Rates and processes of tephra alteration in Surtsey volcano: a combined observational and experimental approach

ICDP支持SUSTAIN钻探项目，该项目旨在调查冰岛Vestmanaeyjar群岛Surtsey火山的形成和热液蚀变。 火山灰和循环流体之间快速而强烈的反应在苏尔特塞的形成和演化中至关重要。 这些玻璃-水相互作用过程在地壳-海洋地球化学收支中也很重要，它们支持特别适应的壳内微生物生命。 该提案要求提供资金，对温度和渗透性在火山灰蚀变过程和速率中的作用进行全面和系统的调查。 预算中还包括一小部分业务费用，没有这些费用，就无法启动持续发展。 这项工作利用X射线计算机显微断层扫描（µ-CT）对火山灰中孔隙空间的分布和连通性进行成像和量化，并将这些参数与火山灰蚀变反应的性质和程度联系起来。 显微镜和微观分析工作将用于识别次生相组合和矿物成分。 对SUSTAIN岩心样品的这些检查将辅之以实验室和实地实验方法，分别利用热液流通池和钻孔培养研究。 在这两条研究路线中，火山灰的圆柱体（直径19毫米）将在高达1 MPa和150°C的受控条件下，在天然或人工溶液中持续15至24个月。 将在实验室中使用伴随的μ-CT测量和流出溶液的化学成分来测量反应进程。 实验结束后，µ-CT测量和随后的显微镜和微分析工作将评估渗透率的空间分布以及次生矿物形成的程度和性质。 将评估Palagonitization和形成第二相（如沸石和雪硅钙石）的相对速率，并将其与渗透率演变联系起来。 这些结果将产生新的见解火山灰蚀变的一般机制及其后果热液质量转移和地质力学相关的纹理发展火山灰机构在年轻的海山和海洋岛屿。 拟议的工作将与SUSTAIN内部合作科学家的相关努力密切协调，以最大限度地提高火山灰蚀变模型的新奇和强度及其对（生物）地球化学过程和岩石力学特性的影响。

ICDP supports the SUSTAIN drilling project aimed at investigating the formation and hydrothermal alteration of Surtsey volcano in the Vestmanaeyjar archipelago, Iceland. Rapid and intense reactions between tephra and circulating fluids were critical in the formation and evolution of Surtsey. These processes of glass-water interaction are also important in crust-ocean geochemical budgets and they support specifically adapted intracrustal microbial life. This proposal requests funds to conduct comprehensive and systematic investigations of the role of temperature and permeability in the processes and rates of tephra alteration. Also budgeted are a fraction of the operational costs, without which SUSTAIN cannot be launched. The work proposed makes use of x-ray computer microtomography (µ-CT) to image and quantify the distribution and connectedness of pore space in tephra and to relate these parameters to the nature and extent of tephra alteration reactions. Microscopic and microanalytical work will be used to identify the secondary phase assemblages and mineral compositions. These examinations of SUSTAIN drill core samples will be complemented by laboratory- and field-based experimental approaches, making use of hydrothermal flow-through cells and borehole incubation studies, respectively. In both lines of study, cylindrical bodies of tephra (19 mm in diameter) will be subjected to natural or artificial solutions for durations between 15 and 24 months and under controlled conditions of up to 1 MPa and 150°C. The reaction progress will be gauged in the laboratory using concomitant µ-CT measurements and chemical compositions of outflow solutions. After termination of the experiments, µ-CT measurements and subsequent microscopy and microanalytical work will assess the spatial distribution of permeability and the extent and nature of secondary mineral formation. The relative rates of palagonitization and formation of secondary phases such as zeolites and tobermorite will be evaluated and related to permeability evolution. These results will yield new insights into the general mechanisms governing tephra alteration and their consequences for hydrothermal mass transfers and geomechanically relevant textural development of tephra bodies in young seamounts and oceanic islands. The proposed work will be closely coordinated with related efforts by collaborating scientists within SUSTAIN to maximize the novelty and strength of the tephra alteration model and its implications for (bio)geochemical processes and rock mechanical properties.