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

大洋中脊代表了地球上火山活动正在产生新的洋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范围的大洋中脊-大西洋中脊产生的火山岩的化学特征。这些测量将被用来了解地幔的哪些成分正在融化，以及火山活动是持续发生还是以脉冲方式发生。这项研究将有助于理解地球的更大演化，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大学的地质博物馆开展一个名为“地球海洋：现在和过去”的互动展览。这次展览将有助于让公众，从学龄前儿童到老年人，了解大洋中脊在地球形成和不断浮出水面过程中的重要性。大洋中脊提供了一个机会，以了解地球地幔的同位素、岩性组成和演化，产生玄武岩岩浆的地下熔融过程，以及产生新的洋壳的喷发方式和频率。虽然在东太平洋隆起等快速扩张的大洋中脊，地壳结构的熔融过程和时间尺度受到很好的限制，但对中大西洋海脊等缓慢扩张的洋脊的研究仍然相对较少。此外，中大西洋海脊还喷发了同位素和地球化学富集型熔岩，反映了海脊下熔融状态下潜在的岩石非均质地幔源域和上升地幔热柱对附近地区的潜在影响。这项研究将限制沿中大西洋海脊45°N段产生同位素多样化洋壳的地幔成分、玄武岩熔岩产生并输送到地表的熔融过程，以及导致轴向火山脊的洋壳结构的时间尺度。为了实现这一目标，研究人员将从大西洋中脊45°N部分采集的一套玄武岩样本中测量常量元素和微量元素丰度、放射性同位素组成和铀衰变系列核素。此外，还将建立MAR地下的层析成像，并与化学和同位素解释相结合。这一多学科的数据集将加强对以下方面的了解：在缓慢扩张的中大西洋海脊之下熔化的地幔岩性；这些熔体如何分离、聚集和输送到地表的时间尺度和过程；以及沿着缓慢扩张的海脊段的新鲜大洋地壳结构的时间进程。这项工作将有助于科学界对地幔的性质和洋壳如何构成有一个更完整、更全面的了解。这笔赠款还将通过在怀俄明大学地质博物馆制作名为“地球海洋：现在和过去”的展览，加强普通公众对地球大洋中脊的了解。这一奖项反映了NSF的法定使命，并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，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.