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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Magnetic fabrics of the Miocene ignimbrites from West-Cameroon: Implications for pyroclastic flow source and sedimentation
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Magnetic fabrics of the Miocene ignimbrites from West-Cameroon: Implications for pyroclastic flow source and sedimentation

机译：西喀麦隆中新世火成岩的磁性结构：对火山碎屑流源和沉积的影响

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摘要

The Miocene ignimbrites of Mounts Bambouto and Bamenda located in the central part of Cameroon Volcanic Line are generally made of welded and non-welded massive lapilli tuff and lithic breccias. These discontinuous deposits cover a total area of 180 km2 with thickness ranging from 25 to 200 m. The different facies contain several lithic fragments of mainly trachytic nature. The devitrified matrix of the welded ignimbrites is constituted by sanidine, anorthoclase, quartz, plagioclase, dinopyroxene, biotite, Fe-Ti oxides and devitrified fiammes. Anisotropy of magnetic susceptibility (AMS) is used to characterize magnetic fabrics and to provide an estimate of flow direction of each ignimbrite sheet. Magnetic mineralogy results from different flow units show that titanomagnetite, titanohematite, maghemite and goethite with grain size ranging from coarse MD to very fine SP are the main magnetic carriers of these ignimbrites. Inferred transport directions based on the AMS data and field indicators show that Bambouto caldera is the source of main pyroclastic deposits of Mount Bambouto. In southwestern Mount Bamenda, Santa-Mbu caldera or Bambouto caldera constituted the probable emission center of Mbengwi, Bamenda and Mbu ignimbrite sheets, whereas magnetic fabrics of Bambili, Sabga and Big Babanki ignimbrites demonstrate that these deposits were emitted from a northeastern source, namely Oku vent in Mount Oku. A small number of subvertical AMS fabrics correspond to rocks possibly modified by an elutriation process.
机译：位于喀麦隆火山线中部的班博图山（Bambouto）和巴门达（Bamenda）的中新世火成岩通常由焊接的和非焊接的块状lapilli凝灰岩和石角砾岩制成。这些不连续的沉积物总面积为180 km2，厚度范围为25至200 m。不同的相包含几个主要为疏松性质的石屑碎片。焊接的火成岩的失透基体由山梨酸，正钙铝石，石英，斜长石，二茂铁，黑云母，Fe-Ti氧化物和失透的火焰组成。磁化率各向异性（AMS）用于表征磁性织物并提供每个火成岩片的流向估计值。不同流动单元的磁性矿物学结果表明，粒度范围从粗MD到非常细SP的钛磁铁矿，钛赤铁矿，磁赤铁矿和针铁矿是这些火成岩的主要磁性载体。根据AMS数据和现场指标推断出的运输方向表明，班博托火山口是班博托山主要热碎屑沉积物的来源。在西南的巴门达山，圣-姆布火山口或班博托火山口构成了姆本威，巴门达和姆布着火层的可能排放中心，而班比里，萨布加和大班班奇火成岩的磁性织物表明这些沉积物是从东北来源即奥库排放的在奥库山发泄。少数亚垂直AMS织物对应于可能通过淘析过程改性的岩石。

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  • 来源
    《Journal of Volcanology and Geothermal Research》 |2011年第4期|p.113-132|共20页
  • 作者

    M. Gountié Dedzo; A. Nédélec; A. Nono; T. Njanko; E. Font; P. Kamgang; E. Njonfang; P. Launeau;

  • 作者单位

    LCE, Department of Earth Sciences, University of Dschang, B.P. 67 Dschang, Cameroon;

    UMR5563-LMTG-OMP, University of Toulouse-CNRS-IRD, 14 Av. Edouard-Belin, 31400 Toulouse, France;

    LCE, Department of Earth Sciences, University of Dschang, B.P. 67 Dschang, Cameroon;

    LCE, Department of Earth Sciences, University of Dschang, B.P. 67 Dschang, Cameroon;

    IDL-FUL, lnstituto Dom Luis. Universidade de Lisboa, 1749-016 Lisboa, Portugal;

    Department of Earth Sciences, University of Yaounde I, B.P. 812 Yaounde, Cameroon;

    Laboratoire de Ceologie, Ecole Normale Superieure, Universite de Yaounde I, B.P. 47, Yaounde, Cameroon;

    UMR-CNRS 6112, Laboratoire de Planetologie et Ceodynamique, Universite de Nantes, rue de la Houssiniere, 44322 Nantes, France;

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  • 正文语种 eng
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  • 关键词

    AMS; magnetic mineralogy; Miocene ignimbrite; caldera; Western-Cameroon;

    机译：AMS;磁性矿物学中新世火成岩;破火山口;喀麦隆西部;

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