For the last 2000 years gold has been mined in the Southern Apuseni Mountains in Romania from both primary (hydrothermal) and secondary (river placer) deposits. The gold-bearing area covers about 900 km2 and represents the richest Au-Ag province in Europe. The ore originating from the Southern Apuseni Mountains is known as “Transylvanian gold”. The hydrothermal deposits studied here are associated with Neogene volcanism and classify as intermediate- to low-sulphidation epithermal type. We studied sixteen samples from nine occurrences, i.e., Roşia Montană, Boteş, Vâlcoi, Căraci, Musariu, Măgura, Săcărâmb, Trestia, and Techereu with electron microprobe analyses (EMPA).
Three elements were identified in these samples, with the following mean values: Au – 71.13 wt%, Ag – 28.33 wt% and Te – 0.15 wt%. They vary significantly more than shown in previous studies. Composition ranges from Au-rich silver (Au0.43Ag0.57) to gold (Au0.79Ag0.21). The compositional heterogeneity is documented at various scales: within the Southern Apuseni Mountains region, within one ore deposit (e.g., Roşia Montană, Vâlcoi-Corabia) or even within a single sample (Trestia occurrence).
Tellurium concentration up to 0.34 wt% is one of the highest found in Transylvanian gold. The studied gold samples outline a specific pattern with relatively high Ag and significant Te content compared with previously published data on primary gold from Southern Apuseni Mountains and various other deposits outside Romania. This pattern can be considered as typical geochemical signature for Transylvanian gold.
These findings on major Transylvanian gold deposits represent sound information for further provenancing studies of ancient gold objects. The consistency of the electron microprobe data and their general availability in laboratories around the world are great advantages compared with those obtained by more sophisticated methods.