Palladium-gold-sulphide mineralization in andesites at Chudnoe deposit (Subpolar Urals)

The Chudnoe gold deposit, located at the Subpolar Urals, is unique. Gold is generally concentrated in fuchsite veins in rhyolites, where associated with palladium and rare earth minerals in the absence of sulphides. Impurities of silver, copper and palladium are characteristic of native gold in fuchsite veins; heterogeneous structure is often noted. In deep horizons the authors established Pd-Au-sulphide mineralization confined to andesites and enclosed by rhyolites. Native gold and palladium arsenoantimonides in andesites most often form inclusions in pyrite, less often in allanite; accompanying minerals: cobaltine (including Pd-containing), galena, sphalerite, chalcopyrite, magnetite. Gold is homogeneous and contains only silver as an impurity, its rate is within 756-875 ‰. The mineral associations of gold in andesites differ sharply from the main mineralization in rhyolites, but with common gold-palladium nature of mineralization, which suggests its formation during a single process, in which the presence or absence of sulfides in host rocks was important. The presence of palladium in the ores and mineralized zones, as well as chromium in the composition of fuchsite, indicates an important role of deep sources of matter.