The Norilsk layered mineralized, platinum-associated ultrabasic-basic intrusions typically contain lower and upper endocontact horizons composed of basic pegmatoids (taxitic gabbro-dolerites and pegmatoid gabbro). In their absence no ore mineralization occurs. The latter forms first an isomorphous admixture of platinoids in sulfide solid solutions and then individual platinoid phases (Pt and Pd). There are two possible ways for high-temperature ore-forming sulfides with an isomorphous admixture of platinoids to form. They crystallize either from a homogeneous sulfide melt or by the interaction of high-temperature metasomatizing fluids with sub-ultrabasic rocks of the parent intrusive, which are the source of ore components recovered, transported, and precipitated by fluids related to the main pegmatoids of this intrusive. The concept of metasomatic-sulfurization origin of the Norilsk Cu-Ni platinum-associated ores is useful in solving the problem of the disbalance between high content of platinoids in the ores and very low volume of magma in the ore-bearing intrusives as well as in overcoming some other compositional constraints on the origin of the ores.
