Michał Skiba

CLAY MINERAL FORMATION DURING PODZOLIZATION IN AN ALPINE ENVIRONMENT OF THE TATRA MOUNTAINS, POLAND

The processes of clay mineral formation were studied in seven podzol profiles developed on granitic regoliths in the Polish part of the Tatra Mountains. The selected profiles have similar parent material and macroscopically represent different stages of soil development (from initial to advanced). Bulk soil material (<2 mm fraction) and separated clay fractions (<2 µm) were studied using a petrographic microscope, X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy-energy-dispersive spectrometry methods. The mineral compositions of the bulk soil samples are more or less the same (quartz, feldspars, mica and minor amounts of other phyllosilicates). The clay fractions are composed of mica and mixed-layer minerals which contain hydrated interlayers of vermiculitic and/or smectitic type, and kaolinite. Smaller amounts of chlorite, feldspars and quartz were also identified. Chlorite is present almost exclusively (except for one profile) in lower soil horizons (C, B/C, B). The amount of minerals with hydrated interlayers increases up the profiles. Kaolinite is present in all the samples except for the lowermost soil horizons (C) of two of the profiles. In some of the B horizons, the formation of hydroxy interlayers within hydrated interlayers is observed. The main processes of clay mineral formation recognized in the soils studied are: inheritance from the parent rocks; crystallization of kaolinite from soil solutions; the formation of dioctahedral vermiculite at the expense of inherited dioctahedral mica, and the formation of dioctahedral smectite at the expense of vermiculite. The recognized sequence of transformation is as follows: M → R0 M-V (12 Å or 14 Å) → R0 M-12 Å V → R1 M-12 Å V → 12 Å V → V-S → S. Observed formation of hydroxy interlayers seems to be pH dependent, starting when the pH ⩾ 4.4. The process of dissolution of primary silicates occurring simultaneously with the transformation is also documented.

CLAY-MINERAL FORMATION IN SOILS DEVELOPED IN THE WEATHERING ZONE OF PYRITE-BEARING SCHISTS: A CASE STUDY FROM THE ABANDONED PYRITE MINE IN WIESCISZOWICE, LOWER SILESIA, SW POLAND

Intense mineral transformations that produce acid soils from weathering zones of pyritebearing rocks, including alterations of layer silicates, are of critical importance to agricultural and environmental interests in various regions of the world. To date, the transformations of layer silicates in these soils have not been studied in detail. The aim of the present investigation was to examine the weathering pathways controlling processes of clay-mineral formation in acidic soils developed near the abandoned pyrite mine in Wieściszowice (Lower Silesia, SW Poland). A sequence of soils, from weakly developed technogenic soils (located on the mine dumps) to well developed natural soils, was selected. Bulk soil material and separated clay fractions were analyzed using X-ray diffractometry, Fouriertransform infrared spectroscopy, and scanning electron microscopy-energy dispersive spectrometry. The profiles analyzed were developed on pyrite-bearing schists containing trioctahedral Mg,Fe-chlorite and dioctahedral micas (muscovite and paragonite). Because of pyrite weathering, all the soils studied were strongly acidic (pH 2.8–4.4). Inherited chlorite and micas (K- and Na-mica) predominated in the clay fractions of soils developed on the mine dumps, whereas clays from natural soils were rich in pedogenic minerals (i.e. smectite, vermiculite, and mixed-layer minerals containing hydrated interlayers). The formation of both vermiculite and smectite at the expense of chlorite was observed in the soils studied. The transformation probably led to smectite formation via intermediate stages of mixed-layer minerals (i.e. chlorite-vermiculite, chlorite-smectite, and/or vermiculite-smectite). The process of chlorite dissolution took place simultaneously with the transformation. Micas were mainly transformed to smectite and mixedlayer mica-smectite. Neoformation of kaolinite occurring in A horizons of the soils investigated was also documented. Metal-hydroxy interlayers in Bw horizons of well developed soils were found. The process of interlayer development appeared to be pH dependent and took place at pH ⩾4.2. The processes of claymineral formation in soils developed in the weathering zone of a pyrite-bearing schist are similar to those occurring in podzols (Spodosols).

Dissolution of anisotropic colloidal mineral particles: evidence for basal surface reactivity of nontronite.

Anisotropic textural and crystallographic properties of phyllosilicate particles often influence the mineral weathering rate. The purpose of this study was to investigate how the changes in mineral surfaces (basal vs. edge) as a result of changes in crystal size control the dissolution of the mineral. Different nano-size fractions of Na-exchanged nontronites (NAu2 and NAu1) were immobilized in a silica gel and then incubated under acidic conditions using HNO(3) at 28 degrees C for 5 days. For each sample, the dissolution behavior was analyzed by measuring the amount of iron released from the mineral lattice. The results showed that for a given pH, a decrease in particle size significantly increased NAu2 and NAu1 dissolution. At pH 1.5, 7.2% of the total iron of the highest size sample of NAu2 was released in solution whereas this proportion increased up to 25% for the smallest size fraction. The percentage of total iron extracted from NAu1 at the same pH (1.5) was less important: 3.5% and 6.5% for higher and smaller size fractions, respectively. The observed increase in dissolution was not directly correlated to the increase in the amount of edge faces, suggesting that all mineral surfaces contributed to mineral dissolution. In the present case this may be related to the fact that 8% and 2% of total iron of NAu2 and NAu1, respectively, are located in the tetrahedral sheet. In conclusion, the basal surface of nontronites plays an important role in the weathering process.

