Serpentinization, redox conditions, and metabolic energy production within shallow portions of subduction zones: windows to carbon cycling and chemosynthetic life driven by modern and ancient serpentinite mud volcanism

俯冲带浅部的蛇纹石化、氧化还原条件和代谢能产生：现代和古代蛇纹岩泥火山驱动的碳循环和化学合成生命的窗口

• 批准号: 453470886
• 负责人: Professor Dr. Wolfgang Bach, since 11/2022
• 金额: --
• 依托单位: Department of Earth and Environmental Sciences
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/453470886?language=en
• 关键词: Serpentinization; redox; conditions; metabolic; energy

Serpentinite mud volcanoes are impressive seamounts at the Mariana forearc seafloor that expel fluids derived from the subducted Pacific plate. These fluids contain abundant serpentinization-derived geofuels (H2, CH4), which provide energy for chemosynthetic life within the mud volcanoes. It has been suggested that serpentinite mud volcanoes are potential sites where life could have originated on Earth. But it has to date not been quantified how much of the life-sustaining geofuels are being produced in the forearc mantle. Moreover, it is poorly constrained what the key biogeochemical processes are that result from the availability of geofuels. And did similar processes supporting chemosynthesis-based ecosystems as well take place in fossil serpentinite mud volcanoes?We propose a comprehensive study to understand the redox conditions in the shallow (<30 km) supra-subduction zone mantle. We will investigate serpentinites from the modern Mariana mud volcanoes as well as from fossil serpentinite mud volcanoes exposed in California and Oregon. Our combined empirical–modeling approach will yield estimates of O and S fugacities, from which concentrations of H2 and H2S of the interacting fluids can be calculated. We will also be able to assess the driving force for a large range of reactions of abiogenic organosynthesis.The source depths of the Mariana mud volcanoes are well known. We plan to reconstruct the source depths of the fossil serpentinite deposits by examining the peak metamorphic conditions, which metamafic clasts included in the serpentinites experienced during subduction. We will conduct petrological and bulk rock-/mineral-chemical work that, coupled with calculated pseudosections, provides reliable depth estimates.We further plan to investigate the ramifications of the serpentinization-related formation of metabolic energy for chemosynthetic life and the carbon cycle. Geochemical signatures of microbial activity preserved within secondary carbonates will be studied. Samples comprise carbonate chimneys from the Mariana mud volcanoes as well as carbonate veins within serpentinite clasts and fossil-rich seep carbonates associated with the serpentinite deposits at the US sites. Lipid biomarkers and compound-specific carbon stable isotope compositions, mineral chemistry, as well as kinetic and thermodynamic modeling will allow reconstructing key biogeochemical processes and the modes of carbonate formation.The proposed work is designed to further our understanding of redox conditions in subduction zones and its consequences for chemotrophic life and the deep carbon cycle in the oceanic lithosphere.

蛇纹岩泥火山是马里亚纳弧前海底令人印象深刻的海山，它排出来自俯冲太平洋板块的流体。 这些流体含有丰富的蛇纹石化衍生的地质燃料（H2，CH 4），为泥火山内的化学合成生命提供能量。 有人认为蛇纹岩泥火山是地球上生命起源的潜在场所。 但迄今为止，还没有量化多少维持生命的地球燃料是在弧前地幔中产生的。 此外，它是什么样的关键地球化学过程，从地球燃料的可用性的限制。 在化石蛇纹岩泥火山中是否也发生了类似的支持化学合成生态系统的过程？我们提出了一个全面的研究，以了解浅（<30公里）的俯冲带地幔氧化还原条件。 我们将调查现代马里亚纳泥火山的蛇纹岩，以及从化石蛇纹岩泥火山暴露在加州和俄勒冈州。 我们结合的热力学建模方法将产生O和S逸度的估计值，从中可以计算相互作用的流体的H2和H2S的浓度。 我们还将能够评估非生物有机合成反应的驱动力。马里亚纳泥火山的源深度是众所周知的。 我们计划通过研究变质作用的峰值条件来重建蛇纹岩化石矿床的源区深度，这些蛇纹岩在俯冲过程中经历了变质镁铁质碎屑。 我们将进行岩石学和大量的岩石/矿物化学工作，再加上计算的伪截面，提供可靠的深度估计。我们进一步计划调查的蛇纹作用相关的代谢能的形成的分支，为化学合成生命和碳循环。 将研究次生碳酸盐中保存的微生物活动的地球化学特征。 样品包括来自马里亚纳泥火山的碳酸盐烟囱，以及蛇纹岩碎屑内的碳酸盐脉和与美国站点蛇纹岩矿床相关的富含化石的渗漏碳酸盐。 脂质生物标志物和特定化合物的碳稳定同位素组成，矿物化学，以及动力学和热力学模拟将允许重建关键的地球化学过程和碳酸盐形成的模式，拟议的工作旨在进一步了解俯冲带的氧化还原条件及其对化养生命和大洋岩石圈深部碳循环的影响。