Experimental Investigations of Peridotite-H2O-CO2 Interactions under Hydrothermal Conditions: A Study of Carbon Sequestration and Abiotic Synthesis of Organic Compounds

在地球表面发现的一些岩石与溶解在地表和地下水中的二氧化碳(CO2)发生反应，可能会导致矿物反应，从流体中去除二氧化碳。这反过来又会在一个称为碳封存的过程中从大气中去除二氧化碳。在适当的条件下，同样的反应可以在一种称为非生物合成的过程中导致有机化合物的形成，这一过程导致从无机化学物种形成有机化合物。如果我们更好地了解涉及天然岩石系统的碳固定过程，我们可能能够设计出通过将大气中的碳锁定在矿物中来减少大气二氧化碳的有效方法。更好地了解有机化合物是如何从无机材料中形成的，以及与矿物的相互作用，将有助于我们更好地了解生活在地球地下深处的微生物如何能够在与有机材料的传统来源隔离的环境中生存和茁壮成长。这项研究提供了基本的实验数据和热力学参数，有助于我们更好地了解海底常见的岩石(即橄榄岩)和陆地上一些地方的岩石如何与充满二氧化碳的水溶液反应，以沉淀蛇纹石(即称为蛇纹岩的过程)和含碳矿物(即碳酸盐)。实验还将研究同样的反应如何将二氧化碳中的碳还原成碳氢化合物，这些碳氢化合物可以作为生活在地球深处岩石和沉积物中的微生物的食物。这项工作的更广泛影响包括通过邀请波多黎各本科生参与研究并将他们作为伍兹霍尔暑期学生研究员带到伍兹霍尔海洋研究所，扩大科学界代表性不足群体的参与。学生将在驻地停留10至12周，并参与实验工作。这项工作还包括波多黎各大学的一名教员马亚格斯和马萨诸塞州伍兹霍尔海洋研究所的研究人员之间的密切互动。其他影响包括对一名女博士生的培训，以及科学家与马萨诸塞州伍兹霍尔附近的法尔茅斯学院高中生之间的互动。与科学院的互动将包括演讲和参观伍兹霍尔的实验实验室，这样学生们就可以第一手了解做科学是什么样子，科学家使用什么工具和方法。为了实现研究目标，实验室实验将在迪克森炸弹中进行，温度在200-300摄氏度，35兆帕，水岩比在天然海底热液系统中发现。每个实验将持续几个月，涉及橄榄岩(二辉橄榄岩)和矿物(橄榄石)与充满二氧化碳的流体的反应。实验的目的是使蛇纹石和碳酸盐矿物从原料中形成和生长。在整个实验期间，将监测流体组成的变化，以及系统固体的组成变化。将特别关注各种碳酸盐矿物的形成和有机化合物的非生物合成，特别是CO2、H2、HCOOH、CO、CH3OH和CH4。RUN反应物和产品将通过岩相学和光谱技术进行表征和检验。利用这些结果数据，将在矿物置换反应和流体化学变化之间建立关联。此外，流体化学的变化将被用来确定蛇纹石和矿物碳化反应的稳定和亚稳定多相平衡、反应路径和动力学速率。反应路径模型将用于Mg-Si-Fe-Al-Ca-Na-K-O-H-C体系，以帮助设计实验并使用热力学和动力学约束分析结果。

The reaction of some rocks found on Earth's surface with carbon dioxide (CO2) dissolved in surface and subsurface waters can result in mineral reactions that remove CO2 from the fluid. This, in turn, removes CO2 from the atmosphere in a process called carbon sequestration. Under the right conditions, the same reactions can cause the formation of organic compounds in a process called abiotic synthesis which results in the formation of organic compounds from inorganic chemical species. If we better understand processes of carbon sequestration involving natural rock systems, we may be able to devise efficient and effective means for reducing atmospheric CO2 by locking atmospheric carbon up in minerals. A better understanding of how organic compounds form from inorganic materials and interactions with minerals will help us better understand how microbes that live deep in Earth's subsurface are able to survive and thrive in environments where they are isolated from conventional sources of the organic material. This research provides fundamental experimental data and thermodynamic parameters that improve our understanding of how rocks (i.e. peridotites) that are common on the seafloor and also that occur in some places on land react with CO2-charged aqueous fluids to precipitate the mineral serpentine (i.e. a process called serpentinization) and minerals containing carbon (i.e., carbonates). Experiments will also examine how the same reactions reduce carbon from CO2 to form hydrocarbons that can serve as food for microbes living deep inside the Earth in rocks and sediments. Broader impacts of the work include broadening participation of groups under-represented in the sciences by engaging Puerto Rican undergraduates in research and bringing them to the Woods Hole Oceanographic Institution as Woods Hole Summer Student Fellows. Students will remain in residence for 10 to 12 weeks and participate in the experimental work. The effort also includes close interaction between a faculty member at the University of Puerto Rico, Mayaguez and researchers at Woods Hole Oceanographic Institution in Massachusetts. Additional impacts include training of a female PhD student and interaction between the scientists and high school students at the Falmouth Academy near Woods Hole MA. The interaction with the Academy will include lectures and visits to the experimental lab at Woods Hole so students can see, first hand, what it is like to do science and what tools and approaches scientists use.To achieve research goals, laboratory experiments will be run in Dixon bombs at temperatures from 200 to 300 C, 35 MPa, and water-to-rock ratios found in natural seafloor hydrothermal systems. Each experiment will last for several months and involve the reaction of peridotite (lherzolite) and minerals (olivine) with CO2-charged fluids. Experiments have been designed to cause the formation and growth of serpentine and carbonate minerals from starting materials. Changes in fluid composition will be monitored over the duration of the experiments, as will the compositional changes in system solids. Special attention will be paid to the formation of carbonate minerals of various types and the abiotic synthesis of organic compounds in particular CO2, H2, HCOOH, CO, CH3OH, and CH4. Run reactants and products will be characterized and examined by petrographic and spectroscopic techniques. Using these resulting data, correlations will be made between mineral replacement reactions and fluid chemical changes. Additionally, changes in fluid chemistry will be used to determine stable and metastable heterogeneous phase equilibria, reaction pathways, and kinetic rates of both serpentinization and mineral carbonation reactions. Reaction path models will be used for the system Mg-Si-Fe-Al-Ca-Na-K-O-H-C both to help design the experiments and analyze results using thermodynamic and kinetic constraints.