本文關(guān)鍵詞：中國天山地區(qū)前寒武紀(jì)地質(zhì)演化過程　出處：《中國科學(xué)院廣州地球化學(xué)研究所》2017年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 前寒武紀(jì)地殼演化 中天山地塊 伊犁地塊 中亞造山帶 構(gòu)造親緣性

【摘要】：中亞造山帶西起烏拉爾山脈,途徑哈薩克斯坦/吉爾吉斯坦天山、中國天山、東至環(huán)太平洋地區(qū);北臨西伯利亞克拉通、東歐克拉通,南由塔里木克拉通、華北-華南克拉通所圍限。作為世界上最大的增生型造山帶之一,它主要由前寒武紀(jì)微陸塊、巖漿弧、海山、蛇綠混雜巖等拼貼形成。造山帶內(nèi)部微陸塊前寒武紀(jì)地殼演化和構(gòu)造起源一直是中亞造山帶早期演化和構(gòu)造研究的核心問題。中亞造山帶南部的中天山地塊和伊犁地塊是解決這些問題的關(guān)鍵所在。通過對中天山地塊和伊犁地塊中-新元古代花崗質(zhì)片麻巖和沉積巖進行系統(tǒng)的巖石學(xué)、地球化學(xué)分析、LA-ICP-MS和SHRIMP U-Pb鋯石定年和鋯石原位Hf同位素分析,確定巖石的形成時代、成巖過程及構(gòu)造熱事件歷史;闡明中天山地塊和伊犁地塊前寒武紀(jì)地殼演化歷史及其與Columbia和Rodinia超大陸演化的關(guān)系;并通過中亞造山帶內(nèi)外部塊體的巖漿、沉積、變質(zhì)、構(gòu)造變形等方面的對比研究來制約中天山地塊和伊犁地塊的構(gòu)造親緣性。中天山地塊主要發(fā)育有一套眼球狀、條帶狀片麻巖和糜棱巖化花崗質(zhì)片麻巖。眼球狀片麻巖侵位于902-930 Ma,條帶狀片麻巖則侵位于806 Ma,而糜棱巖化片麻巖侵位于896 Ma。中天山地塊西段的眼球狀和條帶狀片麻巖呈現(xiàn)出高Al2O3和K2O以及低CaO和NaO的含量,因此呈現(xiàn)出過鋁質(zhì)花崗質(zhì)巖石的特征(ASI=1.09-2.05)。該套片麻巖具有富集輕稀土和相對平坦重稀土元素配分模式以及明顯的負(fù)Eu異常,虧損Nb,Ta,Ti和Sr,以及Pb富集等特征。鋯石Hf同位素表明該套片麻巖具有殼源物質(zhì)的特征(εHf(t)=-10.87~0)。該套片麻巖同時具有古老的Hf模式年齡(1.52-2.47 Ga)和大量的繼承鋯石(0.88-1.41Ga)。這些特點表明,該套片麻巖很可能是通過中天山地塊的變質(zhì)泥巖和硬砂巖部分熔融形成。在中天山地塊東部,眼球狀和糜棱巖化花崗質(zhì)片麻巖也顯示出高Al2O3和Si2O含量特征。該套片麻巖的Cr和Ni和稀土元素特征分別與拉克蘭造山帶典型S型花崗巖和上地殼的相一致。類似地,該套片麻巖也具有富集Hf同位素特征(εHf(t)=-9.00~+1.60)。結(jié)合該套片麻巖中白云母和繼承鋯石特點(1.25-2.21 Ga)表明,中天山東段片麻巖的原巖為S型花崗巖,可能形成于中天山地塊古老基底巖石的部分熔融。對已有的鋯石u-pb年齡和hf同位素總結(jié)表明,中天山地塊經(jīng)歷三期巖漿構(gòu)造熱事件,分別為1.40-1.46ga,0.81-1.01ga和0.73-0.79ga。其中,中元古代時期以地殼生長作用為主(~1.40ga),而后主要以地殼活化改造為主(0.73-1.01ga)。伊犁地塊地區(qū),我們首次識別出伊犁地塊最古老的巖石記錄,主要為細(xì)粒花崗質(zhì)片麻巖、眼球狀片麻巖和糜棱巖化花崗質(zhì)片麻巖(888-1329ma)。鋯石u-pb和鋯石hf同位素特征表明,伊犁地塊新元古代花崗質(zhì)片麻巖與中天山地塊該時期片麻巖的地球化學(xué)特征具有相似的特點,可能為伊犁地塊古老基底巖石部分熔融的產(chǎn)物。伊犁同樣存在三期巖漿構(gòu)造熱事件,分別為1.33ga,0.85-0.99ga和0.76ga。伊犁地塊新元古代主要以大陸地殼活化改造為主(0.76-0.99ga)。中天山地塊前寒武紀(jì)沉積巖表明,中天山地塊最古老地層,星星峽群和卡瓦布拉克群分別沉積于942-1095ma和932-960ma,而并非前人認(rèn)為的古元古代。星星峽群和卡瓦布拉克群具有相似碎屑鋯石年齡頻譜,主要為0.95-1.00ga,1.20-2.00ga(峰值為1.40-1.60ga)和少量的2.60ga碎屑鋯石年齡。相似的年齡頻譜分布和hf同位素特征表明,二者具有相似的物質(zhì)源區(qū)。通過碎屑鋯石形態(tài)特征、碎屑鋯石頻譜特征、hf同位素特征和巖漿作用對比研究認(rèn)為,中天山地塊新元古代的碎屑鋯石主要來自伊犁地塊自身;中元古-古元古代的碎屑鋯石主要來源于中天山地塊和伊犁地塊。少量的2.60ga碎屑鋯石具有它形遠(yuǎn)源搬運特征,可能來自其他古老克拉通。中天山地塊在1.70-2.00ga和1.30-1.60ga時期發(fā)生了顯著的地殼生長作用并伴隨一定的大陸地殼活化作用,而新元古代主要以地殼改造為主(0.95-1.00ga)。伊犁地塊最古老的地層為溫泉群,碎屑鋯石研究表明溫泉群下部沉積巖沉積于845ma-900ma,而溫泉群上部沉積巖沉積于857-880ma,而并非前人認(rèn)為的古元古代。伊犁板塊溫泉群上下部具有類似年齡峰值,主要為0.88-0.95ga,1.10-2.00ga(峰值為1.40-1.60ga)和少量的2.60ga碎屑鋯石年齡。其中,新元古代碎屑鋯石物質(zhì)源區(qū)主要為伊犁板塊的新元古代巖漿巖,而中元古代和古元古代的碎屑物質(zhì)主要來源于伊犁板塊和中天山地塊;對于2.60ga碎屑鋯石其可能為遠(yuǎn)距離搬運的產(chǎn)物。類似地,伊犁板塊存在兩期同時期的地殼生長和活化作用(1.70-1.80 Ga和1.30-1.60 Ga);直到新元古代,中天山地塊具有持續(xù)地殼活化作用改造的特點。