Platinum-iron metallization in intrusive traps of the Siberian Platform

Platinum-iron metallization is a new type of noble-metal ores, since it is dominated by reduced metals and virtually does not contain sulfides, except for sporadically occurring troilite. Discovery of this type of ores convin cingly confirms the existence of the mechanism of extraction, transfer, and accumulation of noble metals in magma, an alternative to a sulfide model. Platinum-iron ores are associated with native iron, which is localized in t he horizon of pegmatoids of the upper endocontact zones in some trap intrus ions of the Siberian Platform. In the Khungtukun intrusion, a magmatic body combines two types of platinum ores: Pt-Fe-ores in the upper endocontact z one and Pt-sulfide ores in the lower zone. A typomorphic paragenesis in Pt- Fe-ores is ferrite + cohenite + wustite + + graphite + kamacite + native co pper + hercynite+/-troilite, and silicates are represented by paragenesis f ayalite + high-Fe clino- and orthopyroxenes. Platinoid concentration in Pt- Fe-ores reaches 9.2 ppm and depends directly on the Cu + Ni + Co content. N oble metals are present in a iron as an isomorphous admixture and are confi ned to sites enriched in nonferrous metals. The average content of platinoi ds in sulfide ores is 0.6 ppm with S-av = 2.26 wt.%. An important genetic peculiarity of Pt-Fe-ores is the presence of glasses w ith obvious signs of silicate-silicate and ore-silicate liquations. Analysi s of parageneses from ores and thermobarogeochemical and chromatographic da ta suggests the formation of Pt-Fe-ores as a result of the interaction of r educed H-C-N fluids with basalt melt, a source of ore components, at 900-12 00 degrees C.