Discovery of terrestrial allabogdanite (Fe,Ni)2P, and the effect of Ni and Mo substitution on the barringerite-allabogdanite high-pressure transition

Abstract

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) 2 P, 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 Fe 2 P (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) 2 P 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.

Nickolayite, FeMoP, a new natural molybdenum phosphide

“…With the exception of nickolayite, all minerals listed in Table 9 were originally discovered in meteorites. Allabogdanite, the high-pressure modification of (Fe,Ni) 2 P (Britvin et al , 2019c), has been described recently in terrestrial pyrometamorphic rocks of the Hatrurim Formation in Israel (Britvin et al , 2021b), however the others remain solely of meteoritic origin. Besides phosphides, two arsenide minerals belong to the Co 2 Si structure type: these are rhodarsenide, (Rh,Pd) 2 As (Tarkian et al , 1997), and palladodymite, (Pd,Rh) 2 As (Britvin et al , 1999).…”

Discovery of terrestrial andreyivanovite, FeCrP, and the effect of Cr and V substitution on the low-pressure barringerite-allabogdanite transition

“…paralava and the related phosphide mineralization of the Zohar wadi belong to the high-temperature formations of the Hatrurim Complex, which is confirmed by the following observation. Pseudowollastonite (polytype 4M; a = 6.8382(2)Å, b = 22.8692(3)Å, c = 19.6208(5)Å, β = 90.656(2)°, our SCXRD data) indicates the high temperature of crystallization, higher than 1200°С, and low pressure (close to ambient pressure) excluding the appearance of "clear" allabogdanite(Swamy and Dubrovinsky 1997;Dera et al 2008;Seryotkin et al 2012;Britvin et al 2021b). Numerous aggregates of barringerite found on the boundary of paralava and hydrogrossular rock indicate temperature crystallization higher than 1350°С, as was established…”

“…The Hatrurim Complex has recently become known as a source of terrestrial phosphides (Britvin et al 2015). Here, besides the phosphides typical of meteorites: schreibersite, Fe 3 P (Britvin et al 2021a), barringerite, Fe 2 P (Britvin et al 2017) and its high-pressure analogallobogdanite (Britvin et al 2021b), nine new phosphides: halamishite, Ni 5 P 4 (Britvin et al 2020a); negevite, NiP 2 (Britvin et al 2020b); nazarovite, Ni 12 P 5 (Britvin et al 2022a); zuktamrurite, FeP 2 (Britvin et al 2019a); transjoardanite, Ni 2 P (Britvin et al 2020c); polekhovskyite, MoNiP 2 (Britvin et al 2022b); murashkoite, FeP (Britvin et al 2019b); nickolayite, FeMoP (Murashko et al 2019); orishchinite, Ni 2 P (Britvin et al 2019c) were discovered. This detection of phosphides in the rocks of the Hatrurim Complex is unexpected.…”

“…Natural barringerite with low Ni (up to 0.1 apfu) and Mo (up to 0.04 apfu) impurities transfers to allobogdanite at 25 ± 3 GPa and at a temperature 1400 ± 100°C (Britvin et al 2021b). On the other hand, Litasov et al (2020) concluded on the basis of theoretical calculations and experimental data that allabogdanite is a lower-temperature phase compared to barringerite, which is stable at the ambient pressure and temperature lower than 500°C.…”

Cyclophosphates, a new class of native phosphorus compounds, and some insights into prebiotic phosphorylation on early Earth

“…Unfortunately, cyclophosphates, although widely used in synthetic chemistry and industry (Bezold et al, 2020), have never been encountered in nature. In the course of ongoing research on natural phosphide assemblages at the Dead Sea basin (Britvin et al, 2015(Britvin et al, , 2021, we have discovered natural cyclophosphate minerals for the first time. We herein provide a brief characterization of their occurrence, explain their origin, and discuss the possible involvement of cyclophosphates in prebiotic phosphorylation reactions that could have occurred on primordial Earth.…”