成于早中生代。本論文主要選擇了西昆侖南巖帶中的花崗質(zhì)巖體及其中暗色微粒包體為研究對象,采用鋯石SHRIMP定年以及礦物化學(xué)、元素地球化學(xué)和Sr-Nd-Hf同位素示蹤相結(jié)合的方法,闡明了它們的源區(qū)和巖漿演化過程,探討其形成的構(gòu)造環(huán)境和動力學(xué)機(jī)制,從而為西昆侖造山帶長期爭論的構(gòu)造演化模式提供新的制約。本次工作對南巖帶中六個代表性巖體(玉其卡帕、慕士塔格、塔爾、庫地南、阿卡阿孜和麻扎巖體)及其中暗色微粒包體開展了研究。除麻扎巖體分布于甜水海地體外,其余巖體均分布于西昆侖地體內(nèi)。本次SHRIMP鋯石U-Pb定年結(jié)果表明,這些巖體及其中暗色微粒包體形成于三疊紀(jì)(～243-209 Ma)。玉其卡帕巖體侵位于中三疊世安尼西期(Anisian) (-243 Ma),主要由二云母花崗巖組成,其巖石組合為二長花崗巖-正長花崗巖-堿長花崗巖,主要造巖礦物為鉀長石、石英、斜長石、黑云母和白云母,部分樣品中含有微量石榴子石,中粒花崗結(jié)構(gòu),片麻狀構(gòu)造。這些花崗巖屬于高鉀鈣堿性系列并且是過鋁質(zhì)的。它們的初始87Sr/86Sr、εNd(T)和鋯石εHf(T)分別為0.7071-0.7077、-4.4--6.3和-3.3。詳盡的元素和同位素地球化學(xué)研究結(jié)果表明,這些花崗巖是在陸-陸碰撞過程中通過前寒武紀(jì)基底變質(zhì)巖“濕”的深熔作用形成的。慕士塔格和塔爾巖體侵位于晚三疊世卡尼期(Carnian) (234-227 Ma),主要由花崗閃長巖和二長花崗巖組成,主要造巖礦物為斜長石、鉀長石、石英、角閃石和黑云母,中粒花崗結(jié)構(gòu),塊狀構(gòu)造,局部片麻狀構(gòu)造。這兩個巖體含有一系列暗色微粒包體,其SHRIMP鋯石U-Pb年齡(233-226 Ma)與寄主巖一致。寄主花崗巖也屬于高鉀鈣堿性系列,但主要是準(zhǔn)鋁質(zhì)的,少量弱過鋁質(zhì)。它們的初始87Sr/86Sr、εNd(T)和鋯石SHf(T)分別為0.7052-0.7104、-3.6-7.3和-3.3N-1.0。詳盡的元素和同位素地球化學(xué)研究表明這些花崗質(zhì)巖石都是由底侵的包體巖漿誘發(fā)下地殼中前寒武紀(jì)變質(zhì)巖石發(fā)生部分熔融而形成的。其中,對于慕士塔格巖體(鄰近麻扎-康西瓦縫合帶)來說,部分熔融作用發(fā)生在正常厚度(40 km)的下地殼,而對于塔爾巖體(遠(yuǎn)離麻扎-康西瓦縫合帶)來說,部分熔融則發(fā)生在加厚(～40-50 km)的下地殼。暗色微粒包體主要是基性的(SiO2=48.0-51.6 wt.%),少量具有中性成分(SiO2= 53.0-54.6 wt.%),并且它們都是鉀質(zhì)的,其地球化學(xué)特征與碰撞后鉀質(zhì)巖漿相似。這些暗色微粒包體具有與寄主巖相似的εNd(T)值,但是它們的初始87Sr/86Sr比寄主巖低,而鋯石εHf(T)值比寄主巖高。詳盡的元素和同位素地球化學(xué)研究結(jié)果表明,包體巖漿起源于受到俯沖組分改造過的巖石圈地幔的部分熔融,其中對于慕士塔格巖體中的包體來說,部分熔融作用發(fā)生在尖晶石相地幔區(qū)域(60 km),而對于塔爾巖體中的包體來說,部分熔融作用則發(fā)生在尖晶石-石榴子石相過渡帶(～60-80 km)。中三疊世安尼西期和晚三疊世卡尼期花崗巖及暗色微粒包體巖石成因特征表明,西昆侖地體和甜水海地體之間的古特提斯洋盆最終閉合發(fā)生在中三疊世安尼西期(Anisian) (-243 Ma),而到了晚三疊世卡尼期(Carnian) (-234-227 Ma),該區(qū)域已進(jìn)入碰撞后階段,古特提斯洋殼斷離(Slab break-off)是形成卡尼期花崗巖及其暗色微粒包體的動力學(xué)機(jī)制。庫地南、阿卡阿孜和麻扎巖體均侵位于晚三疊世諾瑞期(Norian) (215-209 Ma),并且呈現(xiàn)出向南逐漸變年輕的趨勢。庫地南巖體(215 Ma)主要由高鉀鈣堿性花崗閃長巖和二長花崗巖組成,其初始87Sr/86Sr、εNd(T)和鋯石εHf(T)分別為0.7093-0.7099、-4.9-5.4和0.3。元素和同位素數(shù)據(jù)表明該巖體可能是由玄武質(zhì)巖漿底侵誘發(fā)下地殼中前寒武紀(jì)基底變質(zhì)巖發(fā)生部分熔融而形成的。阿卡阿孜巖體(213 Ma)位于庫地南巖體南側(cè),主要由高鉀鈣堿性二長花崗巖、正長花崗巖和堿長花崗巖組成,該巖體含有大量暗色微粒包體。寄主花崗巖的初始87Sr/86Sr、 εNd(T)和鋯石εHf(T)與庫地南巖體相似,分別為0.7071-0.7085、-3.7--4.8和-0.7。因此,該巖體同樣是由包體巖漿底侵誘發(fā)下地殼中前寒武紀(jì)基底變質(zhì)巖發(fā)生部分熔融而形成的。包體主要成分是基性的(Si02含量為48.0-54.9wt.%),并且是鉀質(zhì)的,顯示陸緣弧鉀質(zhì)巖漿的地球化學(xué)特征。它們的初始87Sr/86Sr和εNd(T)分別為0.7071-0.7080和-2.6～-4-5。元素和同位素數(shù)據(jù)表明包體巖漿起源于尖晶石-石榴子石過渡相地幔楔(-60-80 km)的部分熔融。麻扎巖體(209 Ma)位于甜水海地體中,由高鉀鈣堿性英云閃長巖和花崗閃長巖組成,其初始87Sr/86Sr、εNd(T)和鋯石εHf(T)分別為0.7087-0.7097、-6.3～-6.5和-2.8。元素和同位素數(shù)據(jù)表明該巖體是由幔源巖漿與殼源巖漿發(fā)生混合作用而形成的。晚三疊世諾瑞期花崗巖及暗色微粒包體巖石成因特征表明,西昆侖-甜水海聯(lián)合地體在晚三疊世諾瑞期(215-209 Ma)處于活動大陸邊緣環(huán)境,與甜水海地體和喀喇昆侖地體之間的古特提斯洋的北向俯沖有關(guān)。同時結(jié)合甜水海地體自早侏羅世開始發(fā)生陸源紅層磨拉石堆積,我們認(rèn)為歐亞大陸與喀喇昆侖地體(羌塘地塊)最終拼貼作用發(fā)生在早侏羅世。
[Abstract]:Located in the northwest margin of the Qinghai Tibet Plateau, the western Kunlun orogenic belt is located in the northwest margin of the Qinghai Tibet Plateau. It is a combination of the ancient Asian tectonic domain and the Tethys tectonic domain, the transition zone, the north of the Tarim block suture zone and the Tarim block in the north. The south is spliced with the sweet water Haiti body with the mazaja suture suture zone. The view that the West Kunlun orogenic belt has experienced many periods is acceptable. In addition, the history of the western Kunlun orogenic history is also related to the collision of the Eurasian continent with the Qiangtang block and the final welding history. The West Kunlun orogenic belt developed two wake acid deep diagenetic belts, namely the West Kunlun northern rock belt and the western Kunlun Southern rock belt. It