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DFENS: Diffusion Chronometry Using Finite Elements and Nested Sampling
Geochemistry, Geophysics, Geosystems ( IF 2.9 ) Pub Date : 2021-04-04 , DOI: 10.1029/2020gc009303
Euan J. F. Mutch 1, 2 , John Maclennan 1 , Oliver Shorttle 1, 3 , John F. Rudge 4 , David A. Neave 5
Affiliation  

In order to reconcile petrological and geophysical observations of magmatic processes in the temporal domain, the uncertainties in diffusion timescales need to be rigorously assessed. Here, we present a new diffusion chronometry method: Diffusion chronometry using Finite Elements and Nested Sampling (DFENS). This method combines a finite element numerical model with a nested sampling Bayesian inversion, meaning that uncertainties in the parameters contributing to diffusion timescale estimates can be obtained and that observations from multiple elements can be used to better constrain individual timescales. Uncertainties associated with diffusion timescales can be reduced by accounting for covariance in the uncertainty structure of diffusion parameters rather than assuming that they are independent of each other. We applied the DFENS method to the products of the Skuggafjöll eruption from the Bárðarbunga volcanic system in Iceland, which contains zoned macrocrysts of olivine and plagioclase that record a shared magmatic history. Olivine and plagioclase provide consistent pre‐eruptive mixing and mush disaggregation timescales of less than 1 year. The DFENS method goes some way toward improving our ability to rigorously address the uncertainties of diffusion timescales, but efforts still need to be made to understand other systematic sources of uncertainty such as crystal morphology, appropriate choice of diffusion coefficients, initial conditions, crystal growth, and the petrological context of diffusion timescales.

中文翻译:

DFENS:使用有限元素和嵌套采样的计时码表

为了调和岩浆过程在时域的岩石学和地球物理观测,需要严格评估扩散时间尺度的不确定性。在这里,我们提出了一种新的扩散计时法:使用有限元和嵌套采样(DFENS)的扩散计时法。该方法将有限元数值模型与嵌套采样贝叶斯反演相结合,这意味着可以获得用于扩散时标估计的参数不确定性,并且可以使用来自多个元素的观测值更好地约束单个时标。可以通过考虑扩散参数不确定性结构中的协方差来减少与扩散时间尺度相关的不确定性,而不是假设它们彼此独立。我们将DFENS方法应用于来自冰岛Bárðarbunga火山系统的Skuggafjöll火山喷发的产品,该火山系统包含带橄榄石和斜长石的分区巨晶,记录了共同的岩浆历史。橄榄石和斜长石在喷发前的混合和糊状分解的时间尺度均小于1年。该DFENS方法在某种程度上为了提高我们严格地解决扩散时间尺度的不确定性的能力,但仍需要进行了解不确定性的其他系统的来源,如晶体形态,扩散系数的合适的选择,初始条件,晶体生长的努力,以及扩散时标的岩石学背景。其中包含橄榄石和斜长石的带区巨晶,记录了共同的岩浆历史。橄榄石和斜长石在喷发前的混合和糊状分解的时间尺度均小于1年。该DFENS方法在某种程度上为了提高我们严格地解决扩散时间尺度的不确定性的能力,但仍需要进行了解不确定性的其他系统的来源,如晶体形态,扩散系数的合适的选择,初始条件,晶体生长的努力,以及扩散时标的岩石学背景。其中包含橄榄石和斜长石的带区巨晶,记录了共同的岩浆历史。橄榄石和斜长石在喷发前的混合和糊状分解的时间尺度均小于1年。该DFENS方法在某种程度上为了提高我们严格地解决扩散时间尺度的不确定性的能力,但仍需要进行了解不确定性的其他系统的来源,如晶体形态,扩散系数的合适的选择,初始条件,晶体生长的努力,以及扩散时标的岩石学背景。
更新日期:2021-04-23
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