238U and 232Th Series Studies of Arc-related Magmas

与电弧相关的岩浆的 238U 和 232Th 系列研究

• 批准号: 9005232
• 负责人: Mark Reagan
• 金额: $ 5.57万
• 依托单位: University of Iowa
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1990
• 资助国家: 美国
• 起止时间: 1990-07-01 至 1992-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9005232&HistoricalAwards=false
• 关键词: 238U; 232Th; Series; Studies; Arc

This is study of magmatic processes occurring at crust and mantle levels in volcanic arcs using 238U and 232Th decay series systematics. Part of the funding will be used to complete ongoing projects that focus on the processes and lengths of time required to generate and accumulate rhyolite in Cascade arc volcanoes. The volcanoes that are being studied (medicine Lake and Crater Lake) have erupted silicic magmas in the Holocene, and are well-known geologically and geochemically through the work of U.S.G.S. collaborators. Approximately 6-9 months will be necessary to complete the analyses of whole rocks and contained mineral phases for nuclide activities, to determine magma residence times with open-system modeling techniques, and to write up the results. The remainder of the 2-year study period will be used to investigate the origin of mafic magmas that are the geochemical and thermal parents of Central American arc magma systems. We will analyze 20-25 rocks from the Central American arc and sediments from the Cocos Plate for 238U-230Th-226Ra-232Th activities. These same rocks are being analyzed by other scientists for 10Be/Be ratios, Sr, Nd, and Pb isotopic ratios, and B, trace element, and major element concentrations. The goal is to delineate the nature of the subducting slab component in Central American arc magmas, the way it becomes involved in arc magma genesis, and the time scales required for magma generation and transport.

这是对地壳中发生的岩浆作用的研究， 用~（238）U和~（232）Th衰变系列研究火山弧的地幔水平 分类学 部分资金将用于完成 正在进行的项目，重点是过程和时间长度 在Cascade弧中生成和积累流纹岩所需的时间 火山 正在研究的火山（梅迪辛湖 和火山口湖）在全新世爆发了岩浆， 在地质学和地球化学上是众所周知的， 美国地质调查局合作者 大约6-9个月， 必须完成整个岩石的分析， 核素活动的矿物相，以确定岩浆 停留时间与开放系统建模技术，并 把结果写出来。 2年研究期的剩余时间 将被用来调查镁铁质岩浆的起源， 中美洲弧岩浆的地球化学和热母岩 系统. 我们将分析来自中美洲的20-25块岩石， 238 U-230 Th-226 Ra-232 Th的科科斯板块弧和沉积物 活动 其他科学家正在分析这些岩石 科学家们的10 Be/Be比值，Sr，Nd和Pb同位素比值， 和B，微量元素和主量元素浓度。 目标 是描绘俯冲板块成分的性质， 中美洲弧岩浆，它参与弧的方式 岩浆成因，以及岩浆生成的时间尺度 和交通。