World-Class PGE-Cu-Ni Talnakh Deposit: New Data on the Structure and Unique Mineralization of the South-Western Branch

Abstract

The Talnakh deposit is one of the largest PGE-Cu-Ni deposits in the world. It is located inside the NorthWestern part of the Siberian Trap province and consists of three branches. The problem of massive ore origins has been discussed for several decades. The structure of the SouthWestern branch and the mineralogy of related its Cu-rich ore are discussed in this article. The Southern 2 orebody has a deep inclination (45 •) inside the intrusive body, close to its wall, in contrary to the horizontal orebodies of the NorthEastern branch. Mineral composition of the Southern 2 orebody differs from the composition the other orebodies of the Talnakh intrusion as well. It consists ofchalcopyrite, pentlandite with subordinate cubanite, and pyrrhotite. Its specific feature is a large amount of bornite and chalcocite. These minerals occur in disseminated and massive ores. The ores of the other branches of the Talnakh intrusion have chalcopyrite-pyrrhotite compositions whilethe Southern 2 massive ore is enriched in Cu (19.03-25.8 wt %; Cu/Ni = 3.8-8.6) and PGE: ΣPGE changes from 39.1 to 279 ppm, Pd/Pt = 1.3-32. Twelve minerals of the systems Pd-Sn-Cu, Pd-Pb-Bi, Pd-Ni-As, Au-Ag-Pd-Cu, and intermetallics of the Pt-Fe-Cu-Ni types were discovered in ores, but are also widespread in other orebodies. Isoferroplatinum, sperrilite and cooperitewere not found. The unusual structure and composition of the Southern 2 orebody suggest its origin from a separate magma impulse. The correlation between disseminated and massive ores of the Southern 2 orebody in term of chemical and mineralogical composition is evidence of the formation of massive oresin situ, without displacement along the bottom of the massif.

Unique PGE–Cu–Ni Noril’sk Deposits, Siberian Trap Province: Magmatic and Tectonic Factors in Their Origin

“…Additionally, there are economic ore types consisting of rare minerals of the chalcopyrite group such as talnakhite and moikhukite. The second specific feature of the Noril'sk ore is their enrichment in platinum group elements (5-12 ppm in disseminated ore and up to 125 in massive ore [72]. Due to the high PGE tenor, many PGM have been diagnosed [73][74][75][76].…”

A Trace Element Classification Tree for Chalcopyrite from Oktyabrsk Deposit, Norilsk–Talnakh Ore District, Russia: LA-ICPMS Study

“…The rocks are represented by the following petrographic varieties: contact, taxite, picrite (also named plagiodunite and plagiowehrlite) and gabbrodolerite [20,21,[29][30][31][32][33]. A detailed analysis of the geology, petrography, geochemistry, and isotopic characteristics of the intrusion and ores is beyond the scope of this paper and can be found elsewhere [34][35][36][37][38][39][40][41][42][43][44][45][46][47].…”

“…The following ore types are distinguished at the Oktyabrsk deposit [46]: massive, disseminated and veinlet-disseminated (from bottom to top, Figure 1). The massive (rich) copper-nickel ores are found at the lower part of the intrusion, and often are localized within the metasomatic and metamorphic rocks of the lower endo-and exo-contact or even within the Devonian sedimentary rocks of the Mantur and Kureika formations.…”

PGE-Cu-Ni Mineralization of Mafic-Ultramafic Massifs of the Khangai Upland, Western Mongolia

“…The average total of PGE (ΣPGE) content in rocks from the massifs of the Khangai upland (Oortsog, Dulaan, Mankhan, Yamat, and Nomgon) are 15, 3.5, 3.3, 6, and 444 ppb, respectively, and the average ΣPGE in the disseminated sulfide ores in the Nomgon intrusion is higher than in others. These are varied and are lower than those of the world's giant mafic-ultramafic complexes, such as the Neoproterozoic Jinchuan deposit (0.26-135 ppm [16]), Kalatonge (to 489 ppb [61]), Kingash (to 2.9 ppm [62]), and Permo-Triassic Talnakh deposit (39-279 ppm [63]).…”