Natural sheet magnesium silicates are potential sources of divalent cations, which are necessary for the mineralization of CO2 in the carbonates. In order to study the influence of inorganic (HCO3−) and organic (oxalate and citrate) ligands on the kinetics of dissolution of talc and serpentine, experiments were performed in a flow-through reactor at 25°C. Dissolution rates of natural silicates r (mol cm−2 s−1) in solutions of various compositions were calculated at the stationary stage of dissolution after a rapid initial stage, which is characterized by the formation of a surface leached layer depleted in magnesium. The presence of ligands increases the dissolution rate of magnesium silicates due to the formation of surface complexes, which leads to separation of magnesium from the surface and transition into solution. Initial incongruent stage may be the most promising for the development of carbonation technologies, since the minimum removal of the network-forming elements prevents the undesirable formation of secondary minerals (for example, clays), which exclude divalent cations from the carbonation process and greatly reduce the permeability of rocks.
The analysis of the layer-by-layer dynamics of snow chemical parameters in one of the observation points in the Pechora-Ilych biosphere reserve (Yaksha village) in the winter period 2019–2020 was carried out. It is shown that the chemical composition of atmospheric precipitation is more affected by long-range transport of substances. The peculiarities of atmospheric circulation and the regions from which air masses are transferred determine the saturation of precipitation with certain chemical components. The calculation of the trajectories of reverse transport of air masses allowed us to show the regions where air masses can form that come to the research area, carry substances and potentially form the chemical composition of precipitation. It is shown that the calculation of trajectories allows us to estimate the regions that are sources of pollutants entering the atmosphere. In general, this method of studying the chemical composition of snow is very informative and allows you to better understand the factors of its formation.
Experimental data were analyzed on the partitioning of trace elements between minerals (olivine, orthopyroxene, clinopyroxene, and feldspars) and silicate melts. The data span over a wide range of conditions (from 1 atm to 10 GPa and ~1000–2000 °C) and compositions of melt (from ultrabasic to ultrasilicic) and minerals. The dependence of logarithms of partition coefficients (lnDi ) on conditions and compositions was approximated by linear functions of 1/T, P/T (P is pressure, and T is absolute temperature) and compositional parameters of mineral and melt. It was found that Di /Dj values for a number of element pairs are independent of experimental parameters and vary within narrow ranges. The coefficients of Di dependencies on conditions and compositions were estimated by minimization of quadratic deviations of model Di and Di /Dj values from experimental values. The obtained equations can be used to calculate Di values for a number of elements with an accuracy of approximately a factor of 1.2–2.0. The obtained values were applied as an example for a model of formation of mafic melts of mid-ocean ridges through melting of a peridotite source and crystallization of primary magmas under crustal conditions.
A petrogeochemical study of basalts (lithophile elements and Sr-Nd-Pb isotopes, compositions of liquidus olivine and spinel) from the transition zone of the Southwest Indian Ridge in the area of the Du Toit and Andrew Bain faults revealed significant differences in their composition. Within the rift valley adjacent to the faults, tholeiites enriched in Na and depleted in Fe (Na-TOR genetic type) are typical. Deep-type basalts (TOR-1) are present in the western side of the Andrew Bain Fault. The outpouring of these types of magmas reflects a possible change in geodynamic regime during this zone formation: from deeper and higher temperature melting to shallower ones (Sushchevskaya et al., 2022). Differences in the primary melts of tholeiites from the rift valley and the Andrew Bain Transform Fault are also traced in the liquidus olivine compositions. The rift valley olivines are similar to typical Na-TOR olivines with a Mg content of Fo88–87, low Ni and elevated Mn. On the contrary, tholeiite olivines of the Andrew Bain Fault are enriched in Ni and depleted in Mn, which may indicate pyroxenite included in the primary melt formation. This component is either oceanic lithosphere recycled through the deep mantle or fragments of previously formed oceanic crust, which are subsequently involved in melting during the spreading axes jumping. A similar process is typical for the region of the Bouvet Triple Junction, where a significant heterogeneity of the olivine composition in terms of trace-element contents was revealed. The isotope characteristics of the Andrew Bain Fault tholeiites differ in Pb and Sr radiogenic composition and are similar to those of enriched magmas from such Indian Ocean rises as Crozet, Marion and Bouvet, but not from the Konrad and Af. Nikitin Rises. The source of such tholeiite melts is close in composition to the model HIMU type (with high U/Pb), possibly with an admixture of mantle material with EMII characteristics (with elevated Rb/Sr).
