西刚果造山带东缘Inkisi组砂岩岩石学、年代学特征及地质意义
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本文为安哥拉国家地质调查计划(编号:PLANAGEO)项目的成果


Petrographic and chronological characteristics and geological significance of Inkisi Formation sandstones from eastern margin of the west Congo Orogenic Belt
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    摘要:

    西刚果(West Congo)造山带是泛非(Pan- Africa)期圣弗朗西斯科(So Francisco)克拉通与刚果(Congo)克拉通汇聚—碰撞造山的非洲部分,其构造演化备受国内外学者关注,开展该时期地层的研究工作对探讨造山带的构造演化具有重大意义。本文研究选取造山带东缘前陆盆地内安哥拉西北部的Inkisi组砂岩为研究对象,开展了年代学及岩石学等方面的研究。结果表明:Inkisi组砂岩中最小碎屑锆石年龄为588±3. 0 Ma,判别图解指示砂岩形成于碰撞背景下的沉积盆地。Inkisi组砂岩的化学蚀变指数(CIA、CIW、PIA)分别为63. 34~73. 17、70. 82~92. 29、65. 19~89. 56,表明源区为温暖潮湿的古气候条件,并且源岩经历了低中等风化作用。砂岩中发育大量流水沉积构造,Sr/Ba值为0. 07~0. 24<0. 5,粒度分析结果显示河流沉积的特征,这些共同指示该套砂岩形成于河流沉积环境。结合岩石地球化学、年代学及碎屑组分分析结果,本文认为研究区内的Inkisi组砂岩形成于活动大陆边缘背景下与碰撞环境有关的盆地,是泛非期西刚果造山运动的响应,同时也暗示在埃迪卡拉纪—早寒武世时期西刚果碰撞造山运动仍在继续。

    Abstract:

    The West Congo Orogenic Belt is a part of Africa where the San Francisco Craton and Congo Craton converged and collided during the Pan African period. Its tectonic evolution has attracted the attention of scholars both domestically and internationally. Conducting research on the stratigraphy during this period is of great significance for exploring the tectonic evolution of the orogenic belt.Methods: This study selected the Inkisi Formation sandstone in the northwest of Angola in the foreland basin on the eastern edge of the orogenic belt as the research object, and conducted studies on chronology and petrology.Results: The minimum detrital zircon age in the Inkisi Formation sandstone is 588 ± 3. 0 Ma, and the discrimination diagram indicates that the sandstone was formed in a sedimentary basin under a collision background. The chemical alteration indices (CIA, CIW, PIA) of the Inkisi sandstone are 63. 34~73. 17, 70. 82~92. 29, and 65. 19~89. 56, the Sr/Ba values ranging from 0. 07 to 0. 24<0. 5.Conclusions: The petrological and chronological characteristics of the Inkisi sandstone indicate that it was formed in a basin related to collision environments in the context of active continental margins, and is a product of river sedimentary environments. Its source area was warm and humid ancient climate conditions, and the source rocks underwent low to moderate weathering. It is a response to the Pan African West Congo orogeny, and also suggests that the West Congo collisional orogeny continued during the Ediacaran—Early Cambrian period.

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张金龙,张洪瑞,潘志龙,罗迪柯,邢伟伟,刘思林,于龙,贾鹏飞,杨宁,李强.2025.西刚果造山带东缘Inkisi组砂岩岩石学、年代学特征及地质意义[J].地质论评,71(4):2025040007,[DOI].
ZHANG Jinlong, ZHANG Hongrui, PAN Zhilong, LUO Dike, XING Weiwei, LIU Silin, YU Long, JIA Pengfei, YANG Ning, LI Qiang.2025. Petrographic and chronological characteristics and geological significance of Inkisi Formation sandstones from eastern margin of the west Congo Orogenic Belt[J]. Geological Review,71(4):2025040007.

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  • 收稿日期:2025-01-10
  • 最后修改日期:2025-05-09
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  • 在线发布日期: 2025-07-19
  • 出版日期: 2025-07-15