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

协作 RUI：扬马延地区铀系熔化限制

• 批准号: 1061037
• 负责人: Lynne Elkins
• 金额: $ 14万
• 依托单位: Bryn Mawr College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-04-01 至 2015-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1061037&HistoricalAwards=false
• 关键词: Collaborative; RUI; Uranium; Series; Constraints

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.

中大西洋海脊，特别是冰岛以北的北冰洋海段，以相对较慢的速度(约2厘米/年)产生新的地壳。来自北极海脊部分的熔岩被称为埃格文浅滩，其化学和同位素组成反映了比正常山脊玄武岩更丰富的微量元素来源。埃格文浅滩异常浅，毗邻火山扬马延岛，其起源存在争议：其微量元素丰富的熔岩可能表明是热点起源，但熔岩的精确同位素和化学成分与冰岛热点截然不同。扬马延可能覆盖了一个化学成分不同的地幔，其中包含了格陵兰盆地(5300万至5500万年前)地质上最近开放的次大陆物质。这些特征提出了一些问题：简·马延岩浆来源是否不均匀，包含不同类型的岩石，每种岩石都有不同的起源？它加水了吗？它真的含有次大陆地幔的碎片吗？扬·马延是一个迅速崛起的热点吗？异常地幔是否影响附近埃格文浅滩的深度和组成？这些问题影响了我们对地幔的理解，并对大洋中脊系统沿线经历异常火山活动的其他地区(如亚速尔群岛、阿森松岛)产生了影响。更好地了解该地区将提供有关熔融如何发生和导致火山活动以及地球动力学的重要信息？S地幔-地壳系统。利用新的多波束反向散射测深技术，我们将对埃格文浅滩进行第一次高分辨率测绘，以表征其火山活动的性质，并精确定位新的采样。我们将从埃格文浅滩、北部相邻的莫恩斯山脊和扬马延岛附近收集和汇编新的玄武岩，选择未改变的玄武岩玻璃(这是非常新鲜的熔岩物质的迹象)。我们将测量铀、钍和镭同位素，作为地幔来源成分、产生熔岩所发生的熔融量以及熔融和熔体输送的精确时间的指示器。以这种方式限制熔融的时间有助于洞察熔融动力学，包括热点活动的存在。这项工作有助于更广泛的科学努力，以更好地了解洋脊熔融的产生及其对地幔动力学的影响。这项研究支持了一位职业生涯早期的女科学家和一所女子S文科学院的本科生。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。这个项目试图检查冰岛附近的科尔贝恩西山脊的异常熔岩是否存在羽流和/或次大陆岩石圈地幔的特征。尽管一些挖泥船的样本已在手中，但更多精确定位的ROV样本将在德国高分辨率现场测绘巡航到该地区时收集。将对样品进行锶、钕、铅和氢同位素分析，以及U-Th和Th-Ra的分析。目标将是确定熔体的传输、时间和熔体来源。这项工作的广泛影响包括支持一名职业生涯早期的研究人员，该研究人员来自科学界代表性较低的群体，她受雇于一所女子文理学院？S，她将在那里培训本科生最先进的分析铀系列测年技术，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，并参加前往北极的国际海洋邮轮。