中国天山地区前寒武纪地质演化过程

发布时间：2017-12-27 00:17

  本文关键词：中国天山地区前寒武纪地质演化过程　出处：《中国科学院广州地球化学研究所》2017年博士论文　论文类型：学位论文

  更多相关文章： 前寒武纪地壳演化 中天山地块 伊犁地块 中亚造山带 构造亲缘性

【摘要】：中亚造山带西起乌拉尔山脉,途径哈萨克斯坦/吉尔吉斯坦天山、中国天山、东至环太平洋地区;北临西伯利亚克拉通、东欧克拉通,南由塔里木克拉通、华北-华南克拉通所围限。作为世界上最大的增生型造山带之一,它主要由前寒武纪微陆块、岩浆弧、海山、蛇绿混杂岩等拼贴形成。造山带内部微陆块前寒武纪地壳演化和构造起源一直是中亚造山带早期演化和构造研究的核心问题。中亚造山带南部的中天山地块和伊犁地块是解决这些问题的关键所在。通过对中天山地块和伊犁地块中-新元古代花岗质片麻岩和沉积岩进行系统的岩石学、地球化学分析、LA-ICP-MS和SHRIMP U-Pb锆石定年和锆石原位Hf同位素分析,确定岩石的形成时代、成岩过程及构造热事件历史;阐明中天山地块和伊犁地块前寒武纪地壳演化历史及其与Columbia和Rodinia超大陆演化的关系;并通过中亚造山带内外部块体的岩浆、沉积、变质、构造变形等方面的对比研究来制约中天山地块和伊犁地块的构造亲缘性。中天山地块主要发育有一套眼球状、条带状片麻岩和糜棱岩化花岗质片麻岩。眼球状片麻岩侵位于902-930 Ma,条带状片麻岩则侵位于806 Ma,而糜棱岩化片麻岩侵位于896 Ma。中天山地块西段的眼球状和条带状片麻岩呈现出高Al2O3和K2O以及低CaO和NaO的含量,因此呈现出过铝质花岗质岩石的特征(ASI=1.09-2.05)。该套片麻岩具有富集轻稀土和相对平坦重稀土元素配分模式以及明显的负Eu异常,亏损Nb,Ta,Ti和Sr,以及Pb富集等特征。锆石Hf同位素表明该套片麻岩具有壳源物质的特征(εHf(t)=-10.87~0)。该套片麻岩同时具有古老的Hf模式年龄(1.52-2.47 Ga)和大量的继承锆石(0.88-1.41Ga)。这些特点表明,该套片麻岩很可能是通过中天山地块的变质泥岩和硬砂岩部分熔融形成。在中天山地块东部,眼球状和糜棱岩化花岗质片麻岩也显示出高Al2O3和Si2O含量特征。该套片麻岩的Cr和Ni和稀土元素特征分别与拉克兰造山带典型S型花岗岩和上地壳的相一致。类似地,该套片麻岩也具有富集Hf同位素特征(εHf(t)=-9.00~+1.60)。结合该套片麻岩中白云母和继承锆石特点(1.25-2.21 Ga)表明,中天山东段片麻岩的原岩为S型花岗岩,可能形成于中天山地块古老基底岩石的部分熔融。对已有的锆石u-pb年龄和hf同位素总结表明,中天山地块经历三期岩浆构造热事件,分别为1.40-1.46ga,0.81-1.01ga和0.73-0.79ga。其中,中元古代时期以地壳生长作用为主(~1.40ga),而后主要以地壳活化改造为主(0.73-1.01ga)。伊犁地块地区,我们首次识别出伊犁地块最古老的岩石记录,主要为细粒花岗质片麻岩、眼球状片麻岩和糜棱岩化花岗质片麻岩(888-1329ma)。锆石u-pb和锆石hf同位素特征表明,伊犁地块新元古代花岗质片麻岩与中天山地块该时期片麻岩的地球化学特征具有相似的特点,可能为伊犁地块古老基底岩石部分熔融的产物。伊犁同样存在三期岩浆构造热事件,分别为1.33ga,0.85-0.99ga和0.76ga。伊犁地块新元古代主要以大陆地壳活化改造为主(0.76-0.99ga)。中天山地块前寒武纪沉积岩表明,中天山地块最古老地层,星星峡群和卡瓦布拉克群分别沉积于942-1095ma和932-960ma,而并非前人认为的古元古代。