Vol 64, No 6 (2019)


Effect of thermal state on the chemical composition of the mantle and the sizes of the moon’s core

Kuskov O.L., Kronrod E.V., Kronrod V.A.


Based on the joint inversion of seismic and gravity data in combination with the Gibbs free energy minimization method for calculating phase equilibria in the framework of the Na2O-TiO2-CaO-FeO-MgO-Al2O3-SiO2 system, the influence of the thermal state on the chemical composition models of the mantle and the sizes of the Fe-S core of the Moon has been studied. The boundary conditions used are seismic models from Apollo experiments, mass and moment of inertia from the GRAIL mission. As a result of solving the inverse problem, constraints on the chemical composition (concentration of rock-forming oxides) and the mineralogy of a three-layer mantle are obtained. It is shown that regardless of the temperature distribution, the FeO content of 11–14 wt.% and magnesian number MG# 80–83 are approximately the same in the upper, middle and lower mantle of the Moon, but differ sharply from that for the bulk composition of the silicate Earth (Bulk Silicate Earth = BSE, FeO ~8 wt% and MG# 89). On the contrary, estimates of the Al2O3 content in the mantle rather noticeably depend on the temperature distribution. For the considered scenarios of the thermal state with a difference in temperature of 100–200°C at different depths, Al2O3 concentrations increase from 1–5% in the upper and middle mantles to 4–7 wt.% in the lower mantle with garnet amounts up to 20 wt.%. For the “cold” models, the bulk abundance of aluminum oxide in the Moon
is Al2O3 ~1–1.2 × BSE, and for the “hot” models it can be in the range of 1.3–1.7 × BSE. Concentrations of SiO2 to a lesser extent depend on the temperature distribution and constitute 50–55% in the upper and 45–50 wt.% in the lower mantle; orthopyroxene, rather than olivine, is the dominant mineral of the upper mantle. Based on the modeling of the density of Fe-S melts at high Р-Т parameters, the sizes of the lunar core are estimated. The Fe-S core radii with an average density of 7.1 g/cm3 and a sulfur content of 3.5–6 wt.% are in the range of 50–350 km with a most likely value of about 300 km and rather weakly depend on the thermal regime of the Moon. The simulation results suggest that a lunar mantle is stratified by chemical composition and indicate significant differences in the compositions of the Earth and its satellite.

Геохимия. 2019;64(6):567-584
pages 567-584 views

Geochemistry and catagenetic transformation of kerogen from the bazhenov horizon

Kontorovich A.E., Bogorodskaya L.I., Borisova L.S., Burshtein L.M., Ismagilov Z.R., Efimova O.S., Kostyreva E.A., Lemina N.M., Ryzhkova S.V., Sozinov S.A., Fomin A.N., Livshits V.R.


A representative suite of 276 samples was used to study the isotopic and element geochemistry of kerogens from the Bazhenov horizon (Bazhenov Formation and its time equivalents) of the West Siberian sedimentary basin and to construct maps reflecting changes in the elemental composition of kerogen. The elemental composition of kerogen was used to determine the types of organic matter (H and C contents), the initial components of the living matter, the sources of kerogen (H and N contents), diagenetic history of organic matter (S content), the level of catagenetic transformation (C and O contents).

Kerogen from the central, western and southern regions of the West Siberian basin toward the boundary of the Bazhenov horizon pinch-out shows strong enrichment in hydrogen (up to 8–9%) and 12С (δ13С‰ from -35 to -29), suggesting its derivation from the polymer lipids of aquatic origin. Kerogen from the Bazhenov horizon (catagenetic grade MC1) in the northeast of the basin contains much lower hydrogen concentrations (2–4%). A map of organic matter types in the Bazhenov horizon was constructed.

Геохимия. 2019;64(6):585-593
pages 585-593 views

Anoxia markers in the photic layer of the sedimentation basin in the oils of Tatarstan

Smirnov M.B., Poludetkina E.N., Fadeeva N.P.


It is established that the source rocks for the oils of Tatarstan was formed under similar conditions in the presence of anoxia in the photic layer of the sedimentation basin that existed during the whole time of accumulation of the initial organic matter at a considerable thickness of the layer infected with hydrogen sulphide. It is not excluded that disturbances in the existence of anoxia existed or thickness of the infected layer was reduced that resulted in decreasing of anoxia markers content for some oils. Biocenoses of microflora in the sedimentation layer contaminated by hydrogen sulfide demonstrate high stability. Transformation conditions of the buried organic matter in diagenesis and catagenesis were uniform, which manifests itself in approximately the same ratio between the depth of the complete hydrogenation and cyclization of the initial polyene aromatic carotenoids, the closeness of the molecular mass distributions of the C-C bond destruction products of components C40 and relatively small differences in the total concentration of monoaromatic compounds and the sum of hydrogenated analogs of the initial aromatic carotenoids. Analysis of content of the components – anoxia markers throughout the whole Devonian section is needed to establish the complexes that generated oils of Tatarstan.

