In:
Mineralogical Magazine, Mineralogical Society, Vol. 87, No. 3 ( 2023-06), p. 396-406
Abstract:
Rh-rich and Ir-poor erlichmanite–laurite OsS 2 –RuS 2 solid solutions have been discovered at placers in Haraigawa, Misato-machi, Kumamoto, Japan. Microprobe analysis was performed to identify solid solutions containing few sub-components other than Rh. Approximately 10 at.% Rh was found to be present in the solid-solution samples. Structural refinement was performed using four natural samples: Os 0.32 Ru 0.61 Rh 0.07 S 2 , Os 0.49 Ru 0.43 Rh 0.08 S 2 , Os 0.58 Ru 0.33 Rh 0.08 S 2 and Os 0.81 Ru 0.09 Rh 0.10 S 2 . The unit-cell parameters for the solid solutions containing Rh from Haraigawa varied from 5.61826(6) to 5.63142(8) Å. The (Os, Ru, Rh)–S distances in the Os 1 –x–y Ru x Rh y S 2 system were almost constant with a small variation of 0.001 Å. Conversely, the S–S distances varied significantly, with variations approaching 0.1 Å. Rh substitution of Os rather than Ru had a larger impact on the crystal structure. The atomic displacement ellipsoid of both cations and anions was almost spherical, and no elongation along the M –S and S–S bond directions was observed. The bulk Debye temperatures were estimated from the Debye–Waller factor for the sulfide site. The bulk Debye temperatures of pure OsS 2 and RuS 2 were 688 K and 661 K, respectively, which suggests that the melting point of erlichmanite is higher than that of laurite. The high Debye temperature of OsS 2 is inconsistent with the crystallisation of laurite prior to erlichmanite from the primitive magma, which suggests that $f_{\rm S_2}$ , rather than temperature, is the main cause of the known crystallisation order. The presence of several percent Rh has a significant effect on the thermal stability of OsS 2 and lowers the melting point of the erlichmanite solid solution compared to that of the laurite solid solution.
Type of Medium:
Online Resource
ISSN:
0026-461X
,
1471-8022
DOI:
10.1180/mgm.2022.139
Language:
English
Publisher:
Mineralogical Society
Publication Date:
2023
detail.hit.zdb_id:
2034522-7
SSG:
13
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