Measurements of Thermal Transport Properties of Melts vs. Temperature and Composition: Theoretical Implications

火山和火成岩活动，包括产生被称为岩浆的熔体及其随后的运输和冷却，在地球的分层结构如何随着时间的推移而演变和冷却方面起着至关重要的作用。不同成分的熔体产生了地球上各种各样的岩石。地球的冷却速度受到影响，因为熔体可以移动，携带热量，但如果静止不动，则会阻碍热传导，因为它们的热扩散系数低(D)。到目前为止，还没有准确测量D的方法。提出的工作是及时的，因为在高温(T)下精确测量D现在是可能的。从材料科学到地球科学的技术转移使拟议的研究成为可能。虽然这些新数据的直接用途是更好地理解岩石融化和火山作用的过程，以及流动和慢传导热阻抗的平衡，但这些发现将有助于我们理解微观过程，从而揭示热传输的基本物理。因此，这项研究将有助于我们了解地球内部分化的历史。具体地说，将使用激光闪光分析（LFA）来量化远高于熔化温度的熔体中的热传递，该分析缺乏通常存在的接触损失和虚假辐射传递增益的系统误差。虽然LFA是材料科学的行业标准，但研究者的实验室是地球科学中唯一一个追求这种技术的实验室。到目前为止，他们已经测量了少量玻璃成分的D，并且最多比玻璃转变温度高几百度（因为流动终止了悬浮样品的数据收集），然而这些少数结果为熔体行为提供了重要的见解。少量成分融化的结果为复杂岩浆的微观行为提供了新的见解，但迄今为止尚未认识到的涉及红外光子的辐射机制的发现，需要在建立精确的模型之前进行验证，以便将这些数据外推到地球内部的条件。建议：(1)开发一种新的石墨电池，可以在大T范围内测量液态以上的“脆弱”硅酸盐液体的D；(2)独立测量几种具有重要地质意义的熔体的dD/dT，将他们现有的技术应用于不同H2O含量的玻璃，玻璃化转变温度变化很大；(3)确定不同熔岩从玻璃化过渡到超流体状态的D作为T的函数；(4)量化目前数据显示的Si、Fe和Ca的重要影响；(5)基于Dmelt（T，X，P）的结果和公式构建一个新的微观模型，用于后续需要热建模的各种地球科学应用。

Volcanic and igneous activity, which involve through production of melts known as magmas and their subsequent transport and cooling, play a crucial role in how Earth's layered structure has evolved and cooled over time. Melts differing in composition from their source produce various rock types found on the Earth. Earth's cooling rate is affected because melts can move, carrying heat with them, but impede heat conduction if stationary, because they have low thermal diffusivity (D). Up to the present, methods to accurately measure D were not available. The proposed work is timely because accurate measurements of D at high temperatures (T) are now possible. The proposed study is made possible by technology transfer from materials science to geoscience. Although the immediate use for these new data is to better understand the processes of rock melting and volcanism, and the balance of heat transport by flow and heat impedance by slow conduction, the findings will help us to understand microscopic processes and therefore reveal the basic physics of heat transport. Thus, this study thus will potentially contribute to our understanding of the Earth's history of internal differentiation.Specifically, heat transport in melts well above melting temperature will be quantified using laser flash analysis (LFA) which lacks commonly occutring systematic errors of contact losses and spurious radiative transfer gains. Although LFA is the industry standard in materials science, the investigator's laboratory is the only one in Earth science pursuing this technique. Thus far they have measured D of a small number of glass compositions and to at most a few hundred degrees above the glass transition temperature (because flow terminates data collection from suspended samples), yet these few results have provided important insights into melt behavior. Results just above melting of a small number of compositions have provided new insight into microscopic behavior of complex magmas, but the findings of an heretofore unrecognized radiative mechanism involving IR photons, needs to be verified before accurate models can be constructed that permit extrapolation of these data to conditions in Earth's interior. It is proposed to: (1) Develop a new graphite cell enabling measurement of D for 'fragile' silicate liquids above liquidus over a large T range; (2) Independently measure dD/dT of several geologically important melts by applying their current technique to glasses with varying H2O contents, for which the glass transition temperature varies drastically; (3) Determine D as a function of T for diverse lavas from through the glass transition to superliquidus conditions; (4) Quantify effects of Si, Fe, and Ca which their present data indicate are important; (5) Construct a new microscopic model based on the results and formulae for Dmelt(T,X,P), for subsequent use for a variety of Earth Sciences applications that require thermal modeling.