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

熔体热传输特性与温度和成分的测量：理论意义

• 批准号: 1321857
• 负责人: Anne Hofmeister
• 金额: $ 24.29万
• 依托单位: Washington University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-07-01 至 2018-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1321857&HistoricalAwards=false
• 关键词: Measurements; Thermal; Transport; Properties; Melts

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.

火山和火成岩活动，涉及通过生产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发挥着至关重要的作用。在地球上发现的各种岩石类型的组成与其来源不同的熔体。 地球的冷却速率受到影响，因为熔体可以移动，携带热量，但如果静止，则会阻碍热传导，因为它们具有低的热扩散率（D）。到目前为止，还没有准确测量D的方法。建议的工作是及时的，因为现在可以在高温（T）下精确测量D。通过从材料科学到地球科学的技术转移，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了解岩石融化和火山活动的过程，以及流动的热传输和缓慢传导的热阻抗的平衡，但这些发现将有助于我们了解微观过程，从而揭示热传输的基本物理学。因此，这项研究将有助于我们了解地球的内部differentiation.Specifically的历史，在熔融温度以上的熔体热传输将使用激光闪光分析（LFA），缺乏通常occutring接触损失和虚假的辐射传输增益的系统误差进行量化。虽然LFA是材料科学的行业标准，但研究人员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组合物的D，并且最多比玻璃化转变温度高几百度（因为流动终止了悬浮样品的数据收集），但这些少数结果提供了对熔体行为的重要见解。结果刚刚熔化的少数组合物提供了新的洞察复杂的岩浆的微观行为，但迄今未被认识到的辐射机制，涉及红外光子的发现，需要验证之前，可以构建准确的模型，允许这些数据外推到地球内部的条件。建议：（1）开发一种新的石墨池，能够在大的T范围内测量液相线以上的“易碎”硅酸盐液体的D;（2）通过将其现有技术应用于具有不同H2O含量的玻璃，独立测量几种地质上重要的熔体的dD/dT，因为玻璃化转变温度变化很大;（3）确定从玻璃化转变到超液相线条件下不同熔岩的D与T的函数关系;（4）量化Si、Fe和Ca的影响，它们目前的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，用于随后需要热建模的各种地球科学应用。