EVOLUTION OF DIOCTAHEDRAL VERMICULITE IN GEOLOGICAL ENVIRONMENTS – AN EXPERIMENTAL APPROACH

Dioctahedral vermiculite commonly occurs in soils and fresh sediments, but has not been reported in sedimentary rocks. Little is known of the evolution of this mineral during diagenesis. According to the available literature, dioctahedral vermiculite is likely to exhibit strong potential for selective sorption and fixation of K+ involving interlayer dehydration and collapse. he objective of the present study was to investigate the influence of K+ saturation and seawater treatments on the structure o dioctahedral vermiculite. Due to the fact that no dioctahedral vermiculite standard reference material was available, a natural sample of soil clay containing dioctahedral vermiculite was used in the study. The clay was saturated with K+ using different protocols simulating natural processes taking place in soils and marine environments. The solid products of the experiments were analyzed for potassium content using flame photometry. The effect of the treatments used on the structure of dioctahedral vermiculite was studied using X-ray diffraction (XRD). The percentages of the collapsed interlayers were estimated by modeling the XRD patterns based on a whole-pattern multi-specimen modeling technique. All the treatments involving K+ saturation caused K+ fixation and irreversible collapse (i.e. contraction to 10 Å) of at least a portion of the hydrated (vermiculitic) interlayers. Air drying of the K+-saturated samples greatly enhanced the degree of the collapse. The results obtained gave no clear answer as to whether time had had a significant effect on the degree to which irreversible collapse occurred. Selective sorption of K+ from artificial seawater was observed. These results clearly indicate that collapse of dioctahedral vermiculite is likely to occur in soils during weathering and in sediments during early diagenesis. Both processes need to be taken into consideration in sedimentary basin studies.

Influence of redox processes on clay mineral transformation in Retisols in the Carpathian Foothills in Poland. Is a ferrolysis process present

PurposeFerrolysis is a soil-forming process, which involves destruction of clay minerals due to cyclic reduction and oxidation in acidic and periodically wet soils. The main objectives of this study were as follows: (1) to determine the influence of redox processes on clay mineral transformation in Retisols (Albeluvisols) in the Carpathian Foothills in Poland and (2) to verify the occurrence of ferrolysis in Retisols showing various degrees of bleaching.Materials and methodsTwelve representative soil profiles were selected for analysis. All were formed entirely from loess except for two profiles, in which the lowermost horizons (2C) had developed from weathered flysch rocks residuum. Soil mineral analysis was done using x-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and Mössbauer spectroscopy (MS).Results and discussionThe obtained results indicate that the qualitative and quantitative mineral compositions of the clay fraction in the E and Eg horizons obtained from Retisols in the Carpathian Foothills exhibiting marked differences in bleaching (strong, moderate, weak, and lack of bleaching) caused by periodic stagnation of water above a slowly permeable fragipan and cyclic redox processes are the same. The E and Eg horizons are characterized by the presence of 2:1 clay minerals with likely organic interlayer fillings, dioctahedral mica, kaolinite, and chlorite.ConclusionsThe results indicate that (1) redox processes occurring in the soils do not affect clay mineral transformation in Retisols of the Carpathian Foothills in Poland and (2) ferrolysis is not the main soil-forming process operating in these soils. This is most likely because iron-bearing minerals are not abundant in the Retisols and/or undergo eluviation to the lower part of the soil profiles. The lower content of the clay fraction in the E and Eg horizons versus that in the lower soil horizons of the Retisols is related to clay illuviation (lessivage), and not to clay decomposition due to ferrolysis.

Redoximorphic features in Albeluvisols from south-western Ukraine

Polarizing microscopy and scanning electron microscopy were used to determine the distribution, size, shape, and chemical composition of Fe–Mn nodules in Albeluvisols (Retisols) from south-western Ukraine and the relationship of these pedological features with redox processes. Intrusive, impregnative, and depletion features were observed. The highest content of hard nodules is present in the upper part of the solum, indicating that cyclic redox processes occur most often above the illuvial horizon. The nodules are enriched in Fe and Mn (4–14 and 7–40 times, respectively). The chemical composition of the surface of the nodule in contact with microorganisms indicates their crucial role in the accumulation of Fe and Mn and nodule formation.

PREPUBLICATION: Formation of NH4-illite-like phase at the expense of dioctahedral vermiculite in soil and diagenetic environments – an experimental approach

Selective sorption and/or fixation of cations with low hydration energies (e.g. K+, NH4+, Rb+, Cs+) by vermiculites is a well known phenomenon in soil science and it has been described by many investigators since the 1950s. Because most of the available studies deal with trioctahedral vermiculites, cation fixation in dioctahedral vermiculites is not as well understood as fixation by trioctahedral structures. The objective of the present study was to investigate the influence of NH4+ saturation on the structure of a natural dioctahedral vermiculite. Because no dioctahedral vermiculite standard reference material was available, two natural dioctahedral vermiculite-rich soil clay samples were used in the study. The clays were saturated with NH4+ using different protocols to simulate natural processes that likely take place in soils. The degree of NH4+ fixation by the dioctahedral vermiculite was evaluated using X-ray diffraction, elemental N analysis, and infrared spectroscopy. All the treatments that involved NH4+ saturation caused NH4+ fixation and irreversible collapse (i.e. contraction to ~10 Å) of at least a portion of the previously hydrated (vermiculitic) interlayers. Air drying of the NH4+-saturated samples greatly enhanced the degree of the collapse. The results indicated that the collapse of dioctahedral vermiculite leads to the formation of a NH4-illite-like phase that is likely to occur in some soils and sediments that are rich in organic matter. The formation of a NH4-illite-like phase by NHNH4+ fixation in vermiculitic interlayers needs to be taken into consideration in studies that deal with the clay mineralogy of sedimentary basins.