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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Ageochemical and geophysical investigation of the hydrothermal complex of Masaya volcano, Nicaragua
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Ageochemical and geophysical investigation of the hydrothermal complex of Masaya volcano, Nicaragua

机译：尼加拉瓜马萨亚火山热液复合体的时代化学和地球物理研究

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摘要

Masaya volcano, Nicaragua, is a persistently active volcano characterized by continuous passive degassing for more than 150 years through the open vent of Santiago crater. This study applies self-potential, soil CO_2 and ground temperature measurements to highlight the existence of uprising fluids associated to diffuse degassing structures throughout the volcano. The diffuse degassing areas are organized in a semi-circular pattern and coincide with several visible and inferred surface volcanic structures (cones, fissure vents) and likely consist of a network of buried faults and dykes that respectively channel uprising flow and act as barrier to gravitational groundwater flow. Water depths have been estimated by multi-scale wavelet tomography of the self-potential data using wavelets from the Poisson kernel family. Compared to previous water flow models, our water depth estimates are shallower and mimic the topography, typically less than 150 m below the surface. Between 2006 and 2010, the depths of rising fluids along the survey profiles remained stable suggesting that hydrothermal activity is in a steady state. This stable activity correlates well with the consistency of the volcanic activity expressed at the surface by the continuously passive degassing. When compared to previous structural models of the caldera floor, it appears that the diffuse degassing structures have an important effect on the path that shallow groundwater follows to reach the Laguna de Masaya in the eastern part of the caldera. The hydrogeological system is therefore more complex than previously published models and our new structural model implies that the flow of shallow groundwater must bypass the intrusions to reach the Laguna de Masaya. Furthermore, these diffuse degassing structures show clear evidence of activity and must be connected to a shallow magmatic or hydrothermal reservoir beneath the caldera. As such, the heat budget for Masaya must be significantly larger than previously estimated.
机译：尼加拉瓜的马萨亚火山是一种持续活泼的火山，其特征是通过圣地亚哥火山口的露天喷口持续进行了超过150年的被动脱气。这项研究采用了自势，土壤CO_2和地面温度的测量方法，以强调与整个火山中的扩散脱气结构有关的起义流体的存在。弥散的脱气区域以半圆形的形式组织，并与一些可见的和推断的表面火山结构（圆锥体，裂隙喷口）重合，并且可能由掩埋的断层和堤坝组成，它们分别引导起义流并充当重力屏障。地下水流量。使用Poisson核族的小波通过自势数据的多尺度小波层析成像估计了水深。与以前的水流模型相比，我们的水深估计更浅且模仿地形，通常在水面以下不到150 m。在2006年至2010年之间，沿调查剖面上升的流体深度保持稳定，这表明热液活动处于稳定状态。这种稳定的活动与通过连续的被动脱气在地表表达的火山活动的一致性密切相关。当与破火山口底板的先前结构模型相比时，似乎扩散的除气结构对浅层地下水到达破火山口东部的Laguna de Masaya的路径有重要影响。因此，水文地质系统比以前发表的模型更为复杂，我们的新结构模型暗示浅层地下水流必须绕过侵入体才能到达Laguna de Masaya。此外，这些分散的脱气结构显示出明显的活动迹象，必须连接到破火山口下方的浅岩浆或热液储层。因此，Masaya的热量预算必须大大高于以前的估计。

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