Collaborative Research: Understanding the Processes and Timescales of Basalt Petrogenesis and Oceanic Crustal Construction at Slow-Spreading Mid-Ocean Ridges

合作研究：了解缓慢扩张的大洋中脊玄武岩成岩和洋壳构造的过程和时间尺度

• 批准号: 2317705
• 负责人: Richard Aster
• 金额: $ 3.71万
• 依托单位: Colorado State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-07-01 至 2026-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2317705&HistoricalAwards=false
• 关键词: Collaborative; Research; Understanding; Processes; Timescales

Mid-ocean ridges represent regions of the planet where volcanic activity is generating fresh oceanic crust and submarine mountain chains as two tectonic plates spread apart. This project will measure the chemical characteristics of volcanic rock produced along the planet’s largest extent of mid-ocean ridge, known as the Mid-Atlantic Ridge. The measurements will be used to understand which components of the mantle are melting and whether volcanic activity happens continuously or in pulses. This research will aid in understanding the larger evolution of the planet, as mid-ocean ridges serve as the dominant source of new crust on the Earth. Seventy-five percent of the Earth’s magmatic activity occurs at mid-ocean ridges. This work will also help to develop an interactive exhibit at the University of Wyoming’s Geological Museum titled “Earth’s Oceans: Now and in the Past”. This exhibit will help to inform the public, from preschoolers to senior citizens, of the importance of mid-ocean ridges in the formation and continuous resurfacing of the Earth. Mid-ocean ridges offer an opportunity to understand the isotopic and lithological composition and evolution of the Earth’s mantle, the subsurface melt processes which generate basaltic magmas, and the eruptive styles and frequency which give rise to fresh oceanic crust. While the melt processes and timescales of crustal construction are well-constrained at fast-spreading mid-ocean ridges such as the East Pacific Rise, slow-spreading ridges such as the Mid-Atlantic Ridge remain comparatively understudied. Furthermore, the Mid-Atlantic Ridge has been shown to erupt isotopically and geochemically enriched lavas, reflecting potentially lithologically heterogenous mantle source domains in the sub-ridge melting regime and potential nearby influences from upwelling mantle plumes. This research will constrain the mantle components which give rise to isotopically diverse oceanic crust along the 45°N segment of the Mid-Atlantic Ridge, the melting processes by which basaltic lavas are generated and transported to the surface, and the timescales of oceanic crustal construction that result in axial volcanic ridges. To achieve this, researchers will measure major and trace element abundances, radiogenic isotopic compositions, and U-decay series nuclides from a suite of basalt samples collected from the 45°N segment of the Mid-Atlantic Ridge. In addition, tomographic imaging from beneath MAR will be constructed and coupled with the chemical and isotopic interpretations. This multi-disciplinary data set will enhance the understanding of the mantle lithologies which melt beneath the slow-spreading Mid-Atlantic Ridge, the timescales and processes of how these melts are segregated, aggregated, and transported to the surface, and the temporal progression of fresh oceanic crustal construction along slow-spreading ridge segments. This work will help to provide the scientific community with a more complete, global understanding of the nature of the Earth’s mantle and how oceanic crust is constructed. This grant will also enhance the general public’s understanding of the Earth’s Mid-Ocean ridges by creating an exhibit at the University of Wyoming’s Geological Museum titled- “Earth’s Oceans: Now and in the Past”.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.

大洋中脊代表着地球，当两个构造板块分开时，火山活动正在产生新鲜的洋壳和海底山脉。该项目将测量沿地球最大范围的大洋中脊产生的火山岩的化学特征。测量结果将用于了解地幔的哪些成分正在融化以及火山活动是连续发生还是间歇发生。这项研究将有助于了解地幔的更大演化。由于洋中脊是地球上新地壳的主要来源，地球 75% 的磁活动发生在洋中脊。怀俄明州地质博物馆的标题为“地球的海洋：现在和过去”，该展览将有助于让从学龄前儿童到老年人的公众了解洋中脊在形成和持续过程中的重要性。地球表面的重生提供了一个机会来了解地幔的同位素和岩性组成和演化、产生玄武岩岩浆的地下熔化过程以及产生新鲜洋壳的喷发方式和频率。融化过程和地壳构造的时间尺度在快速扩张的洋中脊（如东太平洋海隆）和缓慢扩张的洋中脊（如太平洋海隆）受到很好的限制。此外，大西洋中脊的研究相对较少，已显示出同位素和地球化学丰富的熔岩，反映了下脊熔化状态中潜在的岩性异质地幔源域以及上升的地幔柱的潜在影响。研究将限制沿大西洋中脊北纬 45° 段产生同位素多样化洋壳的地幔成分，熔化过程通过玄武岩熔岩产生并输送到地表，以及形成轴向火山脊的海洋地壳构造的时间尺度。为了实现这一目标，研究人员将测量一组中的主要和微量元素丰度、放射性同位素组成和 U 衰变系列核素。收集自大西洋中脊北纬 45° 段的玄武岩样本 此外，还将构建 MAR 下方的断层扫描成像，并将其与化学和同位素结合起来。这个多学科数据集将增强对缓慢扩张的大西洋中脊下方熔化的地幔岩性、这些熔化物如何分离、聚集和输送到地表的时间尺度和过程以及时间的理解。这项工作将有助于科学界更全面地了解地幔的性质以及洋壳的构成方式。还将通过在怀俄明大学地质博物馆举办题为“地球海洋：现在和过去”的展览，增强公众对地球中洋山脊的了解。该奖项反映了 NSF 的法定使命，并被认为是值得的通过使用基金会的智力优势和更广泛的影响审查标准进行评估来提供支持。