通過系統(tǒng)的巖漿巖和碎屑鋯石研究表明,中天山地塊和伊犁地塊雖然不存在太古代基底巖石,但可能存在古元古代地殼初始物質(zhì)記錄(1.80-2.00 Ga)。中天山地塊和伊犁地塊具有相似的前寒武紀(jì)地質(zhì)演化歷史。二者古老陸核主要形成于中元古代(~1.30-1.40 Ga),并在新元古代早期(0.81-1.01 Ga)發(fā)生強烈的地殼改造作用并固結(jié)形成統(tǒng)一的結(jié)晶基底。中天山地塊在1.70-2.00 Ga和1.30-1.60 Ga時發(fā)生同時期的地殼生長和活化改造作用,隨后在新元古代早期(0.81-1.01 Ga)以地殼改造作用為主。類似地,伊犁地塊也具有相似的特征。在新元古代中期,中天山地塊和伊犁地塊可能都處于大陸地殼伸展環(huán)境(0.73-0.79 Ga)。我們認(rèn)為中天山地塊和伊犁地塊中元古代的地殼生長作用(~1.33-1.46 Ga)和新元代的地殼活化改造作用(0.81-1.01 Ga)是分別對Columbia超大陸裂解和Rodinia超大陸聚合的響應(yīng)過程。通過對中天山地塊和伊犁地塊與其他塊體的巖漿、沉積、變質(zhì)、構(gòu)造變形等方面對比研究發(fā)現(xiàn),在中亞造山帶內(nèi)部,中天地塊和伊犁地塊在新元古代之前具有構(gòu)造親緣性,但二者并非來源于塔里木克拉通和中亞造山帶周緣的西伯利亞克拉通、華北克拉通、華南克拉通、澳大利亞和亞馬遜克拉通。根據(jù)中天山地塊和伊犁地塊顯著的1.40-1.60 Ga巖漿和碎屑鋯石特征,我們認(rèn)為中天山地塊和伊犁地塊在新元古代時期(1.00-0.90 Ga)位于勞倫古陸和東歐克拉通之間,二者可能來源于東歐克拉通。
[Abstract]:The Central Asian orogenic belt rises from the western Ural mountains to Kazakhstan / Kyrgyzstan Tianshan, China Tianshan, east to Pacific Rim, north to Siberia craton, Eastern Europe craton, and south by Tarim Craton and North China Southern China craton. As the world's largest one of the accretionary orogenic belt, which is mainly composed of Precambrian continental blocks, Jiwei magmatic arc, seamounts, OPHIOLITIC MELANGE and collage form. The crustal evolution and tectonic origin of the Precambrian Paleogene in the inner orogenic belt have been the core issue of the early evolution and structure of the Central Asian orogenic belt. The Central Tianshan massif and the Yili massif in the southern part of the Central Asian orogenic belt are the key to solving these problems. The Central Tianshan block and Yili block in the Neoproterozoic granitic gneiss and sedimentary rocks of the petrological and geochemical analysis, LA-ICP-MS and SHRIMP U-Pb zircon dating and in situ zircon Hf isotope analysis, determine the time of formation, diagenesis and tectonic thermal events in the history of rock; clarify the relationship between the Central Tianshan block and Yili block the Precambrian crustal evolution history and its Columbia and Rodinia supercontinent evolution; and through the comparative study of the Central Asian orogenic belt and block magmatic and sedimentary, metamorphic and tectonic deformation, the tectonic affinity to restrict the Central Tianshan block and Yili block. The Middle Tianshan massif is mainly developed with a set of eyeball, banded gneiss and mylonite granitic gneiss. The eyeball gneiss invades 902-930 Ma, and the banded gneiss invades 806 Ma, while mylonite gneiss