Based on the mean contents of elements and their standard deviations estimated in the first part of this research project (Naumov et al, 2022), we compared in detail the distinguished geodynamic settings. In order to compare the compositions of mafic melts, a correction to take into account changes related to the fractionation of main minerals was introduced. The use of numerical criteria made it possible to determine the sequence of elements by the degree of coherence during melting and crystallization of the main magmatic melts. Within this sequence, a regular variation in elemental contents normalized to the average composition of oceanic island melts was established. The melts of mid-ocean ridges show a monotonous increase in normalized contents from the most incompatible (Cs, Ba, U, La, etc.) to compatible elements (Sc, Ni, Cr). The settings of convergent plate boundaries show relative enrichment in the most incompatible elements and significant negative Ta-Nb anomalies relative to neighboring elements. The magmas of continental rifts show the highest enrichment in the most incompatible elements, as well as Pb, Li, and some other elements. Indicator element ratios showing significant variations between the settings were distinguished for mafic melts. Some element ratios are almost identical (within observed variations) in mafic melts from all the settings. The mean element ratios in mafic, intermediate, and silicic magmas show three types of behavior. Some ratios (including the canonic ratios Nb/Ta, Zr/Hf, etc.) in intermediate and silicic magmas are inherited from the composition of mafic melts. Some ratios show irregular changes from mafic to silicic melts (Sr/Cr, F/Th, etc.). There are ratios that changes monotonously and significantly in the sequence from mafic to silicic melts (Ni/Yb, Lu/P, etc.). The variations of element ratios are related to the crystallization differentiation of melts and contributions of geochemically contrasting reservoirs.
The composition of medium volatile organic matter (OM) in the steam-water mixture condensate (SWC) from deep production wells of the Pauzhetsky geothermal field was investigated. Using solid-phase extraction and chromatography-mass spectrometry, 17 organic compounds, including 14 aliphatic and aromatic hydrocarbon (HC), were identified in the studied SWC. These components are highly dominant in the Pauzhetsky hydrothermal system and a number of other geothermal fields in Kamchatka, averaging more than 60 per cent. Due to the peculiarities of the molecular weight distribution of the limiting HCs, the high steam-water mixture condensate temperature (more than 108℃ at the wellhead) and the absence of obviously biogenic components, their origin is attributed to thermogenic processes, which consist in the transformation of organic residues under the action of high temperatures and pressures. The remaining compounds are much less common and are mainly represented by components containing oxygen (ketones, aldehydes, alcohols). The similarity of the spectrum of organic compounds in the Pauzhetka and Uzon CPS may be partly due to their extraction from volcanogenic-sedimentary layers containing buried organic matter.
The phase relationships and distributions of rare earth elements, Sc, Y and Li between aluminofluoride and aluminosilicate melts in the model granite system Si-Al-Na-K-Li-F-O-H at 700 °C, 1 and 2 kbar with a water content from 3 to 50 wt. %. were experimentally studied. Based on the obtained and available experimental data on phase relationships in a granite system saturated with water, fluorine and containing rare elements, a comparison was made with the parageneses of rare-metal cryolite-containing granites from three deposits in Eastern Siberia are Zashikhinsky, Katuginsky and Ulug-Tanzeksky. It has been shown that the processes of liquid immiscibility between granite and salt aluminofluoride melts, which manifest themselves at high contents of fluorine and lithium in the system, contribute to the accumulation of rare elements in salt cryolite-like melts. At a temperature of 700 °C and a pressure of 1 and 2 kbar, crystallization of the aluminofluoride melt occurs in the granite system, from which cryolite is formed. It is in association with cryolite and lithium micas that the considered natural objects contain minerals of rare and rare earth elements containing fluorine, such as pyrochlore, gagarinite, etc. As a result of a comparison of experimental and natural data, the hypothesis about the important role of liquid immiscibility in the formation of cryolite is confirmed. It is assumed that cryolite can serve as a reference mineral for rare metal-rare earth mineralization in granites with high lithium and fluorine content.
