Transition of Metastable Pyrrhotites to a Stable Phase State
- PDF / 567,424 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 35 Downloads / 190 Views
sition of Metastable Pyrrhotites to a Stable Phase State V. V. Onufrienoka, *, A. V. Chzhana, b, G. V. Bondarenkob, c, and G. Yu. Yurkinb, d aKrasnoyarsk
State Agrarian University, Krasnoyarsk, 660049 Russia Siberian Federal University, Krasnoyarsk, 660041 Russia c Institute of Chemistry and Chemical Technology, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk, 660036 Russia dKirensky Institute of Physics, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk, 660036 Russia *e-mail: [email protected] b
Received September 5, 2018; revised March 26, 2020; accepted April 2, 2020
Abstract—Equilibrium phase relations of synthetic minerals prepared by annealing metastable iron sulfides, followed by prolonged isothermal storage in the Earth atmosphere, have been studied by X-ray diffraction. The results demonstrate that prolonged storage of synthetic pyrrhotites annealed at different temperatures makes it possible to identify metastable and stable phases of Fe and S compounds. Keywords: mineral, pyrite, troilite, impurity centers, magnetization DOI: 10.1134/S0020168520090137
INTRODUCTION The FeS2–FeS transition is a topical issue because it is of both theoretical and practical interest. It is known that, decomposing under the effect of an external influence, pyrite (FeS2) converts into pyrrhotite and then to troilite, forming various combinations of phases. Note that the phase relations involved can vary with time [1–4] and that some phases and their relations still remain unexplored [5, 6]. Recent years have seen increasing interest in minerals of space origin. This is due in part to the fact that their formation is influenced by extreme conditions, such as high vacuum and extremely low or extremely high temperatures. One example is troilite (FeS) [7]. In pure form, it is only present in meteorites, so this mineral is of interest from the viewpoint of the formation of planets and mineral resources on them. One mineral forming during underwater volcanic eruptions is pyrrhotite. It has a nonstoichiometric composition and its crystal structure contains cation vacancies [8, 9]. Processes underlying the transition of pyrrhotite minerals to a stable phase state have not yet been studied in sufficient detail. Typically, the transition takes a very long time, which makes it difficult to study experimentally, whereas theoretical predictions can turn out to be wrong in practice. Therefore, it is of interest to carry out prolonged experiments, in which one can observe transformations of minerals under isothermal conditions in the Earth atmosphere. The
formula unit of pyrrhotite has the form Fe1 – xS, where x is the number of vacancies, that is, the average number of vacancies per Fe atom (vacancy density). The magnetic properties of nonstoichiometric ferrimagnets are closely related to the cation vacancy distribution in their structure [10–12]. For example, the structure of pyrrhotite exhibits ferromagnetic spin order in the basal plane and antiferromagnetic order in neighboring planes. Pyrrhotite differs from t
Data Loading...
