Petitgirard S, Borchert M, Andrault D, Appel K, Mezouar M, Liermann H-P
European Synchrotron Radiation Facility (ESRF), Grenoble, France.
Rev Sci Instrum. 2012 Jan;83(1):013904. doi: 10.1063/1.3680573.
Data on partitioning behavior of elements between different phases at in situ conditions are crucial for the understanding of element mobility especially for geochemical studies. Here, we present results of in situ partitioning of trace elements (Zr, Pd, and Ru) between silicate and iron melts, up to 50 GPa and 4200 K, using a modified laser heated diamond anvil cell (DAC). This new experimental set up allows simultaneous collection of x-ray fluorescence (XRF) and x-ray diffraction (XRD) data as a function of time using the high pressure beamline ID27 (ESRF, France). The technique enables the simultaneous detection of sample melting based to the appearance of diffuse scattering in the XRD pattern, characteristic of the structure factor of liquids, and measurements of elemental partitioning of the sample using XRF, before, during and after laser heating in the DAC. We were able to detect elements concentrations as low as a few ppm level (2-5 ppm) on standard solutions. In situ measurements are complimented by mapping of the chemical partitions of the trace elements after laser heating on the quenched samples to constrain the partitioning data. Our first results indicate a strong partitioning of Pd and Ru into the metallic phase, while Zr remains clearly incompatible with iron. This novel approach extends the pressure and temperature range of partitioning experiments derived from quenched samples from the large volume presses and could bring new insight to the early history of Earth.
原位条件下元素在不同相之间的分配行为数据对于理解元素迁移至关重要，尤其是对于地球化学研究。在此，我们展示了使用改进的激光加热金刚石对顶砧（DAC），在高达50 GPa和4200 K的条件下，微量元素（Zr、Pd和Ru）在硅酸盐熔体和铁熔体之间的原位分配结果。这种新的实验装置允许使用法国ESRF的高压光束线ID27，作为时间函数同时收集x射线荧光（XRF）和x射线衍射（XRD）数据。该技术能够基于XRD图谱中漫散射的出现（这是液体结构因子的特征）同时检测样品熔化，并在DAC中激光加热之前、期间和之后使用XRF测量样品的元素分配。我们能够在标准溶液中检测到低至几ppm水平（2 - 5 ppm）的元素浓度。通过对激光加热后的淬火样品上微量元素的化学分配进行映射来补充原位测量，以约束分配数据。我们的初步结果表明，Pd和Ru强烈分配到金属相中，而Zr与铁明显不相容。这种新方法扩展了从大体积压力机淬火样品获得的分配实验的压力和温度范围，并可能为地球早期历史带来新的见解。