The paper discusses the possible conditions and involvement of sources in genesis of the Khokhol-Repyevka batholith granitoids, that build up the Don terrane in the Volga-Don orogen of the East European Craton. In the batholith, three types of granitoids are distinguished – pavlovsk (quartz monzodiorite–granites, mainly pyroxene-free), potudan (quartz monzogabbro–granodiorites containing pyroxene) and hybrid (quartz monzodiorites, monzonites, quartz monzonites). These three types of rocks are spaсely co-located and have a similar age of formation 2050–2080 Ma, similar geochemical characteristics (high contents of Ba, Sr, highly fractionated REE patterns (GdN/YbN= 2–11)), however, they differ in petrographic and isotopic geochemical parameters. Primary isotope characteristics of sources for rocks of the pavlovsk type εNd(t) = +0.2…–3.7, Sri= 0.70335, for potudan εNd(t) = – 1.7 ... –3.8, Sri= 0.70381–0.70910, for hybrid εNd(t) = – 8.8, Sri= 0.70596. Apart from granitoids, two types of leucogranite dikes were found in the batholith. The first type is characterized by εNd(t) = –3.8 and fractionated HREE patterns (GdN/YbN= 2.1–3.8) and could have formed as a result of deep differentiation of pavlovsk-type magma. The second type is with εNd(t) = –7.8 and less fractionated HREE patterns (GdN/YbN = 1.1–1.6), which presumably appeared as a result of melting of a crustal source at shallow depths. Rb-Sr isotope-geochemical characteristics of rocks of the pavlovsk and potudan types indicate their formation from different sources. In total, at least three sources took part in the formation of the Khokhol-Repyevka batholith: 1) lower (or buried oceanic) crust, predominantly of mafic composition and/or enriched mantle, metasomatized in the Proterozoic, the participation of which is reflected in the composition of the Pavlovsk granitoids; 2) an enriched mantle source, probably represented by subcontinental lithospheric mantle (SCLM), possibly metasomatized during the previous stage of geological development of the region, specific for Potudan-type monzonitoids; 3) Archean crust, consisting mainly of TTG gneisses and metasediments, which underwent melting and participated in the formation of part of the leucogranite dikes and hybrid rocks. The results of thermodynamic modeling indicate that the mixing of two melts contrasting in composition – mafic (potudan-type) and intermediate-felsic (pavlovsk-type) can lead to the formation of only part of the composition of hybrid rocks. The formation of the rest was influenced by the contamination of mafic melt by anatectic melts from the Archean crust of the Kursk block.
The article assesses the transformation of the chemical composition of surface waters in the southeastern part of the Khibiny mountain massif after the beginning of development of the Oleniy Ruchey apatite-nepheline ore deposit in 2012. The influence of the Oleniy Ruchey Mine was reflected in an increase in water mineralization (by an order of magnitude) and in a change in the ratio between the basic ions in water objects receiving runoff from mines, rock dumps and tailings, compared to watercourses not affected by the mining enterprise’s activities. Natural hydrocarbonate-sodium water composition with a mineralization of 10 mg/l was transformed into nitrate-sodium or sulfate-calcium. The content of nitrogen group compounds in the water of Lake Komarinoe, which receives wastewater from the tailings pond over the ten-year history of the mining and processing plant, has increased by two orders of magnitude, and the nitrate ion is part of the basic ions. The concentrations of other basic ions and mineralization in this lake increased by an order of magnitude, as well as the content of trace elements (Sr, F, Mo), which are part of the main rock-forming minerals of apatite-nepheline deposits. Increased mineralization (up to 260 mg/l), pH value (up to 10) and a modified chemical composition compared to background objects were noted in mine wastewater. They are characterized by a hydrocarbonate-sodium composition with a large proportion of nitrates and sulfates. Mine wastewater contains increased levels of compounds of nutrients, organic matter and a number of microelements (Al, Fe, Sr, Cu, Mn, Zn and Cr). It has been established that geochemical modifications in the quality of surface water have local characteristic and are typical for water objects receiving wastewater from a mining enterprise, in contrast to metallurgical plants, the atmospheric emissions of which have a polluting effect over tens and hundreds km.