Геохимия. 2019;64(6):594-604
pages 594-604 views

Geochemistry of sillimanite-magnetite-kaolinite of metasomatic rocks of the island of Great Tyuters (gulf of Finland, Russia)

Shcherbakova T.F., Terekhov E.N.


Among the secondary quartzites of the island of the Great Tyuters there are extended linear zones with a capacity of up to 3 meters, clearly visible in detailed satellite images. They are composed of sillimanite-magnetite-kaolinite metasomatites discovered for the first time. The formation of metasomatites is associated with fragmentation of quartzites and the subsequent introduction of fluids of a substance saturated with various components. Metasomatites are enriched with Al2O3 (16–23 wt.%), in contrast to 2–5 wt. per cent of this oxide is present in their substrate – quartzite. In metasomatic rocks dominated by iron oxide, quartzite – ferrous. The rocks do not contain any alkaline and alkaline-earth elements. They are enriched with Zr (146–199 g/t) and a number of other elements, including impurities and rare earth, among which prevail Ce (34 g/t) and La (17 g/t). REE of both breeds is characterized by a small and close degree of fractionation ((La/Yb)n=6.55 and 6.17). Metasomatites on a set of minerals do not differ from quartzites, but differ in their quantitative ratios and composition. Of particular interest is the magnetite of metasomatites. It contains many quartz inclusions with kaolinite edges. Quartz inclusions, in turn, contain inclusions of titanium magnetite crystals. In the formation of metasomatites, there were several stages of the metasomatic process with a changing composition of fluids and different acidity-alkalinity of the mineral formation medium. The development of metasomatites in linear zones, the disintegration of their substrate, the high content of kaolinite – all this gives them a similarity with weathering cows. However, the same set of minerals in metasomatite and its substrate, the complete absence of sulfides and sulfur, the presence of magnetite with double mineral inclusions – such features distinguish these rocks from the classical weathering crust.

Геохимия. 2019;64(6):605-617
pages 605-617 views

Synrift clayey rocks: bulk chemical composition and position on discriminant paleogeodynamic diagrams

Maslov A.V., Podkovyrov V.N., Kotova L.N.


The paper analyzes the bulk chemical composition and distribution of the fields of syn-rift clayey rocks on a number of discriminant paleogeodynamic diagrams. It is shown that, in general, there are significant variations in the bulk chemical composition for syn-rift clayey rocks. Thus, for example, the average SiO2 content varies from 44.74 to 66.42 wt. %, the average content of Al2O3 varies from 16.62 to 29.92 wt. %, and the K2Oaver are in the range 0.24 ... 5.77 wt. %. Based on the distribution of the figurative points of the syn-rift clayey rocks of various objects/riftogenous structures in the F1–F2 diagram, it can be assumed that the sources of fine aluminosilicoclastic were magmatic and sedimentary rocks of a wide range of compositions. The substantial overlap of the fields of various objects in the classification diagrams [(Na2O + K2O)/Al2O3]–[(Fe2O3tot + MgO)/SiO2] and K/Al–Mg/Al indicates, in general, the similarity of the compositions of the syn-rift fine-grained clastic rocks of various types of riftogenic structures. The localization of the composition fields of the clayey rocks of different riftogenous structures on such discriminant paleogeodynamic diagrams as K2O/Na2O–SiO2/Al2O3 and SiO2–K2O/Na2O suggests that they do not allow correctly distinguishing between syn-rift clayey rocks and fine-grained rosks of other geodynamic environments. The position of the syn-rift clayey rocks fields presented in our database on the diagram DF1–DF2 has its own characteristics. In most cases, they occupy a particular position in the areas characterizing collision and rifting environments, and a number of fields are located in all three classification areas of this diagram. A significant part of the midpoints of the syn-rift clayey rocks is localized in the DF1–DF2 diagram in the collision field. It seems that all of the above indicates that the DF1–DF2 diagram also does not allow us to obtain a correct information about the geodynamic nature of terrigenous associations.

Геохимия. 2019;64(6):618-633
pages 618-633 views

Facies structure and quantitative parameters of pleistocene sediments from the east australian continental margin

Levitan M.A., Antonova T.A., Kol'tsova A.V.


