Thalhammerite, Pd9Ag2Bi2S4, a New Mineral from the Talnakh and Oktyabrsk Deposits, Noril'sk Region, Russia

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Distribution of chalcophile and platinum-group elements among pyrrhotite, pentlandite, chalcopyrite and cubanite from the Noril’sk-Talnakh ores: implications for the formation of platinum-group minerals

In most magmatic sulfide deposits, platinum-group elements (PGE) are found both within the structure of the base metal sulfides (BMS), pyrrhotite (Po), pentlandite (Pn), chalcopyrite (Ccp) and cubanite (Cbn) and as platinum-group minerals (PGM). Tellurium, As, Bi, Sb and Sn (TABS) are essential elements in many of these PGM. The potential role of TABS in collecting PGE, and thus forming a PGE deposit, has not been closely investigated. We have determined the concentrations of a full suite of chalcophile elements in Po, Pn, Ccp and Cbn using laser ablation-inductively coupled plasma mass spectrometry on samples from the Noril’sk-Talnakh Ni deposits. In these deposits, the Po-rich ore is thought to represent monosulfide solid solution (MSS) cumulate of the initial sulfide liquid, and the Ccp-rich ore a mixture of the fractionated sulfide liquid and intermediate solid solution (ISS). The BMS from the Po-rich ore contain lower concentrations of TABS, Pd, Pt and Au, and higher concentrations of Mo, Ru, Rh, Re, Os and Ir than BMS from the Ccp-rich ores. This observation is consistent with experimental results which show that TABS, Pd, Pt and Au are incompatible with MSS, whereas the other elements are compatible in MSS. Counter intuitively, in the Po-rich ore, the bulk of the Pd and TABS is hosted by BMS. This is because during crystallization, although only a small amount of the incompatible elements partitioned into the BMS, the fractionated liquid has migrated away; thus, the Po-rich ores represent MSS adcumulates. Therefore, as the Po-rich ores contain very little trapped liquid fraction, the BMS host the bulk of Pd and TABS. In contrast, in the Ccp-rich ore, the bulk of Au, Pd, Pt and TABS is present as PGM or electrum grains. This is because more trapped liquid is present, and as TABS Au, Pd and Pt are not compatible with ISS, they concentrated into the very last sulfide liquid, and crystallized as intergrowths of Pd-Pt-TABS PGM. The TABS then do not appear to collect Pd, Pt and Au but rather all elements are concentrated in the most fractionated sulfide liquid by crystal fractionation

U-Pb age and Hf-Nd-Sr-Cu-S isotope systematics of the Binyuda and Dyumtaley ore-bearing intrusions (Taimyr, Russia)

We present for the first time U-Pb age data and Hf-Nd-Sr-Cu-S isotope signatures for lithologies and associated sulphide ores from the Binyuda and Dyumtaley ultramafic-mafic intrusions located in the limits of the Taimyr Peninsula (Russian Arctic). Zircons are characterized by similar U-Pb ages (245.7 ± 12 Ma at Binyuda and 256.2 ± 0.89 Ma at Dyumtaley), indicating for their close temporal relationship with tholeiite-basalt magmatism of the Siberian Platform. Silicate materials show distinct Hf-Nd-Sr isotope signatures (εHf = -3.8 ± 1.3, ɛNd = -3.8±0.4 and87Sr/86Sri = 0.70588 ± 0.00013 at Binyuda and εHf = 9.5 ± 2.5, ɛNd = 4.2 ± 0.7 and87Sr/86Sri = 0.70474 ± 0.00020 at Dyumtaley). The determined Hf-Nd-Sr variability is interpreted to represent a primary source signature of the lithological units. An important role of the juvenile component is clearly pronounced for the Dyumtaley intrusion, whereas a major contribution from a subcontinental mantle or essentially crustal source is inferred for the Binyuda intrusion. These signatures clearly manifest deviation from those typical of the ore-bearing intrusions from the Noril’sk Province, characterized by protracted magmatic evolution with significant time span of zircon and baddeleyite U-Pb ages (from ca. 350 to 230 Ma), relatively constant εNd values (ca. +1 ± 0.5), highly heterogeneous εHf (from -2.3 to 16.3) and87Sr/86Sri (from 0.70552 to 0.70798). In terms of Cu-isotopes, the majority of the analyzed sulphide samples fall within a tight cluster of δ65Cu values (-0.66 ± 0.24‰ at Binyuda and 0.4 ± 0.1‰ at Dyumtaley), characteristic of the ores from the economic Ni-Cu-PGE deposits at Talnakh. In contrast, notable difference in δ34 S values typifies sulphide ores at Binyuda and Dyumtaley (1.5 ± 0.4 and 11.4 ± 0.6‰ respectively). We suggest that the Cu-S isotope characteristics of the sulphide ores reflect their primary signature rather than a result of mixed sources or magmatic fractionation of stable isotopes. However, the latter possibility cannot be ruled out for heavy S isotope composition of sulphide ore at Dyumtaley. Samples of the disseminated sulphide ore from the Dyumtaley intrusion approach δ34S-δ65Cu parameters of the economic ores at Talnakh (Noril’sk Province) and might be considered as the most prospective for targeting the massive Ni-Cu-PGE sulphide ores