星星峡群和卡瓦布拉克群具有相似碎屑锆石年龄频谱,主要为0.95-1.00ga,1.20-2.00ga(峰值为1.40-1.60ga)和少量的2.60ga碎屑锆石年龄。相似的年龄频谱分布和hf同位素特征表明,二者具有相似的物质源区。通过碎屑锆石形态特征、碎屑锆石频谱特征、hf同位素特征和岩浆作用对比研究认为,中天山地块新元古代的碎屑锆石主要来自伊犁地块自身;中元古-古元古代的碎屑锆石主要来源于中天山地块和伊犁地块。少量的2.60ga碎屑锆石具有它形远源搬运特征,可能来自其他古老克拉通。中天山地块在1.70-2.00ga和1.30-1.60ga时期发生了显著的地壳生长作用并伴随一定的大陆地壳活化作用,而新元古代主要以地壳改造为主(0.95-1.00ga)。伊犁地块最古老的地层为温泉群,碎屑锆石研究表明温泉群下部沉积岩沉积于845ma-900ma,而温泉群上部沉积岩沉积于857-880ma,而并非前人认为的古元古代。伊犁板块温泉群上下部具有类似年龄峰值,主要为0.88-0.95ga,1.10-2.00ga(峰值为1.40-1.60ga)和少量的2.60ga碎屑锆石年龄。其中,新元古代碎屑锆石物质源区主要为伊犁板块的新元古代岩浆岩,而中元古代和古元古代的碎屑物质主要来源于伊犁板块和中天山地块;对于2.60ga碎屑锆石其可能为远距离搬运的产物。类似地,伊犁板块存在两期同时期的地壳生长和活化作用(1.70-1.80 Ga和1.30-1.60 Ga);直到新元古代,中天山地块具有持续地壳活化作用改造的特点。通过系统的岩浆岩和碎屑锆石研究表明,中天山地块和伊犁地块虽然不存在太古代基底岩石,但可能存在古元古代地壳初始物质记录(1.80-2.00 Ga)。中天山地块和伊犁地块具有相似的前寒武纪地质演化历史。二者古老陆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)发生强烈的地壳改造作用并固结形成统一的结晶基底。中天山地块在1.70-2.00 Ga和1.30-1.60 Ga时发生同时期的地壳生长和活化改造作用,随后在新元古代早期(0.81-1.01 Ga)以地壳改造作用为主。类似地,伊犁地块也具有相似的特征。在新元古代中期,中天山地块和伊犁地块可能都处于大陆地壳伸展环境(0.73-0.79 Ga)。我们认为中天山地块和伊犁地块中元古代的地壳生长作用(~1.33-1.46 Ga)和新元代的地壳活化改造作用(0.81-1.01 Ga)是分别对Columbia超大陆裂解和Rodinia超大陆聚合的响应过程。通过对中天山地块和伊犁地块与其他块体的岩浆、沉积、变质、构造变形等方面对比研究发现,在中亚造山带内部,中天地块和伊犁地块在新元古代之前具有构造亲缘性,但二者并非来源于塔里木克拉通和中亚造山带周缘的西伯利亚克拉通、华北克拉通、华南克拉通、澳大利亚和亚马逊克拉通。根据中天山地块和伊犁地块显著的1.40-1.60 Ga岩浆和碎屑锆石特征,我们认为中天山地块和伊犁地块在新元古代时期(1.00-0.90 Ga)位于劳伦古陆和东欧克拉通之间,二者可能来源于东欧克拉通。
[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)
【学位授予单位】：中国科学院广州地球化学研究所
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P534.41
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