Fluids in the continental crust are capable of concentrating gold into ore bodies in a wide variety of settings, ranging from intrusion-related, disseminated porphyry Cu-Au (-Mo) associations, epithermal (low- and high-S), volcanogenic massive sulfide, Carlin, to orogenic shear zone-hosted deposits. In combination and together with the Archaean to Palaeoproterozoic palaeoplacer deposits that were derived from primary shallow crustal gold sources, they account for more than 90 % of all known gold. Considerable efforts have been made in characterizing the various kinds of crustal gold deposits in terms of their mineralogy, mineral chemistry as well as their fluid inclusion characteristics. Nonetheless the ultimate questions of the source of the gold and the source of the gold-transporting fluids remain without definite answers. The extent to which orogenic gold deposits formed in response to magmatic activity and/or metamorphic fluid circulation remains ambiguous as does the extent to which gold has been continuously recycled by crustal fluids over the past three billion years or periodically added to the continental crust from juvenile sources.

A focus specifically on epithermal gold seems most appropriate at this meeting, considering that the region around Rosia Montana in west-central Romania, the previous Hungarian Verespatak, has been the most important gold-producing province in Europe for more than 2000 years. Today one of Europe’s largest known gold deposits is located in Chelopech, west-central Bulgaria. Both are epithermal deposits (low- and high-sulphidation, respectively) and highlight the enormous significance of crustal fluids, here in Upper Cretaceous to Tertiary volcanic arcs, for the concentration of gold into ore bodies.