is distributed in the southern side of the ulitac kuldi suture belt, formed in the Paleozoic (mainly in the early Paleozoic), and the Southern rock belt is distributed in the northern side of the Mazha Connecticut suture belt and formed in the early Mesozoic. This paper mainly selected the granitic rock mass in the Southern rock belt of West Kunlun and its dark particle inclusion body as the research object, and adopted zircon dating for SHRIMP years as well. The combination of mineral chemistry, elemental geochemistry and Sr-Nd-Hf isotope tracer illustrates their source and magma evolution processes, and discusses the tectonic setting and dynamic mechanism of their formation, thus providing a new system for the long debated tectonic evolution model of the western Kunlun orogenic belt. Yuch Kappa, moussata, tal, cutan, a CAD and Mazha rock mass and its dark microparticle inclusions were studied. Except the Mazha rock mass distributed in the sweet water Haiti in vitro, the rest of the rock mass were distributed in the West Kunlun area. The SHRIMP zircon U-Pb dating results showed that these rocks and its dark microparticle inclusions were formed in the Triassic period ( ~ 243-209 Ma). The jade kappa pluton invades the middle three epoch (-243 Ma), mainly composed of two mica granite, and its rock assemblage is two granite - syenite alkali granite. The main rock forming minerals are potash feldspar, quartz, plagioclase, biotite and muscovite, and some of the samples contain a small amount of pomegranite in some samples. These granites belong to the high potassium calc alkaline series and are peraluminous. Their initial 87Sr/86Sr, epsilon Nd (T) and zircon epsilon Hf (T) are 0.7071-0.7077, -4.4--6.3 and -3.3. detailed elemental and isotopic geochemical studies show that these granites are through the cold front during land land collisions. The "wet" deep melting of the basilar metamorphic rocks of the martial arts was formed. The moustagg and the Al plutons were invaded in the late three Carney period (Carnian) (234-227 Ma), mainly composed of granodiorite and two granitic granite. The main rock forming minerals were plagioclase, potassium feldspar, quartz, amphibolite and biotite, medium granitic structure, lump structure, and local flax. The two rocks contain a series of dark particle inclusions, and the SHRIMP zircon U-Pb age (233-226 Ma) is the same as the host rock. Host granite also belongs to the high potassium calc alkaline series, but it is mainly quasi aluminous and a small amount of weakly peraluminous. Their initial 87Sr/86Sr, epsilon Nd (T) and zircon SHf (T) are 0.7052-0.7104, -3.6-7.3 and -3.3N-1.0., respectively. The elemental and isotopic geochemical studies have shown that these granitic rocks are formed by partial melting of the Precambrian metamorphic rocks in the lower crust induced by the underclad magma, and the partial melting of the moustigg rock (adjacent to the Mazha connecticw suture zone) occurs below the normal thickness (40 km). For the shell, for the tar rock mass (far away from the Mazha Connecticut suture zone), the partial melting occurs in the lower crust of thickening (to 40-50 km). The dark colored particles are mainly based on the base (SiO2=48.0-51.6 wt.%), a small amount of SiO2= 53.0-54.6 wt.