CAREER: Experimental Investigation of the Transport Properties of Sulfide Melts at Upper Mantle Conditions

这个职业奖被设计为一个实验研究，以了解熔融的硫化铁是如何渗透到地球内部的。熔融的硫化铁是地球内部重要的地球化学和地球物理成分。它们在地球内部的流动性塑造了地球的结构和动力学，因此，研究深度硫化物的行为是理解地球演化的关键。在与地球上地幔相关的压力和温度条件下，将对硫化铁熔体进行两种性质的测量，电导率和粘度。当与地球物理观测相结合时，这些结果有可能探测到深层硫化物熔体的存在，并估计它们在小（毫米）和大（公里）尺度上的流动性，这可能导致对地球表面测量到的一些地球物理异常的重新解释。实验数据集也将与其他类地行星的内部有关。研究成果将与一项广泛的教育倡议相结合，该倡议包括帮助圣地亚哥联合学区的K-12学校教师在他们的课程中推广地球科学研究。研究人员和她的团队将与斯克里普斯海洋学研究所（SIO）和圣地亚哥联合学区（SDUSD）的科学教育负责人合作，围绕该项目的实验结果为教师设计培训讲习班。几名本科生和研究生以及一名博士后研究员将作为该项目的一部分得到支持。硫化物熔体的连通性和流动性似乎高度依赖于熔体相的组成以及氧化还原条件，这表明有必要研究熔体化学和氧化还原条件对硫化物熔体输运性质的影响。高压和高温实验将在UCSD-SIO和APS-GSECARS进行高达10 GPa和高达1700°C的实验。重点将放在影响硫化物熔体流动性的两个参数：化学和氧化还原条件。样品组成为Fe-S-O-Ni-Cu体系，氧逸度范围为IW-1至IW+4，对应于铁-钨（IW）氧化还原缓冲液。实验结果将应用于不同的构造背景，其中化学和氧化还原条件增强了硫化物熔体的互联性，并且地球物理（地震、电磁）观测表明上地幔不同深度的异常。硫化化合物输运性质的研究包括矿物物理学和地球物理学，与经济地质学（例如，与矿床形成有关的金属输运）、行星科学（例如，金属-硅酸盐分异）以及金属工业（例如，金属合金的强度和塑性）有关。围绕该项目的科学成果设计的教育倡议将支持将下一代地球科学标准纳入K-12级教学实践的努力。这次与科学教育专家的新颖合作将对SDUSD学生的地球科学教育产生直接影响。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This CAREER award is designed as an experimental study to understand how molten iron sulfides percolate inside the Earth. Molten iron sulfides are crucial geochemical and geophysical components of our planet's interior. Their mobility inside the planet has shaped the structure and dynamics of the Earth, and thus, studying the behavior of sulfides at depth is key to understanding the Earth's evolution. The measurements of two properties, electrical conductivity and viscosity, will be conducted on iron sulfide melts over a wide range of pressure and temperature conditions that are relevant to the Earth's upper mantle. When combined with geophysical observations, these results have the potential to detect the presence of sulfide melts at depth and estimate their mobility at small (mm) and large (km) scales, which may lead to the reinterpretation of some geophysical anomalies that are measured on the Earth's surface. The experimental data set will also be relevant to the interior of other terrestrial planets. The research outcomes will be integrated with an extensive education initiative that consists of helping K-12 schoolteachers at the San Diego Unified School District promote earth science research into their courses. The investigator and her group will be working with science education leaders at Scripps Institute of Oceanography (SIO) and San Diego Unified School District (SDUSD) to design training workshops for the teachers around the experimental results from this project. Several undergraduate and graduate students, as well as one postdoc researcher will be supported as part of this project.The interconnectivity and mobility of sulfide melts seem to depend highly on the composition of the melt phase as well as on redox conditions, suggesting that there is a fundamental need to study the effect of melt chemistry and redox conditions on the transport properties of sulfide melts. High-pressure and high-temperature experiments will be conducted up to 10 GPa and up to 1700°C at UCSD-SIO and APS-GSECARS. Emphasis will be placed on two parameters affecting sulfide melts' mobility: chemistry and redox conditions. Sample compositions will be in the Fe-S-O-Ni-Cu system and oxygen fugacity will range from IW-1 to IW+4, corresponding to the Iron-Wüstite (IW) redox buffer. Experimental results will be applied to different tectonic contexts where the chemistry and redox conditions enhance sulfide melt interconnectivity and where geophysical (seismic, electromagnetic) observations indicate anomalies at different depths in the upper mantle. This investigation of the transport properties of sulfide compounds encompasses mineral physics and geophysics, and is relevant to economic geology (e.g., metal transport related to ore deposit formation), planetary science (e.g., metal-silicate differentiation), as well as metal industry (e.g., strength and plasticity of metal alloys). The education initiative that will be designed around the scientific outcomes of the project supports efforts that integrate next generation earth science standards into instructional practices at the K-12 level. This novel collaboration with science education specialists will have direct impact on the earth science education of SDUSD students.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.