华北克拉通中部造山带中条山地区古元古代盆地演化

    The Paleoproterozoic basin evolution of the Zhongtiao Mountain region in the Trans-North China Orogen, North China Craton

    • 摘要: 对华北克拉通中部造山带南部中条山地区古元古代中条群和担山石群岩石组合及地层详细调查研究,认为中条群为一套由粗碎屑岩-泥质岩-碳酸盐岩组成的多旋回沉积岩,变质砂岩地球化学特征显示,中条群经历了早期相对稳定到后期较活跃的转变。结合前人碎屑锆石年龄、源区特征和火山岩夹层年龄得出,中条群形成于2.1 Ga左右的活动大陆边缘弧后盆地。担山石群为一套砾岩-砂岩组成的磨拉石建造,碎屑锆石年龄显示,担山石群形成于1.85 Ga左右的碰撞造山阶段的前陆盆地内。结合前人研究,认为中条山地区古元古代盆地演化模式为,约2.1 Ga开始,西部陆块的前导洋向东部陆块活动大陆边缘之下持续俯冲,东部陆块西缘活动大陆边缘弧后盆地沉积了中条群,约1.85 Ga开始,东部陆块与西部陆块之间的大洋闭合,陆陆碰撞开始,中条群发生挤压褶皱变形,陆壳加厚及随后的快速抬升和剥蚀形成前陆盆地的担山石群磨拉石。中条山地区古元古代弧后盆地向前陆盆地的转化支持华北克拉通最初西部陆块向东俯冲,经历了约1.85 Ga的东、西陆块碰撞并最终克拉通化的演化模式。

       

      Abstract: This paper conducted detailed investigations of the lithological assemblages and stratigraphy of the Zhongtiao Group and the Danshanshi Group in Zhongtiao Mountain region, Trans-North China Orogen (NTCO), North China Craton. The Zhongtiao Group comprises of a suit of metamorphic sedimentary rocks, consisting of multicyclic sedimentary rocks composed of clastic rocks, mudstones and carbonate rocks. The geochemical characteristics of the metamorphic sandstone show that the Zhongtiao group experienced a transition from early relative stability to late activity. The age and source characteristics of detrital zircons from the Zhongtiao Group and age of intercalated volcanic rock indicate that they were deposited in a back-arc basin of active continental margin from ~2.1 Ga. The Danshanshi Group is a series of conglomerates and sandstones forming a molasse basin during the collisional orogeny stage at ~1.85 Ga. Taken together, we present a brief scenario for the evolution of the sedimentary basin in Zhongtiao mountain region. From ~2.1 Ga, the eastward-directed subduction of the ocean between western block and eastern block, back-arc basin (Zhongtiao Group) developed behind the arc that located in the west margin of eastern block. At ~1.85 Ga, the ocean between western block and eastern block closed, resulting in the collision of the two blocks along TNCO, the Zhongtiao Back-arc basin underwent fold deformation and resulting in the crustal thickening followed by rapid exhumation/uplift, which shifted the back-arc basin to foreland basins. The Danshanshi molasse basin is formed in foreland basin. Such a shift from the back-arc basins to foreland basins in the Late Paleoproterozoic supports the model that the collision between Eastern and Western blocks occurred at ~1.85 Ga.

       

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