The journal was founded in 1993. Scientific journal in the field of petrology and related sciences.

The journal is published 6 times a year in Russian and English languages. The name of the English version is Petrology.

The journal is presented in many databases, including the Web of Science, Scopus and RSCI.

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Vol 31, No 3 (2023)


pages 219-220 views
The origin of olivine basalts from Medvezhya Mount (Avachinsky group of volcanoes, Kamchatka): The evidence of assimilation of sulfide-bearing cumulates
Savelyev D.P., Gorbach N.V., Portnyagin M.V., Shcherbakov V.D.

The role and conditions of liquid immiscibility and crystallization of sulfide phase during evolution of subduction related magmas remains to be a debated topic, which bears relevance to mechanisms of porphyry copper deposit formation and evolution of the continental crust. We studied rare volcanic rocks with inclusions of magmatic sulfides in olivine – the basalts of Medvezhya Mount in the Avachinsky group of volcanoes. The rocks belong to primitive (Mg# = 66 mol. %) middle-K island arc olivine basalts. Olivine with normal zoning predominate (~98%) among phenocrysts. The olivine compositions are typical for Kamchatka basalts, except for an unusual trend of increase of MnO content from 0.20 to 0.55 wt. % and decrease of Fe/Mn from 60 to 35 with change of olivine composition from Fo87.8 to Fo78.2. Olivines of this group contain numerous inclusions of minerals of the spinel group varying in composition from chromium spinel to magnesian magnetite. Olivine phenocrysts with sulfide inclusions are characterized by the absence or weak reverse zoning and reduced contents of Ca, Ni, Mn, Cr, and Al. The estimated crystallization temperatures for olivines of the prevailing type are 1036–1241°C, for sulfide-bearing olivines – 1010–1062°C. The data suggest that crystallization of the main olivine population occurred under relatively shallow conditions and was accompanied by strong oxidation of the magmas. On the contrary, the zoning and composition features of sulfide-bearing olivine suggest its xenogenic origin and probable crystallization at conditions of deep crust from low temperature water-rich and/or low-Ca magmas. The results obtained confirm the possibility of saturation of oxidized island-arc magmas with sulfide phase at lower crustal conditions, but show that this process is rare and not typical for low-pressure crystallization stage.

Petrologiâ. 2023;31(3):221-237
pages 221-237 views
Magnesian Basalts of the Medvezhia Caldera: Main Magmas and Their Sources on the Example of the Menshiy Brat Volcano (Iturup Island)
Kuzmin D.V., Nizametdinov I.R., Smirnov S.Z., Timina T.Y., Shevko A.Y., Gora M.P., Rybin A.V.

The paper represents new data on the formation conditions of basalts from post-caldera volcano Menshiy Brat (Medvezhia caldera, Iturup Island). Liquidus mineral assemblage is composed of olivine (Fo up to 90.1 mol. %) and chromium spinel (Cr# = 0.46–0.6), which crystallized at 1090–1170°С and oxygen fugacity NNO +0.6 (σ = 0.2) – NNO +0.2 (σ = 0.14). The study of melt inclusions in the liquidus olivine demonstrated that its parental melts have low-alumina, low-potassium compositions with up to 15.5 wt. % MgO and with an average water content of 5.5 wt. %. The data on volatile contents in the olivine-hosted melt inclusions suggest that the basic melts appeared due to partial melting of essentially peridotitic source with a small admixture of an olivine-free component at 1225°С under active influence of the slab-related fluids. These fluids were separated from the subducting slab at 670–705°С and depths of 95–105 km beneath the Iturup Island. The results of this study enhance our understanding of the evolution of basic magmas that serve as a heat and volatile supply during the formation of large calderas.

Petrologiâ. 2023;31(3):238-263
pages 238-263 views
Conditions and Magmas Sources of Summit and Flank Eruptions of the Klyuchevskoy Volcano in 2020–2021: Isotope (Sr-Nd-Pb-O)-Geochemical Data
Cherkashin R.I., Bergal-Kuvikas O.V., Chugaev A.V., Larionova Y.O., Bindeman I.N., Khomchanovsky A.L., Plutakhina E.Y.

