The investigation of the chemical and structural variations of copper and silver sulphides by SRS (A case study of Mineralogical and Geochemical applications of X-ray absorption spectroscopy)

Abstract

The ABS2 sulphides (A=Cu, or Ag), B=As, Sb, Bi) are a naturally occurring group of minerals, typically found in polymetallic vein deposits. Behind chemically simple, the minerals have a complex structure and undergo several temperature/composition phase transitions. In this study, synchrotron radiation is used to collect Ag, As, Bi, Cu, Cd, Hg and Sb K-edge EXAFS data from a series of synthetic sulphosalts. EXAFS are used to characterize and determine the local structure behavior. Analysis of the spectra has provided direct evidence about the coordination environment, the structural and electronic environments of major and minor cations within the substituted phases. In this study, M (metal or semimetal)-S bond distances of emplectite, chalcosibite, miargyrite and smithite minerals were determined by EXAFS and XANES methods.

Keywords


[1] Brown G.E., Calas G., Waychunas G.A., Petia J., X-ray absorption spectroscopy and its application in mineralogy and geochemistry, Reviews in Mineralogy (Min. Soc. Am.), 18 (1988) pp. 431-512.

[2] Calas G., Brown G.E., Waychunas G.A., Petia J., X-ray absorption spectroscopic studies of silicate glasses and minerals, Phys. Chem. Minerals 15 (1987) pp. 19-29.

[3] Charnock J.M., Garner C.G., Pattrick R.A.D., Vaughan D.G., Investigation into the nature of copper and silver sites in argentian tetrahedrites using EXAFS srectroscopy, Phys. and Chemistry of Minerals, 15 (1988) pp. 296-299.

[4] Manceau A., Calas G., Nickel-bearing clay minerals. 2. Intracrystalline distribution of nickel: an x-ray absorption study, Clay Minerals 21 (1986) pp. 341-360.

[5] Razmara M.F., Henderson C.M.B., Pattrick R.A.D., The crystal chemistry of the solid solution series between chalcostibite and emplectite, Mineralogical Magazine, 61 (1997) pp. 79-81.

[6] Razmara, M.F., The chemistry, structure and solid solution of Ag(Sb, As,Bi)S2 and the effect of Cd, Hg and Zn substitution into Ag (Sb, As, Bi)S2, PhD thesis, The University of Manchester (1997).

[7] Hofmann W., Strukturelle und morphologische zusammenhange bei erzen vom formeltyp ABC2. I. Die struktur von wolfsbergit CuSbS2 and Emplektit CuBiS2. Under Beziehungen zuder struktur von Antimonit Sb2S3, Z. Krist. 84 (1932) pp. 177-203.

[8] Porthine J.C., Nowacki W., Refinement of the crystal structure of emplectite CuBiS2, Z. Krist. 141 (1975) pp. 387-402.