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

洋中脊代表了地球上火山活动产生新鲜海洋地壳和海底山脉的区域，因为两个构造板块分开了。该项目将测量地球上最大范围的中洋脊（即中大西洋脊）产生的火山岩的化学特征。这些测量结果将用于了解地幔的哪些部分正在融化，以及火山活动是连续发生还是脉冲发生。这项研究将有助于理解地球的大进化，因为大洋中脊是地球上新地壳的主要来源。地球上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大学地质博物馆举办一个名为“地球的海洋：现在和过去”的互动展览。这次展览将帮助公众，从学龄前儿童到老年人，了解大洋中脊在地球形成和不断重新浮出水面的重要性。洋中脊为了解地幔的同位素、岩性组成和演化、产生玄武岩岩浆的地下熔融过程以及形成新海洋地壳的喷发方式和频率提供了一个机会。虽然快速扩张的洋中脊（如东太平洋隆起）的融化过程和地壳构造的时间尺度受到了很好的限制，但对缓慢扩张的洋中脊（如中大西洋洋中脊）的研究相对较少。此外，中大西洋洋脊已被证明喷发出同位素和地球化学富集的熔岩，反映了洋脊下熔融机制中潜在的岩性非均质地幔源域和上涌地幔柱的潜在附近影响。本研究将对大西洋中脊45°N段形成同位素多样性海洋地壳的地幔组分、玄武岩熔岩形成并运至地表的熔融过程以及形成轴向火山脊的海洋地壳构造的时间尺度进行约束。为了实现这一目标，研究人员将测量从大西洋中脊45°N段收集的一套玄武岩样品中的主要元素和微量元素丰度，放射性同位素组成和u衰变系列核素。此外，将构建MAR下方的层析成像，并与化学和同位素解释相结合。这一多学科数据集将增强对缓慢扩张的中大西洋洋脊下方熔融的地幔岩性，这些熔融体如何分离、聚集和运输到地表的时间尺度和过程，以及沿着缓慢扩张的洋脊段的新鲜海洋地壳构造的时间进展的理解。这项工作将有助于科学界对地幔的性质和海洋地壳的构造有一个更完整、更全面的了解。这笔拨款还将通过在怀俄明大学地质博物馆举办一个名为“地球的海洋：现在和过去”的展览，提高公众对地球大洋中脊的认识。该奖项反映了美国国家科学基金会的法定使命，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。

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.