桂西二叠系铝土岩系中的灾变事件记录研究
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P588.24;P53

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广西地质矿产勘查开发局项目 (GXDK202432); 广西矿产地质志续编与产品服务项目(KD-[2024]-XZ-065)


The records of catastrophic events in the Permian bauxite rock series in western Guangxi
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    摘要:

    灾变事件赋存着重要的地质信息,其遗迹具有经济和科学价值,发现和研究灾变事件是解决地质问题的方法之一,也是提高地质科学认识水平的途径。本文通过桂西地区铝土矿床野外调查、显微特征研究和含铝岩系重金属元素分析,列举桂西地区二叠系含铝岩系主要灾变事件,阐释其形成诱因。含铝岩系灾变事件主要为火山灰季、重金属异常和地震幕。火山灰降落时长跨度可达10 Ma,火山灰岩性从基性到酸性均有出现,属岛弧钙碱性岩浆系列。相对于华北、黔北等铝土矿矿集区,桂西含铝岩系中Cr强烈富集,剖面平均值为400×10-6~900×10-6,Ni在部分剖面中强烈富集,平均值300×10-6~600×10-6,Cd在大多数剖面中富集,Co在少数剖面中富集,在含酸性火山灰的岩层中Sb、As强烈富集,Cr、Ni、Cd、Sb、As、Co等6种元素构成重金属异常; 地震遗迹可见软变形、震浊积岩、小地堑等。火山灰降落和地震幕的诱因应为印支板块与华南板块的俯冲形成岛弧岩浆和火山喷发,同时弧后盆地拉张引发了地震。火山灰不仅为含铝岩系提供了铝、铁等物质,并且提供了重金属,导致重金属异常。

    Abstract:

    Catastrophic events contain important geological information, and their relics have economic and scientific value. Discovering and studying catastrophic events is one of the methods to solve geological problems and also a way to improve the understanding of geological science. This article lists the main catastrophic events of the Permian bauxite rock series in western Guangxi basing on field investigations, microscopic feature studies, and analysis of heavy metal elements in the bauxite-bearing rock series, and explains their formation. The main catastrophic events in bauxite-bearing rock formations are volcanic ash season, heavy metal anomalies and earthquake episode. The duration span of volcanic ash deposition can extend to 10 Ma, and the lithology of volcanic ash varies from basic to acidic, showing the arc-related calc-alkaline magma series. Compared to bauxite ore concentration areas in the North China and North Guizhou, the bauxite-bearing rock series in studied sections of western Guangxi is strongly enriched in Cr, with an average value of 400×10-6 to 900×10-6, whereas Ni is strongly enriched in some sections, with an average value of 300×10-6~600×10-6, Cd is enriched in most sections, but Co is enriched in few sections. In addition, Sb and As are greatly enriched in the rocks with felsic volcanic ash. Six elements including Cr, Ni, Cd, Sb, As, and Co constitute heavy metal anomalies. The seismic relics include soft deformation, seismic turbidite, and small graben, etc. The triggering factors for volcanic ash fall and seismic episode were probably the subduction of the Indosinian plate beneath the southwestern margin of the South China plate, which formed island arc magmas and volcanic eruptions, meanwhile the back arc basin tension caused earthquakes. Volcanic ash not only provides substances such as aluminium and iron for bauxite-bearing rock series, but also heavy metals which generated to heavy metal anomalies

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张启连,王学恒,周辉,等, 2025. 桂西二叠系铝土岩系中的灾变事件记录研究[J]. 岩石矿物学杂志, 44(4):823~838.
ZHANG Qi-lian, WANG Xue-heng, ZHOU Hui, et al, 2025. The records of catastrophic events in the Permian bauxite rock series in western Guangxi[J]. Acta Petrologica et Mineralogica, 44(4): 823~838.

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  • 收稿日期:2024-02-04
  • 最后修改日期:2024-12-26
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  • 在线发布日期: 2025-07-18
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