The role of emulsions in magmatic sulfide deposits

硅酸盐与硫化物熔体之间的液体不混溶是岩浆硫化物矿床形成的重要前提。这些都是世界上最有价值的金属资源之一，形成了Ni- cu - co -铂族元素（PGE）矿床（例如，萨德伯里和诺里尔斯克，两个最大的Ni和cu硫化物矿床，以及地球上第二大和第三大PGE富集区；Naldrett, 2011）。令人惊讶的是，液体不混溶性的结构证据，冷冻乳剂，到目前为止还没有得到详细的研究，这是本博士候选人提案的主题。将解决三个目标：(1)将对乳化液结构的可变性（例如不同的球形和相互连接的乳化液）进行结构和化学研究，并将其与相似的结构（例如网状硫化物，碎屑破碎）和乳化液的宿主岩石进行比较，以研究硫化物的放置历史和在放置过程中乳化液的形成。这个目标的样品来自世界各地各种各样的岩浆硫化物矿床。(2)澳大利亚Nova矿床的乳剂通常与硫化物包裹的大硅酸盐晶体有关。假设是这些晶体在乳剂中生长是由于条件的变化，比如冷却。生长后，当两种熔体分离时（由于熔体运动缓慢），乳状液中的硅酸盐熔体部分漂浮起来，留下硫化物晶体。为了验证这一点，这些晶体将在结构和化学上与乡村岩石进行比较。(3)迄今为止未描述的乳液结构包括氧化物-磷灰石涂层在靠近包岑（Sora，德国）的硫化豆荚的乳液的硅酸盐液滴上。假设这种涂层代表硅酸盐和硫化物熔体之间的第三种熔体，并起到乳化剂的作用，这在任何地质背景下都没有被描述过。硫化物和硅酸盐熔体之间的物理屏障将阻止它们之间元素的“传统”分配，因此，微量元素（除了结构观察）将用于研究和解释这种新的乳液结构。这三个目标将有助于更好地理解岩浆硫化物矿床的形成和就位过程。这将为其他研究人员分类和区分乳剂，并将它们与在不同过程中形成的相似纹理区分开来奠定基础。野外乳化液的识别有助于岩浆硫化物矿床的勘探，使其从乳化液（通常存在于陡峭侵入接触体的亚经济硫化物中）向主矿体方向发展。

Liquid immiscibility between silicate and sulfide melt is an important prerequisite to form magmatic sulfide deposits. These are amongst the most valuable metal resources in the world, forming Ni-Cu-Co- platinum group element (PGE) deposits (e.g., Sudbury and Noril’sk; the two largest accumulations of Ni- and Cu-sulfides and the second and third largest PGE enrichments on Earth; Naldrett, 2011). Surprisingly, the textural evidence for liquid immiscibility, frozen emulsions, are not studied in detail so far and this is the topic of this proposal for a PhD candidate. Three objectives will be addressed:(1) The variability of emulsion textures (e.g. different spheroidal and interconnected emulsions) will be texturally and chemically studied and compared to similar textures (e.g. net-textured sulfides, clast fragmentation) and the host rocks of the emulsions to study the emplacement history of sulfides and emulsion formation in the course of that emplacement. The samples for this objective come from a large variety of magmatic sulfide occurrences worldwide.(2) Emulsions from the Nova deposit (Australia) are typically associated with large silicate crystals embedded by sulfides. The hypothesis is that these crystals grew within the emulsion due to changing conditions, such as cooling. After growth, the silicate melt portion of the emulsion floated up when both melts separated (due to slowing movement of the melts), leaving the crystals in the sulfides behind. To test this, the crystals will be texturally and chemically compared to the country rocks.(3) A hitherto undescribed emulsion texture comprises oxide-apatite coatings on silicate droplets of an emulsion from sulfide pods near Bautzen (Sora, Germany). The hypothesis is that this coating represents a third melt between silicate and sulfide melt and acted as an emulsifier, which has not been described before in any geological context. This physical barrier between the sulfide and the silicate melt would prevent a "conventional" partitioning of elements between them and, therefore, trace elements (besides textural observations) will be used to study and interpret this new emulsion texture.All three objectives will help to better understand the processes involved in the formation and emplacement of magmatic sulfide deposits. It will create a foundation for other researchers to classify and discriminate emulsions and to distinguish them from similar textures, which formed in different processes. The identification of emulsions in the field can help exploration for magmatic sulfide deposits in directing them from the emulsion, which is usually found in sub-economic sulfides on steep intrusive contacts, towards the main orebody.