Rhenium-Osmium Isotope Study of the Mantle

9711454沃克这项提议是通过对超镁铁质岩石的分析，随着时间的推移，继续表征不同地幔区域的Os同位素组成，这些岩石在其他方面具有良好的地球化学和同位素特征，并且具有相对较高的Os浓度和较低的Re/Os比值。Re-Os同位素在解释方面可能特别有用的具体问题是：(1)通过晚期吸积作用添加到地球上的物质的性质，(2)晚期吸积物质在整个地幔中的均一化速度，(3)洋壳重新循环进入某些梅源的性质和速率，(4)地幔与外核之间化学交换的存在和水平，(5)次大陆岩石圈龙骨的发展年代学，以及(6)各种现代和古代储集层中高度亲铁元素的分布。PI将分析代表上大洋岩石圈物质(太古代至现代蛇绿岩)和来自可能的地幔热柱的物质(太古宙和元古界科马提岩和铁皮榴石)的超镁铁质岩浆系统。将从每个地点对整个岩石和矿物分离进行分析。

9711454 Walker This proposal is to continue characterization of the Os isotopic composition of various mantle domains through time, via the analysis of ultramafic rocks that are otherwise geochemically and isotopically well-characterized, and that have relatively high Os concentrations and low Re/Os ratios. Specific issues that Re-Os isotopes may be particularly useful in elucidating are: (1) nature of material added to the Earth via late accretion, (2) the rate at which late accreted materials were homogenized throughout the mantle, (3) the nature and rate at which oceanic crust has been recycled back into certain plum sources, (4) the existence of, and level of chemical exchange between the mantle and outer core, )5) the chronology of development of subcontinental lithospheric keels, and (6) the distribution of highly siderophile elements in various modern and ancient reservoirs. The PI will analyze ultramafic magmatic systems that represent upper oceanic lithospheric materials (Archean through recent ophiolites) and materials derived from likely mantle plumes (Archean and Proterozoic komatiites and ferropicrites). Both whole rock and mineral separates will be analyzed from each location.