invades 896 Ma. The gneisses and banded gneisses in the west section of the Middle Tianshan massif show high Al2O3 and K2O contents, and low CaO and NaO contents. Therefore, they show the characteristics of peraluminous granitic rocks (ASI=1.09-2.05). The gneiss is characterized by enrichment of light rare earth elements and relatively flat heavy REE distribution patterns, and obvious negative Eu anomalies, loss of Nb, Ta, Ti and Sr, and Pb enrichment. Hf isotopes of zircon indicate that the set of gneiss has the characteristics of shell source material (epsilon Hf (T) =-10.87~0). The set of gneiss has an ancient Hf model age (1.52-2.47 Ga) and a large number of inherited zircons (0.88-1.41Ga). These characteristics indicate that the set of gneiss is probably formed by partial melting of metamorphic mudstone and hard sandstone in the Middle Tianshan massif. In the eastern part of the Middle Tianshan massif, the eyeball and mylonite granitic gneiss also showed high Al2O3 and Si2O content. Cr and Ni and the characteristics of rare earth elements of gneisses respectively and the Lachlan orogen typical S type granite and consistent upper crust. Similarly, the set of gneiss also has the characteristics of enrichment of Hf isotopes (epsilon Hf (T) =-9.00~+1.60). Combined with the characteristics of muscovite and inherited zircon in this gneiss (1.25-2.21 Ga), it is indicated that the protolith of gneiss in Zhongtian Shandong section is S type granite, probably formed in partial melting of ancient basement rocks in the Middle Tianshan massif. The existing zircon U-Pb ages and HF isotopes concluded that the Middle Tianshan massif experienced three periods of magmatic tectonic thermal events, namely 1.40-1.46ga, 0.81-1.01ga and 0.73-0.79ga. Among them, the Middle Proterozoic era was dominated by the growth of the crust (~1.40ga), and then mainly by the transformation of crustal activation (0.73-1.01ga). In the Yili block area, we first identified the oldest rock records in Yili block, mainly granitic gneisses, gneisses and mylonitic granitic gneiss (888-1329ma). Zircon U-Pb and zircon Hf isotopic characteristics indicate that the geochemical characteristics of Neoproterozoic granitic gneiss and gneiss in the Yili Tianshan massif are similar to those of the Middle Tianshan massif, which may be the product of partial melting of the Yili basement. There are also three phase magmatic tectonic thermal events in Yili, which are 1.33ga, 0.85-0.99ga and 0.76ga respectively. The