Amalgamation of the North China Craton: Key issues and discussion
Amalgamation of the North China Craton: Key issues and discussion
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DOI：
10.1016/j.precamres.2012.09.016
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发表时间：
2012-12
影响因子：
3.8
通讯作者：
Guochun Zhao;Peter A. Cawood;San-zhong Li;S. Wilde;M. Sun;Jian Zhang;Yanhong He;C. Yin
中科院分区：
文献类型：
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作者：
Guochun Zhao;Peter A. Cawood;San-zhong Li;S. Wilde;M. Sun;Jian Zhang;Yanhong He;C. Yin
地质和地球物理资料表明，华北克拉通的前寒武纪基底是由多个微陆块合并而成。关于断块的数量、形成时间和形成方式等问题一直存在争议，特别是在以下几个问题上存在争议：(1)导致东、西断块沿跨华北造山带合并的碰撞事件时间；(2)东西板块俯冲的极性；(3)在~ 2.1Ga与东部地块碰撞的古大陆块体（富平地块）的有效性；(4)北陆北缘古元古代的构造环境；(5)西地块孔雀岩带高压、超高温麻粒岩相事件的构造性质；(6)东部地块古元古代胶辽基带的构造环境。通过对现有地层、构造、地球化学、变质和地质年代学数据的分析和整合，可以建立一个内部一致和连贯的模型，用于古元古代NCC各太古宙块体的组合和稳定。TNCO获得的所有变质年龄都在1.85Ga左右，这表明克拉通西部和东部地块的最终合并发生在~ 1.85Ga。TNCO的构造特征为扇形，构造特征为顶向nw和顶向se分别向西北和东南方向逆冲。这种模式对东西板块碰撞组合的俯冲极性没有约束。TNCO岩石圈、地幔和软流圈的构造在中生代和新生代发生了明显的改变/替换，因此这些构造的现今方位即使与古元古代克拉通的组合有关，也不能用来推断相关的俯冲极性。没有独特的构造资料或可用的变质资料来支持一个古老的大陆块体的存在，该大陆块体介入东西方块体之间，并在~ 2.1Ga与东部块体碰撞。现有资料也与北陆构造带北缘古元古代内蒙古-河北北造山带的存在不一致，该造山带是在~ 2.3Ga通过外来弧的增生形成的，并在1.92-1.85Ga并入古元古代哥伦比亚（努纳）超大陆。我们将该推断造山带的河北北部部分解释为TNCO的一部分，将内蒙古部分解释为一个独立的陆块（阴山地块）。古元古代孔达利岩带将该地块与鄂尔多斯地块隔开。孔大理岩带的高压/中压麻粒岩相变质事件被认为是在~ 1.95Ga时由银山地块与鄂尔多斯地块碰撞形成西部地块的结果，而在~ 1.92Ga时，孔大理岩带内的UHT变质作用则与碰撞后伸展过程中幔源岩浆的底沉降或侵入有关。东部地块的胶辽集带可能是在2.2 ~ 1.9 ga古元古代裂陷形成龙岗和朗林地块，并在随后的盆地闭合和碰撞中形成的。
Geological and geophysical data indicate that the Precambrian basement of the North China Craton (NCC) formed by amalgamation of a number of micro-continental blocks. The number of blocks, when they existed and how they came together are controversial, and in particular the following issues are disputed: (1) the timing of collisional event(s) leading to the amalgamation of the Eastern and Western blocks along the Trans-North China Orogen (TNCO); (2) the polarity of the subduction between the Eastern and Western blocks; (3) the validity of an old continental block (Fuping Block) that collided with the Eastern Block at ∼2.1Ga; (4) the tectonic setting of the northern margin of the NCC in the Paleoproterozoic; (5) the tectonic nature of high-pressure (HP) and ultrahigh temperature (UHT) granulite-facies events in the Khondalite Belt of the Western Block; and (6) the tectonic setting of the Paleoproterozoic Jiao-Liao-Ji Belt in the Eastern Block. Analysis and integration of available stratigraphic, structural, geochemical, metamorphic and geochronologic data enable the development of an internally consistent and coherent model for assembly and stabilization of the various Archean blocks of the NCC in the Paleoproterozoic. All metamorphic ages obtained for the TNCO are around 1.85Ga, which establishes that the final amalgamation of the Western and Eastern blocks of the craton occurred at ∼1.85Ga. The TNCO is characterized by a fan-shaped pattern of structural features, with the top-to-the-NW and top-to-the-SE thrusting in the northwest and southeast, respectively. This pattern does not constrain subduction polarity for the collisional assembly of the Eastern and Western blocks. Structures in lithospheric mantle and asthenosphere in the TNCO have been significantly modified/replaced in the Mesozoic and Cenozoic, and hence the present-day orientation of these structures, even if they relate to Paleoproterozoic assembly of the craton cannot be used to infer associated subduction polarity. There are no unique structural data or available metamorphic data to supporting the existence of an old continental block that intervened between the Eastern and Western Blocks, which collided with the Eastern Block at ∼2.1Ga. Available data are also inconsistent with the existence of the Paleoproterozoic Inner Mongolia-North Hebei Orogen along the northern margin of the NCC that formed through accretion of an exotic arc at ∼2.3Ga and incorporated into the Paleoproterozoic Columbia (Nuna) Supercontinent at 1.92–1.85Ga. We interpret the north Hebei portion of this inferred orogen as part of the TNCO, and the Inner Mongolian portion as an independent continental block (Yinshan Block). This block is separated from the Ordos Block by the Paleoproterozoic Khondalite Belt. The high-/medium-pressure granulite facies metamorphic event in the Khondalite Belt is considered to have resulted from collision between the Yinshan and Ordos blocks to form the Western Block at ∼1.95Ga, whereas the ∼1.92Ga UHT metamorphism within the belt was related to the underplating or intrusion of mantle-derived magmas during the post-collisional extension. The Jiao-Liao-Ji Belt in the Eastern Block likely formed through Paleoproterozoic rifting to form the Longgang and Langrim blocks, and subsequent basin closure and collision in the period 2.2–1.9Ga.