Developing a novel magmatic hygrometer using hydrogen in plagioclase

使用斜长石中的氢开发新型岩浆湿度计

• 批准号: 2438295
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2020
• 资助国家: 英国
• 起止时间: 2020 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2438295
• 关键词: Developing; novel; magmatic; hygrometer; using

Direct analysis of volatile concentrations in nominally anhydrous minerals (NAMs) represents a promising alternative to standard methods, as NAMs can incorporate trace concentrations of hydrogen, primarily in the form of hydroxyl defects, within their crystal structures (e.g., Bell and Rossman, 1992; Johnson and Rossman, 2004; Aubaud et al., 2004). NAMs can serve as a proxy for determining magmatic water concentrations if a partition coefficient between the hydrogen in the mineral of interest and melt is known at the relevant conditions. Previous studies on NAMs have typically utilised olivine and pyroxene (e.g., Wade et al., 2008; Lloyd et al., 2016), as their early crystallization from mafic melts enables insight into the water contents during the early stages of magma differentiation. However, comparably little work has been done on feldspars, despite their ubiquitous presence in volcanic rocks over a wide compositional and temperature range. Hence, this project aims to develop a novel technique of estimating magmatic water contents using plagioclase feldspar, by quantifying hydrogen partitioning between plagioclase and silicate melts and hydrogen diffusion through plagioclase.

直接分析名义上无水矿物（NAM）中的挥发物浓度代表了标准方法的一种有前途的替代方法，因为NAM可以在其晶体结构中掺入痕量浓度的氢，主要以羟基缺陷的形式存在（例如，Bell和Rossman，1992年;约翰逊和Rossman，2004年; Aubaud等人，2004年）。NAMS可以作为一个代理确定岩浆水的浓度，如果在有关条件下的矿物和熔体中的氢之间的分配系数是已知的。以前对NAM的研究通常使用橄榄石和辉石（例如，Wade等人，2008; Lloyd等人，2016年），因为它们从镁铁质熔体中早期结晶，使人们能够深入了解岩浆分异早期阶段的水含量。然而，几乎没有工作已经做了菱镁矿，尽管他们普遍存在于火山岩在广泛的成分和温度范围。因此，本项目旨在开发一种新的技术，估计岩浆水含量使用斜长石，通过量化氢之间的斜长石和硅酸盐熔体和氢扩散斜长石的分配。