Time-resolved XAS to study laser shock-induced transformation from siderite to magnetite

Siderite (FeCO3) is a common carbonate mineral in iron-bearing sedimentary settings and soils. It is present on Earth in a large variety of environments, which can be targets of impacts, and it has also been identified in meteorites. Two previous studies on natural siderite have demonstrated the shock-induced decomposition of siderite into iron oxides and carbon-bearing species that could explain the origin of magnetite in the Martian meteorite ALH84001 as due to a shock event. Both studies have been performed on recovered samples and give no clues on the timing and mechanisms of this transformation (e.g. peak shock or adiabatic release). In this proposal, we aim at in-situ observation of such transformation by time-resolved X-ray Absorption Spectroscopy during laser shock compression by exploiting the capability of the new High-Power Laser Facility (HPLF) at the ESRF.菱铁矿（Siderite, FeCO₃）是含铁沉积环境与土壤中常见的碳酸盐矿物。该矿物广泛分布于地球各类可作为撞击靶区的环境中，且已在陨石中被检出。此前两项针对天然菱铁矿的研究已证实，冲击作用可诱导菱铁矿分解为氧化铁与含碳物种，该结果可解释火星陨石ALH84001中磁铁矿的成因系冲击事件所致。上述两项研究均基于回收样品开展，未能阐明该转变的发生时序与作用机制（例如冲击峰值阶段或绝热释放过程）。在本研究提案中，我们拟依托欧洲同步辐射光源（ESRF）新建的高功率激光装置（High-Power Laser Facility, HPLF）的实验能力，通过激光冲击压缩过程中的时间分辨X射线吸收光谱法，对该转变过程开展原位观测。