Investigations of the meteoritic mineral (Fe,Ni)₃P

Abstract

A survey is presented on some characteristic features of meteoritic (Fe,Ni) 3 P which is an abundant and important minor phase of most iron meteorites. This mineral (named schreibersite/rhabdite) plays a decisive role during the formation of the so-called Widmanstätten pattern. Different transmission as well as scanning electron microscopic techniques have been applied to get more precise information about the real structure of the phosphide crystals, their chemical composition and the metal distribution across the phoshide/ kamacite interface. X-ray crystal structure determinations have been performed for selected (Fe,Ni) 3 P -cystals from various iron meteorites (Toluca, North Chile, Watson, Orange River, Morasko, Agpalilik, Odessa, Canyon Diablo). These experiments revealed a metal ordering, i.e. for the three non-equivalent metal positions a different substitution of Fe by Ni has been found. The perfection of the brittle (Fe,Ni) 3 P samples differs appreciably and seems to be dependent on the thermal history of each individual meteorite. Moreover, inside Ni-rich rhabdite crystals small monocrystalline inclusions of CrN (carlsbergite) have been detected.

Study of iron meteorite Sikhote–Alin and extracted iron–nickel phosphides using Mössbauer spectroscopy with high velocity resolution

“…Basing on relative areas S of spectral components we can suppose that component 2 (S = 36.64%) related to M1 sites, components 3 and 4 (total S = 21.39%) related to M3 sites, and components 5 and 6 (total S = 36.92%) related to M2 sites. In this case occupation of M1 and M2 sites by Fe was the same while that of M3 sites was lower that correlated with the data [2]. Higher values of H eff for M1 and M3 sites in comparison with those for M2 site correlated with data for Fe 3 P [6] in which larger magnetic moments were found for M1 and M3 sites in iron phosphide.…”

“…There were only five sextets for phosphide while previous studies demonstrated the presence of six sextets [5,6]. It was shown that Fe/Ni distribution between M1, M2 and M3 sites in schreibersite from Sikhote-Alin meteorite was Fe, Fe and Ni [2]. Basing on relative areas S of spectral components we can suppose that component 2 (S = 36.64%) related to M1 sites, components 3 and 4 (total S = 21.39%) related to M3 sites, and components 5 and 6 (total S = 36.92%) related to M2 sites.…”

“…The crystal structure of synthetic Fe 3 P and meteoritic phosphides was similar and demonstrated three crystallographic sites for metal atoms denoted as M1, M2 and M3 [1]. X-ray crystal structure of schreibersite and rhabdite extracted from various meteorites showed different Fe substitution by Ni in nonidentical sites [2,3]. Schreibersite from iron meteorites has been studied only in a few cases using Mössbauer spectroscopy while rhabdite was not studied yet due to tremendous difficulties of phosphides extraction in required quantities.…”

Investigation of microstructure and thermophysical properties of Morasko iron meteorites

“…The mean Fe/Ni ratio in schreibersite is 2.8, and in rhabdite it is 1.13. The chemical composition of kamacite, taenite, schreibersite, rhabdite and cohenite of Morasko meteorites is similar to the composition established in other coarse octahedrites, and in other Morasko samples [2,4,14,20,27,28]. Morasko belongs to IAB-MG chemical group, i.e.…”

“…The nucleation of iron-nickel phosphides: schreibersite and rhabdite, in the temperature range between 800°C and 400°C during the cooling of asteroids, takes place during the formation of Widmanstätten structure in iron meteorites [1][2][3][4][5]20,27,28]. Clarke and Goldstein [28] distinguished four types of extraterrestrial phosphides found in various iron meteorites: (i) massive schreibersite nucleated heterogeneously at about 800°C, (ii) rhabdite homogeneously nucleated inside kamacite at about 600°C, (iii) schreibersite heterogeneously nucleated at grain boundaries and taenite borders at approximately 500°C, and (iv) microrhabdite homogeneously nucleated at 400°C.…”