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Volcanic edifice slip events recorded on the fault plane of the San Andrés Landslide, El Hierro, Canary Islands
Tectonophysics ( IF 2.9 ) Pub Date : 2020-02-01 , DOI: 10.1016/j.tecto.2019.228317
Jan Blahůt , Ivanka Mitrovic-Woodell , Ivo Baroň , Miloš René , Matt Rowberry , Pierre-Henri Blard , Filip Hartvich , Jan Balek , Stavros Meletlidis

Abstract Volcanic flank collapses often result in giant debris avalanches that are capable of travelling tens of kilometres across the ocean floor and generating tsunamis that devastate distant communities. The San Andres Landslide on El Hierro, Canary Islands, represents one of the few places in the world where it is possible to investigate the landslide mass and fault planes of a volcanic collapse structure. In this study, a new conceptual model for the development of this enormous slump is presented on the basis of structural geological and geomorphological measurements, petrological and microstructural analyses, and cosmogenic radionuclide dating. Structural geological and geomorphological measurements indicate that the fault plane records two distinct events. Petrological and microstructural analyses demonstrate that a thin layer of frictionite covers the surface of the fault in contact with an oxidised tectonic breccia that transitions into the underlying undeformed basanite host rock. This frictionite comprises a heterogeneous cataclastic layer and a translucent silica layer that are interpreted to represent two separate slip events on the basis of their architecture and crosscutting relationships. Cosmogenic 3He dating reveals a maximum exposure age of 183 ± 17 ka to 52 ± 17 ka. Arguments are presented in support of the idea that the first slip event took place between 545 ka and 430 ka, prior to significant clockwise rotation of El Hierro, and the second slip event took place between 183 ka and 52 ka, perhaps in association with one of the giant debris avalanches that occurred around that time. This is the first time that more than one slip event has been recognised from the fault plane of the San Andres Landslide. It is also believed to be the first time a silica layer resulting from frictional melt has been described in a volcanic setting.

中文翻译:

加那利群岛埃尔耶罗圣安德烈斯滑坡断层面上记录的火山大厦滑移事件

摘要 火山侧翼坍塌通常会导致巨大的碎片雪崩,这些雪崩能够穿越海底数十公里,并引发海啸,摧毁遥远的社区。位于加那利群岛 El Hierro 的圣安德烈斯山体滑坡是世界上少数几个可以调查火山崩塌结构的滑坡体和断层平面的地方之一。在这项研究中,基于构造地质和地貌测量、岩石学和微观结构分析以及宇宙放射性核素测年,提出了这种巨大滑坡发展的新概念模型。构造地质和地貌测量表明断层面记录了两个不同的事件。岩石学和微观结构分析表明,断层表面覆盖着一层薄薄的摩擦岩,与氧化的构造角砾岩接触,该角砾岩过渡到下面的未变形的黑玄武岩主岩。这种摩擦岩包括一个异质碎裂层和一个半透明的二氧化硅层,根据它们的结构和横切关系,它们被解释为代表两个独立的滑动事件。宇宙成因 3He 测年显示最大暴露年龄为 183 ± 17 ka 至 52 ± 17 ka。提出的论点支持第一次滑动事件发生在 545 ka 和 430 ka 之间,在 El Hierro 显着顺时针旋转之前,第二次滑动事件发生在 183 ka 和 52 ka 之间,可能与一个发生在那个时候的巨大碎片雪崩。这是第一次从圣安德烈斯滑坡的断层面识别出不止一个滑移事件。这也被认为是第一次在火山环境中描述由摩擦熔体产生的二氧化硅层。
更新日期:2020-02-01
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