The problem of the world-class PGE-Cu-Ni Norilsk deposits’ origin has attracted geologists for several decades. The main goal of this study is to determine the specific features of ore-bearing intrusions in comparison with thousands of similar barren intrusions widespread within the Siberian igneous province, and to establish their genesis. As a result of statistical processing of previously published isotope-geochemical data and obtained by the authors, systematic differences were found in the distribution of the isotopic ratio of Nd in ore-bearing and barren intrusions, as well as in volcanic rocks at the Norilsk region. Thus, ore-bearing rocks in ten deposits (Talnakh, Kharayelakh, Norilsk 1, South-Maslovsky, North-Maslovsky, Norilsk 2, Chernogorsky, Zub-Mrksheydersky, Pyasino-Vologochansky, Imangdinsky), different in Ni and PGE reserves, show a very narrow range of Nd isotopic ratio, Ԑ_Nd(T) = 1.0 ± 1.0 (2σ, N = 139), whereas barren and volcanic rocks are characterized by a rather wide Ԑ_Nd(T) range, from −10 to +7 units (N = 256). Furthermore, ore-bearing intrusions are characterized by reduced and compact variations of the La/Lu ratio due to lower concentrations of light lanthanides. For the first time the authors studied two new intrusions penetrated by MD-48 and MD-60 boreholes drilled by Norislkgeologia LLT at the eastern part of the Mikchangda area. Their economic values are still unclear and should be estimated using geochemical methods. Both intrusions lie in the Devonian rocks, have similar thickness and mineral composition, but differ in textural and structural features, which indicate a rapid crystallization of the MD-48 intrusion. According to the contents of the major oxides, the rocks in MD-48 and MD-60 are identical, but they differ in U/Nb, La/Sm, and Gd/Yb ratios. It is important that the rocks in the MD-60 borehole are characterized by Ԑ_Nd(T) = 1.0 ± 0.6 (2σ) and fall into the range of ore-bearing intrusions, whereas the rocks in MD-48 have Ԑ_Nd(T) 2.4 ± 0.9, and, thus, are outside of ore-bearing intrusions. Therefore, Ԑ_Nd(T) values can be used as a local criterion for the estimation of economic potential of mafic intrusions, which is demonstrated for the Mikachangda area.

Prospecting efforts to located Au mineralization within the Altai-Sayan fold area (ASFA) over previous decades have revealed that Devonian epithermal Au-Ag mineralization is more widespread than previously recognized. The preservation of this type of mineralization in Paleozoic rocks offers new prospects for the exploration of Au-Ag deposits in the underexplored region of Gornaya Shoria. The Kalarskoe epithermal Au-Ag occurrence represents Devonian epithermal mineralization within the Kaburchak cluster, Gornaya Shoria, Russia. This occurrence is confined to zones of argillic alteration that were superimposed on previously formed propylites. The argillic-altered rocks host quartz-sulfide veinlet zones. The mineralization of the Kalarskoe site is characterized by a high abundance of sulfide minerals: commonly, 5%–10%; often, up to 20%; and in some cases, up to 60%–70%. The ore minerals are represented by pyrite, arsenopyrite, sphalerite, galena, chalcopyrite, fahlores, native Au, and electrum, as well as by the sulfosalts Pb, Bi, Ag, Cu, and the tellurides of Au, Ag, and Pb. Based on mineralogical observations, at least four generations of sulfide mineral formations are distinguished within the ore occurrence. The mineralization of the Kalarskoe ore occurrence may be assigned to the intermediate sulfidation (IS) type. The results of the (U,Th)-He dating of pyrite from the pyrite-arsenopyrite massive body (pyr-3 and 4) revealed the protracted history of the mineralization in the intervals from ~399 to ~371 Ma. The obtained results substantially enhance the prospecting models for the exploration of epithermal Au-Ag deposits in the western part of the Altai-Sayan fold area (ASFA).