Lithological and facies zonality of Neopleistocene and Eopleistocene sediments of Australian seas is described firstly. Processing of these maps and isopach schemes by A.B. Ronov volumetric method gave us an opportunity to calculate quantitative parameters of sedimentation for different types of Pleistocene sediments. It was revealed the dominance of carbonate sediments comparatively to other sediment groups. In Neopleistocene carbonate planktic sediments and lithogenic sediments accumulated more intensively than in Eopleistocene.

Геохимия. 2019;64(6):634-643
pages 634-643 views

Biogenic factors of geochemical uranium anomalies formation in subsurface waters near to Novosibirsk chemical concentrates plant slurry storage

Safonov A.V., Boguslavskii A.E., Boldyrev K.A., Zayceva L.V.


This article presents data on the possible impact of aerobic and anaerobic microbiological processes in the upper aquifers to uranium migration t sulfate and nitrate polluted waters near to Novosibirsk chemical concentrate plant. Uranium immobilization is possible in local areas, with high content of organic substances and the most important microbiological process is the redox potential reduction due to aerobic respiration. After that in anaerobicс conditions redox-dependent uranium reduction can be expected. Moreover, in the presence of sulfate ions, further anaerobic processes of microbial sulfate reduction and iron reduction lead to the formation of iron sulphide, which plays the significant role of an antioxidant buffer in the case of oxygen migration.

Геохимия. 2019;64(6):644-650
pages 644-650 views

Short communications

Natural kaersutite: ftir, raman, thermal and thermochemical investigations

Ogorodova L.P., Gritsenko Y.D., Vigasina M.F., Melchakova L.V.


A thermochemical study of the natural oxo-amphibole ─ kaersutite Na0.4K0.3(Ca1.6Na0.4)(Mg2.9Fe0.82+Al0.7Ti0.6Fe0.53+)[Si6.1Al1.9O22](OH)0.2O1.8.(alkaline basalts of Mongolia) was performed on a Tian-Calvet microcalorimeter. The enthalpy of formation from the elements ∆fH el0(298.15 K) = – 12102 ± 16 kJ/mol) was obtained by the method of high-temperature melt solution calorimetry. The entropy, enthalpy and Gibbs energy of the formation of the end-members of the isomorphic series kaersutite NaCa2Mg3TiAl[Si6Al2O22]O2 – ferri-kaersutite NaCa2Mg3TiFe3+[Si6Al2O22]O2 were estimated.

Геохимия. 2019;64(6):651-657
pages 651-657 views

Experimental study of silicates phosphatization in conditions of the supergene zone (hornblende, orthoclase, labrador)

Savenko A.V.


Experimental verification of the hypothesis of silicates phosphatization in conditions of the supergene zone was carried out. In addition to previous experiments with clay minerals (kaolinite and montmorillonite), phosphatization of aluminosilicates of other structural types (hornblende, orthoclase, and labrador), which for 9 months interacted with 1.2–6.0 mM orthophosphate solutions over a wide range of acidity, was studied. The existence of common for all minerals close to the linear dependence between changes in the concentrations of phosphorus and silicon in solution Δ[Si] ≈ –Δ[P]. is ascertained. The possibility of aluminosilicates substitution with phosphate minerals at relatively low concentrations of dissolved phosphorus, corresponding to the phosphate content in soil solutions, is proved.

Геохимия. 2019;64(6):658-663
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New isotope-hydrogeochemical data on the Bang spring (Kuang Binh province, central Vietnam)

Novikov D.A., Van P., Tuyen D., Thu D., Hoan T.


New isotope hydrogeochemical data on two types of thermal water from the Bang spring (Kuang Binh province, central Vietnam) are reported in the work. The first type includes HCO3–Cl–Na–Mg water with extremely low mineralization (44–87 mg/dm3) and pH variations from weakly acidic to weakly alkaline values (5.71–7.84). The second type includes HCO3–Na water with mineralization up to 256–659 mg/dm3 and pH 8.03 to 8.51. The studied types differ significantly in temperature: 24.3–34.5°C in the first type and 62.1–97.1°C in the second type. The analysis of the distribution of oxygen (δ18O) and hydrogen (δD) isotopes carried out for the first time confirms different genetic nature of these hydrogeochemical water types. The first type has an atmospheric genesis (δ18O = –7.3…–6.2‰ and δD = –51.4…–39.3‰), while the second type restricted to the Kien Giang–Bang intersection zone has a deeper source (δ18O = –1.6…–1.3‰ and δD = –22.2…–21.4‰). The tritium (3H) data also point to different circulation times of these waters. The formation time of the HCO3–Cl–Na–Mg waters does not exceed 50 years (3H = 4.3–11.1 ТЕ), while that of HCO3–Na water may reach more than 1000 years (3H = 0.5 ТЕ).

Геохимия. 2019;64(6):664-672
pages 664-672 views

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