Experimental Calibration of the Olivine-melt Ni Thermometer Under Hydrous Conditions: Applications to Hygrometry, Oxybarometry and Olivine Phenocryst Growth Rates

含水条件下橄榄石熔体镍温度计的实验校准：在湿度测定、氧压测定和橄榄石斑晶生长速率中的应用

• 批准号: 1551344
• 负责人: Rebecca Lange
• 金额: $ 34万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1551344&HistoricalAwards=false
• 关键词: Experimental; Calibration; Olivine; melt; Ni

Water plays a unique role in the planetary evolution of Earth, particularly at subduction zones. The recycling of oceanic water into the mantle at subduction zones, the tectonic setting where continental crust forms, triggers partial melting and the formation of hydrous basalts, which differentiate to form continental crust, unique to Earth within our solar system. One of the many challenges associated with the study of hydrous basalts is that current thermometers cannot be accurately applied to them. The goal of this project is to calibrate a Ni-based olivine-melt thermometer, which is independent of melt water contents and can thus be applied to hydrous basalts to obtain accurate temperatures of formation. It will also allow the concentration of water in basaltic liquids to be determined at the onset of crystallization. This project will engage two Ph.D. graduate students and at least three undergraduate students, who will be trained in the operation of various experimental apparatus and analytical techniques, as well as thermodynamic modeling; all of these tools and skills have important applications in material science. The project will support students from underrepresented groups in a research team that has demonstrated a commitment to expanding the diversity of those in the sciences.The specific goals of this proposal are to perform hydrous phase-equilibrium experiments in a cold-seal apparatus under controlled fO2 and fH2O conditions on a variety of natural basalt and basaltic andesite liquids over a range of temperature and pressure, which will enable calibration of how these parameters, together with melt composition, affect the partitioning of Ni between olivine and liquid. In addition, the depression of the olivine liquidus as a function of melt water content (up to ¡Ü 8 wt%) will be experimentally mapped out for several melt compositions. Once a well-calibrated thermometer and hygrometer are in hand, it will be applied to 100 basalts from the Mexican and Cascades volcanic arcs and compared to results from olivine-hosted melt inclusions. Two additional experimental goals are to measure crystal growth rates of olivine phenocrysts under hydrous melt conditions, especially for natural samples that contain olivine with diffusion-limited growth textures, and to test whether Fe-Mg KD values obtained in hydrous olivine-melt experiments can be used to place constraints on the oxidation state of natural basalts.

水在地球的行星演化中扮演着独特的角色，特别是在俯冲带。 大洋水在俯冲带（大陆地壳形成的构造环境）再循环进入地幔，引发部分熔融和含水玄武岩的形成，这些玄武岩分化形成大陆地壳，这是我们太阳系内地球所特有的。 与含水玄武岩研究相关的许多挑战之一是，目前的温度计无法准确地应用于它们。 本项目的目标是校准镍基橄榄石熔体温度计，这是独立的熔融水含量，因此可以应用于含水玄武岩，以获得准确的温度形成。 它还将允许在结晶开始时确定玄武质液体中水的浓度。 该项目将聘请两名博士。研究生和至少三名本科生，他们将接受各种实验仪器和分析技术的操作以及热力学建模的培训;所有这些工具和技能在材料科学中都有重要的应用。 该项目将支持一个致力于扩大科学领域多样性的研究小组中代表性不足的群体的学生。该提案的具体目标是在一个冷密封装置中，在受控的fO 2和fH 2O条件下，在各种天然玄武岩和玄武安山岩液体上，在一定温度和压力范围内，这将使得能够校准这些参数与熔体组成一起如何影响镍在橄榄石和液体之间的分配。 此外，橄榄石液相线的下降作为熔体水含量的函数（高达~8wt%）将实验绘制出几个熔体组成。 一旦一个校准良好的温度计和湿度计在手，它将被应用于100个玄武岩从墨西哥和喀斯喀特火山弧，并比较结果从橄榄石托管熔融包裹体。 两个额外的实验目标是测量晶体生长速率的橄榄石斑晶在含水熔体条件下，特别是对于天然样品，含有橄榄石与扩散限制生长纹理，并测试是否铁镁KD值在含水橄榄石熔体实验中获得可以用来放置约束天然玄武岩的氧化态。