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

火山和火成岩活动涉及到被称为岩浆的熔体的产生及其随后的运输和冷却，在地球分层结构如何随着时间的推移而演变和冷却方面发挥着至关重要的作用。组成不同于其来源的熔岩产生了地球上发现的各种岩石类型。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，就会阻碍热传导，因为它们的热扩散率(D)很低。到目前为止，还没有准确测量D的方法。这项拟议的工作是及时的，因为现在可以准确地测量高温(T)下的D。这项拟议的研究是通过从材料科学向地球科学的技术转移而实现的。虽然这些新数据的直接用途是更好地了解岩石融化和火山作用的过程，以及流动热传输和慢传导热阻抗之间的平衡，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，这项研究可能有助于我们理解地球内部分异的历史。具体地说，在远高于熔化温度的熔体中，热传输将使用激光闪光分析(LFA)来量化，该分析缺乏常见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，但研究员的实验室是地球科学中唯一追求这项技术的实验室。到目前为止，他们已经测量了少量玻璃成分的D，最高可高出玻璃转变温度几百度(因为流动终止了对悬浮样品的数据收集)，但这些少数结果为熔体行为提供了重要的见解。上述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，但涉及红外光子的迄今未被认识的辐射机制的发现需要得到验证，然后才能建立准确的模型，允许将这些数据外推到地球内部的条件。建议：(1)发展一种新的石墨盒，能够在较大的T范围内测量液线以上“易碎”硅酸盐液体的D；(2)独立地测量几种地质上重要熔体的Dd/Dt，方法是将目前的技术应用于具有不同H2O含量的玻璃，其玻璃转变温度变化很大；(3)确定从玻璃转变到超液相线条件下不同熔岩的D作为T的函数；(4)量化Si、Fe和Ca的影响，它们的现有数据表明这些影响是重要的；(5)基于DMelt(T，X，P)的结果和公式构建新的微观模型，以供随后需要热模拟的各种地球科学应用使用。

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.