SGER: Melt Generation and Transport During Basalt Petrogenesis: Constraints from Measurements of 227Ac-231Pa Activity Ratios

SGER：玄武岩成岩过程中熔体的生成和传输：227Ac-231Pa 活度比测量的限制

• 批准号: 0228677
• 负责人: Kenneth Sims
• 金额: $ 5.7万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-08-01 至 2004-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0228677&HistoricalAwards=false
• 关键词: SGER; Melt; Generation; Transport; During

Uranium-series isotopes have provided unique insight into geochemical rates and processes during genesis of basaltic magma from the earth's mantle. Specifically, recent measurements of the longer-lived isotopes of the U-decay series have placed important constraints on melting rates (related to solid mantle upwelling rates) and melt fractions. However, there have been relatively few measurements of the shorter-lived isotopes of the U decay series in basaltic samples. As a result, time-dependant parameters such as melt transport rates and magma storage times are not well known. To better constrain these parameters, under this SGER award, the PIs propose to measure short-lived 227Ac (t1/2 =21.8 y) in young basaltic samples from mid-ocean spreading centers and intraplate volcanoes like Hawaii. This geochronologic system has the potential to be an important chronometer for dating of young mid-ocean ridge basalts in the time range of 10-100 years. Development of a new counting technique for 227Ac has simplified its analysis making this research possible for the first time.

铀系同位素为地球地幔玄武岩岩浆形成过程中的地球化学速率和过程提供了独特的见解。具体地说，最近对铀衰变系列中寿命较长的同位素的测量对熔化速率(与固体地幔上涌速率有关)和熔体分数施加了重要的限制。然而，在玄武岩样品中对U衰变系列的较短寿命同位素的测量相对较少。因此，熔体运移速率和岩浆储存时间等与时间相关的参数并不是很清楚。为了更好地约束这些参数，根据SGER的这一奖项，PI建议测量来自大洋中部扩张中心和夏威夷等板内火山的年轻玄武岩样品的短期227Ac(t1/2=21.8y)。这一年代学系统有可能成为一种重要的年代学方法，用于10-100年的年轻大洋中脊玄武岩的测年。一种新的227Ac计数技术的发展简化了其分析，使这项研究首次成为可能。