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.

了解地球矿物在极端条件下的热传导率和热扩散率对于了解地球的物理和化学过程及其演变非常重要。地幔热传输速率对地球磁场的存在和稳定至关重要。地幔内部的温度分布取决于对流、传导和辐射的传热速率。了解这些过程需要了解作为压力和温度函数的热导率。地球和行星内部物质的热导率是控制核幔热历史及其动力学的关键参数之一。它们与行星吸积和分异过程、地幔和地核温度的时间演化以及地球磁场的产生有关。在本项目中，拟采用泵浦-探测脉冲激光技术测定地球关键矿物在高P-T条件下的热导率。为了确定晶格热导率，将使用时间和空间分辨的光谱辐射和/或时域热反射测量穿过样品的热通量及其时间历程。这些测量将应用于下地幔矿物和铁和富铁合金。为了推断辐射热导率，将研究这些地幔矿物在高P-T条件下（高达150 GPa和6000 K）的紫外-红外光谱范围内的光谱。对于光学性质的原位高温测量，将采用可见光和红外光谱范围内的宽带光谱系统，该系统使用超连续谱和非线性混合脉冲激光源，并结合时间分辨多通道探测器（条纹相机，增强型CCD和阵列MCT探测器）。这些技术将被应用于研究下地幔矿物，硅酸盐熔体和行星冰。这些实验数据将直接估计在相关的P-T条件下，地球深部物质热导率的辐射和传导部分。知识的深度依赖的地幔的热导率将补充地幔对流建模，其中一系列可能的动态结构的预测取决于假设的热导率的最新进展。因此，PI的工作将为这些模型和我们目前对地球内部的理解提供关键的测试。