Asthenospheric melting and melt-induced evolution of the lithosphere beneath the Colorado Plateau and the Basin and Range from a seismic characterization of mantle layering

根据地幔分层的地震特征研究科罗拉多高原和盆地山脉下方岩石圈的软流圈熔融和熔融引起的演化

• 批准号: 2045264
• 负责人: James Gaherty
• 金额: $ 8.31万
• 依托单位: Northern Arizona University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-07-01 至 2022-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2045264&HistoricalAwards=false
• 关键词: Asthenospheric; melting; melt; induced; evolution

Partial melting in the Earth's upper mantle plays a key role in controlling surface volcanism. It also impacts the evolution of tectonic plates and the deformation of the hot mantle underneath, called the asthenosphere. In recent years, the continental United States has been blanketed by EarthScope's Transportable Array, a program that deployed thousands of seismic instruments. The collected data provide unprecedented new constraints on the structure of the uppermost mantle, informing its dynamics and history of formation and alteration. Here, the researchers analyze the data from the Colorado Plateau, an area with ancient Proterozoic crust. This area has remained relatively undeformed through multiple compression episodes and subsequent extension of the surrounding Basin and Range. The rise of the Plateau from near sea level to its current elevation is not well understood. The volcanism of the Basin and Range is now actively encroaching on the ancient Plateau. By combining seismology and thermodynamic modeling, the team maps out the partial melt and alteration of the uppermost mantle. This project brings new light on the past evolution and present state of an important region of the southwestern United States. It also supports an early-career female scientist, the principal investigator, and provides training to an undergraduate student in the field of seismology.The team investigates the Colorado Plateau region, where disparate tectonic settings are juxtaposed within a small geographical area. The researchers use surface-wave dispersion data and information derived from S-to-P receiver functions about sharp velocity gradients in the upper mantle. They calculate accurate seismic-velocity models which employ a geologically reasonable layered framework. The models build on the Principal Investigator's previous work with receiver functions, which provides the layered lithosphere-asthenosphere framework in which to invert the dispersion data. The team combine seismic analysis with thermodynamic modeling in a self-consistent way to estimate regional velocity structures. The modeling accounts for the composition, pressure and temperature, as well as melt fraction at depth. These estimates are constrained by compositional and temperature data from the abundant volcanism and xenoliths in the area.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

地球上地幔的部分熔融在控制地表火山活动中起着关键作用。它还影响构造板块的演化和下方热地幔（称为软流圈）的变形。近年来，美国大陆已被 EarthScope 的可移动阵列覆盖，该计划部署了数千台地震仪器。收集到的数据为最上地幔的结构提供了前所未有的新约束，揭示了其动力学以及形成和变化的历史。在这里，研究人员分析了来自科罗拉多高原的数据，该地区拥有古老的元古代地壳。通过多次压缩以及随后周围盆地和山脉的扩展，该区域保持相对未变形。高原从接近海平面上升到目前海拔的过程尚不清楚。盆地和山脉的火山活动现在正在积极侵蚀古老的高原。 通过结合地震学和热力学模型，研究小组绘制出了最上地幔的部分熔化和蚀变。 该项目为美国西南部一个重要地区的过去演变和现状提供了新的线索。它还为一位职业生涯早期的女科学家（首席研究员）提供支持，并为一名本科生提供地震学领域的培训。该团队调查了科罗拉多高原地区，该地区的一个小地理区域内并置有不同的构造环境。研究人员使用表面波色散数据和从 S-to-P 接收器函数获得的有关上地幔急剧速度梯度的信息。他们计算了精确的地震速度模型，该模型采用了地质上合理的分层框架。这些模型建立在首席研究员之前的接收函数工作的基础上，该函数提供了分层的岩石圈-软流圈框架，可在其中反演色散数据。该团队以自洽的方式将地震分析与热力学建模相结合，以估计区域速度结构。该模型考虑了成分、压力和温度，以及深度的熔体分数。这些估计受到该地区丰富的火山活动和捕虏体的成分和温度数据的限制。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。