Improving the usefulness of eclogitic garnet as a diamond indicator mineral

由于即使在具有经济品位的矿床中金刚石的丰度也极低（低于百万分之一），因此，更丰富的“指示矿物”被非常成功地用于指导新发现的勘探。对于橄榄岩，地球地幔中最丰富的金刚石源岩，这种方法是如此先进，以至于可以从回收的少量指示矿物颗粒中得出关于尚未发现的矿床的可靠预测，例如，在冰川冰碛物取样时。对于榴辉岩，地球地幔中第二大金刚石来源，指示矿物评估的可靠性要低得多。主要的指示矿物榴辉岩石榴石，目前不允许我们预测钻石稳定的深度来源，也没有确定的化学特征表明这种石榴石与碳（钻石）的关联。此外，在指示矿物评估过程中，难以将感兴趣的石榴石颗粒（地幔榴辉岩）与没有任何金刚石组合的地壳背景分开。在这个项目中，我们将使用大量的榴辉岩矿物样品（约。2600粒），并测定主量和微量元素的化学成分。这不仅可以在勘探过程中改进石榴石分类，而且还有望产生更可靠的、基于痕量元素的高压（钻石稳定）来源和与钻石相关的特征。

Because of the extremely low abundance of diamond even in deposits with economic grades (less than 1 parts per million), more abundant "indicator minerals" are used very successfully to guide exploration to new finds. For peridotite, the most abundant source rock of diamond in Earth's mantle, this methodology is so advanced that robust predictions about yet undiscovered deposits can be derived from a small number of indicator mineral grains recovered, e.g., during sampling of glacial till. For eclogite, the second most important source of diamond in Earth's mantle, indicator mineral assessment is much less reliable. The principal indicator mineral, eclogitic garnet, currently does not allow us to predict an origin from depths where diamond would be stable nor are there established chemical signatures that would indicate an association of such garnets with carbon (diamond). In addition, difficulties persist during indicator mineral assessment to separate garnet grains of interest (mantle eclogites) from crustal background without any diamond association. In this project we will use a large number of eclogitic mineral samples (ca. 2600 grains) and determine major and trace element chemical compositions. This will not only allow for improved garnet classification during exploration, but is also expected to yield more reliable, trace element-based signatures for a high pressure (diamond stable) origin and an association with diamond.