Gold-magnetite mineralization and hosted antigoritic serpentinites of the Kaganskiy massif (Southern Urals) have been studied. Data on ore mineralogy, gas and isotopic composition of mineralizing fluid have been obtained. A fluid has a metamorphic origin and is characterized by the water composition (XH2o - 0.975-0.978, XCo2 = 0.019-0.020), high oxidation degree promoting of isomorphic including in silicate minerals (olivine up to 0.4 %, chrisotile - up to 4.4 %, antigorite - up to 6.9 %). Isotopic composition of antigorite (6,80 = 5.2 %o, 6D = —127.7 %o) corresponds to the isotopic composition of the continental ophiolitic lizardite-chrisotile serpentinites.