Greenockite and zincian greenockite in epithermal polymetallic AgAuTe mineralization, Tinos Island, Hellas: Description and conditions of formation
Tombros, Stylianos; St. Seymour, Karen; Spry, Paul G.; Williams-Jones, Anthony
published: Dec 2, 2005
ArtNo. ESP154018201001, Price: 29.00 €
Greenockite-CdS and zincian greenockite-(Cd0.65Zn0.35)S were identified in low sulfidation epithermal Au–Ag–Te mineralization at Panormos Bay, Tinos Island, Hellas. Both minerals occur in stage VII of nine ore paragenetic stages as minute moderately reflective grains, up to 15 μm in length. The zincian greenockite displays a gray-bluish color, with a slight gray to gray-yellow anisotropy and yellowish to brownish-red internal reflections. It is intergrown with greenockite that coexists with stage VII – wurtzite, siderite, smithsonite and magnetite.Based on silicate, sulfide, and carbonate stabilities and fluid inclusion data, the approximate conditions of formation of stage VII and of zincian greenockite and greenockite are estimated to have been near 215 °C, at a hydrostatic pressure of 115 to 125 bars, fS2 = 10−14.1 to 10−14.5, fO2 = 10−44.2 to 10−44.6, pH = 6.1 and aH2S(aq) = 10−3.6. For this temperature of formation and from previously published experimental data it is suggested that the Panormos Bay zincian greenockite has a wurtzite structure. The zinc and cadmium ion content of stage VII solutions is estimated as 0.09 and 0.34 ppm, at 115 and 125 bars respectively.It is suggested that substitution of cadmium by zinc is a rather complicated process depending on precipitation mechanism, pH, fO2, aH2S and possibly aCl− of the fluid, associated with local mineral-fluid equilibrium.