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

ICDP支持SUSTAIN钻井项目，该项目旨在调查冰岛Vestmanaeyjar群岛Surtsey火山的形成和热液变化。在Surtsey的形成和演化过程中，tephra与循环流体之间的快速和强烈反应至关重要。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地壳内微生物生命。该提案要求资金对温度和渗透率在温度变化过程和速率中的作用进行全面和系统的调查。预算中还包括运营费用的一小部分，没有这些费用，SUSTAIN就无法启动。提出的工作是利用x射线计算机微断层扫描（µ-CT）来成像和量化麻黄中孔隙空间的分布和连通性，并将这些参数与麻黄蚀变反应的性质和程度联系起来。显微和微量分析工作将用于确定次级相组合和矿物组成。对SUSTAIN岩心样品的这些检查将由实验室和实地的实验方法加以补充，分别利用热液流经细胞和钻孔孵化研究。在这两项研究中，圆柱形的麻药体（直径19毫米）将在高达1mpa和150°C的受控条件下置于自然或人工溶液中，持续时间为15至24个月。反应过程将在实验室使用伴随的微ct测量和流出溶液的化学成分进行测量。实验结束后，微ct测量以及随后的显微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。研究人员将对沸石和托伯莫里石等次生相的形成和古岩化的相对速率进行评价，并将其与渗透率演化联系起来。这些结果将对控制温体蚀变的一般机制及其对年轻海山和海洋岛屿温体热液质量传递和地质力学相关结构发育的影响提供新的见解。拟议的工作将与SUSTAIN内合作科学家的相关工作密切协调，以最大限度地提高tephra蚀变模型的新颖性和强度，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.