Gold deposits and occurrences of the Greater Caucasus, Georgia Republic: Their genesis and prospecting criteria

More than 60 gold-bearing lodes and placers in the Svaneti district occur along the thrust between the Southern Slope and Main Zones. Lode gold potential was first recognized in the historic placer district in the 1980s, with many auriferous quartz veins cutting Middle Jurassic igneous rocks. Brecciated veins in the 18 t Au Lukhra deposit cut a small granodioritic to dioritic stock; the latter intrudes Devonian schist immediately north of the thrust. Presently, there are three recognized ore zones in the deposit, with the most significant occurring over an area 140 m in length and 12 m-wide, with typical grades of 7 to 9 g/t Au. Reconnaissance fluid-inclusion studies of ore samples from the Lukhra deposit indicate minimum trapping temperatures of 220 °C. Measurements of δ18Oquartz of about 10‰ suggest buffering of isotopic composition by the igneous host rocks.