Cm. Cardile et al., AU-197 MOSSBAUER STUDY OF AU2S AND GOLD ADSORBED ONTO AS2S3 AND SB2S3SUBSTRATES, Geochimica et cosmochimica acta, 57(11), 1993, pp. 2481-2486
Au-197 Mossbauer spectra were measured for crystalline Au2S and for go
ld adsorbed onto colloidal As2S3 and Sb2S3 substrates. The spectrum fo
r Au2S is characterised by a quadrupole split doublet which has been d
econvoluted into two overlapping doublets. The spectra for adsorbed go
ld on colloidal As2S3 and Sb2S3 are similar in appearance to that of A
u2S and have isomer shifts (IS) and quadrupole splitting (QS) values w
hich are characteristic of gold in the +1 oxidation state, coordinated
to two sulphur electron donors in an approximately linear geometry. T
he Au-197 Mossbauer data confirm that the gold occurs on the As2S3 and
Sb2S3 substrates as a surface complex and has not been electrochemica
lly reduced to elemental gold (Au0). These data further emphasize the
role of surface chemistry in the scavenging and concentrating of gold
by sulphide mineral surfaces from hydrothermal fluids in high-temperat
ure ore-forming systems (e.g., epithermal environments), as well as in
seafloor hydrothermal systems, where sulphide minerals are precipitat
ing near the seafloor-seawater interface.