Mechanics and Applications of Titanium Isotope Fractionation in Terrestrial Magmas

在地球和月球表面喷发的岩浆为研究地球和月球地幔的成分不均质性和动力学以及地壳岩浆储集层的岩浆演化提供了广泛的机会。然而，经典的地球化学工具往往给出不完整或模棱两可的重要问题的答案，如：在部分熔融和岩浆演化过程中涉及哪些矿物？地幔来源和由此产生的岩浆的水分含量是多少？过去火山活动的构造背景能从岩浆成分中推断出来吗？这个博士项目的目的是利用新的钛稳定同位素系统来回答这些问题。在可用于同位素研究的众多化学元素中，钛具有独特的能力，能够唯一地追踪氧化矿物参与岩浆成因和演化的过程[1]。学生将对岩浆岩及其矿物进行超高精度的钛稳定同位素测量[2]，以研究与陆地和月球岩浆的生成和演化有关的一系列问题。分析工作将在卡迪夫大学新设立的最先进的同位素地球化学实验室进行。此外，学生将使用加的夫大学最近安装的FEG-SEM(场发射枪扫描电子显微镜)设备来确定选定样品中钛的预算。这个系统的设计是为了能够在大范围内以高空间分辨率快速绘制矿物成分图。结合数据集将使学生能够实现以下研究目标：1.确定部分熔融和岩浆分异过程中的钛同位素分配效应。测量一系列月球样品的钛稳定同位素组成，以模拟月球岩浆海洋的演化。评价熔体含水率和氧逸度对岩浆分异过程中钛同位素行为的影响。确定一系列陆地熔岩的钛稳定同位素组成，并在此过程中确定它们的水分含量和它们所处的构造背景。总体而言，该项目将使人们能够更清楚地了解地球和月球上岩浆的产生和演化。参考文献：[1]小米并购等人。(提交给EPSL)地球和月球岩浆作用的钛稳定同位素研究[2]Millet M-A和Dauphas N.(2014)双峰高分辨率MC-ICPMS J.分析超精密钛稳定同位素测量。在…。光谱，2014,1444-1458

Magmas erupted at the surface of the Earth and Moon offer a wide array of opportunities to study the compositional heterogeneity and dynamics of the terrestrial and lunar mantles, as well as magma evolution in crustal magma reservoirs. However, classical geochemical tools often give incomplete or ambiguous answers to important questions such as: what minerals are involved during partial melting and magma evolution? What is the water content of the mantle source and resulting magma? Can the tectonic setting of past volcanism be inferred from magma compositions?The aim of this PhD project is to use the novel titanium stable isotope system to provide answers to these questions. Amongst the flurry of chemical elements available for isotopic study, titanium has the unique ability to be able to solely trace the involvement of oxide minerals in magma genesis and evolution[1]. The student will perform ultra-high precision Ti stable isotope measurements[2] of magmatic rocks and their minerals to study a range of questions related to the generation and evolution of terrestrial and lunar magmas. Analytical work will be carried out in the newly set up state-of-the-art isotope geochemistry laboratory at Cardiff University. In addition, the student will use the recently installed FEG-SEM (Field Emission Gun - Scanning Electron Microscope) facility at Cardiff University to determine the budget of Ti in selected samples. This system is designed to enable rapid mapping of mineral compositions at high spatial resolution over large areas.The combined dataset will allow the student to attain the following research objectives:1. Determine Ti isotope partitioning effects during partial melting and magma differentiation.2. Measure the Ti stable isotope composition of a range of lunar samples in order to model the evolution of the lunar magma ocean.3. Evaluate the effects of melt water content and oxygen fugacity on the behaviour of Ti isotope during magma differentiation.4. Determine the Ti stable isotope composition of a range of terrestrial lavas and, in doing so, their water content and the tectonic context in which they were emplaced. Overall, this project will allow for a much clearer understanding of magma generation and evolution on the Earth and Moon. References:[1] Millet M-A et al. (submitted to EPSL) Titanium stable isotope investigation of magmatic processes on the Earth and Moon[2] Millet M-A and Dauphas N. (2014) Ultra-precise titanium stable isotope measurements by double-spike high resolution MC-ICP-MS J. Anal. At. Spectrom., 2014, 1444-1458