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：俄勒冈州立大学题目：用40Ar-39Ar方法对近海脊海山进行辐射测年这项研究将继续开发来自海底的火山岩的40Ar-39Ar辐射测年方法，年龄范围在100,000年及以上。我们将专门将这些新方法应用于扩张海脊附近的海底火山群和线条。这些单独的火山提供了海脊系统下地幔流动和融化的采样，比扩张的海脊轴线提供的集中的、通常是均匀的采样更广泛。40Ar-39Ar增量加热法优于其他方法，因为K在海底火山岩中普遍存在，分析方法得到了很好的检验和描述，在最佳条件下可以测量到1%的分析不确定度。我们将通过确定东太平洋海隆Rano Rahi油田的一大批火山链和火山团的年龄关系来解决有关扩张海脊附近地壳增生过程的几个一级问题。这些火山链和火山群是由MOAI计划从“超快”扩张海脊剖面(15-19#161#S)收集的。我们的主要目标是：(1)确定近山脊火山是否主要是山脊外浅地幔熔融的空间或时间记录，(2)确定吸积带的宽度，并确定这是否主要具有2维或3维几何形状，以及(3)评估产生海山的局部熔融来源是否长期存在。