U-Th-Ra disequilibria in basalts from the Mid-Atlantic Ridge 6-11°S: Constraints on melting, mixing and time-scales of magmatic processes

大西洋中脊 6-11°S 玄武岩中的 U-Th-Ra 不平衡：对岩浆过程的熔化、混合和时间尺度的限制

• 批准号: 5441103
• 负责人: Professor Dr. Karsten Matthias Haase
• 金额: --
• 依托单位: Forschungseinheit Magmatische und Hydrothermale Systeme
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2004
• 资助国家: 德国
• 起止时间: 2003-12-31 至 2009-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/5441103?language=en
• 关键词: Th; Ra; disequilibria; basalts; Mid

... We propose to study the U, Th, and Ra isotopic compositions of zero-age MORB samples from the slow-spreading Mid-Atlantic Ridge between 6 and 11°S. This part of the spreading axis shows large variations in axial depth, crustal thickness and samples melts with significant variations in major and trace element geochemistry as well as Sr, Nd, and Pb isotopic composition. The existing data indicates a complex interplay of variations in mantle sources, binary mixing and degree of magma differentiation during melt ascent. In the first year wie suggest to determine U, Th and Ra isotope compositions of fresh young samples along the axis and from young ( 200.000 years) near- axis seamounts to evalute the depth and extent of melting, the mantle composition, porosity and upwelling rate and the mixing processes along a propagating ridge segment. In the second year wie propose to investigate the timing of magma evolution and eruption processes on this spreading axis on the basis of U series isotope data and stratigraphic mapping and sampling of selected volcanic structures of the working area.

..。我们建议研究大西洋中部海脊在6-11°S之间缓慢伸展的零年龄MORB样品的U、Th和Ra同位素组成。这部分扩张轴的轴向深度、地壳厚度变化很大，样品熔体的常量和微量元素地球化学以及锶、钕和铅同位素组成也有显著变化。现有数据表明，在熔体上升过程中，地幔来源的变化、二元混合和岩浆分异程度之间存在复杂的相互作用。在第一年，我们建议测定沿中轴线的新鲜年轻样品和年轻的近轴线海山(200.000年)的U、Th和Ra同位素组成，以评估熔融的深度和程度、地幔成分、孔隙度和上升率以及沿传播脊段的混合过程。在第二年，WIE建议根据U系列同位素数据和对工作区选定的火山构造进行地层填图和取样，研究该扩张轴上岩浆演化和喷发过程的时间。