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首页> 外文期刊>Journal of Volcanology and Geothermal Research >The ～1245 yr BP Asososca maar eruption: The youngest event along the Nejapa-Miraflores volcanic fault, Western Managua, Nicaragua
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The ～1245 yr BP Asososca maar eruption: The youngest event along the Nejapa-Miraflores volcanic fault, Western Managua, Nicaragua

机译：〜1245年BP Asososca maar喷发：尼加拉瓜西部马那瓜Nejapa-Miraflores火山断裂沿线最年轻的事件

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摘要

The Asososca Tephra comprises the asymmetrically distributed, well-stratified phreatomagmatic products of the 1245 +125/-120 yr BP Asososca maar eruption West of Managua, Nicaragua. It is the youngest eruptive unit related to the monogenetic volcanism concentrated along the N-S trending Nejapa-Miraflores active fault and intersecting E-W to NE-SW and NW-SE minor faults. The close relationship between monogenetic volcanism and the structural-local tectonic framework is evidenced by the lineament domains and vent alignment patterns identified by remotely sensed images and DEMs of the research area. The Asososca maar lake bathymetry suggests that the crater was formed by coalescing vents migrating during the eruptive event. The Asososca Tephra dominantly consists of accidental lithics disrupted from the underlying stratigraphic units observed inside and around the maar crater. Dry base-surge bedsets are dominant throughout the eruptive unit, showing fades variation from proximal, cross-stratified beds to mid-distal plane-parallel and wavy-parallel beds. Grain-size analyses indicate that base surges transported dominantly -1,0, and 1φ sized particles at the bedload in form of traction carpets, while fine ash material in continuous suspension was minimal. Juvenile fragments were only identified in the finer fractions, varying from vesiculated scoriae to dense sideromelane fragments. SEM analyses suggest that the Asososca eruption resulted from a highly efficient fuel-coolant interaction between a tholeiitic basaltic melt and an aquifer hosted in a shallow level (between 50 and 200 m) of olivine-bearing scoria ash and lapilli beds. The explosion triggered the country-rock comminution and the production of moss-like, fused-shaped, and blocky ash-shards with stepped surfaces, quenching cracks, pitting, alteration skins, and adhered particles, all indicative of phreatomagmatic fragmentation. The very recent age of the Asososca maar eruption confirms that the densely inhabited Managua area is volcanically active and that hazard studies should focus on the potential for phreatomagmatic eruptions.
机译：Asososca Tephra包括尼加拉瓜马那瓜以西的1245 + 125 / -120 BP BP Asososca maar喷发的不对称分布，分层良好的磁岩产物。它是与单基因火山作用有关的最年轻的喷发单元，沿着南北向的内贾帕-米拉弗洛雷斯活动断层集中，并与东-西与南北-南-东南小断层相交。研究区的遥感图像和DEM识别出的线性区域和喷口排列模式，证明了单基因火山作用与构造局部构造框架之间的密切关系。 Asososca maar湖的测深表明，火山口是由爆发事件期间汇聚的喷口合并而成。 Asososca Tephra主要由偶然的岩性组成，这些岩性是由在玛尔陨石坑内部和周围观察到的潜在地层单元所破坏的。在整个喷发单元中，干基涌浪床组占主导地位，显示出从近端，交叉分层床到中远端平面平行和波浪平行床的衰落变化。粒度分析表明，基流在牵引床中以牵引地毯的形式主要输送-1,0和1φ大小的颗粒，而连续悬浮液中的细灰物质则很少。仅在较细的级分中鉴定出了少年碎片，从囊状鳞屑到致密的侧铁线虫碎片不等。 SEM分析表明，Asososca火山喷发是由高渗性玄武质熔体和含水浅层（50-200 m之间）含橄榄石的灰渣和青金石层之间的含水层之间的高效燃料-冷却剂相互作用引起的。爆炸触发了乡村岩石的粉碎，并产生了苔藓状，熔融状和块状灰烬，这些碎片具有阶梯状的表面，淬火的裂纹，点蚀，蚀变的表皮和粘附的颗粒，所有这些都表明发生了岩浆碎裂。 Asososca火山喷发的最近年龄证实了人口密集的马那瓜地区是火山活动区，危害研究应集中在岩浆喷发的潜力上。

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  • 来源
    《Journal of Volcanology and Geothermal Research》 |2009年第4期|292-312|共21页
  • 作者

    Natalia Pardo; Jose Luis Macias; Guido Giordano; Paola Cianfarra; Denis Ramon Avellan; Fabio Bellatreccia;

  • 作者单位

    Departamento de Vulcanologia, Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Coyoacdn, C.P. 04510, Mexico, D.F., Mexico;

    Departamento de Vulcanologia, Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Coyoacdn, C.P. 04510, Mexico, D.F., Mexico;

    Dipartimento di Scienze Geologiche, Universitd Roma Ire, Largo S. Leonardo Murialdo 1,00146 Roma, Italy;

    Dipartimento di Scienze Geologiche, Universitd Roma Ire, Largo S. Leonardo Murialdo 1,00146 Roma, Italy;

    Departamento de Vulcanologia, Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Coyoacdn, C.P. 04510, Mexico, D.F., Mexico Centra de Investigationes Geocientificas (CIGEO), Managua, Nicaragua;

    Dipartimento di Scienze Geologiche, Universitd Roma Ire, Largo S. Leonardo Murialdo 1,00146 Roma, Italy;

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  • 正文语种 eng
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  • 关键词

    base surge; phreatomagmatic eruption; pyroclastic density current; SEM; volcanic glass; lineament swarm;

    机译：基本激增岩浆喷发;火山碎屑密度电流扫描电镜火山玻璃线虫群;

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