Mantle Metasomatism and the Origin of Diamonds

地幔中的水量可能超过世界上所有的海洋、湖泊和河流。 90年代在地幔矿物中发现水作为羟基（OH）是非常重要的，但这些矿物可能在金伯利岩中从深处上升到表面时发生了变化，金伯利岩也是钻石的宿主。 然而，最近在钻石中含有的矿物“ringwoodite”（Mg 2SiO 4）中发现了水，这表明水可以在地球地幔深处的矿物中存在很长时间。 钻石中的矿物包裹体被认为是保持原始状态，因为它们被包裹在地球地幔数百英里深处，钻石就是在那里形成的。 它们是我们所拥有的地球100英里深部分的唯一样本，也是这项提议的主题。 特别是，地幔中的流体形成了金刚石，含水交代流体可以揭示金刚石及其包裹体形成的条件。 拟议研究的主要目标有几个，都与理解交代，热液，碳酸盐岩系统有关，该系统携带构成地球内水的“隐藏水库”的超临界流体的签名。 钻石中的矿物包裹体将从100个含金刚石捕虏体中选出，该团队先前已经研究并发表了这些捕虏体。 具体而言，该研究将侧重于钻石包裹体的化学性质，特别是其挥发物含量和同位素组成（例如，硅酸盐中的OH和D/H值;硫化物中的Cl-F-S）。这一更新期将充分利用该团队有效抛光钻石的能力，同时在一个表面上暴露其众多的矿物包裹体。 通过对这几种内含物进行阴极射线发光成像，将有可能对其进行取样，以进一步研究其相对年龄，并可能在单个钻石的生长寿命期间重新创建变化的交代流体的化学性质，可能覆盖数百万年。

The amount of water in the mantle of the Earth may exceed that in all the oceans, lakes, and rivers of the world. The finding of water as hydroxyl (OH) in mantle minerals in the 90's was highly significant, but these minerals may have been altered upon ascent from depths to the surface in the kimberlites, also the host for diamonds. However, a recent discovery of water in the mineral 'ringwoodite' (Mg2SiO4) included in a diamond has demonstrated that water can reside within minerals deep in the Earth's mantle for a long time. Mineral inclusions in diamonds are thought to have remained pristine since their encapsulation hundreds of miles deep in the Earth's mantle, where diamonds are formed. They are the only samples we have of the 100 mile-deep portions of the Earth and are the subject of this proposal. In particular, it is the fluids in the mantle that formed the diamonds, the water-bearing metasomatic fluids, which can reveal the conditions responsible for formation of diamonds as well as their inclusions. The main objectives of the proposed research are several, all associated with understanding the metasomatic, hydrothermal, carbonatitic system that carries the signatures of the super-critical fluids that constitute the 'hidden reservoir' of water within the Earth. The mineral inclusions in diamonds will be chosen from the 100 diamondiferous xenoliths, upon which this team has previously studied and published. Specifically, the study will focus on the chemistry of diamond inclusions, particularly their volatile contents and isotope compositions (e.g., OH and D/H values in silicates; Cl-F-S in sulfides). This renewal period will capitalize on this team's ability to effectively polish diamonds, exposing their numerous mineral inclusions simultaneously on one surface. With cathodoluminescence imaging of these several inclusions, it will be possible to sample them for further studies of their relative ages and possibly recreate the chemistry of the changing metasomatic fluids during the individual diamond's lifetime of growth, covering perhaps 10's of millions of years.