Unique PGE-Cu-Ni Oktyabr’skoe Deposit (Noril’sk Area, Siberia, Russia): New Data on Its Structure and Mineralization

The present work involves a study of the internal structure, rock and ore compositions of the Oktyabr’skoe deposit. Two massive orebodies, C-3 and C-4, located in the north and south of the deposit central part are related to gabbro-dolerites subdivided by the Devonian sediments in space. Despite the closely similar structure and composition of the intrusive rocks, the disseminated and massive ores prove to display different chemical and mineralogical compositions. The C-3 orebody consists mostly of tetragonal chalcopyrite and pyrrothite, while the C-4 orebody appears to enclose sulfur-poor chalcopyrite group minerals, namely, talnakhite, putoronite etc. The C-4 orebody turns out to be rich in Cu and PGE in respect of the C-3 one. This ore-associated mineralogical diversity appears to result from differing fs2 taking place during the sulfide melts relating crystallization. It is also suggested that the orebodies, as originating from different portions of magmas, culminated in the formation of two intrusive branches.