Thermal conductivity of Deep Earth's materials studied by fast pulsed laser techniques

通过快速脉冲激光技术研究地球深部材料的热导率

• 批准号: 1520648
• 负责人: Alexander Goncharov
• 金额: $ 24.39万
• 依托单位: Carnegie Institution of Washington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-01 至 2018-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1520648&HistoricalAwards=false
• 关键词: Thermal; conductivity; Deep; Earth; materials

Knowledge of thermal conductivity and thermal diffusivity of the Earth's minerals under extreme conditions is important for understanding the physical and chemical processes and their evolution in the Earth. The rate of the heat transport through the mantle is crucial for the existence and stability of the Earth's magnetic field. The temperature distribution inside the Earth's mantle depends on the rate of heat transfer by convection, conduction, and radiation. An understanding of these processes requires knowledge of the thermal conductivity as a function of pressure and temperature. Thermal conductivity of materials in Earth and planetary interiors is one of the key parameters controlling the thermal history of the core and mantle and their dynamics. These are related to the processes of planetary accretion and differentiation, the time evolution of mantle and core temperatures, and the generation of the Earth's magnetic field. In this project, it is proposed to determine the thermal conductivity of the Earth's key minerals under high P-T conditions by using pump-probe pulsed laser techniques. To determine the lattice thermal conductivity, the heat fluxes across the sample and their time history using time- and spatially resolved spectroradiometry and/or time-domain thermoreflectance will be measured. These measurements will be applied to lower mantle minerals and also Fe and Fe-rich alloys. To infer the radiative thermal conductivity, the optical spectra of these mantle minerals in the ultraviolet-to-infrared spectral range at high P-T conditions (up to 150 GPa and 6000 K) will be studied. For in situ high-temperature measurements of the optical properties, broad band optical spectroscopy systems in visible and infrared spectral ranges will be employed which use supercontinuum and nonlinearly mixed pulsed laser sources in combination with time-resolved multichannel detectors (streak camera, intensified CCD, and array MCT detector). These techniques will be applied to study lower mantle minerals, silicate melts, and planetary ices. These experimental data will give a direct estimate of the radiative and conduction parts of the thermal conductivity of deep Earth materials at the relevant P-T conditions. Knowledge of the depth-dependent thermal conductivity of the Earth's mantle will complement recent advances in mantle convection modeling, where a range of possible dynamic structures are predicted depending on the assumed thermal conductivity. Thus, the PI's work will provide a crucial test of these models and our current understanding of the Earth's interior.

在极端条件下，地球矿物质的热导率和热扩散率的了解对于理解物理和化学过程及其在地球中的演变很重要。通过地幔的热传输速率对于地球磁场的存在和稳定性至关重要。地球内部内部的温度分布取决于对流，传导和辐射的传热速率。对这些过程的理解需要了解导热率作为压力和温度的函数。地球和行星内部材料的导热率是控制核心和地幔及其动力学的热历史的关键参数之一。这些与行星积聚和分化的过程，地幔和核心温度的时间演变以及地球磁场的产生有关。在该项目中，建议通过使用泵探针脉冲激光技术在高P-T条件下确定地球关键矿物的热导率。为了确定晶格导热率，将测量样品及其时间历史的热通量，并使用时间和空间分辨的光谱测定法和/或时间域的热心率进行测量。这些测量将应用于低地幔矿物质以及Fe和Fe丰富的合金。为了推断辐射导热率，将研究这些地幔矿物的光谱在高P-T条件下（高达150 GPA和6000 K）下的紫外线至边红外光谱范围。对于光学特性的原位高温测量，将采用可见和红外光谱范围中的宽带光谱系统，使用超脑和非线性混合脉冲激光源与时期分辨的多物料摄像机结合使用（Streak Multichanl camera）（Streak Multichanel detctors，Intensified CCD和Array Mctector）。这些技术将应用于研究下地幔矿物质，硅酸盐熔体和行星冰。这些实验数据将直接估计深层材料在相关的P-T条件下的热导率的辐射和传导部分。了解地球地幔的深度依赖性导热率的知识将补充地幔对流建模的最新进展，其中预测一系列可能的动态结构，具体取决于假定的导热率。因此，PI的工作将为这些模型提供至关重要的测试，以及我们当前对地球内部的理解。