Norilskite, (Pd,Ag)7Pb4, a new mineral from Noril'sk-Talnakh deposit, Russia

Norilskite, (Pd,Ag)7Pb4 is a new platinum-group mineral discovered in the Mayak mine of the Talnakh deposit, Russia. It forms anhedral grains in aggregates (up to ∼400 μm) with polarite, zvyagintsevite, Pd-rich tetra-auricupride, Pd-Pt bearing auricupride,Ag-Au alloys, (Pb,As,Sb) bearing atokite, mayakite, Bi-Pb-rich kotulskite and sperrylite in pentlandite, cubanite and talnakhite. Norilskite is brittle, has a metallic lustre and a grey streak. Values of VHN20 fall between 296 and 342 kg mm–2, with a mean valueof 310 kg mm–2, corresponding to a Mohs hardness of ∼4. In plane-polarized light, norilskite is orange-brownish pink, has moderate to strong bireflectance, orange-pink to greyish-pink pleochroism, and strong anisotropy; it exhibits no internal reflections. Reflectancevalues of norilskite in air (Ro, Re' in %) are: 51.1, 48.8 at 470 nm, 56.8, 52.2 at 546 nm, 59.9, 53.5 at 589 nm and 64.7, 55.5 at 650 nm. Sixteen electronmicroprobe analyses of natural norilskite gave an average composition: Pd 44.33, Ag 2.68, Bi 0.33 and Pb 52.34, total99.68 wt.%, corresponding to the empirical formula (Pd6.56Ag0.39)∑6.95(Pb3.97Bi0.03)∑4.00 based on 4 Pb + Bi atoms; the average of eight analyses on synthetic norilskite is: Pd 42.95, Ag 3.87 and Pb 53.51, total 100.33wt.%, corresponding to (Pd6.25Ag0.56)∑6.81Pb4.00. The mineral is trigonal, space group P3121, with a = 8.9656(4), c = 17.2801(8) Å, V = 1202.92(9) Å3 and Z = 6. The crystalstructure was solved and refined from the powder X-ray diffraction data of synthetic (Pd,Ag)7Pb4. Norilskite crystallizes in the Ni13Ga3Ge6 structure type, related to nickeline. The strongest lines in the powder X-ray diffraction patternof synthetic norilskite [d in Å (I) (hkl)] are: 3.2201(29)(023,203), 2.3130(91)(026,206), 2.2414(100)(220), 1.6098(28)(046,406), 1.3076(38)(246,462), 1.2942(18)(600), 1.2115(37)(22.12,12.13), 0.9626(44) (06.12,60.12). The mineral is named for the locality, the Noril'sk district in Russia.© The Mineralogical Society of Great Britain and Ireland 2017. The attached document is the authors’ preproof accepted version of the journal article, which is made available under a Creative Commons CC-BY-NC-ND license: https://creativecommons.org/licenses/by-nc-nd/4.0/. You are advised to consult the publisher’s version if you wish to cite from it