Geochemical Evolution of the Mantle

这一更新建议将锶、钕、铅、锶等放射性示踪系统应用于地幔基性和超镁铁质岩石，以进一步圈定地幔储集层的特征、在地幔中的位置及其成因和演化模式。P.I.s建议对来自端员地幔储集层DMM、EMI、EM 2和HIMU最明显的地区的大洋玄武岩进行大量的Os同位素研究。将对EM2和HIMU岛的超镁铁质捕虏体进行分析，并与伴生的玄武岩进行对比。将通过对阿森松岛和喀麦隆线玄武岩的Os同位素示踪研究来探索新的地幔储集层的识别，该储集层被认为是下地幔。地幔演化的早期阶段(2.5-3.7b.y.)将通过太古宙镁铁质岩石原生岩浆矿物的锶、钕、铅和锶研究来进行研究。为了利用Re/Os系统在研究早期地幔过程(增生和核形成)和现代过程(从储存在下地幔中的古代洋壳衍生出的羽流)方面的固有优势，P.I.建议研究控制Re和Os的地球化学行为的参数。这将包括岩浆和地幔矿物(硅酸盐、硫化物、氧化物和金属)之间Re和Os分配的自然研究，以及Re-Os在金属、硅酸盐熔体和硫化物液体之间的溶解和分配的实验研究。

This renewal proposal will apply the Sr, Nd, Pb, and Os radiogenic tracer systems to mantle-derived mafic and ultramafic rocks to further delimit the character of mantle reservoirs, their location in the mantle and their mode of origin and evolution. The P.I.s propose extensive Os isotope studies of oceanic basalts from localities where the end-member mantle reservoirs DMM, EMI, EM 2 and HIMU are most strongly evident. Ultramafic xenoliths from EM 2 and HIMU islands will be analyzed to compare with the associated basalts. The recognition of a new mantle reservoir, proposed to be lower mantle, will be explored by Os isotope tracer studies of basalts from the islands of Ascension and the Cameroon Line. The early stages of mantle evolution (2.5 - 3.7 b.y.) will be studied by Sr, Nd, Pb and Os studies of primary magmatic minerals from Archean mafic rocks. An to utilize the inherent strengths of the Re/Os system in studying both early mantle processes (accretion and core formation) and present-day processes (derivation of plumes from ancient oceanic crust stored in the lower mantle), the P.I.s propose to study the parameters which control the geochemical behavior of Re and Os. This will involve both natural studies of the Re and Os partitioning between magma and mantle minerals (silicate, sulfide, oxide and metal), and experimental studies of Re - Os solubility and partitioning between metal, silicate melt and sulfide liquid.