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.

...我们建议研究南纬 6° 至 11° 之间缓慢扩张的大西洋中脊零年龄 MORB 样本的 U、Th 和 Ra 同位素组成。这部分扩张轴显示出轴向深度的巨大变化。 、地壳厚度和样品熔化，主量元素和微量元素地球化学以及 Sr、Nd 和 Pb 同位素组成存在显着变化。现有数据表明地幔来源、二元混合和变化之间存在复杂的相互作用。在第一年，我们建议测定沿轴和年轻（200.000 年）近轴海山的新鲜样本的 U、Th 和 Ra 同位素组成，以评估融化的深度和程度。第二年，我们建议研究岩浆演化和喷发过程的时间。轴的基础是 U 系列同位素数据以及工作区域选定火山结构的地层测绘和采样。