Minerals formed at high pressures are sensitive indicators of extreme pressure-temperature conditions that occur in nature. The discovery of the high-pressure polymorph of (Fe,Ni)2P, allabogdanite in the surficial pyrometamorphic rocks of the Hatrurim Formation (the Mottled Zone) surrounding the Dead Sea basin in Israel is the first terrestrial occurrence of a mineral previously only found in iron meteorites. Stepwise annealing experiments demonstrate that allabogdanite is metastable at ambient pressure and that it irreversibly transforms into its low-pressure polymorph, barringerite, upon heating to 850 ± 50 °C. High-pressure, high-temperature diamond-anvil cell (DAC) experiments confirm the results of annealing experiments. The DAC data indicate that Hatrurim allabogdanite is metastable below 7.4 GPa, and the low-to high-pressure phase transition (barringerite → allabogdanite) occurs at 25 ± 3 GPa and 1400 ± 100 °C. The observed transition pressure of Hatrurim allabogdanite is significantly higher than that of pure synthetic Fe2P (8 GPa) due to partial substitution of Fe for Ni (4 wt%) and Mo (2.5 wt%). Because the influence of substituting impurities on the conditions of phase transitions can be unexpectedly strong, our findings confirm that caution should be exercised when extrapolating data from experiments on synthetic compounds to natural systems. Based on the discovery of terrestrial allabogdanite (Fe,Ni)2P coupled with experiments probing the phase transitions in this natural composition, we contend that terrestrial allabogdanite formed via transformation from barringerite and posit potential scenarios of its formation.

中文翻译：

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陆相铝镁石(Fe,Ni)2P的发现及Ni和Mo取代对巴林石-铝镁石高压转变的影响

在高压下形成的矿物是自然界发生的极端压力-温度条件的敏感指标。在以色列死海盆地周围的 Hatrurim 组（斑驳带）的表层热变质岩中发现了 (Fe,Ni)2P 的高压多晶型物，这是一种以前仅在地球上发现的矿物。铁陨石。逐步退火实验表明，allabogdanite 在环境压力下是亚稳态的，并且在加热到 850 ± 50 °C 时，它不可逆地转变为其低压多晶型物 barringerite。高压、高温金刚石砧座 (DAC) 实验证实了退火实验的结果。DAC 数据表明，Hatrurim allabogdanite 在 7.4 GPa 以下是亚稳态的，低压到高压相变（barringerite → allabogdanite）发生在 25 ± 3 GPa 和 1400 ± 100 °C。由于 Fe 部分取代了 Ni (4 wt%) 和 Mo (2.5 wt%)，因此观察到的 Hatrurim allabogdanite 的转变压力明显高于纯合成 Fe2P (8 GPa)。由于取代杂质对相变条件的影响可能出乎意料地强烈，我们的研究结果证实，在将合成化合物的实验数据外推到自然系统时应谨慎行事。基于对陆地盐雾石 (Fe,Ni)2P 的发现以及探索这种天然成分中相变的实验，我们认为陆生盐雾石是通过从巴林格石转化形成的，并假设其形成的潜在场景。