Two concentration peaks of sulfide minerals in differentiated traprocks of Siberian Platform

The proved tendency of chalcopyrite (with pyrite and pyrrhotite) to accumulate in the relatively ferruginous tops of the traprock intrusions and of pyrrhotite (with pyrite and chalcopyrite) in their relatively magnesial bottoms has no behavioral analogy with any of the petrogenic constituents, but shows a correlation with the behavior of sulfur. This “two-peak” phenomenon is explainable, by liquation of the sulfidic melt accompanied by fractionation by gravity concurrent with upward migrations of sulfur and the chalcophiles, as volatile mobile compounds, on gradual cooling of the sulfidic melt. — V.P. Sokoloff