{"title":"扩散:岩石年代学的障碍与机遇","authors":"M. Kohn, S. Penniston‐Dorland","doi":"10.2138/RMG.2017.83.4","DOIUrl":null,"url":null,"abstract":"Many of the approaches in petrochronology are rooted in the assumption of equilibrium. Diffusion is an expression of disequilibrium: the movement of mass in response to chemical potential gradients, and isotopes in response to isotopic gradients. It is extremely important that we be aware of how the effects of diffusion can place obstacles across our path towards petrochronologic enlightenment. Conversely the effects of diffusion also provide opportunities for understanding rates, processes, and conditions experienced by rocks. The enormity of the field does not permit us to provide a comprehensive review of either the mathematics of diffusion or quantitative data that have been obtained relevant to the interpretation of diffusive processes in rocks and minerals. Many resources cover these topics, including RiMG volume 72 ( Diffusion in Minerals and Melts ; Zhang and Cherniak 2010) and several textbooks (Crank 1975; Glicksman 2000). Particularly relevant to the discussion of petrochronology are summaries of the theory and controls on diffusion (Brady and Cherniak 2010; Zhang 2010), as well as diffusion rates in feldspar (Cherniak 2010a), accessory minerals (Cherniak 2010b), garnet (Ganguly 2010), mica, pyroxene, and amphibole (Cherniak and Dimanov 2010), and melts (Zhang and Ni 2010; Zhang et al. 2010). Rather than duplicate that material, our goal is to explore the obstacles and opportunities presented by the effects of diffusion as they inform the rates of petrologic processes. 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Many resources cover these topics, including RiMG volume 72 ( Diffusion in Minerals and Melts ; Zhang and Cherniak 2010) and several textbooks (Crank 1975; Glicksman 2000). Particularly relevant to the discussion of petrochronology are summaries of the theory and controls on diffusion (Brady and Cherniak 2010; Zhang 2010), as well as diffusion rates in feldspar (Cherniak 2010a), accessory minerals (Cherniak 2010b), garnet (Ganguly 2010), mica, pyroxene, and amphibole (Cherniak and Dimanov 2010), and melts (Zhang and Ni 2010; Zhang et al. 2010). Rather than duplicate that material, our goal is to explore the obstacles and opportunities presented by the effects of diffusion as they inform the rates of petrologic processes. 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引用次数: 29
摘要
岩石年代学中的许多方法都是建立在平衡假设的基础上的。扩散是不平衡的一种表现:质量的运动响应于化学势梯度,同位素响应于同位素梯度。非常重要的是,我们要意识到扩散的影响如何在我们走向岩石年代学启蒙的道路上设置障碍。相反,扩散效应也为了解岩石的速率、过程和条件提供了机会。这一领域的巨大范围不允许我们对扩散的数学或已获得的与解释岩石和矿物中的扩散过程有关的定量数据进行全面审查。许多资源涵盖了这些主题,包括环第七十二卷(矿物和熔体的扩散;Zhang and Cherniak 2010)和一些教科书(曲克1975;Glicksman 2000)。与岩石年代学的讨论特别相关的是对扩散的理论和控制的总结(Brady and Cherniak 2010;Zhang 2010),以及长石(Cherniak 2010a)、副矿物(Cherniak 2010b)、石榴石(Ganguly 2010)、云母、辉石、角闪石(Cherniak and Dimanov 2010)和熔体(Zhang and Ni 2010;Zhang et al. 2010)。我们的目标不是重复这些材料,而是探索扩散效应所带来的障碍和机会,因为它们通知了岩石过程的速率。为了实现这一目标,我们强调关键原则和说明性例子。扩散效应的定量解释假设了许多可能影响化学或同位素传输的因素的可预测性,包括温度、初始和边界条件、水和氧的逸度、其他组分的活性、多种扩散机制和晶体化学(元素取代到不同晶体位置的“耦合”)。此外,提取有意义的年龄、事件持续时间和温度需要……
Diffusion: Obstacles and Opportunities in Petrochronology
Many of the approaches in petrochronology are rooted in the assumption of equilibrium. Diffusion is an expression of disequilibrium: the movement of mass in response to chemical potential gradients, and isotopes in response to isotopic gradients. It is extremely important that we be aware of how the effects of diffusion can place obstacles across our path towards petrochronologic enlightenment. Conversely the effects of diffusion also provide opportunities for understanding rates, processes, and conditions experienced by rocks. The enormity of the field does not permit us to provide a comprehensive review of either the mathematics of diffusion or quantitative data that have been obtained relevant to the interpretation of diffusive processes in rocks and minerals. Many resources cover these topics, including RiMG volume 72 ( Diffusion in Minerals and Melts ; Zhang and Cherniak 2010) and several textbooks (Crank 1975; Glicksman 2000). Particularly relevant to the discussion of petrochronology are summaries of the theory and controls on diffusion (Brady and Cherniak 2010; Zhang 2010), as well as diffusion rates in feldspar (Cherniak 2010a), accessory minerals (Cherniak 2010b), garnet (Ganguly 2010), mica, pyroxene, and amphibole (Cherniak and Dimanov 2010), and melts (Zhang and Ni 2010; Zhang et al. 2010). Rather than duplicate that material, our goal is to explore the obstacles and opportunities presented by the effects of diffusion as they inform the rates of petrologic processes. To achieve this goal, we emphasize key principles and illustrative examples.
Quantitative interpretation of the effects of diffusion assumes predictability of numerous factors that may affect chemical or isotopic transport, including temperature, initial and boundary conditions, water and oxygen fugacities, activities of other components, multiple mechanisms of diffusion, and crystal chemistry (‘coupling’ of the substitution of elements into different crystallographic sites). Additionally, the extraction of meaningful ages, durations of events, and temperatures requires …
期刊介绍:
RiMG is a series of multi-authored, soft-bound volumes containing concise reviews of the literature and advances in theoretical and/or applied mineralogy, crystallography, petrology, and geochemistry. The content of each volume consists of fully developed text which can be used for self-study, research, or as a text-book for graduate-level courses. RiMG volumes are typically produced in conjunction with a short course but can also be published without a short course. The series is jointly published by the Mineralogical Society of America (MSA) and the Geochemical Society.