發(fā)布時(shí)間：2018-04-21 12:42

  本文選題：塔里木西南 + 鋯石年代學(xué)　； 參考：《中國(guó)地質(zhì)科學(xué)院》2016年博士論文

【摘要】：塔里木克拉通是中國(guó)最重要的克拉通之一,前寒武紀(jì)基底主要出露于塔里木周緣。塔里木西南地區(qū)古元古代侵入雜巖、中新元古代火山-沉積地層以及近年來(lái)發(fā)現(xiàn)的中元古代巖漿巖對(duì)塔里木西南地體的構(gòu)造演化與地殼增生的研究具有非常重要的意義。本文在總結(jié)前人成果的基礎(chǔ)上,通過(guò)詳細(xì)的野外調(diào)查,對(duì)塔里木西南地區(qū)的前寒武紀(jì)巖漿巖、沉積地層進(jìn)行了系統(tǒng)分析和總結(jié),以探索塔里木西南前寒武紀(jì)構(gòu)造演化及地殼增生。赫羅斯坦雜巖巖性以A型花崗巖和S型花崗巖為主,形成于2.4-2.3 Ga,并在-1.9 Ga遭受了強(qiáng)烈的變質(zhì)作用。地球化學(xué)特征表明,A型花崗巖和S型花崗巖分別來(lái)源于太古代的基性地殼巖石和變雜砂巖和/或長(zhǎng)英質(zhì)泥砂巖部分熔融。阿孜拜勒迪巖體巖性主要為二長(zhǎng)花崗巖,LA-ICP-MS U-Pb定年結(jié)果顯示其形成于1.4 Ga左右。地球化學(xué)特征指示該巖體為典型的A型花崗巖,其成因可能是由于基性巖漿上涌,導(dǎo)致早元古代基性下地殼部分熔融,并且在此過(guò)程中還有不同程度古元古代新生地殼的加入。通過(guò)碎屑鋯石LA-ICP-MS U-Pb測(cè)年,綠片巖相變質(zhì)和強(qiáng)烈褶皺的塞拉加茲塔格群(SG)火山-沉積地層的沉積時(shí)限為860-830Ma之間；相比之下,低綠片巖相變質(zhì)、強(qiáng)烈變形埃連卡特群(AG)中碎屑巖為820-800 Ma；而未發(fā)生變形和變質(zhì)的上新元古界碳酸鹽-碎屑巖-冰磧巖地層恰克馬克力克群(QG)沉積時(shí)代應(yīng)不早于760 Ma。其中QG中兩次冰期分別可以和塔里木北緣貝義西冰期和特瑞愛(ài)肯冰期進(jìn)行對(duì)比。綜合年代學(xué)、地球化學(xué)、碎屑鋯石年齡譜、巖石組合以及巖石變質(zhì)變形特征,塔里木西南地體在2.4-2.3 Ga時(shí)處于裂谷構(gòu)造背景。隨后在1.9 Ga左右發(fā)生造山事件,使塔里木西南地體匯聚到Columbia超大陸之下,而后在1.4 Ga時(shí)該超大陸已經(jīng)開(kāi)始發(fā)生裂解。直到1.0-0.9Ga,大洋沿著塔里木西南地體南緣和澳大利亞克拉通北緣發(fā)生匯聚,形成了以喀拉喀什群(KG)為代表的火山弧。而860-830 Ma之間,由于大洋沿著塔里木西南地體北緣俯沖,形成了弧后盆地,沉積了塞拉加茲塔格群(SG)。之后,弧后盆地閉合,在820-800 Ma時(shí)形成了前陸盆地,沉積了埃連卡特群(AG)。直到760 Ma塔里木基底的聚合事件才結(jié)束。前寒武紀(jì)地質(zhì)單元鋯石的U-Pb年代學(xué)及Hf同位素組成顯示地殼的增生時(shí)間為3.8-3.6Ga、2.4-2.2 Ga、1.0-0.7Ga。塔里木西南地體早前寒武紀(jì)地殼增生與塔里木克拉通其他前寒武紀(jì)地體完全不同。此外,不同塊體之間Columbia超大陸聚合和裂解的時(shí)間也并不相同。由此推測(cè)塔里木早前寒武紀(jì)基底可能來(lái)源于不同的大陸塊體,直到新元古代才拼合在一起。
[Abstract]:The Tarim craton is one of the most important cratons in China. Gu Yuan's ancient intrusive complex, MesoNeoproterozoic volcanic-sedimentary strata and Mesoproterozoic magmatic rocks discovered in recent years are of great significance to the study of tectonic evolution and crustal accretion in southwest Tarim area. On the basis of summing up the achievements of predecessors, this paper makes a systematic analysis and summary of the Precambrian magmatic rocks and sedimentary strata in southwest Tarim by detailed field investigation. To explore the Precambrian tectonic evolution and crustal accretion in southwest Tarim. The lithology of Herostein complex is mainly A-type granite and S-type granite formed in 2.4-2.3 Ga and suffered strong metamorphism at -1.9 Ga. The geochemical characteristics indicate that the A-type and S-type granites are derived from Archean basic crustal rocks and metamorphic sandstone and / or felsic mudstone, respectively. The lithology of the Azzi Bayerdi body is mainly composed of two feldspar granites, LA-ICP-MS U-Pb dating results show that it was