The progress in the study of the Noril’sk Cu-Ni-PGE sulfide deposit in Russia

The Noril’sk Cu-Ni sulfide deposit, existing in the Siberia Trap, is located at the northwest corner of Russian Siberia. As the largest Cu-Ni sulfide ore district, it consists of two orefields, i.e., Noril’sk and Talnakh. The flood basalts, Noril’sk type, Lower Talnakh type and the later intrusions constitute the four magmatic rock types in the ore district. Both the Noril’sk intrusion and the Lower Talnakh intrusion have been mineralized, but only the former one is of economic value. There are three main ore types, i.e., massive ores, breccia ores and disseminated ores. The existence or nonexistence of massive ores is one of the most important differences between the Noril’sk intrusion and the Lower Talnakh intrusion. Although there are four common opinions among the numerous published papers, many debates remain existent: ①The age data of the P-T time of magmatic rocks and ore deposition reveal that these ore deposits are related to the flood basalts in time and space; nevertheless, due to lack of direct geological evidence, it is hardly possible to know the relations between the orebodies and the flood balsalts. ②The mantle source magma underwent a crustal contamination in the ore-forming process, and disputes focus on three aspects, namely, at which magmatic stage did the contamination happen? What was the degree of the contamination? What was the contamination essential for the ore deposit? ③The ore elements (eg., Cu, Ni and PGE) were precipitated from the magma, but where did these elements come from? Did they come from crust or from mantle? All the publications hold that the mantle source of the ore elements played the leading role; nevertheless, no one can exclude the opinion that the Proterozoic sediments and the Siberia basement might have supplied the ore elements. ④Sulfide segregation played an important role in the ore-forming process. Up till now, all the reseachers have agreed that there was one sulfide segregation in the deep magma chamber as the granitic lower-most crustal contamination. The most hot debate is that whether there existed another sulfide segregation in the shallow magma chamber near the ore-bearing magmatic rocks. Although there are no ultimate common opinion on the ore genesis, the authors still believe that some ore-controlling factors are valid in Noril’sk area.