New geological, geochemical, and geochronological (U-Pb zircon) data obtained on the greenstone rocks of the Kichany structure from the Archean Tiksheozero greenstone belt made it possible to clarify and supplement the previously proposed stratification schemes. The composition of the identified sequences, the order and duration of their formation have been specified. The Archean supracrustal rocks are divided into three sequences. The lower sequence (previously not identified) is represented by a bimodal series: tholeiitic metabasalts and felsic metavolcanics, with subordinate metagraywackes. It has been formed for over 20 million years (from 2788 ± 5 to 2766 ± 9 Ma). Sm–Nd data obtained on basaltic metaandesites (Sm–Nd model age 2.86 Ga and εNd = 2.92) indicate their mantle nature. Metarhyolites from the lower sequence with a Sm–Nd model age of 2.89 Ga and εNd = 2.59 were generated from a source with a short residence time. The differentiated volcanic series of the upper sequence (from basalts to dacites) has been also formed for about 20 million years (2738 ± 7–2716 ± 7 Ma). The parental melts for the intermediate–felsic metavolcanics of the upper sequence are variably enriched in ancient crustal matter. The oldest rocks with a Sm–Nd model age of 2.84 Ga and εNd = 2.67 were formed during the Early Neoarchean crust-forming event. The younger rocks have a different contribution of ancient crustal material: significant contribution for dacites (Sm–Nd model age of 3 Ga and εNd = 0.4) and less significant contribution for dacitic andesites (Sm–Nd model age of 2.89 Ga and εNd = 1.73). In the Paleoproterozoic (from 1786 ± 11 to 1796 ± 6 Ma), the supracrustal rocks of the Kichany structure underwent metamorphic transformations.
The processes of albite ordering in the range of low temperatures 500–150°Cat a pressure of 0.5–1 kbar in alkaline solutions of sodium hydroxide with an excess of silica have been experimentally studied.Based on the data of our experiments and literature data on the ordering of albites and felsic plagioclases, dependences have been derived that make it possible to estimate the temperature from the degree of their structural ordering.The temperatures for plagioclase-bearing parageneses of various natural complexes of the greenschist facies of metamorphism have been determined.
The paper presents materials on experimental study of pargasite stability. On the example of calcic amphibole, experimental modeling of the processes occurring in the conditions of volcanic hearth at pressures up to 5 kbar was carried out. The phase diagram of pargasite was clarified. The occurring reactions and their parameters are revealed. Based on the experimental data obtained, the stability of pargasite is controlled by three reactions. The first reaction takes place in the area of low water pressure less than 1 kbar – dehydration reaction:Prg = Fo + Sp + Di + Ne + An +H2O. The second reaction takes place in the area of water pressure more than 1.2-1.5 kbar and temperature around 1100°C. Pargasite decomposition is controlled by incongruent melting:Prg = Fo + Sp +{Di+Ne +An}L+H2O. The third reaction takes place in the same pressure range as the previous one, but at lower temperatures ~1050°C. This reaction determines the pargasite liquidus in the melt and is related to the interaction between the amphibole and the coexisting melt:Prg + L= Fo + Sp + Di +{Ne +Pl}L+H2O.Presumably, the activity of the melt silicaaSiO2has the greatest impact on the pargasite liquidus.
The results of the geochemical study of loose sediments of the catchment basin and bottom sediments of Lake Chistoye, located in the Northern Priokhotye, showed that the lake was formed at the beginning of the early Holocene about 11200 cal. years ago. Terrigenous sedimentation dominates in it, i. e. the geochemical characteristics of sediments are determined by the particle sizes. Thin grain size sediments have low SiO2, Na2O, K2O, CaO, and Sr contents; and are enriched with Al2O3, TiO2, MgO, Fe2O3, and V. Changes in the nature of sedimentation may be due to climatic reasons and may be associated with cold Bond events. In the Early Holocene, mostly thin silts were deposited in Lake Chistoye. The impulse of “coarse-grained” sediments (140 microns) enriched with silica occurred (9760–9650) and 8810 cal. years ago. A noticeable accumulation of relatively coarse-grained sediments occurred at the very beginning of the Middle Holocene 8540–6920 cal. years ago, as well as 6140 and 4450 cal. years ago. For the Late Holocene, the input of detrital material with increased SiO2 contents was noted in the range of 3470–850 cal. years ago.