formed at about 1.4 Ga. The geochemical characteristics indicate that the rock body is a typical A-type granite, and its genesis may be caused by the upwelling of the basic rock mass, which leads to the partial melting of the early Proterozoic basic lower crust, and the addition of Gu Yuan's new crust to different degrees in the process. Based on the LA-ICP-MS U-Pb dating of clastic zircon, the sedimentary time between the volcanic and sedimentary strata of greenschist facies metamorphic and strongly folded Seragatag group is between 860-830Ma and low-greenschist facies metamorphism. The strongly deformed Ellenkat Group (AGG) was 820-800 Ma, while the Upper Neoproterozoic carbonate, clastic rock and moraine strata in the Upper Neoproterozoic carbonate, clastic rock and moraine formation should have been deposited no earlier than 760 Ma. The two glacial ages in QG can be compared with the Beyesi glacial and Teriecan glacial periods in the northern margin of Tarim. Combined with geochronology, geochemistry, age spectrum of clastic zircon, rock assemblage and metamorphic deformation, the southwestern Tarim body is in the rift tectonic setting at 2.4-2.3 Ga. Then orogenic events occurred around 1.9 Ga, which led the southwest of Tarim to converge below the Columbia supercontinent, and then the supercontinent began to break up at 1.4 Ga. Up to 1.0-0.9Ga, the ocean converges along the southern margin of the southwest Tarim body and the northern margin of the Australian craton, forming a volcanic arc represented by the Karakash group KG. However, between 860-830 Ma, the ocean subducted along the northern margin of the southwest Tarim body, forming a back-arc basin and depositing the Seragaztag group. After that, the back-arc basin was closed and the Foreland basin was formed at 820-800 Ma, and the Allenkat group was deposited. It was not until 760 Ma that the aggregation of the Tarim basement ended. The U-Pb geochronology and HF isotopic composition of zircon from the Precambrian geological unit indicate that the crustal accretion time is 3.8-3.6 Gaan2.4-2.2 GaS1.0-0.7Ga. The early Precambrian crustal accretion of the southwest Tarim platform is completely different from other Precambrian terraces in the Tarim craton. In addition, the time of Columbia supercontinent polymerization and cracking is different between different blocks. It is inferred that the early Precambrian basement of Tarim may have originated from different continental blocks until the Neoproterozoic.
【學(xué)位授予單位】：中國(guó)地質(zhì)科學(xué)院
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：P542;P313

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