CSEDI Collaborative Research: Integrating Seismological, Rheological and Petrological Studies of Melt Production in Subduction Zones

CSEDI 合作研究：整合俯冲带熔体生产的地震学、流变学和岩石学研究

• 批准号: 1067689
• 负责人: Karen Fischer
• 金额: $ 4.01万
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-15 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1067689&HistoricalAwards=false
• 关键词: CSEDI; Collaborative; Research; Integrating; Seismological

The most explosive, deadly volcanic eruptions occur in subduction zones. Their occurrence and explosivity is intimately tied to the transport of water and other volatiles to great depth, and its release into hot mantle or along the plate boundary. Yet, understanding how volatiles released from subducting plates produce melts within the mantle wedge of subduction zones remains a challenge. A series of recent seismic and petrologic projects in subduction zones and results from the laboratory have dramatically increased the available information on these processes, and preliminary analyses of these data have begun to place bounds on the extent and depths of melting, style of melt transport, and variations between sites. This proposal plans to take the next step, the integration of geophysical observations, geochemical measurements, and rheological models, to address fundamental problems regarding melting process in the mantle. We will compare recent results from the Nicaragua-Costa Rica subduction zone, which exhibits strong along-strike variations in geophysical and geochemical observations, with those from the Marianas where volcanoes sample across-strike from the arc front to active back-arc spreading center. Broadband imaging in Central America and the Marianas indicates a region of flowing hot mantle from seismic attenuation and P-wave velocities, mantle fabric from shear-wave splitting measurements, and the geometry of melt transport from Vp/Vs anomalies. These results also show clear along-strike variations in most parameters, interpretable as variations in slab hydration, melt transport, and mantle wedge H2O content. In both regions, extensive sampling and analysis of volcanic products has provided for the first time direct measurement of magmatic water content, which appears to vary in tandem with classic indicators of slab fluid/sediment in Central America, and with distance from the arc front in the Marianas. The integration of these observations will be made possible by advances in our understanding of mantle rheology in the presence of water and melt, including both experimental and theoretical breakthroughs, for example on the behavior of melt under shearing conditions and on the physical controls on grain size, and on quantitative parameterizations of melt fabric. Our approach will be to integrate all datasets in a consistent manner, then iteratively test theoretical predictions against them. Results should distinguish models of melt generation and transport, for example of vertical porous flow, inclined flow, or ascent of cold diapirs. Once calibrated, the relationships needed to make these comparisons will be made available to interpret structure in other subduction zones and regions of melt production globally. The integration of disparate observations is a key step in making them understandable to a wide audience, and this integrated multidisciplinary approach will be tested in undergraduate classrooms and graduate seminars. The calibration of relationships between seismic observables and thermodynamic melting parameters should be broadly applicable and serve to enhance infrastructure for research.

俯冲带中最爆炸，致命的火山喷发发生。 它们的发生和爆炸性与水和其他挥发物的运输密切相关，并释放到热地幔或沿板边界中。 然而，了解从俯冲板中释放的挥发物如何在俯冲带的地幔楔内产生熔体仍然是一个挑战。 俯冲区域中的一系列地震和岩石学项目以及实验室的结果大大增加了有关这些过程的可用信息，并且这些数据的初步分析已经开始在融化的程度和深度，融化风格，熔体运输方式以及站点之间的变化方面构成界限。该提案计划采取下一步，地球物理观测，地球化学测量和流变学模型的整合，以解决有关地幔熔化过程的基本问题。我们将比较尼加拉瓜 - 科斯塔rica俯冲带的最新结果，该区域在地球物理和地球化学观测中表现出巨大的沿撞击变化，以及来自玛丽安娜的玛丽安娜（Marianas）的火山从弧线跨弧线到活动的跨盘群进行到活跃的背面差异中心。 中美洲和玛丽安娜的宽带成像表明，地震衰减和p波速度，剪切波分裂测量的地幔织物以及从VP/VP异常的熔体传输的几何形状。 这些结果还显示了大多数参数的明显沿形式变化，可以解释为平板水合，熔体传输和地幔楔H2O含量的变化。在这两个区域中，火山产品的广泛采样和分析都是首次直接测量岩浆水含量，它们似乎与中美洲的经典板流体/沉积物指标有所不同，并且距离玛丽安娜的弧线距离。通过在存在水和熔体的情况下，我们对地幔风湿病的理解，包括实验性和理论突破，例如在剪切条件下的行为以及对晶粒尺寸的物理控制以及梅尔特材料的定量参数化的物理控制方面，将实现这些观察结果的整合。我们的方法是以一致的方式集成所有数据集，然后迭代地测试针对它们的理论预测。结果应区分熔融产生和运输的模型，例如垂直多孔流动，倾斜流或冷底盘的上升。一旦校准，将使这些比较所需的关系可以在全球其他俯冲带和熔体生产区域中解释结构。不同观察的整合是使他们对广泛的受众可以理解的关键步骤，并且这种综合的多学科方法将在本科教室和研究生研讨会中进行测试。地震可观察物与热力学融化参数之间关系的校准应广泛适用，并用于增强基础设施的研究。