Behavior of gold in hydrothermal-metasomatic processes in the Alkhanai gold-ore region, East Transbaikalia

Three stages of hydrothermal metasomatism have been established in two ore- magmatic systems of different ages (resulted from intrusive dioritic: (T-J( 1)) and volcanogenic (J(3)-K-1) rhyolite-dacitic magmatism) in the Alkhanai gold-ore region. In the former system, gold-ore mineralization is represen ted by stockwork gold-apatite-quartz-feldspar association and in the latter , by finely disseminated metasomatic gold-pyrite association in beresites o f adular-hydromica facies and hydrothermal-veined gold-quartz-beresite asso ciation. By the mechanism of An concentration and the kind of association w ith ore-hosting metasomatites this mineralization corresponds to conjugate- synchronous, synchronous, and retarded types of hydrothermal-metasomatic or e formation. The horizontal and vertical mineral-geochemical zoning of meta somatic and hydrothermal formations and the geological and physicochemical conditions of their development are considered.