• Economic and Environmental Geology
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• v.39 no.6 s.181
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• pp.643-651
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• 2006

The Pb-Ag-Bi-S system minerals such as galena-matildite solid solutions, cosalite and heyrovskyite occur in the Nakdong As-Bi deposits. Galena-matildite solid solutions commonly coexisting with native bismuth fill in microfractures of pyrite grains and form irregular shapes. Cosalite forms composite grains including native bismuth, heyrovskyite and Bi-Te-S system minerals in the matrix of quartz vein. Matildite from the Nakdong deposits has an end member composition, $Ag_{1.07-1.11}Bi_{1.12-1.20}S_2$, and an excess concentration of $0.3{\sim}2.4$ mole % $Bi_2S_3$ compared to the stoichiomeoic value. PbS concentrations in $PbS-AgBiS_2$ solid solutions do not exceed 54 mole %. The average chemical composition of cosalite in the study area is $Pb_{1.79}Bi_{2.29}Ag_{0.12}S_5$. Pb is slightly depleted compared to the ideal composition, but the concentrations of Ag and Cu reach as much as 1.47 wt.% and 0.27 wt.%, respectively. Heyrovskyite has the chemical formula of $Pb_{5.01}Ag_{0.26}Bi_{2.70}S_9$ suggesting that there occurs the coupled substitution of $2Bi^{3+}$ for $3Pb^{2+}$ as well as that of $Ag^++Bi^{3+}$ for $2Pb^{2+}$. The genetic condition of Pb-Ag-Bi-S system minerals can be confined to the temperature of $220{\sim}270^{\circ}C$ and the pressure below 200 bars.

• Economic and Environmental Geology
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• v.25 no.1
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• pp.17-25
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• 1992

South ore deposits of the Dunjeon gold mine is a fissure-filling vein emplaced in the Cretaceous granodiorite, skarnized and/or hornfelsified Ordovician Dumudong Formation. Mineralization can be divided into three distinct depositional stages on the basis of vein structure and mineral assemblages. Sb, Bi sulfosalts minerals, such as tetrahedrite, bournonite, boulangerite, cosalite, lillianite, heyrovskyite, unknown Pb-Bi-Sb-S mineral, native Sb, native Bi and Au-Ag minerals are mainly deposited in stage II. The formation temperature and sulfur fugacties of Sb, Bi minerals in the stage II deduced from thermodynamic considerations are from $172^{\circ}$ to $378^{\circ}C$ and $10^{-10.6}$ to $10^{-19.4}$ atm. Those temperatures are good agreement with temperature data obtained by fluid inclusion study which has reported already.