Collaborative Research: Mantle Volatiles in an Emerging Ocean Basin: H2O, CO2, and He & Ar Isotopes in Basalts from the Gulf of Aden Spreading Center System

合作研究：新兴洋盆中的地幔挥发物：H2O、CO2 和 He

• 批准号: 1259916
• 负责人: Peter Michael
• 金额: $ 7万
• 依托单位: University of Tulsa
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-08-01 至 2018-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1259916&HistoricalAwards=false
• 关键词: Collaborative; Research; Mantle; Volatiles; Emerging

Continental rifts and ocean spreading ridges are key places where volatile elements are exchanged between Earth's interior and its surface. Volatiles play a central role in the initiation of rifting/spreading, in volcanic evolution, and in associated geologic hazards. This research characterizes major volatile concentrations (H2O and CO2) and mantle source tracers (helium and argon isotopes) in magma erupted along the mid-ocean ridge in the Gulf of Aden in the Arabian Sea because this is a mid-ocean spreading center in its early stages of formation and evolution. The research also quantifies the flux of water coming from the mantle in the region. The Gulf of Aden is a unique locality for this work because it is a young ocean basin influenced by flow from the Afar mantle plume under the Horn of Africa. The plume affects the base of the Arabian lithosphere along the Red Sea and the western part of the Gulf of Aden; and its widespread influence is thought to result from the channeling of asthenospheric magma from the plume to the spreading center by rifts. However, the Afar Plume's apparent weaker penetration into the Gulf of Aden is not well understood and may be related to tectonic segmentation/discontinuities of the spreading ridge. The research will analyze submarine basalt glasses that were collected from previous oceanographic and sampling expeditions to the area for major element composition, volatile concentrations (CO2, H2O, Cl, F and S), and He and Ar isotopes. Initial results for Aden basalt glasses reveal a strong plume signal that may become rapidly attenuated with distance from the plume axis. Project goals are to determine how partial melting and degassing control mantle volatile signatures in young ocean spreading centers. Geochemical evidence (e.g., 3He/4He, 40Ar/36Ar, 4He/40Ar*, CO2/Nb, H2O/Ce) in about 40 basalt glasses from this region will be used to make this determination. Results of the study allow us to quantify variation in the volatile flux from the Afar plume and the upper mantle along the length of this emerging ocean basin between 44°E and 57°E. The results also provide a basic framework needed for geophysical and geodynamic models in terms of model input for regional and smaller scale variations in mantle composition, partial melting, and the heat and mass flux associated with the evolution from continental rifting to oceanic spreading. Broader impacts of the work include support of graduate and undergraduate students at two institutions, one in an EPSCoR state (Oklahoma), leverages existing samples collected with prior NSF support, and utilization of NSF-funded analytical facilities at Oregon State University and the University of Tulsa. Results will be described on institutional web pages as well as NSF-funded publically available data systems. Findings will also be incorporated into classes taught by the investigators.

大陆裂谷和海洋扩张脊是地球内部和表面之间挥发性元素交换的关键场所，在裂谷/扩散的引发、火山演化以及相关地质灾害中发挥着核心作用。沿着墨西哥湾洋中脊喷发的岩浆中的（H2O和CO2）和地幔源示踪剂（氦和氩同位素）亚丁位于阿拉伯海，因为这是形成和演化早期阶段的海洋中部扩散中心，该研究还量化了来自该地区地幔的水通量，亚丁湾是这项工作的独特地点。因为它是一个年轻的海洋盆地，受到非洲之角下方阿法尔地幔柱流的影响，该地幔柱影响了红海沿岸的阿拉伯岩石圈底部和亚丁湾西部地区，并且其影响被认为是广泛的。结果然而，阿法尔岩浆对亚丁湾的明显较弱渗透尚不清楚，这可能与扩张脊的构造分割/不连续性有关。分析从之前对该地区的海洋学和采样探险中收集的海底玄武岩玻璃的主要元素成分、挥发性浓度（CO2、H2O、Cl、F 和 S），以及亚丁玄武岩玻璃的初步结果揭示了强烈的羽流信号，该信号可能会随着距羽流轴的距离而迅速减弱。该项目的目标是确定部分熔融和脱气如何控制年轻海洋扩散中心的地幔挥发特征。 （例如，3He/4He、40Ar/36Ar、4He/40Ar*、CO2/Nb、H2O/Ce）约 40该地区的玄武岩玻璃将用于进行这一测定，研究结果使我们能够量化阿法尔地幔柱和上地幔在 44°E 至 57°E 之间这一新兴海洋盆地长度上的挥发通量的变化。研究结果还提供了地球物理和地球动力学模型所需的基本框架，包括地幔成分、部分熔融以及与大陆裂谷到海洋扩张演化相关的热量和质量通量的区域和较小尺度变化的模型输入。这项工作的主要内容包括对两个机构的研究生和本科生的支持，其中一个机构位于 EPSCoR 州（俄克拉荷马州），利用先前在 NSF 支持下收集的现有样本，以及利用 NSF 资助的俄勒冈州立大学和塔尔萨大学的分析设施。结果将在机构网页以及国家科学基金会资助的公开数据系统上进行描述，研究结果也将纳入研究人员教授的课程中。