Investigation of Fe Isotope Fractionation During Magmatic Differentiation at the Skaergaard Intrusion

斯卡尔加德岩体岩浆分异过程中铁同位素分馏的研究

• 批准号: 1430219
• 负责人: Adriana Heimann Rios
• 金额: $ 25.71万
• 依托单位: East Carolina University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1430219&HistoricalAwards=false
• 关键词: Investigation; Fe; Isotope; Fractionation; During

Magma evolution is responsible for the wide range of igneous rocks observed on Earth as well as their varied chemical compositions and the genesis of associated economic mineral deposits. Of fundamental importance for understanding magmatic evolution and planetary formation processes are detailed geochemical studies of large simple igneous systems. Layered mafic-ultramafic igneous complexes are not only useful for understanding magmatic differentiation processes but also important economically for being the main source of platinum group elements, Cr, Ni, Cu, and Fe ore deposits. Iron isotope studies can help unravel the formation processes of these igneous complexes as well as their mineral deposits because the different isotopes of Fe can potentially partition into different phases during diverse processes, including crystallization of minerals from the melt, assimilation of country rocks, and reactions between rocks and late-stage hydrothermal fluids. Within individual crystals Fe isotopes can also diffuse through various minerals at different rates and may also reflect equilibrium (magmatic) or non-equilibrium (kinetic) processes. Improvements in the precision of Fe stable isotope measurements of bulk rocks and minerals by multi collector inductively coupled plasma mass spectrometry (MC-ICP-MS) show that significant variations exist in high-temperature mafic and ultramafic terrestrial crustal and mantle igneous rocks, lunar mafic rocks, and meteorites. These findings promise success for understanding magmatic differentiation and planetary formation processes. However, the current knowledge of Fe isotope compositions of individual minerals and fractionations among them in these rocks is still limited, and the causes, mechanisms, and implications of Fe isotope fractionations in high-temperature terrestrial and extraterrestrial igneous systems are still poorly understood. Only a very limited number of igneous intrusions have been investigated in detail with Fe isotopes. In addition, in situ Fe isotope measurements of individual minerals in extraterrestrial rocks are not available and only very few exist for terrestrial rocks. This means that Fe isotope compositions previously measured in bulk minerals may well be, in many cases, an average of the complex compositions recorded during crystal growth, diffusion, or late-stage hydrothermal alteration. This project will determine the extents, causes, and mechanisms of Fe isotope fractionations in a simple high-temperature magmatic system combining Fe and O isotope analysis of bulk-rocks and minerals with high-spatial resolution in situ Fe and O isotope analysis of minerals by femtosecond laser ablation (fs-LA) MC-ICP-MS and secondary ion mass spectrometry (SIMS), respectively, in the mafic-ultramafic layered intrusion of Skaergaard, Greenland, the most studied intrusive complex on Earth. This intrusion exemplifies a highly differentiated magma chamber originated from a single, large, magma body that underwent extensive, closed-system evolution through fractional crystallization that later underwent hydrothermal alteration. The results of this research will help understand the processes of formation of mafic-ultramafic layered intrusions and their host magmatic mineral deposits and has implications for understanding planetary differentiation processes.The emphasis of this project is on systematic, high resolution, inter-mineral Fe isotope fractionations and in situ intra-mineral Fe isotope compositions (by fs-LA-MC-ICP-MS). Because fs-LA-MC-ICP-MS is a new technique in geochemistry, this research will help develop the method that may ultimately benefit the broader geoscience community. Detailed bulk-rock and mineral Fe and O isotope compositions combined with in situ Fe isotope compositions, mineral chemistry, O isotope cooling temperatures, bulk-rock major and trace element compositions, and modeling will produce the most comprehensive and detailed study of a single large igneous intrusion. Oxygen isotope compositions will help discern high-temperature magmatic Fe isotope compositions (equilibrium) from kinetic and late-stage hydrothermal effects. All these data together will help identify the origin of the measured fractionations (fractional crystallization, chemical diffusion, thermal diffusion, late-stage hydrothermal alteration). The inter-mineral Fe isotope fractionation factors as a function of temperature calculated for Skaergaard will be useful for understanding those in other terrestrial igneous systems, lunar and Martian rocks, and other planetary bodies. Because large samples are hard to obtain from meteorites, this study will provide much needed information to determine the best approach for extraterrestrial sample studies. The results of this work will improve our understanding of large-scale evolution of Fe isotopes at the intrusion level as well as small scale, Fe isotope heterogeneities within crystals. This project combines the expertise of mineralogy, petrology, economic geology, geochemistry, and Fe and O isotope geochemistry of the PI and collaborators from the University of Wisconsin-Madison. This project will support an early career female scientist, fund two M.S. theses and undergraduate student researchers, and support the development of the physical infrastructure for research on state-of-the-art high-temperature isotope geochemistry at East Carolina University. This collaboration will also provide graduate and undergraduate students at ECU the experience of working with state-of-the-art analytical facilities at UW-Madison and interact with top leaders in geochemistry.

