Serpentinisation, fluid flow, hydrogen and methane production at magma-poor margins: an example from the West Iberia margin

岩浆贫乏边缘的蛇纹石化、流体流动、氢气和甲烷的产生：来自西伊比利亚边缘的例子

• 批准号: 396827560
• 负责人: Professorin Dr. Marta Perez-Gussinye, Ph.D.
• 金额: --
• 依托单位: GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/396827560?language=en
• 关键词: Serpentinisation; fluid; flow; hydrogen; methane

A key challenge in Earth system science today is to quantify the fluxes of elements that are exchanged between crust, ocean and atmosphere as a result of tectonics. First steps towards this effort have focused on estimating element fluxes during hydrothermal circulation at mid-ocean ridges. These studies, however, have ignored the thermodynamics and kinetics of water-rock reactions, which greatly affect those fluxes. In addition, element fluxes during extension at continental margins remain practically unexplored. Continental margins are often found on both sides of present oceans, hence occupy an area of the sea-floor that is similar to or larger than that of mid-ocean ridges.This project focuses on estimating the amount of serpentinization-derived H2 and CH4 fluxes produced during hydrothermal circulation within actively extending lithosphere at magma-poor margins. The importance of these margins in the global cycle of H2 and CH4 resides not only on the amount they produce, but also on the fact that they host serpentinite-based hydrothermal systems of lower temperature ( < 200°C) than those at mid-ocean ridges, where chemosynthetic communities can thrive. This project gathers expertise in three modelling components, tectonic deformation during extension, hydrothermal circulation and thermodynamics of water-rock reactions, which will be coupled to evaluate H2 and CH4 fluxes. Our results will be benchmarked against one of the best, if not the best, set of observations currently available at a continental margin: a 3D multichannel and wide-angle seismic survey and three iODP expeditions at the magma-poor West Iberia margin. Hydrothermal circulation at this margin occurred during extension ~112 M yrs ago, hence its pattern is poorly constrained. To circumvent this problem we intend to give a range of H2 and CH4 fluxes that are compatible with plausible hydrothermal flow patterns and the data. These estimates will be extrapolated to other less well-known magma-poor margins in order to assess their importance in the global production of H2 and CH4, and evaluate their potential for hosting sub-seafloor chemosynthetic life and, in the future, its consequences for the global carbon cycle. This a challenging project that will produce know-how in key areas of Earth sciences in order to quantify elements fluxes between crust and ocean and enhance our understanding of the Earth system feedbacks.

当今地球系统科学的一个关键挑战是量化地壳、海洋和大气之间因构造而交换的元素通量。这项工作的第一步侧重于估计大洋中脊热液循环期间的元素通量。然而，这些研究忽略了水岩反应的热力学和动力学，这极大地影响了这些通量。此外，大陆边缘伸展期间的元素通量实际上仍未得到探索。大陆边缘通常分布在现今大洋的两侧，因此所占的海底面积与洋中脊相似或更大。本项目的重点是估算在岩浆贫乏的大陆边缘，在活跃伸展的岩石圈内，在热液循环过程中，由蛇纹岩化作用产生的H2和CH4通量。这些边缘在全球H2和CH4循环中的重要性不仅在于它们产生的数量，还在于它们拥有温度低于（< 200°C）的蛇纹岩热液系统，而这些热液系统比中洋脊的热液系统更低，在中洋脊，化学合成群落可以茁壮成长。该项目收集了三个建模组成部分的专业知识，即伸展期间的构造变形、热液循环和水岩反应热力学，这些将结合起来评估H2和CH4通量。我们的结果将以目前大陆边缘最好的观测结果之一（如果不是最好的话）为基准：在岩浆贫乏的西伊比利亚边缘进行的3D多通道和广角地震勘探和三次iODP考察。该边缘的热液循环发生在约1.12亿年前的伸展过程中，因此其模式不受约束。为了规避这个问题，我们打算给出一个范围内的H2和CH4通量，是兼容的合理的热液流模式和数据。这些估计数将外推到其他不太知名的岩浆贫乏边缘，以评估它们在全球H2和CH4生产中的重要性，并评价它们承载海底以下化学合成生命的潜力及其未来对全球碳循环的影响。这是一个具有挑战性的项目，将产生地球科学关键领域的专门知识，以量化地壳和海洋之间的元素通量，并提高我们对地球系统反馈的理解。