Nature and assembly of microcontinental blocks within the Paleo-Asian Ocean
Nature and assembly of microcontinental blocks within the Paleo-Asian Ocean
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DOI：
10.1016/j.earscirev.2017.01.012
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发表时间：
2017-01
影响因子：
12.1
通讯作者：
Jian‐Bo Zhou;S. Wilde;Guochun Zhao;Jie Han
中科院分区：
文献类型：
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作者：
Jian‐Bo Zhou;S. Wilde;Guochun Zhao;Jie Han
中国大陆桥的微陆块包括东段的中国东北地块（包括额尔古纳、兴安、松辽和吉木斯汗卡地块），西段的哈萨克斯坦-伊犁-中天山和准噶尔地块，中段的图瓦-蒙古地块和北山地块。这些微陆块的基底主要由太古宙-古元古代结晶岩和/或中新元古代花岗岩类及变质杂岩组成，表明CAOB中的大多数所谓的陆块可以被视为微陆块。CAOB东段锆石年龄谱显示4个年龄峰，分别为495 Ma、780 Ma、1825 Ma和2600 Ma，与CAOB中段和西段的锆石年龄相似。此外，在大多数地块中也存在1000 Ma全球“格伦维尔”构造事件的证据，表明CAOB中的微大陆具有共同的构造历史。晚泛非变质作用发生在500 Ma左右，影响了CAOB内的所有微大陆，形成了一条横贯中国东北、长达1300 km的单一变质带，并将其命名为“中国东北孔兹岩带”。在西伯利亚板块南缘也有一条沿着长达1000 km的萨扬-贝加尔造山带。我们认为，CAOB的微大陆起源于Rodinia的一部分，沿着全球格伦维尔造山带（1100-750 Ma）。750-600 Ma Rodinia裂解后，各微陆块沿着冈瓦纳大陆边缘，靠近华南和塔里木盆地。在~ 600 Ma，这些块体从冈瓦纳东部分离，并与增生的杂岩一起向北（今天的坐标）漂移，穿过古亚洲洋到达西伯利亚板块南缘，在泛非晚期发生碰撞。
The microcontinental blocks in the CAOB include the combined NE China blocks (comprising the Erguna, Xing'an, Songliao and Jimusi-Khanka blocks) in the eastern segment of the CAOB, the Kazakhstan-Yili-Central Tianshan and Junggar blocks in the western segment of the CAOB, and the Tuva-Mongolia blocks and Beishan block in the central segment of the CAOB. The basement in these microcontinental blocks mainly consists of Archean to Paleoproterozoic crystalline rocks and/or Meso-Neoproterozoic granitoids and metamorphic complexes, indicating that most of the so-called blocks in the CAOB can be regarded as microcontinental fragments. Zircon age spectra from the eastern segment of the CAOB reveal four age peaks at 495 Ma, 780 Ma, 1825 Ma and 2600 Ma, which is similar to those recorded in the central and western segments of the CAOB. In addition, evidence of the global ‘Grenvillian’ tectonic event at 1000 Ma is also present in most blocks, indicating that the microcontinents in the CAOB have a common tectonic history. Furthermore, late Pan-African metamorphism at ~ 500 Ma affects all the microcontinents in the CAOB, with this granulite-facies event forming a single metamorphic belt that extends for > 1300 km across NE China, and named the “NE China Khondalite Belt” in the eastern segment of the CAOB. There is also a corresponding > 1000 km-long Sayang–Baikal orogenic belt along the southern margin of the Siberia Craton. We propose that the microcontinents of the CAOB originated as part of Rodinia along the global Grenville Orogenic Belt (1100–750 Ma). At 750–600 Ma, after the break-up of Rodinia, the various microcontinental blocks were located along the margin of Gondwana, close to the South China and Tarim cratons. At ~ 600 Ma, these blocks became detached from eastern Gondwana and, together with accreted complexes, drifted to the north (present-day co-ordinates) across the Paleo-Asian Ocean to the southern margin of the Siberia Craton, where collision took place during the late Pan-African.