CSEDI: Collaborative Research:Development of Geochemical Tests for Detection of Core-Mantle Interaction

地球化学中的一个基本问题是，在地球冷却循环中，是否存在伴随着热量从地核向地幔转移的化学交换。以前有人提出，如果在来自地幔柱的熔岩中检测到186 Os/188 Os和187 Os/188 Os比值的某些耦合变化，则表明从外核到从核幔边界上升的地幔柱的少量质量转移。为了研究这个问题，186 Os/188 Os和187 Os/188 Os比值的岩石从两个地幔柱衍生，海洋岛屿玄武岩系统将被精确测量。还有强有力的质量平衡证据表明，地核的182 W/184 W比大约是周围地幔的万分之二。这种信号的一部分可以转移到羽流中，就像Os同位素一样。因此，将开发技术来检查相同的地幔柱衍生岩石的W同位素在5-15百万分之一的水平，这可能是必要的检测核心组成部分。Os和W同位素的能力，作为示踪剂的核心输入地幔柱需要很好地了解金属/硅酸盐的分配行为，这些和有关的元素，在高压条件下。因此，高压分区将进行实验研究。最后，各种物理机制的核心金属转移到地幔将被考虑和评估。

A basic question in geochemistry is whether or not there is chemical exchange accompanying the transfer of heat from the core to the mantle in the cooling cycle of the Earth. It has been previously proposed that minor mass transfer from the outer core to a mantle plume rising from the core-mantle boundary would be indicated if certain, coupled variations in 186Os/188Os and 187Os/188Os ratios are detected in lavas derived from the plume. To examine this issue, 186Os/188Os and 187Os/188Os ratios of rocks from two plume-derived, ocean island basalt systems will be precisely measured. There is also strong mass balance evidence that the core has a 182W/184W ratio that is approximately 2 parts in 10,000 lower than the ambient mantle. A portion of this signal could be transferred to a plume, as with the Os isotopes. Consequently, techniques will be developed to examine the same plume-derived rocks for W isotopes at the 5-15 parts per million level that will likely be necessary to detect a core component. The ability of Os and W isotopes to serve as tracers of core input to mantle plumes require a good understanding of metal/silicate partitioning behavior of these and allied elements, under high-pressure conditions. Consequently, high-pressure partitioning will be examined experimentally. Finally, a variety of physical mechanisms of the transfer of core metal into the mantle will be considered and evaluated.