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.

...我们建议研究从6到11°S之间缓慢膨胀的中大西洋山脊中零年龄的MORB样品的U，TH和RA同位素组合物。扩散轴的这一部分显示出轴向深度，地壳厚度和样品融化的大量变化，其主要和痕量元素地球化学以及SR，ND和PB同位素组成的变化显着。现有数据表明，熔融上升过程中地幔源，二元混合和岩浆分化程度的变化相互作用。在第一年中，WIE建议确定新鲜样品的U，TH和RA同位素组成，沿轴和Young（200。000年）接近轴的封口，以评估熔化的深度和程度，地幔组成，孔隙率和上升速率以及上升速度以及沿繁殖脊段的混合过程。在第二年，根据U系列同位素数据以及工作区域选定的火山结构的采样，研究了该扩散轴上岩浆演化和喷发过程的时机。