An original database compiled by the authors on volatile components of mineral-hosted fluid inclusions currently includes 12 470 analyses from 480 publications and was used to calculate the average gas phase composition of fluids that formed hydrothermal deposits throughout the Earth’s geological evolution, from the Archean to Cenozoic. The paper reviews the methods used in the study, their potential errors, and limitations. Characteristics of the gas composition of fluids are traced for more than 300 ore deposits of Au, Sn, W, Cu, Cu, Pb, Zn, Sb, Mo, and U. The dominant volatile component of natural mineralizing fluids in the Earth’s crust is carbon dioxide, regardless of the geologic age. The fluids contain subordinate amounts of reduced carbon species (methane) and nitrogen, as well as minor amounts of hydrogen sulfide and some other gases. The Cenozoic fluids commonly contain more nitrogen than methane. These relations are occasionally also found in the Precambrian fluids. The CO2/CH4 ratio as an indicator of the redox state of the system notably increased over the Earth’s geological history.
The paper presents newly obtained and summarizes preexisting data of long-term geochronological and isotope studies of orogenic mesothermal gold deposits in the world’s largest Lena metallogenic province and reviews interpretations of their genesis. Geochronologic data indicate that the gold mineralization was formed during three ore-forming Paleozoic events. The early Late Ordovician–Early Silurian (450–430 Ma) event produced the abundant veinlet—disseminated gold–sulfide mineralization in Neoproterozoic carbonaceous terrigenous–carbonate rocks of the Baikal–Patom foldbelt (BPB). The mineralization was formed simultaneously with regional metamorphic processes. The rejuvenation of hydrothermal activity in the BPB resulted in gold-bearing quartz veins, which was produced in the Middle Carboniferous (340–330 Ma) in relation to postcollisional granitoid magmatism. The latest ore-forming event occurred in the Early Permian (290–280 Ma) and affected exclusively in Precambrian structures of the Baikal-Muya foldbelt (BMB). It was synchronous with the development of intraplate alkaline and subalkaline magmatism in the region. Newly obtained and preexisting isotopic-geochemical (87Sr/86Sr, 143Nd/144Nd, Pb–Pb, and δ34S) data indicate that the mesothermal ore-forming systems of northern Transbaikalia were heterogeneous in their isotopic characteristics, which distinguishes them from the ore–magmatic (intrusion-related type) systems. Comparison of the Sr, Nd, and Pb isotopic composition of the ores and rocks, including magmatic rocks coeval with the gold mineralization, indicates that the Precambrian continental crust was the dominant source of mineral-forming components for the hydrothermal systems of the gold deposits. The contribution of the magmatic source to the genesis of the orogenic gold mineralization was limited and is identifiable only for the Early Permian ore-forming systems of the BMB, for which the input of metals from alkaline mafic melts was suggested.
New data on the U–Pb age (SHRIMP-II) and trace element composition (SIMS) of zircon from gneisses of the Khapchan Group of the Khapchan terrane of the Anabar Shield are presented. Zircon grains contain relicts of magmatic zircon, the protolith and source areas of which are difficult to specify. The only zircon in this group with the least altered core preserved the 207Pb/206Pb protolith age of 1971 ± 19 Ma. During granulite metamorphism, the zircon was subjected to the impact of fluid enriched in incompatible elements. The disurbances affected both the U–Pb isotope system (zircon age was “reset” at metamorphic age of 1920–1930 Ma) and composition of zircon, magmatic cores of which were significantly recrystallized in a solid state or dissolved by fluid up to the practically complete disappearance of primary zircon. In both the cases, zircon was sharply enriched in incompatible elements (Ca, Ti, Pb, Sr, Ba, and some others) owing to fluid effect, while preserved cores seemed to be rimmed by a new zircon population (CL-black). The REE distribution patterns in the recrystallized cores acquired a “bird’s wing” profile atypical for zircon. When the fluid lost its reactivity, the main part of the zircon grain crystallized, typical of granulite zircon. This zircon population is less enriched in incompatible element than the cores are. The horizontal pattern of HREE distribution is consistently repeated, which indicates the co-crystallization of zircon and garnet. The estimated crystallization temperature of the main part of zircon varies in a narrow range of 800–830°C. All zircon domains in the Wetherill concordia diagram form a single trend with a zero lower intercept and an upper intercept confirmed by concordant cluster with an age around 1920–1930 Ma. This value corresponds to the age of regional Paleoproterozoic granulite metamorphism. A unique feature of zircon from the Khapchan gneisses is that its cores did not retain the age marks of the protolith, but were completely reset during metamorphism both in terms of the U-Pb system and the trace element composition, which can be explained by the extremely high intensity of fluid impact during the granulite facies metamorphism superimposed on the rocks of the Khapchan terrane of the Anabar Shield.
