Mineralogy and origin of the distal volcanosedimentary deposit at the Haellefors silver mine, Bergslagen, central Sweden
In the Zn-Pb-Ag deposit of Hiillefors silver mine, four types of sulfide ores are recognized: l) stratabound ore associated with manganiferous iton ores, 2) arsenopyritebearing stratiform (stratabound ?) ore, 3) galena-rich fissures, 4) galena-arsenopyrite veins. Type 3 and 4 are thought to originate by remobilization from types I and 2, respectively. The antipathetic behavior of arsenopyrite with magnetite in the stratabound ores probably reflects environmental conditions during the deposition and early diagenesis. Metamorphic, hydrothermal remobilization led to the formation of many Ag, Pb and Sb minerals. Results of electron-microprobe analyses indicate that the principal sources of silver are argentian galena, freibergite and pyrargyrite. The silver content of galena (up to 0.17 wt.9o) has a linear relation with its antimony content. Tetrahedritegroup minerals contain ll.3 to 31.6 fi.qo Ag. An extremely silver-rich freibergite (48,2 wt.9o Ag) exceeds the previously reported maximum (42,5 wt.Vo).
Ag-Cu and As-Sb exchange energies in tetrahedrite-tennantite fahlores
Fahlerz group sulfosalts having the general structural formula (Ag, Cu){sup III}{sub 6}((Ag, Cu){sub 2/3}(Fe, Zn){sub 1/3}){sup IV}{sub 6}(As, Sb){sub 4}S{sub 13} have been equilibrated with the assemblage electrum + pyrite + chalocopyrite in reversed exchange experiments. Control of log (a{sub s}) at {minus}6.0 was maintained by abundant FeS{sub 2} + (Fe{sub .05}Zn{sub .95})S and minimum vapor space. Reversal brackets demonstrate that the Ag/(Ag + Cu) and As/(As + Sb) ratios in this sulfosalt are strongly correlated, at a fixed composition of coexisting electrum. Evaluated in the context of the thermochemical model of Sack et al. (1987), these results indicate that the molar Gibbs energy of the reciprocal reaction Ag{sub 10}Fe{sub 2}Sb{sub 4}S{sub 13} + Cu{sub 10}Fe{sub 2}As{sub 4}S{sub 13} {r equilibrium} Ag{sub 10}Fe{sub 2}As{sub 4}S{sub 13} + Cu{sub 10}Fe{sub 2}Sb{sub 4}S{sub 13}, ({Delta}{bar G}{sup 0}{sub 34}) is 12.25 {plus minus} 1.92 kilocalories. This provides a crucial missing parameter for the thermodynamic calculations the authors have developed earlier. This model is applied to calculation of end-member activities; integration with studies of hydrothermal fluids in ore-forming systems is planned.
Tin sulphides from the deposit of Brunswick Tin mines Limited
Properties, phase relations; stannite, kesterite, stannoidite, mawsonite, and unknown phase; New Brunswick