In 2021 a unique event occurred on Klyuchevskoy volcano (Kamchatka). After more than 30 years dominance of terminal eruptions a flank vent was formed. It was named after corresponding member of the Academy of Sciences USSR G.S. Gorshkov. The eruption began immediately after the end of the summit crater activation in 2020–2021 at an altitude of 2850 m in the northwestern part of the volcano, where no manifestations of flank volcanism were observed earlier. This paper presents geochemical and isotopic Sr-Nd-Pb-O data for lavas of the summit and flank eruptions of the Klyuchevskoy volcano in 2020–2021. A comparative petrographic analysis was carried out and the chemical composition of the Ol, Cpx, Pl phenocrysts of these lavas was analyzed. The lavas of both eruptions are alumina andesitic basalts of normal alkalinity. Variations of basic oxides in the lavas of the summit eruption and in the lavas of the G.S. Gorshkov vent are SiO2 53.1–53.2 wt. % and 51.6–53.2 wt. %, MgO 5.6 wt. % and 5.5–6.0 wt. %; respectively. Estimates of temperatures and pressures of plagioclase crystallization showed that for lavas of the summit eruption they were 1210–1118°С and 12.3–3.6 kbar, for lavas of the flank vent 1203–1119°С and 9.0–3.3 kbar. The content of the main elements, the proximity of the conditions of plagioclase generations, and the features of variations in the chemical composition of Ol, Cpx, and Pl phenocrysts in the lavas of both eruptions indicate the genetic relationship of the magmas that fed the summit and flank eruptions. The lavas of the summit eruptions of 2016, 2020–2021, as well as the lavas of the previous summit eruptions of the Klyuchevsky volcano, are characterized by highly sustained Sr-Nd-Pb isotopic characteristics: 87Sr/86Sr = 0.703625–0.703626, 143Nd/144Nd = 0.513085–0.513102, 206Pb/204Pb = 18.3148–18.3179). Isotopic ratios 207Pb/204Pb (15.5022–15.5107) and 208Pb/204Pb (37.9597–38.0143) are significantly higher for the lavas of the last summit and flank eruptions than for all Klyuchevskoy’s lavas of the past, which indicates more complex processes of magma evolution at crustal levels. The values of δ18O = 6.49–7.39 rel. units (SMOW) in the lavas of the considered eruptions are consistent with previously published data on the Klyuchevsky volcano. The lavas of the Gorshkov vent are enriched with Ba, Zr, Sr and other incompatible elements at constant values of MgO in comparison with the lavas of the last summit eruptions, which indicates differences in the ways of evolution of their magmas. Sharply increased values of the 87Sr/86Sr ratio (0.703673–0.703743) in the lavas of the G.S. Gorshkov vent, not previously observed in the lavas of the Klyuchevsky volcano, testifies to intensive assimilation of crustal matter by the initial melts in the northwestern part of the volcano.

Petrologiâ. 2023;31(3):264-280
pages 264-280 views
New Data on the Rock and Mineral Composition of Kharchinsky and Zarechny Volcanoes (Central Kamchatka depression): Heterogeneity of the Mantle Source and Peculiarities of Magma Evolution in Crust
Gorbach N.V., Nekrylov N.A., Portnyagin M.V., Hoernle K.

The Kharchinsky and Zarechny volcanoes and the Kharchinsky Lake zone of monogenetic cones are unique eruptive centers of magnesian lavas located above the northern margin of the Pacific Plate subducting beneath Kamchatka. This work presents new geochemical data on the composition of rocks (55 samples) and minerals (over 900 analyses of olivine, pyroxenes, amphibole, and plagioclase) of these centers analyzed by XRF and LA-ICP-MS (rocks) and electron microprobe (minerals). Most of the studied rocks are represented by magnesian (Mg# = 60–75 mol. %), medium-K basalts and basaltic andesites. Moderate-magnesian (Mg# = = 52–59 mol. %) basaltic andesites are present among the monogenic cones of the Kharchinsky Lake. The rare rock varieties include high-K basalts-basaltic andesites of dikes in the center of the Kharchinsky volcano and magnesian andesites (Mg# = 58–61 mol. %) of the extrusions of Zarechnу volcano. The distribution of trace element contents in these samples demonstrates the enrichment of large-ion lithophile elements, light REEs and depletion of high field strength elements and heavy REEs typical of arc rocks. High-K basalts and basaltic andesites show anomalous enrichment in Ba (>1000 ppm), Th (>3.8 ppm), U (>1.8 ppm), Sr (>800 ppm, Sr/Y > 50) and light REE (La > 20 ppm); their compositions are close to those of low-Si adakites. Basalts and basaltic andesites contain high-Mg olivine phenocrysts (up to Fo92.6) and clinopyroxene (Mg# up to 91 mol. %). The rocks show petrographic and geochemical signs of fractional crystallization along with the processes of mineral accumulation and magma mixing. Some of the olivine phenocrysts show high NiO contents (up to 5000 ppm) and elevated Fe/Mn ratio (up to 80), interpreted as evidence of participation of the pyroxenite source in the magma generation processes. The use of Ca/Fe and Ni/Mg ratios allowed us to distinguish the composition fields and evolution trends of olivines associated with different sources – peridotite and pyroxenite, formed by the reaction of mantle wedge peridotites and high-Si melts of the subducted oceanic crust. The new data are consistent with other evidence of melting of the subducted Pacific plate edge beneath the northern part of the Central Kamchatka depression at the Kurile-Kamchatka and Aleutian subduction zone junction and testify to significant heterogeneity of the mantle in this area.