Neoproterozoic in Yili massif mainly was reformed by continental crust activation (0.76-0.99ga). The Precambrian sedimentary rocks in the Middle Tianshan massif indicate that the most ancient strata in the Middle Tianshan massif, the XINGXINGXIA group and the kava Braque group, are deposited in 942-1095ma and 932-960ma, rather than the Paleoproterozoic. Xingxia gorge and kava Braque group have similar clastic zircon age spectrum, mainly 0.95-1.00ga, 1.20-2.00ga (peak value 1.40-1.60ga) and a small amount of 2.60ga detrital zircon age. Similar age spectrum distribution and Hf isotopic characteristics indicate that the two have similar material source regions. The detrital zircon morphology, detrital zircon spectrum, Hf isotopic characteristics and magmatism is considered that in the Tianshan block in the Neoproterozoic detrital zircons mainly from the Yili block itself; in Proterozoic Proterozoic detrital zircon mainly originates from the Central Tianshan block and Yili block. A small amount of 2.60ga detrital zircon is characterized by its distant source transport, which may come from other ancient craton. The Mesozoic Tianshan massif played a significant role in crustal growth during the period of 1.70-2.00ga and 1.30-1.60ga, and accompanied by a certain activation of the continental crust. The Neoproterozoic is mainly crustal alteration (0.95-1.00ga). The oldest stratum in Yili block is the hot spring group. The detrital zircon study indicates that the sedimentary rocks in the lower part of the hot spring group are deposited in 845ma-900ma, while the sedimentary rocks on the upper part of the hot spring group are deposited on 857-880ma, rather than the Paleoproterozoic. The upper and lower part of the Yili plate hot spring group has a similar age peak, mainly 0.88-0.95ga, 1.10-2.00ga (peak value 1.40-1.60ga) and a small amount of 2.60ga detrital zircon age. Among them, the Neoproterozoic detrital zircon source area is mainly Neoproterozoic magmatic rocks of the Yili plate, while the Mesoproterozoic and Paleoproterozoic clastic materials are mainly derived from the Yili plate and the zhongtianshan massif. For 2.60ga detrital zircon, it may be a product transported remotely. Similarly, the Yili plate has two stages of the same period of crustal growth and activation (1.70-1.80 Ga and 1.30-1)
【學(xué)位授予單位】：中國科學(xué)院廣州地球化學(xué)研究所
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：P534.41
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本文編號：1339459