岩浆的进化负责在地球上观察到的各种火成岩及其多样化的化学成分以及相关的经济矿物沉积物的起源。 对于理解岩浆进化和行星形成过程的基本重要性是对大型火成岩系统的详细地球化学研究。 分层的镁铁质 - 乌尔塔拉毛皮火成岩复合物不仅对了解岩浆分化过程有用，而且在经济上也是铂金元素元素，CR，Ni，Cu和Fe Ore矿床的主要来源。 铁同位素研究可以帮助阐明这些火成岩复合物的形成过程及其矿物质沉积物，因为FE的不同同位素可以在各种过程中可能将不同的阶段分为不同的阶段，包括从熔体中结晶的矿物质，乡村岩石的同化以及岩石和后期水热液之间的反应。 在各个晶体中，Fe同位素也可以以不同的速度通过各种矿物扩散，并且还可以反映平衡（岩浆）或非平衡（动力学）过程。 通过多收集器电感耦合等离子体质谱法（MC-ICP-MS）对Fe稳定同位素测量的精确度的改善表明，高温镁铁质和超跑的地壳和地幔无知的岩石，Lunar Mafic Rocks和Meterites和Meterites和Metereorites中存在显着变化。 这些发现有望成功理解岩浆分化和行星形成过程。 但是，当前对单个矿物质的Fe同位素组成以及它们中的分馏中的知识仍然有限，并且在高温地面和外物地球象征系统中，Fe同位素分馏的原因，机制和含义仍然很少。 使用FE同位素详细研究了火成岩的数量非常有限。 此外，在外星岩石中单个矿物质的原位FE同位素测量不可用，而陆地岩石中只有很少的矿物质。 这意味着先前在散装矿物质中测量的Fe同位素组成很可能是在许多情况下，在晶体生长，扩散或晚期热液变化过程中记录的复合成分的平均值。 该项目将在简单的高温岩浆系统中确定Fe同位素分馏的经验，原因和机制，该系统结合了Fe和O对散装岩石和矿物质的同位素分析，以及高空间分辨率的原位分辨率和O型矿物质的高空间分析，并通过feStecond lasecond Laser Ablation（FS-la）和Sims Mc-la specpration and Specterightionaly（fs-la）分析。镁铁质粉刺层次分层，格陵兰岛Skaergaard，是地球上研究最多的侵入性复合物。 这种侵入体现了一个高度分化的岩浆腔，起源于一个大型的岩浆体，该体通过分数结晶进行了广泛的封闭系统演化，后来经历了水热改变。 The results of this research will help understand the processes of formation of mafic-ultramafic layered intrusions and their host magmatic mineral deposits and has implications for understanding planetary differentiation processes.The emphasis of this project is on systematic, high resolution, inter-mineral Fe isotope fractionations and in situ intra-mineral Fe isotope compositions (by fs-LA-MC-ICP-MS). 由于FS-LA-MC-ICP-MS是地球化学的一种新技术，因此这项研究将有助于开发最终使更广泛的地球科学社区受益的方法。 详细的散装岩石和矿物Fe和O同位素组合物结合了原位Fe同位素组成，矿物化学，O同位素冷却温度，散装岩石的主要和微量元素组成以及建模将产生对单个大型侵入的最全面和详细的研究。 氧同位素组成将有助于辨别高温岩浆Fe同位素组成（平衡），并从动力学和晚期热液效应中辨别出。 所有这些数据一起将有助于确定测量分馏的起源（分数结晶，化学扩散，热扩散，晚期水热改变）。 Skaergaard计算的温度的矿物质Fe同位素分馏因子将有助于理解其他陆地火成岩系统，月球和火星岩石以及其他行星物体中的那些。 由于很难从陨石中获得大型样品，因此这项研究将提供急需的信息，以确定外星样品研究的最佳方法。 这项工作的结果将提高我们对侵入水平的Fe同位素大规模演变以及晶体内Fe同位素异质性的理解。该项目结合了矿物学，岩石学，经济地质学，地球化学以及PI的FE和O同位素地球化学的专业知识，以及威斯康星大学 - 麦迪逊分校的合作者。 该项目将支持早期的职业女科学家，资助两名M.S.这些和本科生的研究人员，并支持东卡罗来纳大学最先进的高温同位素地球化学研究的物理基础设施的发展。 这项合作还将为ECU的研究生和本科生提供与UW-Madison的最先进的分析设施合作并与地球化学顶级领导者互动的经验。

项目成果

SIMS matrix effects in oxygen isotope analysis of olivine and pyroxene: Application to Acfer 094 chondrite chondrules and reconsideration of the primitive chondrule minerals (PCM) line

• DOI: 10.1016/j.chemgeo.2022.121016
• 发表时间: 2022-07
• 期刊: Chemical Geology
• 影响因子: 3.9
• 作者: Mingming Zhang;K. Fukuda;M. Spicuzza;G. Siron;A. Heimann;Alexander Hammerstrom;N. Kita;T. Ushikubo;J. Valley