Nontraditional Types of Platinum Metal Ores in the Norilsk-Type Sulfide Deposits

In the Norilsk deposits, the increased concentrations of platinum metals have long been known from the rich sulfide ores in near-bottom parts of a magmatic body. Another Pt-bearing horizon is confined to pegmatoids and occurs in the upper endocontact intrusion zone. The ore-bearing rocks are petrographically characterized in short, and an occurrence of sulfides and chrome spinellide is specified. There are two low-sulfide types of noble ores: Pt-Cr-type (with Cl2O3 up to 10 wt.% in rock) and Pt-low-sulfide-chromiteless type (with Cr2O3 less than 0.1 wt.%). The Pt/Pb value is 0.34 and 0.20, respectively. The (Pt + Pb)/S ratio (in wt. ppm) in these rocks is less than· unity, often it is equal to 3–4, sometimes reaching 295. The main concentrator is sperrylite and for palladium, the Pb – As – Sb system minerals. An isomorphic impurity of platinoids is sulfides reaching 9520 ppm in melnikovite contributes significantly to the platinum mineralization of rocks. The recognition of various low-sulfide types of platinum metals extends the prospects of their finding among small sulfide deposits and ore occurrences related to the layered trap intrusions known in the Siberian Platform.