南华盆地新元古代成冰纪成锰作用及其成矿背景
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本文为国家自然科学基金资助项目(编号:41763006、41673060)、中国地质调查局中国矿产地质志项目(编号:DD20190379)及贵州省人才基地资助项目(编号:RCJD2018-21)的成果


Metallogenesis and mineralization backgrounds of Neoproterozoic Cryogenian manganese deposits in Nanhua Basin
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    摘要:

    南华盆地成冰系大塘坡组锰矿是我国最重要的锰矿产地之一,它形成于成冰纪Sturtian冰川事件之后,其成矿背景及形成机理一直是研究的重点。在系统总结Sturtian冰川事件起始与结束时间、南华裂谷盆地结构演化及古气候演变等重大地质事件的最新研究进展的基础上,综合分析了南华盆地大型沉积型锰矿成矿作用过程与这些重大地质事件之间的联系。揭示了南华盆地Sturtian冰期的启动和结束与全球其他地区基本一致,分别发生在~717 Ma和~660 Ma之前。同时,对南华系大塘坡锰矿成矿时代进行了约束,大约形成于~660 Ma之前。在新元古代中期Rodinia超大陆裂解作用的影响下,南华裂谷盆地内部发育一系列由同沉积断层控制的地垒—地堑次级盆地。沿同沉积断层运移的热液流体为大塘坡锰矿的形成提供了大量的成矿物质,并对大塘坡锰矿的发育具有明显的控制作用。化学蚀变指数(CIA)、锂同位素(δ7Li)及锇同位素组成(187Os/188Os)等风化指标显示,南华盆地Sturtian冰期晚期至间冰期大塘坡期早期的气候为寒冷干燥,随后转为温暖湿润并很快变为寒冷干燥。至大塘坡中晚期,气候逐渐由寒冷干燥恢复至温暖湿润,并一直保持至大塘坡晚期。整体来看,Sturtian冰期结束后,南华盆地表层海水逐渐氧化,深部沉积水体出现局部间歇式氧化环境,裂陷阶段热液和陆源输入的Mn2+被氧化为MnO2发生沉淀,并在底部伴随着有机质的埋藏及早期成岩作用而最终形成菱锰矿。

    Abstract:

    The Neoproterozoic Cryogenian Datangpo manganese of the Nanhua Basin that was formed after Cryogenian Sturtian glaciation has been one of the major manganese production sites,the mineralization backgrounds and development mechanism of which have received much more attention.The initiation and termination ages of the Sturtian glaciation and the mineralization ages of the Datangpo manganese deposits,the architectural evolution of the Nanhua Basin,the weathering intensity and climatic conditions,and the formation mechanism of the Cryogenian manganese deposits were reviewed.Methods:This paper systematically summarized the commence and termination ages of the Sturtian glaciation elsewhere around the world,the tectonic architecture of the Nanhua Basin and the paleoclimate evolution during the deglaciation of the Neoproterozoic Cryogenian;meanwhile.the causal relationship between the metallogenesis of depositional manganese deposits of the Nanhua Basin and the aforementioned major geological events were comprehensively documented.Results: The Sturtian glaciation of the Nanhua Basin initiated at ~ 717 Ma and terminated before ~ 660 Ma.The syndepositional fault-controlled horst and graben subbasins were formed in the interior of the Nanhua Rift Basin.The weathering indices such as chemical index of alteration (CIA),Li isotope (δ7Li) and Os isotopic composition (187Os/188Os) are indicative of a cold and arid climate of the Nanhua Basin during the late Sturtian glaciation to early interglacial Datangpo Age.The climatic condition changed into a warm and humid climate,quickly returned into a cold and arid climate until the middle to late Datangpo Age,and then transited into a warm and humid climate that persisted into late Datangpo Age.The surface seawater of the Nanhua Basin was well oxygenated after the Sturtian glaciation; meanwhile,the deep water was dominated by anoxia with intermittently oxic condition.Conclusions: The initiation and termination of the Sturtian glaciation of the Nanhua Basin took place most likely synchronously with elsewhere around the world.The mineralization timing of the Cryogenian Datangpo manganese deposits likely developed before ~ 660 Ma.The hydrothermal fluids provided considerable amounts of metallogenesis materials for the Datangpo manganese deposits and dictated their developments,which were precipitated, and were accompanied by organic matter burial and microbe- mediated to transferred into rhodochrosite during early diagenesis.

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付勇,郭川.2021.南华盆地新元古代成冰纪成锰作用及其成矿背景[J].地质论评,67(4):67040973-67040991,[DOI].
FU Yong, GUO Chuan.2021. Metallogenesis and mineralization backgrounds of Neoproterozoic Cryogenian manganese deposits in Nanhua Basin[J]. Geological Review,67(4):67040973-67040991.

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  • 收稿日期:2021-03-15
  • 最后修改日期:2021-05-28
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  • 在线发布日期: 2021-07-19
  • 出版日期: 2021-07-15