Vol CLIII, No 5 (2024)

The age of the Thunderstone granite, which is the pedestal of the Bronze Horseman monument to Peter the Great in Saint Petersburg, is dated at ~1595 Ma. This age was obtained by U-Pb dating of accessory zircon separated with a jewelry gravel from the biotite flakes. The study was carried out on a secondary ion microprobe SIMS SHRIMP-IIe at the Center of Isotopic Research of the Karpinsky Institution (Saint Petersburg). 15 local U-Pb isotopic analyses were performed on 12 zircon crystals. It is not yet possible to recognize the source of the Thunder Stone, since granites of the same age have not yet been found either in the Vyborg batholith (1665—1615 million years), or in the Salminsky batholith (1547—1535 million years), or in other granite intrusions located in the proximity of Saint Petersburg. Thus, the Thunder Stone seems to confirm the historically established idea about its uniqueness and hints that its homeland should be sought among the manifestations of the yet unidentified phases of Early Riphean granitoid magmatism in the nearest regions.

The paper describes the occurrence of so-called mustard gold, which forms independent grains and rims that replace calaverite (AuTe₂) in the adularia-quartz veins of the Evevpenta epithermal ore occurrence in Kamchatka, Russia. Four types of mustard gold were identified: (1) pure mustard gold, (2) mustard gold containing areas and veinlets of homogeneous native gold, (3) mustard gold with remnants of Ag sulfides (Au-Ag), and (4) mustard gold intergrown with oxygen-containing compounds of Fe and Mn. It is hypothesized that the mustard gold at the Evevpenta formed as a result of calaverite (AuTe₂) replacement during the late hydrothermal stage. We propose that the chemical composition of mustard gold serves as its distinguishing feature and can indicate the geological and genetic types of gold deposits.

This article presents the results of studies of noble metal and polymetal mineralization from the zone of late superimposed carbonatization in phlogopite peridotites of the Mesoproterozoic peridotite-shonkinite massif Spiridon-Ty. These rocks are characterized by high concentrations of noble metals (Au up to 0.51 ppm and Ag up to 18 ppm) and polymetals (Cu up to 1.55 wt %; Pb up to 0.17 wt %; Zn up to 0.15 wt %). It has been established that the ore mineralization is sulfide-sulfosalt with native Cu, Ag, and Au. Sulfides and sulfosalts are represented by bornite, chalcopyrite, covellite, galena, sphalerite, tennantite, and gersdorfite. It was determined that the primary noble metal and polymetal mineralization was formed under the following conditions: T ≈ 395—280 °C, lgfS₂ ≈ 10^–6.5—10^–9.9 atm, lgfO₂ ≈10^–37 atm and pH of the hydrothermal solution ≈ 5.5—7.8. Covellite is an intermediate mineral in the oxidation of primary sulfide minerals and was formed at T ≈ 190—110 °C and lgfS₂ ≈ 10^–10—10^–12 atm. Native copper is a late oxidation mineral of sulfide minerals and formed at T ≤ 110 °C and lgfS₂ ≤ 10^–31 atm. The results obtained allow us to consider the potassium alkaline-ultrabasic massifs of the Kola alkaline province as a possible source of noble metal and polymetal ores.

The chemical composition of hundred vanadinite specimens from 17 occurrences worldwide was studied by electron microprobe and the new and literature data on its chemical composition were summarized. Vanadinite is a supergene mineral: no reliable data indicating that vanadinite may be hypogene have been found, although its analogue is synthesized in a wide temperature range: from 25 to 1000 °C. The overwhelming majority of vanadinite specimens have a composition close to the ideal formula, Pb₅(VO₄)₃Cl. Phosphorus and/or arsenic-rich vanadinite (> 0.5 apfu P and/or As) is rare, as well as a Cr-bearing variety of this mineral. According to the data available today, isomorphism between V, As and P in natural vanadinite–pyromorphite–mimetite system is incomplete unlike synthetic system Pb₅(T⁵⁺O₄)₃Cl (T = V, P, As) in which full miscibility occurs, even at low temperatures. For the vanadinite–mimetite series, the compositional range from V_3.00As_0.00 to As_2.15V_0.85 has been recorded while the vanadinite–pyromorphite series is so far represented almost only by the vanadinite part: from V_3.00P_0.00 to P_1.50V_1.50. Two new finds of the so-called endlichite (an intermediate member of the vanadinite–mimetite series with a V: As ratio of ~1:1, data on which were previously based only on wet chemical analyses published in 1885) were made. The calcium content in all vanadinite samples studied in this work does not exceed 0.2 apfu, and the contents of other elements with atomic numbers >8, excepting Pb, Ca, V, P, As and Cl, are below their detection limits by electron microprobe.

Information is provided about the recipients of the 2024 N. I. Koksharov Medal of the Russian Mineralogical Society: L. Z. Reznitsky, Senior Researcher at the Institute of the Earth’s Crust of the Siberian Branch of the Russian Academy of Sciences, and Chen Jinhua, Professor at Guangxi University (China). L. Z. Reznitsky is a researcher of the mineralogy of peculiar Cr-V-containing metamorphic rocks of the Southern Baikal region and the co-author of the discovery of 15 new mineral species. Chen Jinhua is a specialist in the field of mineral flotation, including the active use of quantum chemical modeling methods.