Isotopic constraints on the distribution of chalcophile elements in magmatic systems.

硫是地球上最重要的挥发性元素之一，硫在地球表面和地幔之间的循环支配着地球大气层和水圈的演化以及重要经济元素的分布。然而，人们对地球上的硫循环以及S和亲硫元素在岩浆中的富集性知之甚少。这种富集被认为反映了硫化物的饱和(1)，这是岩浆分异和熔体中溶解的SO42-转化为硫化物(S2-)的结果。如果熔体达到S饱和，亲硫元素的高度相容意味着它们将分解成硫化物液体，冷却时，这些硫化物液体将进一步分相和出溶，形成贱金属矿床。目前尚不清楚岩浆源的非均质性、构造环境和熔体氧化状态对亲硫元素富集的相对作用。本文将利用新的稳定同位素来限制地幔来源的不均质性、氧化态、分异作用和硫化物饱和度在岩浆亲硫元素富集中的作用。该项目最初将重点放在人们熟知的可证明硫化物饱和的钙碱性岩浆岩和斯卡尔加德侵入体(格陵兰)，这是一种主要的层状镁铁质侵入体，矿化层由晚期硫化物流体形成(2)。该项目将扩展到研究与主要的碱性热液矿床有关的岩浆岩，并根据学生的兴趣，还可以纳入硫化物和硅酸盐液体之间稳定同位素分馏的实验研究(例如，3)。这个博士项目是NERC“供应矿产安全”联盟的一部分，该联盟涉及10所英国大学和6名博士后研究人员和5名博士后。学生最初将专注于归档钙碱性岩浆套件和斯卡尔加德样品，以探索岩浆分异过程中铁、锌、铜和潜在的Se稳定同位素分馏。该项目还可以纳入硅酸盐-硫化物亲硫元素分配和稳定同位素分馏的实验研究，这些研究将在爱丁堡大学进行。然后，学生将扩展该项目，以考虑岩浆活动与热液矿藏有关的更复杂的地点。实地考察和样本采集的目标地点包括克里普尔克里克(科罗拉多州)、图瓦图/瓦图库拉(斐济)和克隆库里(澳大利亚)。最后，学生将开发稳定同位素分馏和亲硫元素在岩浆分异过程中行为的定量模型，总体目标是了解岩浆中亲硫元素的丰度。

Sulfur is one of the Earth's most important volatile elements and sulphur cycling between the Earth's surface and mantle governs the evolution of the Earth's atmosphere and hydrosphere and the distribution of economically important elements. However, little is known about the sulfur cycle on Earth and the enrichment of S and chalcophile elements in magmas. This enrichment is believed to reflect sulfide saturation (1), which is a consequence of magmatic differentiation and the conversion of the SO42- dissolved in the melt into sulfides (S2-).. If melts become S saturated, the high compatibility of chalcophile elements means they will partition into sulfide liquid, and on cooling, these sulfide liquids will undergo further phase separation and exsolution to form base-metal ore deposits. However, these processes are poorly constrained and it is not clear what the relative roles of magma source heterogeneity, tectonic setting and melt oxidation state on chalcophile element enrichment are.This PhD will use novel stable isotopes to constrain the roles that mantle source heterogeneity, oxidation state, differentiation and sulfide saturation play in generating magma chalcophile element enrichment. The project will initially focus on well-understood calc-alkaline magma suites where sulfide saturation can be demonstrated and the Skaergaard Intrusion (Greenland), a major layered mafic intrusion with mineralized horizons formed from late-stage sulfide fluids (2). The project will expand to consider magmatic rocks associated with major alkaline-associated hydrothermal mineral deposits and depending on the students' interests, could also incorporate experimental studies of stable isotope fractionation between sulphide and silicate liquids (e.g., 3).This PhD project is part of a NERC "Security of Supply Minerals" consortium involving 10 UK Universities and a cohort of 6 postdoctoral researchers and 5 PhD students. The student will initially focus on archive calc-alkaline magma suites and Skaergaard samples in order to explore Fe, Zn, Cu and potentially Se stable isotope fractionation during magmatic differentiation processes. This project could also incorporate experimental studies of silicate-sulfide chalcophile element partitioning and stable isotope fractionation, these would be carried out at the University of Edinburgh. The student will then expand the project to consider more complex localities where magmatism is associated with hydrothermal mineral deposits. Target localities for fieldwork and sample collection include Cripple Creek (Colorado), Tuvatu/Vatukoula (Fiji) and Cloncurry (Australia). Finally the student will develop quantitative models of stable isotope fractionation and chalcophile element behaviour during magmatic differentiation with the overall goal of understanding chalcophile element enrichment in magmas.