EAGER: Thermo-hydro-chemical modeling framework for mid-ocean ridge hydrothermal systems

EIGER：大洋中脊热液系统的热-水-化学模拟框架目标是利用一类迅速发展的计算机模型，增进对发生在称为大洋中脊的65 000公里长的海底山脉海底热液系统之下的大型热液系统的了解。海水在海底岩石中循环时发生的化学交换影响海水中离子的平衡，并影响碳循环和地球气候。由此产生的对海底岩石的修改也影响了大陆火山活动和地球地幔的化学演化。该方法使用了现代热-水-化学建模程序和大规模并行计算。它是组织、解释和扩展几十年来从MOR热液系统研究中收集的数据的一种全新的方法。这些模型提供了一种方法，可以将观测结果概括为预测工具，可用于推断热液系统在不断变化的条件下如何运行。这类信息对更广泛的地球科学界来说是必不可少的。计算机模拟方法处于开发的早期阶段，因此受益于探索性研究的特别资金。从这个项目中获得的知识将提高理解地球气候是如何受自然过程控制的能力，以及为什么气候和海洋化学在过去的地质历史中是不同的。这一结果还将增强美国研究界使用高性能计算研究自然地球过程的能力。该项目的一个关键部分是通过参加正在进行的国际讲习班和短期课程，使包括学生在内的其他研究人员能够接触到这种方法。具体来说，这项研究涉及调整和开发协议，以使用过去40年来开发的热-水-化学(THC)程序ToughReact来模拟大洋中脊的热液过程。THC模型明确地将流体流动、热传递和矿物-流体化学反应耦合在一起，因此可以阐明影响水热系统行为的许多和可变参数之间的相互关系。研究计划包括运行数百次不同参数的模拟，通过一系列逐渐增加的复杂性来确定物理特征(热流、孔隙度、渗透率、裂缝间距、循环深度)和化学特征(裂缝和基质矿物学、蚀变矿物学、矿物-流体反应动力学)与流体化学演化、矿物蚀变和喷口流体成分模式的关系。这一进程是从稳态流动的二维模拟开始的，化学和矿物学演化持续了数百年，海底扩张将岩石移动一段相当于一到两个模拟网格区块的距离所需的大约时间。稳态模拟可以探索不同展布速率、不同循环深度、不同岩性结构、不同渗透率结构和不同加热剖面的流体循环和温度/蚀变分布的主要特征。下一步将通过将岩石基质及其伴随的温度和矿物学从海脊移开，并在海脊轴线添加新的热岩来模拟二维海底扩张。拟议的调查结果可能会对地球科学、海洋科学、行星科学和气候科学界产生广泛的影响。除了对海底热液系统的工作原理产生新的见解外，该项目还将为将现代的、多组分的反应性运输模拟应用于海洋地质和地球物理中更广泛的问题奠定基础。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

EAGER: Thermo-hydro-chemical modeling framework for mid-ocean ridge hydrothermal systemsThe objective is to use a rapidly developing class of computer models to advance understanding of the large-scale hydrothermal systems that occur beneath the 65,000 km-long submarine system of mountain ranges referred to as mid-ocean ridges (MOR). The chemical exchange that occurs as seawater circulates through seafloor rocks affects the balance of ions in seawater and influences the carbon cycle and Earth’s climate. The resulting modifications to the ocean floor rocks also affect continental volcanism and the chemical evolution of Earth’s mantle. The proposed approach uses modern thermo-hydro-chemical modeling codes and massively parallel computation. It is a fundamentally new way to organize, interpret, and extend data that have been gathered from decades of study of MOR hydrothermal systems. The models provide a way to generalize observations into predictive tools that can be used to infer how the hydrothermal systems operate under changing conditions. This type of information is essential to the broader Earth science community. The computer modeling approach is at an early stage of development and hence benefits from special funding for exploratory research. The knowledge derived from this project will improve the ability to understand how Earth’s climate is controlled by natural processes, and why climate and ocean chemistry were different in the geologic past. The results will also enhance the capabilities of the U.S. research community for using high-performance computing to study natural Earth processes. A key part of the project is to make the approach accessible to other researchers, including students, through participation in ongoing international workshops and short courses. In detail, the research involves adapting and developing protocols for using the Thermo-hydro-chemical (THC) code ToughReact, that has been developed over the past 40 years, to simulate the hydrothermal processes at midocean ridges. THC models explicitly couple fluid flow, heat transfer, and mineral-fluid chemical reactions, and hence can clarify the interrelationships between the many and variable parameters that affect the behavior of hydrothermal systems. The research plan involves running hundreds of simulations, with varying parameters, through a sequence of gradually increasing complexity to determine how physical characteristics (heat flux, porosity, permeability, fracture spacing, depth of circulation) and chemical characteristics (fracture and matrix mineralogy, alteration mineralogy, mineral-fluid reaction kinetics) relate to patterns of fluid chemical evolution, mineral alteration, and vent fluid compositions. The progression is to start with 2-dimensional simulations of steady state flow with chemical and mineralogical evolution proceeding for hundreds of years, the approximate time required for seafloor spreading to move the rocks a distance equal to one or two simulation grid blocks. The steady state simulations can be used to probe the main features of fluid circulation and temperature/alteration distribution for configurations representing different spreading rates, which also represent different circulation depths, lithologic structure, permeability structure, and heating profiles. The next step will be to simulate seafloor spreading in 2D, by migrating the rock matrix with its attendant temperature and mineralogy away from the ridge and adding new hot rock at the ridge axis. The results of the proposed investigation could have wide-ranging impacts in the Earth science, ocean science, planetary science, and climate science communities. In addition to producing new insights into the workings of seafloor hydrothermal systems, this project will lay groundwork for advancements in the application of modern, multi-component reactive transport simulations to broader problems in marine geology and geophysics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.