Collaborative Research: Fingerprinting source-to-sink connections for deep-marine vitriclastic deposits and their association to caldera formation on Axial Seamount

世界上最活跃的火山省份都在海底。由于形成大陆的厚地壳岩石的干扰很少，而且海底喷发的岩浆更接近且更能代表其在地幔中的来源，过去 50 年的海底火山研究有助于改变我们对岩浆和岩浆房动力学和演化的认识。它们还提高了我们对地球及其构造板块如何运作以及地壳和地幔储层之间地球化学元素循环的理解，反之亦然。 话虽这么说，除了少数以岛屿形式出现在海洋之上的火山外，大多数海底火山都位于海面以下数千米处，因此很难知道它们何时或如何喷发。 这项研究将通过检查沉积在海平面以下 1,400 米、距俄勒冈州西海岸约 500 公里的轴状火山破火山口及其周围的火山产生的沉积物，提高我们对这些过程的了解。该研究的重点是了解轴状火山破火山口形成的历史，确定玻璃碎屑形成的机制及其在海底火山地层学研究中的适用性。 Axial 是世界上监测和采样最彻底的海山。分析中将使用由沉积岩芯、勺袋和岩石组成的样本以及分辨率为 1 米的破火山口测深图，以及沉积学、地层学和地球化学分析方法。 该项目的更广泛影响包括支持两名早期职业科学家、研究生培训以及使用国家科学基金会资助的新的主要海洋观测计划网络。影响还包括与两名性别在科学领域代表性不足的科学家的合作，两人都受雇于爱达荷州和罗德岛州 EPSCoR 州（即没有获得大量联邦资助的州）的机构。其他影响包括与德国和法国科学家的国际合作，以及通过制作有关火山和火山喷发的教学材料向 K-5 学校进行推广。该研究的目标是确定轴海山在火山口形成期间的物理和化学演化，并增加我们对海底火山喷发类型、破碎过程和玻璃质扩散机制的了解。要测试的假设包括（1）玻璃碎屑沉积物的物理和化学特征可用于确定其喷发、碎裂和扩散起源，（2）岩相记录与岩浆退缩和破火山口塌陷相关的岩浆储层加深。技术将使用 X 射线衍射和扫描电子能色散光谱检查玻璃碎屑的矿物学，以限制其起源的温度和化学条件。氢和氧的稳定同位素以及 Cl/K2O 比率将用于确定玻璃质碎裂和海水同化到岩浆期间的岩浆-海水相互作用。将进行详细的形态、结构和粒度分析，以确定碎屑是否具有风岩浆起源。将从玻璃质样品中提取的样品通过二次离子质谱法测量橄榄石中 80 种玻璃包裹体的岩浆挥发物。

The most active volcanic provinces in the world are under the sea. Because there is little interference from the thick crustal rocks that form the continents and because the magmas that erupt on the seafloor are closer to and more representative of their source in the mantle, submarine volcanic studies over the last 50 years have helped to transform our knowledge of magma and magma chamber dynamics and evolution. They have also improved our understanding of how the Earth and its tectonic plates work and the cycling of geochemical elements between crustal and mantle reservoirs and vice versa. This being said, with the exception of a few that peek above the ocean as islands, most seafloor volcanoes lie thousands of meters below the sea surface making it very difficult to know when or how they are erupting. This research will improve our knowledge of these processes by examining volcanically generated sediments deposited in and around the Axial Volcano caldera 1,400 meters below sealevel and about 500 km off the west coast of Oregon. The research is focused on understanding the history of Axial Volcano caldera formation and determining the mechanisms of vitriclastic formation and the applicability of their use in volcanic stratigraphic studies on undersea volcanoes. Axial is the most thoroughly monitored and sampled seamount in the world. Samples consisting of sediment cores, scoop bags, and rocks as well as bathymetric maps of the caldera at 1 meter resolution will be used in the analysis as will sedimentologic, stratigraphic, and geochemical analytical approaches. Broader impacts of the project include support of two early career scientists, graduate student training, and use of the new, major, NSF-funded Ocean Observing Initiative network. Impacts also include collaboration with two scientists whose gender is under-represented in the sciences, both of whom are employed at institutions in the EPSCoR states (i.e., states that do not receive significant amounts of federal funding) of Idaho and Rhode Island. Other impacts include international collaboration with German and French scientists and outreach to K-5 schools by producing materials for instruction on volcanoes and volcanic eruptions.Goals of the research are to define the physical and chemical evolution of Axial Seamount through the time of caldera formation and increase our understanding of submarine volcano eruption styles, fragmentation processes, and vitriclast dispersal mechanisms. Hypotheses to be tested include (1) the physical and chemical characteristics of vitriclastic deposits can be used to fingerprint their eruption, fragmentation, and dispersal origins and (2) lithofacies record magma reservoir deepening associated with magma withdrawal and caldera collapse.Technical The mineralogy of vitriclasts will be examined using X-ray diffraction and scanning electron energy dispersive spectroscopy to constrain their temperature and chemical conditions of origin. Stable isotopes of Hydrogen and Oxygen as well as Cl/K2O ratios will be used to determine magma-seawater interaction during vitriclast fragmentation and seawter assimilation into the magma. A detailed morphometric, textural, and grain size analysis will be carried out to determine if clasts are of phreatomagmatic origin. Magmatic volatiles will be measured in 80 glass inclusions in olivine by secondary ion mass spectrometry from samples taken from vitriclasts.