In contrast to the developed areas of the Middle and Southern Urals, the hard-to-reach and eroded northern territories of the Ural folded system remain poorly studied, which determines a large number of unevaluated gold ore occurrences and single industrial objects. The Karyernoe gold ore occurrence is located among the Middle Paleozoic volcanic-clastic rocks of the Toupugol-Khanmeishorsky gold ore district on the eastern slope of the Polar Urals. The volcanic rocks show signs of early stratabound pyrite-like mineralization, which is cut by veins and dikes of the Sobsky (D1-2) and Musyur (C1-2) complexes. A new approach – (U,Th)-He pyrite dating – was used in order to determine the age of the sulfide mineralization of the Karyernoe ore occurrence, located on the flank of the Novogodnee ore field. (U,Th)-He pyrite ages (n=7) varies in a wide range from 402 to 425 Ma. Given the petrographic and mineralogical-geochemical observations, obtained data suggest the presence of at least two stages of rock mineralization: wenlock-ludlow – 424±6 Ma; and a later Early Devonian – 402±6 Ma, which is probably associated with the intrusion of Sob complex granitoids into the rocks of the Toupugolskaya formation. The obtained ages of the sulfide mineralization of the Karyernoe ore occurrence are significantly older than the age values established for large gold ore objects of the district: Petropavlovskoye and Novogodnee-Monto deposits (~382 million years). Taking into account the position of the Karyernoe ore occurrence on the flank of the Novogodnee ore field, it can be assumed that the disseminated and layered sulfide impregnation of the volcanic rocks of the Toupugolskaya formation could have acted as one of the sources of sulfur and ore metals for later stages of sulfide mineralization in the Toupugol-Khanmeishorsky district.

An Erratum to this paper has been published: https://doi.org/10.1134/S001670292522001X

The main techniques used for gas extraction from solid geological samples for geochronological studies are their thermal destruction either in an isothermal mode, for example in a double vacuum furnace, or under the action of laser radiation. Approaches based on the use of laser technologies are more express and have a low-background. The article describes an original high-vacuum experimental setup based on an ytterbium fiber optic laser for gas extraction from milligram samples of rocks and minerals in a scanning mode. In the proposed configuration, a static vacuum of 10^–8 Torr can be achieved in the high vacuum laser cell. Heating of individual mineral grains to a temperature of over 1800°C is ensured. Using the example of the international standard for (U,Th)–He dating—Durango apatite—it is demonstrated that the laser installation ensures complete extraction of radiogenic helium from the mineral and can be used for isotope-geochronological studies.

This paper is focused on tourmaline from quartz veins associated with rare-metal granites of the Severny (Northern) Pluton, Chukotka, within which the Erguveem, Kekurnoe, Stremitelnoe, and Glubokoe tin deposits have been discovered, with the giant Pyrkakai tin deposit located close to the south border of the pluton. Tourmalines from four host types have been described: replacement lenses (RL) in pegmatoid pockets and three types of quartz veins cutting through granite rocks of the pluton. Tourmalines have been studied with electron microprobe, laser ablation inductively coupled plasma mass-spectrometry (LA-ICP-MS), Mössbauer spectroscopy, and Raman spectroscopy. The tourmalines are classified as fluor-dravite, dravite, oxy-dravite, fluor-schorl, schorl, oxy-schorl, foitite, oxy-foitite, magnesio-foitite, and ferro-bosiite. Ferro-bosiite from the type III veins is Sn-bearing. Leading substitutions in the tourmalines are Al + ^WO^2– ↔ Fe²⁺ + ^WOH^–(F^–), X-site vacancy + Al ↔ Na + Fe²⁺, and Fe³⁺ ↔ Al. An increase in the Fe³⁺/Fe_tot value from 10% in the RL tourmalines to 14% in the type III vein tourmalines along with abundant ferro-bosiite in the latter, indicate an increase in oxidation potential. This increased oxidation potential possibly contributed to a cassiterite deposition. Raman data are consistent with composition of the tourmalines.