Gold from the historic ore deposit “Anna” – Zlaté Hory Ore District, Jeseníky Mts., Czech RepublicArticle PDF
Gold from the historic ore deposit “Anna” – Zlaté Hory Ore District, Jeseníky Mts., Czech Republic
Small gold sheets corresponding to electrum-to-silver-rich gold (35–65 at. % Ag) were found in lenticular quartz-carbonate veins hosted by sericite phyllites of the Cu-deposit Anna (Zlaté Hory – North Ore District). The amount of other minerals including chalcopyrite, pyrrhotite, sphalerite, anatase, rutile, and albite is low. The lower fineness of gold in comparison with formerly analyzed gold sheets from quartz vein of the Zlaté Hory Ore District (6–25 at. % Ag) is probably related to Ag-richer sulphide-bearing environment, in which the veins formed during the metamorphic mobilization. The supergene products are dominated by iron oxohydroxides (goethite), undetermined hydrated manganese oxides, malachite, rare supergene chalcopyrite, native copper, and secondary gold (with fineness of 840–850). Quartz-hosted aqueous fluid inclusions homogenized mostly between 160 and 280 °C. Two compositional types of fluid inclusions were found: (i) dominating low-salinity (0–12 wt. % NaCl eq.) Na-(Mg,Fe)-Cl, and rare highsalinity (up to 25 wt. % NaCl eq.) Na-Ca-Cl brines. These data are consistent with late-metamorphic origin of the fluid phase. The participation of brines can explain both the presence of sulphides in vein and high Ag contents in primary gold, since high-salinity fluids have a high complexation capacity for heavy metals.
Miroslav Nepejchal, Žižkova 8, 787 01 Šumperk, Czech Republic, e-mail: firstname.lastname@example.org
Zdeněk Dolníček, Department of Geology, Palacký University, 17. listopadu 11, 771 46 Olomouc, Czech Republic, e-mail: email@example.com
Bohuslav Fojt, Institute of Geological Science, Masaryk University, Kotlářská 2, 611 37 Brno, e-mail: firstname.lastname@example.org
Kateřina Mičudová, Department of Geology, Palacký University, 17. listopadu 11, 771 46 Olomouc