New compositional data concerning Au-Ag alloys from the northern part of Roşia Montană deposit, Metaliferi Mountains, Romania

This paper presents the results of the new investigations by optical microscopy, scanning electron microscopy (SEM) and electron-probe micro-analysis (EPMA) performed on samples collected from Orlea adit from Rosia Montană Au-Ag deposit, Romania. Based on composition, three types of Au-Ag alloy were described. At Rosia Montană, galena, pyrite, chalcopyrite and sphalerite are intimately associated with gold, electrum and tellurium-bearing minerals. At Rosia Montană, the precipitation of Au-Ag alloy with variable composition can be assigned to compositional changes of the parent hydrothermal solutions during deposition due to boiling, fluid dilution and cooling.