Radiometric Dating of Near-Ridge Seamounts by the 40Ar-39Ar Method

用 40Ar-39Ar 法对近海脊海山进行辐射测年

• 批准号: 9811136
• 负责人: Robert Duncan
• 金额: $ 10.07万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-11-15 至 2000-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9811136&HistoricalAwards=false
• 关键词: Radiometric; Dating; Near; Ridge; Seamounts

9811136 Duncan Institution: Oregon State University Title: Radiometric dating of near-ridge seamounts by the 40Ar-39Ar method This research will continue development of 40Ar-39Ar radiometric dating methods for volcanic rocks from the ocean floor, in the age range 100,000 years and older. We will apply these new methods specifically to clusters and lineations of undersea volcanoes near the spreading ridges. Such individual volcanoes provide a sampling of the flow and melting of the mantle beneath ridge systems that is broader than the focused, often homogenized sampling presented by the spreading ridge axis. The 40Ar-39Ar incremental heating method is superior to others because of the common occurrence of K in ocean floor volcanic rocks, analytical methods are well-tested and described, and in optimum circumstances measurements can be made to analytical uncertainties of 1%. We will address several first-order questions about crustal accretion processes near spreading ridges by determining the age relations of a large collection of volcano chains and clusters in the Rano Rahi field, East Pacific Rise, collected by the MOAI program from the "superfast" spreading ridge section (15-19#161#S). Our principal goals are: (1) to determine whether the near-ridge volcanoes present predominantly a spatial or temporal recording of off-ridge, shallow mantle melting, (2) to define the width of the accretionary zone, and determine whether this has a predominantly 2- or 3-dimensional geometry, and (3) to assess whether localized sources for melting that produce seamounts persist for long periods.

9811136 邓肯研究所：俄勒冈州立大学 标题：用 40Ar-39Ar 方法对近山脊海山进行放射性测年 这项研究将继续开发 40Ar-39Ar 辐射测年方法，用于海底火山岩的年龄范围为 100,000 年及以上。 我们将把这些新方法专门应用于扩张山脊附近的海底火山群和火山线条。 这些单独的火山提供了山脊系统下方地幔流动和熔化的样本，其范围比扩张的山脊轴呈现的集中的、通常均质的样本更广泛。 40Ar-39Ar增量加热方法优于其他方法，因为K在海底火山岩中普遍存在，分析方法经过充分测试和描述，在最佳情况下测量可以达到1%的分析不确定度。我们将通过确定东太平洋隆起拉诺拉希地区大量火山链和火山群的年龄关系，解决有关扩张脊附近地壳增生过程的几个一阶问题，这些火山链和火山群是由 MOAI 程序从“超快”扩张中收集的。山脊部分（15-19#161#S）。 我们的主要目标是：（1）确定近山脊火山是否主要呈现出山脊外、浅地幔融化的空间或时间记录，（2）定义增生带的宽度，并确定其是否具有主要是 2 维或 3 维几何形状，(3) 评估产生海山的局部熔化源是否持续存在很长时间。