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: 1259964
• 负责人: David Graham
• 金额: $ 29.22万
• 依托单位: Oregon State University
• 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 2016-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1259964&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.

大陆裂谷和洋脊是挥发性元素在地球内部和表面之间交换的关键场所。挥发物在裂谷/扩张的开始、火山演化和相关的地质灾害中起着核心作用。这项研究的特点主要挥发性浓度（H2O和CO2）和地幔源示踪剂（氦和氩同位素）的岩浆喷发沿着在阿拉伯海的亚丁湾洋中脊，因为这是一个洋中扩张中心在其形成和演化的早期阶段。 该研究还量化了该地区来自地幔的水通量。 亚丁湾是这项工作的一个独特地点，因为它是一个年轻的海洋盆地，受到非洲之角下阿法尔地幔柱流动的影响。地幔柱影响着沿着红海和亚丁湾西部的阿拉伯岩石圈底部;其广泛的影响被认为是由于软流圈岩浆通过裂谷从地幔柱流向扩张中心。然而，阿法尔烟柱对亚丁湾的穿透力明显较弱，这一点尚未得到很好的理解，可能与扩张脊的构造分段/不连续有关。 该研究将分析从以前的海洋学和采样考察中收集到的海底玄武岩玻璃，以确定主要元素组成，挥发性浓度（CO2，H2O，Cl，F和S）以及He和Ar同位素。亚丁玄武岩玻璃的初步结果揭示了一个强大的羽流信号，可能会成为迅速衰减与距离羽流轴。项目目标是确定部分熔融和脱气如何控制年轻海洋扩张中心的地幔挥发性特征。 地球化学证据（例如，3 He/4 He，40 Ar/36 Ar，4 He/40 Ar *，CO2/Nb，H2O/Ce）进行测定。研究结果使我们能够量化阿法尔羽流和上地幔沿沿着44°E至57°E之间这一新兴洋盆长度的挥发性通量的变化。结果还提供了一个基本的框架，地球物理和地球动力学模型输入的区域和较小规模的变化，地幔成分，部分熔融，以及热量和质量通量与大陆裂谷到海洋扩张的演变。 这项工作的更广泛影响包括支持两个机构的研究生和本科生，一个在EPSCoR州（俄克拉荷马州），利用现有的样本收集与以前的NSF支持，并利用NSF资助的分析设施在俄勒冈州州立大学和塔尔萨大学。研究结果将在机构网页以及国家科学基金会资助的实验室可用数据系统上进行描述。调查结果也将纳入调查人员讲授的课程。