The zone of serpentinite melange in the Kamchatsky Mys Peninsula was found to contain high-magnesium ultramafic volcanic rocks, viz., plagioclase picrite (oceanite) with a MgO concentration of 22.5–25

Contents of platinum group elements (PGE—Os, Ir, Ru, Rh, Pt, and Pd) and rhenium in basalts of different geochemical types from the ophiolite complex of the Kamchatsky Mys Peninsula have been determined by the isotope dilution-mass spectrometry method. The total contents of PGE in different basalts are commensurate (1.4-3.6 ppb), but the element ratios vary considerably. A specific feature of the rocks is the low degree of PGE fractionation (Pd/Ir = 0.9-6.6, Pt/Pd = 1.0-7.3), which makes them similar to the Hawaiian tholeiitic basalts and picrites. The most fractionated PGE pattern is observed for alkali basalt (Pd/Ir = 6.6), and the least fractionated one, for E-MORB (Pd/Ir = 1.7). The similarity of the PGE patterns of basalts of different geochemical types suggests their similar mantle sources. We propose a model explaining the geochemical features of the basalts of the Kamchatsky Mys ophiolite complex by an impurity of the Earth’s core material in the plume source. The Ir/Pd-Ru/Pd and Pd/10-Ir-Ru discrimination diagrams can be used to identify enriched (plume) basalts based on their PGE content.

More than 250 magnetic spherules 40–200 µm in size were mechanically separated from a ferromanganese crust sample of Fedorov Guyot in the Magellan Seamounts. The composition of the spherules corresponds to stony-iron and iron (with a nickel admixture) meteorites oxidized to varying degrees. The surface morphology and the internal texture of these spherules are similar to modern micrometeorites. Some spherules have a zonal structure with a core consisting of unoxidized nickel iron, with a nickel content of 7.5%–53% and a cobalt admixture up to 3.7%. Microinclusions (up to 0.5 μm) of rhodium platinum were found for the first time in a spherule consisting of wüstite and magnetite in the ferromanganese crust. The presence of cosmogenic spherules in the sample studied indicates the accumulation of a certain fraction of platinoids in the ferromanganese crusts due to the burial of cosmic dust in them.

Heterogeneous grains in the heavy fractions of the placers of the Olkhovaya-1 river (Kamchatka Cape Peninsula, Eastern Kamchatka, Russia) containing Au-Ag, Au-Cu, and Au-Ag-Cu particles were analyzed using scanning electron microscopy, electron-probe microanalysis, and X-ray powder diffractometry. The analyses showed that auricupride dominates in some grains, whereas in others, the main phases are tetra-auricupride or Ag-rich and (or) Au-rich alloys. It was revealed that in the central parts of some grains of exsolution structures, auricupride Cu_3.04–2.74Au_0.96–1.26 (Ag < 1 wt.%) occurs in intergrowths with low-fineness Ag_0.86–0.67Au_0.09–0.33Cu_<0.05 solid solutions (160‰–480‰), and tetra-auricupride Cu_1.12–0.87Au_0.88–1.11Ag_<0.02 (Ag < 2 wt.%) occurs with higher-fineness Au_0.73–0.62Ag_0.2–0.38Cu_<0.07 solid solutions (520‰–850‰). We also observed, mainly in the peripheral parts of the grains, insignificant amounts of secondary phases that were compositionally similar to Cu₂Au, Cu₃Au₂, Au₃Cu₂, Au₂Cu, Au₃Cu, high-fineness gold with impurities of Cu and occasionally Ag (>850‰), and pure gold. In intergrowths with auricupride and tetra-auricupride, we also observed earlier-formed silicates (garnet, pyroxene, chlorite, epidote, titanite), syngenetic sulfides (pyrrhotite, bornite, galena), and later minerals (chalcocite, covellite, anilite, cuprite, goethite, etc.). The XRD analysis of the peripheral parts of some grains showed the presence of auricupride (Cu₃Au), tetra-auricupride CuAu (I) and Cu(Au_0.92Ag_0.08) (II), and gold. The profiles show the absence of peaks of the Au₃Cu phase and other Au-Ag-Cu phases identified by the EMPA, which is likely due to their low concentrations in the samples or their structural similarity to gold. It is assumed that the probable source of Au-Ag-Cu mineralization in the Olkhovaya-1 river placers is located in the upper reaches of watercourses that erode the ultrabasic massif of Mounts Soldatskaya and Golaya (Kamchatka Cape Peninsula).

—: 2720 cosmic spherules extracted from ferromanganese crusts sampled at two guyots of the Magellan Seamounts were studied using a scanning electron microscope. In comparison with collections of modern cosmic spherules, our samples are significantly richer in I-type spherules (consisting of Fe oxides, often with a Fe–Ni metal core). The compositions of 406 metal cores were analyzed. Six spherules with cores significantly enriched in Co (>5 wt %) were found; these were the first spherules of this composition ever found worldwide. Such a high Co content in the cores cannot be explained by the evolution of a micrometeorite of chondrite composition at its melting. Some groups of the spherules have either elevated or lower Co concentrations than those expected according to the evolutionary trend of spherules at oxidation during the atmosphere entry. These groups apparently reflect the composition of the initial micrometeorites. It is proposed to use the composition of the cores of cosmic spherules to reveal the time variation in the composition of cosmic dust entering the Earth. Several spherules were found with small cores compared to the oxide shell; these cores are characterized by the presence of a significant amount of platinum group elements (PGE) (up to 2.4 wt % PGE). The averaged composition of PGE in the high-Ni core, which is the richest in PGE, shows a pattern close to that of chondrite. The collection contains 23 spherules that host PGE nuggets. In three spherules, micrometer-sized nuggets with various PGE were found (one nugget is Os + Ir + Ru, and two others contain all PGE). In 20 spherules, nanometer-sized nuggets of rhodium platinum were found. The largest nugget (3 μm) has PGE ratios close to chondritic, with the exception of a significant depletion in Pd.

A detailed description of alkali water springs (pH > 10) found within the ultrabasic massif of Mount Soldatskaya in the Kamchatsky Mys Peninsula in Kamchatka is presented for the first time. The chemical composition of the springs and the dependence of the ratios and concentrations of some components on pH are indicative of the fact that these waters were involved in the present-day serpentinization of ultrabasic rocks. The springs with the highest alkali levels (pH 12.3) contain dissolved hydrogen at a concentration of about 0.6 mmol/l. The isotopic composition behavior of carbonate travertines deposited from these springs (δ ¹³ C and δ ¹⁸ O) differs from the known trend of “meteogenic” travertines related to serpentinization of ultrabasic rocks in Oman and California. The age of travertines determined by the radiocarbon method is close to modern.