Petrologiâ. 2023;31(3):281-299
pages 281-299 views
Subduction and Oceanic Magmatism Records in Plutonic Rocks of the Kamchatsky Mys Ophiolite, Eastern Kamchatka
Bazylev B.A., Portnyagin M.V., Savelyev D.P., Ledneva G.V., Kononkova N.N.

The paper presents petrographic, mineralogical, and geochemical data on dunites, pyroxenites, peridotites, and gabbroids of the Kamchatsky Mys ophiolite. These data were acquired to distinguish cogenetic assemblages of igneous rocks, gain an insight into their geodynamic settings, and test various criteria of genetic links between the different magmatic rocks of ophiolites. The ultramafic and mafic rocks are shown to belong to two series, which differ in the compositions of the primary minerals, bulk rocks, and estimated trapped melts. The rocks of these series are found out to have been produced by geochemically different melts in different geodynamic settings, and during different episodes of mantle magmatism. The rocks of the high-Ti series (gabbro of the Olenegorsk massif, dunite and melanogabbro xenoliths in them, and vein gabbro in these xenoliths) crystallized from N-MORB melts in an oceanic spreading center. The rocks of the low-Ti series (dunite, pyroxenite, and gabbro veins in the residual spinel peridotites of the Mount Soldatskaya massif, as well as pyroxenite, peridotite, and gabbro alluvium and diluvium in the central and western parts of the peninsula) crystallized from water-rich boninite melts in relation to initial subduction magmatism. Taken into account the absence of boninite lavas from the Kamchatsky Mys ophiolite, the plutonic ultramafic rocks (including the rocks of the veins) might be the only evidence of subduction boninitic magmatism in the ophiolites. It was demonstrated that conclusions about the geodynamic settings of plutonic ultramafic and mafic rocks and recognition of cogenetic relations of these rocks with spatially associated basalts are more reliable when derived from the compositions of the trapped melts, which are estimated from their bulk geochemistry and primary mineral compositions, than when they are based on the mineral compositions only.

Petrologiâ. 2023;31(3):300-320
pages 300-320 views
Sulfide Mineralization in Pyrometamorphosed Upper Crustal Xenoliths, Bezymianny Volcano, Kamchatka
Davydova V.O., Shcherbakov V.D., Nekrylov N.A., Plechov P.Y., Yapaskurt V.O.

Bezymianny volcano supply on the surface numerous xenoliths, revealing the composition of the crust containing the magmatic system and the processes occurring within it. In this study, we present data on the xenoliths from the upper crust that were partially melted and recrystallized (pyrometamorphosed) in the shallow chamber of Bezymianny volcano. Some xenoliths contain relics of primary igneous associations, and some contain relics of prepyrometamorphic hydrothermally alteration. Thus, protoliths of pyrometamorphosed rocks could be reconstructed, and hydrothermal processes could be determined for rocks previously altered with fluids. The most common xenoliths are moderate-K andesites, basaltic andesites, and basalts from Kamen and Bezymianny volcanoes. During pyrometamorphism, a new microgranoblastic paragenesis forms, consisting of homogenous pyroxenes, plagioclase, and Fe-Ti oxides, sometimes surrounded by glass. Xenoliths of plateau basalts from the Klyuchevskaya group of volcanoes (high-K trachyandesitic basalts) are less common. Some of plateau basalt xenoliths contain trace of quartz-carbonate-sulfide mineralization, which was formed before the capture of xenoliths and their pyrometamorphism. A hydrothermally altered rock was melted and recrystallized after xenoliths were captured by magma, resulting in a Fe-wollastonite-hedenbergite association (sometimes with garnet), which is not typical for Bezymianny. The copper content of these xenoliths is anomalously high (up to 1500 ppm).

Petrologiâ. 2023;31(3):321-346
pages 321-346 views

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