The nature of kimberlitic and mantle fluid and diamond preservation

金伯利岩是形成钻石原生矿床的最深岩浆（>150 公里深度）。它们充满了仅在大陆内发现的胡萝卜形状的管道。金伯利岩的起源与深部地幔的过程有关。金伯利岩将钻石从地幔运送到地表，并在上升过程中部分溶解它们。溶解会影响钻石的商业价值和金伯利岩管的钻石等级。金伯利岩富含挥发物的性质在钻石溶解中起着重要作用。目前尚不清楚金伯利岩含有多少以及何种挥发物。缺乏这方面的知识阻碍了我们对金伯利岩起源的理解。该研究调查了金伯利岩岩浆和地幔流体的挥发分含量和流体系统，并利用这些信息对金伯利岩的成因、原生熔体成分和地幔来源提出了新的约束；了解金伯利岩就位期间的条件以及地表喷发的机制；并了解是什么原因导致地幔中的钻石遭到破坏。该计划将使用一种新方法，该方法基于我最近的实验研究中发现的金伯利岩岩浆流体相与钻石表面特征之间的关系，以研究天然金伯利岩的流体系统。我的实验结果表明，流体中的 H2O/CO2 比率决定了钻石的溶解特征类型。经过新方法的实验校准后，来自 Lac de Gras 金伯利岩（加拿大西北地区）的天然钻石块将用于收集有关钻石表面特征的详细数据，以确定这些金伯利岩中岩浆流体的成分和演化。该研究还将利用传统分析技术对Lac de Gras金伯利岩和金伯利岩指示矿物进行矿物学、地球化学和岩石学研究，以寻找一些地球化学流体指标，了解岩浆流体在金伯利岩岩浆结晶和喷发中的作用。获得的数据将有助于更好地了解金伯利岩的起源和克拉通下地幔的过程，有助于预测金伯利岩管中钻石的保存情况和质量。

Kimberlites are the most deep-seated magmas (>150 km depth) that form primary deposits of diamonds. They fill carrot-shape pipes found only within continents. The origin of kimberlites is linked to processes in the deep mantle. Kimberlites transport diamonds from the Earth's mantle to the surface and partially dissolve them during the ascent. The dissolution impacts the commercial value of diamonds and the diamond grade of a kimberlite pipe. Volatile-rich nature of kimberlites plays an important role in diamond dissolution. It is not well known how much and what kind of volatiles kimberlites contain. Lack of such knowledge obscures our understanding of the origin of kimberlites. The proposed research investigates volatile content and fluid system of kimberlite magmas and the mantle fluid, and uses this information to put new constraints on the origin, primary melt composition and mantle source of kimberlites; to learn about conditions during emplacement and the mechanism of kimberlite eruption at the surface; and to understand what causes diamond destruction in the mantle. The program will use a new method based on the relationship between the fluid phase of kimberlite magma and the surface features on diamonds discovered in my recent experimental study to investigate fluid system of natural kimberlites. The results of my experiments show that the H2O/CO2 ratio on the fluid determines the type of dissolution features on diamonds. After experimental calibration of the new method, natural diamond parcels from Lac de Gras kimberlites (N.W.T., Canada) will be used to collect detailed data on the diamond surface features in order to determine composition and evolution of magmatic fluid in these kimberlites. The research will also use traditional analytical techniques to study mineralogy, geochemistry and petrography of the Lac de Gras kimberlites and kimberlite indicator minerals in order to find some geochemical fluid indicators and to understand the role of magmatic fluid in the crystallization and eruption of kimberlite magmas. The obtained data will provide better understanding of the origin of kimberlites, processes in subcratonic mantle, will help to predict preservation and quality of diamonds in a kimberlite pipe.