THE AKTEPE SILVER - ARSENIDE DEPOSITS, UZBEKISTAN

Ores rich in native silver at the Aktepe orefield near Tashkent, Uzbek istan, are similar to the arsenide - silver ores of the Cobalt-Gowgand a region, Canada. The Aktepe ores occur as shoots and lenses in narrow fissures within a middle Paleozoic gabbro massif which is surrounded by Upper Paleozoic felsic volcanics and syenite intrusions. Widespread deuteric propylitization of the massif preceded ore deposition. The o re consists mainly of native silver, which is accompanied by native ar senic and bismuth, allargentum, dyscrasite, acanthite, numerous sulfid es and sulfosalts, and by a Ni-Co-Fe arsenide and sulfarsenide assembl age similar to that of Cobalt-Gowganda. The Aktepe gangue minerals are mainly calcite, ferroan dolomite, and chlorite, and the veins are bor dered by a wallrock-alteration assemblage of sericite-quartz-carbonate -pyrite. A difference from Cobalt-Gowganda is that the Aktepe carbonat es are iron-rich, a feature which is attributed to a genetic relations hip with the iron-rich host gabbros.