The results of long-term studies of the conjugate distribution of methane (CH4) and sulfide sulfur (Ssulfide) concentrations in the bottom sediments of watercourses of the steppe zone of the European part of Russia are analyzed. In addition to CH4 and Ssulfide, Eh and pH values, humidity and density were determined in different sediment horizons; CH4, dry residue, and pH values were determined in water. Concentrations of CH4 in the watercourses vary from <0.1 to 2007.0 μL/L (median 24.3 μL/L), with the largest number of values (72
The paper presents geochemical study of bottom sediments from the MSU structure located on the large Gydratny Fault in the Central Basin of Lake Baikal at a depth of 1380 m. The first detailed data on the spatial variations in the qualitative and quantitative composition of the pore waters are presented. Pioneering data were obtained on Li, B, and Sr contents in the pore water of the sediments. It has been established that fluids are actively discharged within the MSU structure, and the main pathways of their near-surface migration are confined to the tops of hills of this structure on the downthrown fault block. The fluids are highly mineralized (up to 2900 mg/L), showing the highest mineralization ever found in Lake Baikal sediments. The waters are significantly enriched in Mg, Li, B, and Sr but depleted in K. The waters are thought to be generated by the processes of authigenic formation and illitization of smectite at depths of 1 to 2.5 km in the sedimentary sequence. The maximum values of concentration gradients are recorded in the pore waters of the sediments of the western hill, which may indicate a gradual westward shift of the center of the fluid seepage activity along the fault.
The effective solubilities (maximum contents) of Ta and Nb in model felsic lithium-fluoride melts of variable alkalinity and alumina content were experimentally determined at the dissolution of Ta–Nb and Nb minerals: pyrochlore, microlite, ilmenorutile, and ferrotapiolite at T = 650–850°C and P = 100 and 400 MPa. The Ta and Nb partitioning in the mineral-melt systems was also studied. When pyrochlore is dissolved in granitoid melts at P = 100 MPa and T = 650–850°C, the highest effective solubilities of Nb (0.7–1.8 wt
The paper reports the detailed studies of drilling cores from peat deposits of the Vydrino bog with a thickness of 4.4 m and an age of 13 100 cal. years. The peat is composed of fen, transitional, and raised types. The early-diagenetic transformations of peat sediments are considered, and the distribution of elements, the formation of authigenic minerals, and the chemical composition of bog waters are studied. The destruction of organic matter begins from the upper intervals of peat at the early diagenetics stage. Pyrograms do not have clearly defined high-temperature peaks, “rudiments” of the macromolecular structure of kerogen, which indicates a low degree of transformation of peat organic matter. The high abundance of organotrophic, ammonifying, nitrifying, and phosphate-mobilizing microorganisms, and the low abundance of Fe- and Mn-oxidizing microorganisms, and sulfate-reducing bacteria are revealed. The presence of organotrophic microorganisms throughout the section indicates that the biogeochemical processes of the carbon cycle span the entire peat sequence. The low S(II) content indicates the low intensity of sulfate reduction. The fen peat is characterized by the high contents of Si, Al, Fe, Ca, Sr, Ba, Zr, La and anomalous contents of Cu, Zn, which is caused by the peatland formation under conditions of rich mineral nutrition. The ash part of the transitional peat demonstrates a decrease in the contents of Si, Fe, Sr, Br, K Si, Ca, Ba, Cu, Zn and La, which reflects the gradual weakening of the connection of the peat deposit with the underlying rocks. The near-surface horizon of raised peat is characterized by an increase in the contents of K, Mn, Zn, Hg, Pb and As, which is accompanied by an increase in atmospheric dust and anthropogenic impact on the bog ecosystem in the 20th and 21st centuries. The bog waters of the fen peat are characterized by the high contents of the main ions, Al, Fe, Mn, Sr, while the transitional peat shows a decrease in DOC, SO_4^2 - , HCO_3^ - , Al, Fe, Ni, Ca, Mg. The oligotrophic stage peat deposit layer is characterized by the development of Fe oxides and hydroxides, the presence of vivianite is noted for transitional peats, and the eutrophic stage layer includes rhodochrosite and sulfides of Fe, Cu, and Zn.
