Mantle volatiles and attenuation in the East African Rift

东非裂谷的地幔挥发物和衰减

• 批准号: 1849700
• 负责人: Maryjo Brounce
• 金额: $ 39.26万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-04-01 至 2024-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1849700&HistoricalAwards=false
• 关键词: Mantle; volatiles; attenuation; East; African

The mantle under the East African Rift features one of the most prominent geophysical anomalies observed in Earth's upper mantle, defined by a broad region of very low seismic wave speeds. Though increased mantle temperatures could slow seismic wave speeds, constraints from erupted lava compositions indicate that the mantle in this region is warm, but not hot enough to account for the observed maximum slowness of seismic waves. Elevated concentrations of volatile elements (e.g., water, carbon) in the mantle can also slow seismic wave speeds, but these are unconstrained for the mantle along the East African Rift. Quantifying the abundance of water and carbon in the mantle in this region is critical to describing the magmatism that has occurred along the length of the rift, and its relationship to the process of rifting itself. Additionally, reconciling geophysical and geochemical models for the mantle in this region is a key test of the current understanding of Earth's mantle more broadly. This work will inform future field and experimental campaigns by presenting a synthesis of information that can be gleaned by existing sample sets and geophysical data sets. In addition to the scientific impacts, this work broadens the participation of underrepresented groups and supports several undergraduate and graduate students. This work will also inform an exhibit for the University of California-Riverside (UCR) Earth Sciences Museum.If the mantle is significantly water- or carbon-rich, this could lead to mantle melting at higher pressures and lower temperatures than for a dry and carbon-free mantle. The presence of melts may also slow seismic wave speeds. This work will constrain the mantle source volatile composition at individual volcanic edifices and assess the importance of elevated volatiles, temperatures, and melts on the extreme nature of the geophysical anomaly under the rift, and to the initiation and evolution of the rift itself. This work will test existing, quantitative relationships between petrological descriptions of the mantle and the properties of seismic waves in this region.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.

东非大裂谷下的地幔是地球上地幔中观察到的最突出的地球物理异常之一，由一个非常低的地震波速度的广阔区域定义。虽然地幔温度的升高可能会减慢地震波的速度，但来自喷发熔岩成分的限制表明，该地区的地幔是温暖的，但还不足以解释观测到的地震波的最大慢度。挥发性元素的浓度升高（例如，地幔中的水、碳）也可以减慢地震波的速度，但这些对沿着东非大裂谷的地幔来说是不受约束的。量化该地区地幔中的水和碳的丰度对于描述沿着裂谷长度发生的岩浆活动及其与裂谷过程本身的关系至关重要。此外，协调该地区地幔的地球物理和地球化学模型是对目前更广泛地了解地球地幔的关键考验。这项工作将通过综合现有样本集和地球物理数据集收集的信息，为今后的实地和实验活动提供信息。除了科学影响，这项工作扩大了代表性不足的群体的参与，并支持一些本科生和研究生。这项工作还将为加州大学河滨分校（UCR）地球科学博物馆的一个展览提供信息。如果地幔明显富含水或碳，这可能导致地幔在比干燥和无碳地幔更高的压力和更低的温度下熔化。熔融物的存在也可能减缓地震波的速度。这项工作将限制在个别火山机构的地幔源挥发性成分和评估的重要性，挥发物，温度升高，并融化的极端性质的地球物理异常下的裂谷，和裂谷本身的启动和演变。这项工作将测试现有的，定量关系之间的岩石学描述的地幔和属性的地震波在这一region.This奖项反映了NSF的法定使命，并已被认为是值得的支持，通过评估使用基金会的知识价值和更广泛的影响审查标准。