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.

大洋中脊代表了地球上火山活动正在产生新的海洋地壳和海底山脉的地区，因为两个构造板块分开了。该项目将测量地球上最大的大洋中脊（称为大西洋中脊）沿着产生的火山岩的化学特性。这些测量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脉冲发生。这项研究将有助于了解地球的更大演变，因为大洋中脊是地球上新地壳的主要来源。地球75%的岩浆活动发生在大洋中脊。这项工作还将有助于在怀俄明州大学地质博物馆举办题为“地球海洋：现在和过去”的互动展览。这次展览将有助于向从学龄前儿童到老年人的公众宣传洋中脊在地球形成和不断重塑表面方面的重要性。大洋中脊提供了一个机会，可以了解地球地幔的同位素和岩性组成及演变、产生玄武岩浆的地下熔融过程以及产生新洋壳的喷发方式和频率。在东太平洋海隆等快速扩张的洋中脊，地壳构造的融化过程和时间尺度受到很好的限制，而对大西洋中脊等缓慢扩张的洋中脊的研究则相对不足。此外，中大西洋海岭已被证明爆发同位素和地球化学富集的熔岩，反映潜在的岩性异质性地幔源域的次脊熔融制度和潜在的附近的影响，从上涌地幔柱。这项研究将限制造成沿大西洋中脊北纬45°段沿着同位素多样化的洋壳的地幔成分、玄武岩熔岩产生和输送到表面的熔融过程以及造成轴向火山脊的洋壳构造的时间尺度。为了实现这一目标，研究人员将测量从大西洋中脊45°N部分收集的一套玄武岩样品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。此外，将建立MAR下方的断层成像，并结合化学和同位素解释。这一多学科数据集将提高对缓慢扩张的中大西洋海岭下融化的地幔岩性的理解，这些熔体如何分离、聚集和输送到表面的时间尺度和过程，以及沿着缓慢扩张的海岭段的新洋壳构造的时间进展。这项工作将有助于使科学界对地幔的性质和海洋地壳的构成有一个更全面的了解。这笔赠款还将通过在怀俄明州大学地质博物馆举办一个名为“地球海洋：现在和过去”的展览来提高公众对地球海洋中脊的认识。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。