%, and they are all potassium, and their geochemical characteristics and post collisional potassic magma Similar. These dark particle inclusions have the values of epsilon Nd (T) similar to host rocks, but their initial 87Sr/86Sr is lower than the host rock, and the zircon epsilon Hf (T) values are higher than the host rocks. The partial melting occurs in the spinel phase mantle region (60 km) in the pluton pluton, while the partial melting occurs in the transition zone of the spinel - Garnet (~ 60-80 km) for the peritenite in the Tuli rock mass. In the middle three, the Carney period and the late three fold phase of the granite and the dark particle perittite The Shi Chengyin characteristics indicate that the final closure of the ancient Tethys oceanic basin between the West Kunlun and the sweet water Haiti body occurred in the middle three epoch (Anisian) (-243 Ma), and to the late three fold Carnian (-234-227 Ma), the region had entered the post collision stage, and the Gut Tis oceanic crust (Slab break-off) was a Carney stage. The kinetic mechanism of rock and its dark colored particulate inclusions. The Kutan, Al Kuda and Mazha intrusions are all invaded in the late three period (Norian) (215-209 Ma), and present a trend towards the south. The Kutan rock mass (215 Ma) is mainly composed of high potassium calc alkaline granodiorite and two granitic granite, and its initial 87Sr/86Sr, Nd (T). The zircon epsilon Hf (T), respectively, 0.7093-0.7099, -4.9-5.4 and 0.3. elements and isotopic data indicate that the rock mass may be formed by partial melting of the Precambrian basement metamorphic rocks in the lower crust of the basaltic magma. The alkamia rock mass (213 Ma) is located on the south side of the Kutan rock mass, mainly from the high potassium calc alkaline two granitic granite. The granite and alkali feldspar are composed of a large number of dark particle inclusions. The initial 87Sr/86Sr, epsilon Nd (T) and the zircon epsilon Hf (T) of host granite are similar to the cutan rock mass, respectively, 0.7071-0.7085, -3.7--4.8 and -0.7., therefore, the rock mass also occurred in the Precambrian basement metamorphic rock in the lower crust of the lower crust induced by the Bao Tiyan pulp underplating. The main components of the inclusions are based on the base (Si02 content 48.0-54.9wt.%) and are potassium, indicating the geochemical characteristics of the epicontinental arc potassic magma. Their initial 87Sr/86Sr and epsilon Nd (T) are 0.7071-0.7080 and -2.6 to -4-5. elements and isotopic data, respectively, indicating that the inclusion magma originated from the spinel garnet. The partial melting of the crossing mantle wedge (-60-80 km). The Mazha rock mass (209 Ma) is located in the sweet water Haiti body and consists of high potassium calc alkaline diorite and granodiorite. Its initial 87Sr/86Sr, epsilon Nd (T) and zircon epsilon Hf (T) are 0.7087-0.7097, -6.3 to -6.5, and -2.8. elements and isotopes, indicating that the rock mass was derived from the mantle derived magma and Ke Yuanyan. The formation of the mixture of the pulps. The formation of the late three Permian granite and dark granitic xenoliths showed that the West Kunlun - the sweet water Sea joint body was in the active continental margin in the late three fold (215-209 Ma), related to the North subduction of the ancient Tethys ocean between the sweet water Haiti body and the Karakoram. Combined with the early Jurassic, the Haiti body of sweet water began to accumulate in the early Jurassic. We believe that the final collage of the Eurasian continent and the Karakoram block (Qiangtang block) occurred in the early Jurassic.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：P588.121;P548

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