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

ICDP支持旨在调查冰岛Vestmanaeyjar群岛Surtsey火山的形成和热液改造的持续钻探项目。在Surtsey的形成和演化中，Tephra和循环流体之间的快速而强烈的反应是至关重要的。这些玻璃-水相互作用过程在地壳-海洋地球化学预算中也很重要，它们支持特定适应的壳内微生物生命。该提案要求提供资金，对温度和渗透率在非洲大陆蚀变过程和速率中的作用进行全面和系统的调查。预算中还包括运营成本的一小部分，如果没有这些成本，就无法启动可持续发展。提出的工作利用X射线计算机显微层析成像(µ-CT)来成像和定量地确定盖板中孔隙空间的分布和连通性，并将这些参数与盖板蚀变反应的性质和程度联系起来。将使用显微和微量分析工作来确定第二相组合和矿物组成。对持续钻芯样品的这些检查将得到实验室和现场实验方法的补充，分别利用热液流动池和钻孔培养研究。在这两条研究路线中，直径19 mm的圆柱形Tephra主体将在1 Mpa和150°C的受控条件下，在15至24个月的时间内接受天然或人工溶液的处理。反应进度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进行测量。实验结束后，将进行微CT测量以及随后的显微镜和显微分析工作，以评估渗透率的空间分布以及次生矿物形成的程度和性质。将评估沸石和托贝莫来石等次生相形成的相对速率，并将其与渗透率演化相关。这些结果将使人们对年轻的海山和海洋岛屿中的热液物质转移及其对热液物质转移和与地质力学有关的结构发展的影响的总体机制有了新的认识。拟议的工作将与在可持续发展中合作的科学家的相关工作密切协调，以最大限度地提高特弗拉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性质的影响。

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.