NSFGEO-NERC: Imaging the magma storage region and hydrothermal system of an active arc volcano

NSFGEO-NERC：对活弧火山的岩浆储存区域和热液系统进行成像

• 批准号: NE/X000656/1
• 负责人: Timothy Minshull
• 金额: $ 59.23万
• 依托单位: University of Southampton
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2025
• 资助国家: 英国
• 起止时间: 2025 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FX000656%2F1
• 关键词: NSFGEO; NERC; Imaging; magma; storage

Our project will use a powerful and only recently available geophysical technique to probe the interior of the hydrothermal system of an active volcano and thus gain unique new insights into how such systems work. Our target is Brothers volcano in the Pacific "Ring of Fire" about 400 km north of New Zealand. This volcano hosts one of the most active submarine hydrothermal systems in the world. It has been a focus for international study over the past two decades, culminating in scientific drilling in 2018 to recover samples and make measurements up to depths of nearly 450 m below the seafloor. Consequently it arguably the best-studied volcano of its type in the world. Hydrothermal fluids circulate in almost all volcanic systems, and this circulation is the main mechanism of chemical and heat exchange between the solid Earth and the oceans. Water sinking into the crust is heated by hot or molten rocks a few kilometres below the surface, then returns to the surface. Chemicals are exchanged with the rocks and can become concentrated in the rising fluids. Molten rock itself is an additional source of water and also gases. These fluids can vent vigorously into the ocean. As they cool and mix with seawater, the elements concentrated within them precipitate, sometimes forming large deposits containing metals such as copper and gold. Studies of the fluids, their deposits on the seabed and the surrounding altered rock have shown that: venting may either be focused or diffuse; vent fluids can have a variety of compositions, temperatures and origins; and the nature of the fluids can change as the volcano evolves. However, little is known about what lies beyond the few hundred metres depth range that can be accessed by drilling. Thus the shape of flow paths at depth and their relationship to the underlying hot or molten rock remain poorly understood. Our experiment involves using a powerful transmitter that sends electromagnetic waves into the volcano and measuring the resulting electromagnetic fluctuations using receivers on the seafloor and others towed behind the transmitter. Our measurements will be sensitive to the electrical resistivity beneath the seabed down to depths of several kilometres. Solid volcanic rocks have high resistivities, but rocks become much more conductive when they start to melt, resulting in a large contrast. Hot hydrothermal fluids are even more conductive, particularly when they are salty. Metallic mineral deposits at or close to the seabed can be more conductive again. Thus our proposed controlled source electromagnetic (CSEM) techniques can be used to image all of these features. Three-dimensional CSEM imaging is now feasible, and we will generate such images for the first time at a submarine volcano, thus achieving unprecedented resolution.We will use our resistivity image to estimate the size, shape, temperature and melt content of the heat source beneath the hydrothermal system; the temperature and salinity of the hydrothermal fluids and the shape of the pathways that they take within the crust; and the size and shape of the resulting mineral deposits. We will combine these images with results from international collaborators, including major new experiments involving sending sound waves through the volcano and further drilling and computer modelling of its evolution over time. Our results will show how the shape and internal structure of the heat source below and the faulting of the crust above that heat source drive patterns of hydrothermal circulation and thus the chemical alteration of the crust. This understanding can then be applied to other volcanoes where the subsurface structure is less well known. We will also determine the relative contributions of circulating seawater and fluids released from the heat source to the formation of mineral deposits near the seafloor, and work with partners in the mining industry to assess implications for exploration for such deposits now on land.

我们的项目将使用一种强大且仅最近可用的地球物理技术来探测活跃火山的水热系统的内部，从而获得对这种系统如何工作的独特新见解。我们的目标是在新西兰以北约400公里处的太平洋“火环”的兄弟火山兄弟。该火山是世界上最活跃的海底热液系统之一。在过去的二十年中，这一直是国际研究的重点，最终在2018年进行了科学钻探，以回收样品，并将测量最高到海底近450 m的深度。因此，它可以说是世界上最好的火山。水热流体几乎在所有火山系统中循环，这种循环是固体和海洋之间化学和热量交换的主要机制。水沉入地壳中的水被热或熔融岩石在地面以下几公里处加热，然后返回表面。化学物质与岩石交换，并可以集中在上升的液体中。熔融岩石本身是水的附加来源，也是气体。这些液体可以大力排出海洋。当它们冷却并与海水混合时，集中在其中的元素会沉淀，有时会形成含有铜和金等金属的大沉积物。对流体的研究，它们在海床上和周围改变的岩石上的沉积物表明：通风可以聚焦或弥漫；排气流体可以具有多种组成，温度和起源；随着火山的发展，液体的性质可能会改变。但是，对于可以通过钻孔访问的几百米深度范围的范围内，知之甚少。因此，深度处流动路径的形状及其与潜在的热或熔融岩石的关系仍然知之甚少。我们的实验涉及使用强大的发射器，该发射器将电磁波发送到火山中，并使用海底上的接收器和发射机后面的其他接收器测量所得的电磁波动。我们的测量将对海底下方到几公里深处的电阻率敏感。固体火山岩具有高电阻率，但是岩石开始融化时会变得更大，导致对比度很大。热热液液的导电更具导电性，尤其是当它们咸时。金属矿物质沉积物或靠近海床的矿物质可以再次引导。因此，我们提出的受控源电磁（CSEM）技术可用于成像所有这些功能。现在可行的三维CSEM成像，我们将在海底火山上首次生成此类图像，从而实现前所未有的分辨率。我们将使用我们的电阻率图像来估计水热系统下方热源的大小，形状，温度，温度和融化含量；水热流体的温度和盐度以及它们在地壳内的途径的形状；以及所得矿物沉积物的大小和形状。我们将将这些图像与国际合作者的结果相结合，包括涉及通过火山发送声波的主要新实验，以及随着时间的推移进化的进一步钻孔和计算机建模。我们的结果将显示下面热源的形状和内部结构以及上面的地壳的断层，热源驱动热液循环的模式，从而驱动了地壳的化学改变。然后可以将这种理解应用于地下结构不太众所周知的其他火山。我们还将确定从热源释放的循环海水和液体对海底附近的矿物沉积物形成的相对贡献，并与采矿业的合作伙伴一起评估对目前在土地上的这种沉积物的影响。