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

岩浆系统中亲铜元素分布的同位素限制。

基本信息

批准号：
1768937
负责人：
金额：
--
依托单位：
University of Cambridge
依托单位国家：
英国
项目类别：
Studentship
财政年份：
2016
资助国家：
英国
起止时间：
2016 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=studentship-1768937
关键词：
Isotopic constraints distribution chalcophile elements

项目摘要

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.

硫是地球上最重要的挥发性元素之一，地球表面和地幔之间的硫循环控制着地球大气圈和水圈的演化以及重要经济元素的分布。然而，人们对地球上硫的循环以及岩浆中硫和亲铜元素的富集情况知之甚少。这种富集被认为反映了硫化物饱和（1），这是岩浆分异和溶解在熔体中的SO 42-转化为硫化物（S2-）的结果。如果熔体变得S饱和，亲硫元素的高相容性意味着它们将分配到硫化物液体中，并且在冷却时，这些硫化物液体将经历进一步的相分离和出溶以形成贱金属矿床。然而，这些过程的约束性较差，岩浆源区的不均匀性，构造背景和熔体氧化态对亲铜元素富集的相对作用尚不清楚，本博士将使用新的稳定同位素来约束地幔源区的不均匀性，氧化态，分异和硫化物饱和度在产生岩浆亲铜元素富集中的作用。该项目最初将侧重于充分了解的钙碱性岩浆套，其中硫化物饱和度可以证明和Skaergaard侵入体（格陵兰岛），一个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）。该项目将扩大到考虑与主要碱相关热液矿床有关的岩浆岩，并根据学生的兴趣，还可以包括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“供应矿物安全”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名博士生。学生将首先专注于档案钙碱性岩浆套件和Skaergaard样品，以探索岩浆分异过程中的Fe，Zn，Cu和潜在的Se稳定同位素分馏。这一项目还可以包括硅酸盐-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床相关的更复杂的地方。实地工作和样本采集的目标地点包括克里普尔溪（科罗拉多）、图瓦图/瓦图库拉（斐济）和克隆库里（澳大利亚）。最后，学生将开发岩浆分异过程中稳定同位素分馏和亲铜元素行为的定量模型，总体目标是了解岩浆中亲铜元素的富集。