Collaborative RUI: Uranium-Series Constraints on Melting in the Jan Mayen Region

大西洋中脊，特别是冰岛北部北冰洋的部分，以相对缓慢的速度（约2厘米/年）产生新的地壳。来自被称为Eggvin Bank的北极脊段的熔岩的化学和同位素组成反映了比普通脊玄武岩更丰富的微量元素来源。Eggvin Bank异常浅，毗邻火山喷发的扬马延岛（Jan Mayen Island），该岛的起源存在争议：其富含微量元素的熔岩可能暗示了一个热点的起源，但熔岩的精确同位素和化学成分与冰岛热点截然不同。扬马延可能覆盖在一个化学性质不同的地幔上，其中包含了格陵兰盆地（5300万至5500万年前）最近地质学上开放的次大陆物质。这些特征引发了一系列问题：扬马延岩浆源是否不均匀，是否包含不同的岩石类型，每种岩石类型都有不同的起源？水分充足吗？它真的含有次大陆地幔的碎片吗？扬马延是一个快速上涌的热点吗？异常地幔是否影响了附近艾格文滩的深度和组成？这些问题影响了我们对地幔的理解，对其他经历异常火山活动的海洋中脊系统地区（如亚速尔群岛、阿森松岛）也有影响。更好地了解该地区将提供有关融化如何发生并导致火山活动以及地球动力学的重要信息。S幔壳系统。利用新的多波束后向散射测深技术，我们将对Eggvin Bank进行首次高分辨率测绘，以表征其火山活动的性质，并精确定位新的采样。我们将收集和整理来自Eggvin Bank、北部邻近的Mohns Ridge和附近的Jan Mayen Island的新鲜玄武岩，选择未改变的玄武岩玻璃（表明非常新鲜的熔岩物质）。我们将测量铀、钍和镭的同位素，作为地幔源组成、产生熔岩的熔融量以及熔融和熔融运输的精确时间的指标。以这种方式限制融化的时间可以深入了解融化动力学，包括热点活动的存在。这项工作有助于广泛的科学努力，以更好地了解洋脊的熔体产生及其对地幔动力学的影响。这项研究支持一名早期职业女性科学家和一名女性？美国文理学院。这些学生将有机会学习和接受最先进的地球化学科学研究方法的培训。本项目旨在检查来自冰岛附近科尔拜西山脊的地球化学异常熔岩，以寻找羽流和/或次大陆岩石圈地幔的特征。虽然已经从挖泥船中获得了一些样本，但德国的高分辨率实地测绘巡航船将收集更多精确定位的ROV样本。样品将分析Sr， Nd， Pb和Hf同位素，以及U-Th和Th-Ra。目标将是确定熔体的输送和时间以及熔体的来源。这项工作的更广泛影响包括支持一名来自科学领域代表性不足的群体的早期职业调查员，他受雇于一名女性？在那里，她将培训本科生最先进的铀系列分析测年技术，并担任导师。其他影响还包括与英国和德国科学家的国际合作，允许学生在其他实验室进行交叉培训，并参加到北极的国际海洋学巡航。

The Mid-Atlantic Ridge, particularly its segments in the Arctic Ocean north of Iceland, produce new crust at a relatively slow rate (~2 cm/yr.). Lavas from the Arctic ridge segment known as the Eggvin Bank have chemical and isotopic compositions that reflect a more trace element-rich source than normal ridge basalts. The Eggvin Bank, which is anomalously shallow, is adjacent to the volcanic Jan Mayen Island, whose origins are disputed: its trace element enriched lavas may suggest a hotspot origin, but the precise isotopic and chemical compositions of the lavas are distinct from the Iceland hotspot. Jan Mayen may instead overlie a chemically distinct mantle, containing trapped subcontinental material from the geologically recent opening of the Greenland Basin (53-55 million years ago). These characteristics raise a number of questions: is the Jan Mayen magma source heterogeneous, containing different rock types that each had different origins? Is it hydrated? Does it indeed contain pieces of subcontinental mantle? Is Jan Mayen a rapidly upwelling hotspot? Does anomalous mantle affect the depth and composition of the nearby Eggvin Bank? These questions impact our understanding of the mantle, with implications for other regions along the mid-ocean ridge system that experience anomalous volcanism (e.g. the Azores, Ascension). A better understanding of the region will provide important information about how melting occurs and leads to volcanic activity and about the dynamics of the Earth?s mantle-crust system.Using new multibeam backscatter bathymetry techniques, we will conduct the first high-resolution mapping of the Eggvin Bank, to characterize the nature of its volcanism and to precisely target new sampling. We will collect and compile fresh basaltic rocks from the Eggvin Bank, the adjacent Mohns Ridge to the north, and nearby Jan Mayen Island, selecting unaltered basaltic glass (an indication of very fresh lava material). We will measure uranium, thorium, and radium isotopes as indicators of mantle source composition, of the amount of melting occurring to produce the lavas, and of the precise timing of melting and melt transport. Constraining the timing of melting in this way provides insight into the melting dynamics, including the presence of hotspot activity.This work contributes to broad scientific efforts to better understand melt generation at ocean ridges and its implications for mantle dynamics. The research supports an early-career woman scientist and undergraduate students at a women?s liberal arts college. These students will have the opportunity to learn and receive training in state-of-the-art geochemical scientific research methods.This project seeks to examine geochemically anomalous lavas from the Kolbeinsey Ridge near Iceland for the presence of signatures of plumes and/or subcontinental lithospheric mantle. Although some samples from dredges are in hand, additional precisely located ROV samples will be collected on a German high-resolution field mapping cruise to the area. Samples will be analyzed for Sr, Nd, Pb, and Hf isotopes, as well as U-Th and Th-Ra. Goals will be to determine melt transport and timing and melt sources.Broader impacts of the work include support of an early-career incvestigator from a group under-represented in the sciences who is employed at a women?s liberal arts college where she will train undergraduate students in state-of-the-art analytical Uranium series dating techniques and serve as a mentor. Additional impacts also include international collaboration with UK and German scientists and allow students to cross train in other laboratories and participate in an international oceanographic cruise to the Arctic.