Geology and Geochemical Assessment of Maastrichtian Coal Quality in Abocho area, Northern Anambra Basin, Nigeria

Detailed geologic mapping and geochemical analysis of coal samples around Abocho area, northern Anambra Basin, Nigeria was conducted in order to assess the quality of the coals in the area. Proximate and ultimate analyses were carried out on coal samples from the Mamu Formation to determine its chemical characteristics. Physical analysis was also carried out on the coal samples to determine the specific gravity, density and hardness. Geochemical analysis was also carried out on the associated rocks in the study area (Abocho), particularly Shales and Clays to determine their major oxides composition. The area is composed of the Maastrichtian Mamu Formation overlain by the Ajali Sandstone of the same age both dipping between 16°E and 19°E. The geologic mapping of Abocho area revealed two mappable lithologic units: The Mamu Formation and the Ajali Sandstone. The Proximate analyses indicates that the coal contains an average 7.15%, 35.53%, 36.24% of moisture content, volatile matter and fixed carbon respectively. These burns to generate 4,339 kcal/kg calorific value with 20.80% ash yield. The result of the ultimate analysis shows 57.81% organic carbon, 4.15% hydrogen, 8.41% oxygen, 1.39% nitrogen and 0.3% Sulphur. The physical analysis revealed that, the coal has an average specific gravity of 1.5g/cm, average density of 1.4g/cm3 and average hardness of 1.2. These characteristics qualify the coal to be ranked as high volatile sub-bituminous to marginal lignite. The coal is thus, suitable for combustion, gasification, electric power generation and industrial uses. Geochemical results show that the Shale contains 60% Silica (SiO2) and 26%Alumina (Al2O3) constituting 86% of bulk chemical composition. The Clay contains 70% Silica (SiO2) and 25% Alumina (Al2O3), constituting 95% of bulk chemical composition. The occurrences of CaO, NaO and K2O which are the major component of feldspar in clay suggests the clay to be of granitic origin possibly from Oban massif, east of the Anambra Basin. It also suggests low feldspar content.

Lithochemical features of Vendian clay rocks of the Shkapovo-Shikhan depression: In search of camouflage pyroclastics

Research subject. Vendian clay rocks of the Shkapovo-Shikhan depression, which is situated in the east of the Volga-Ural region, and volcanic tuffs present among the Vendian deposits (Sylvitsa and Asha groups) on the western slope of the Middle and South Urals.Material and methods. The research was conducted using data on the content of the main rock-forming oxides in about 70 samples of clay rocks and volcanic tuffs. On this basis, a number of indicator ratios (lithochemical modules) were calculated. These calculated values, as well as the contents of some rock-forming oxides, were compared with both the available data on volcanic tuffs and literature threshold values, which differentiate “ordinary sedimentary rocks” from those presumably comprising camouflage pyroclastics.Results. It is impossible to draw any definite conclusion regarding the presence of camouflage pyroclastics in the clay rocks of the Staropetrovo, Salikhovo and Karlin formations of the Shkapovo-Shikhan depression based exclusively on lithochemical studies. It seems that the investigated samples either contain no camouflage pyroclastics, or its amount is rather small.Conclusions. In order to reliably establish the presence of camouflage pyroclastics in the Vendian deposits of the Shkapovo-Shikhan depression, research into the bulk chemical composition of clay rocks should be continued both on a more representative sample collection and using geochemical methods.

Specifics of bulk chemical composition of virgin forest cambisols within the Ukrainian Carpathians

Material composition is one of the most vital components of soil analysis and it which allows to determine the bulk or elemental composition, to get an insight into the total content of chemical elements per the genetic horizons of a soil profile against the soilforming rock, and to identify the direction of soil formation processes, that is, to establish the genesis of soils. The study objective supposed both the identification of bulk chemical composition (BCC) specifics peculiar to cambisols (acc. the WRB) located beneath different virgin forest ecosystems and the change caused by the composition of soil-forming rock, specifics of mountainous terrain and climatic conditions. The study subject is cambisol of virgin (beech and coniferous) ecosystems formed at the eluvium-deluvium flysch with prevailing sandstones, argillites and siltstones. The study scope is bulk chemical composition of beech and coniferous forest cambisols within the Ukrainian Carpathians and its transformation. Comparative-geographical, comparative-profile, analytical and statistical methods have been used accounting for the above objective. The bulk chemical composition has been determined under the method devised by E.V. Arinushkina. Recalculations and ratios have been used to analyse data on the bulk chemical composition of soils. Our article provides the results of the study of bulk chemical composition of cambisols located beneath beech and the coniferous virgin forests. Changes occurred in this, one of the most conservative, soil substance, under the influence of phytocenotic diversity of virgin forest ecosystems and soil species, are analysed, the nature and direction of changes as well as their main regularities are identified. Molecular ratios for the genetic soil horizons are calculated since they testify the removal of elements outside the soil profile boundaries and are the main factor used to assess the direction of cambisols soil-forming process. The article considers the content of constitutional water and the ratio of change in the siliceous soil part. Results obtained allow suggesting intrinsic weathering in the soils under study. Major reasons of changes in the bulk chemical composition of virgin forest cambisols are caused by the character of vegetation, its aggressiveness with respect to the soil mineral content, by climatic features that affect processes of soil formation in mountainous areas depending on the vertical zonality, and by the composition of soil-forming rocks being the substrate for the studied soils. SiO2, Al2O3, Fe2O3 oxides form the predominant bulk chemical composition of virgin forest cambisols in the Ukrainian Carpathians. Their total content ranges from 65.59 to 87.56 %. The mineral base of virgin forest cambisols is SiO2 and its content in virgin forest cambisols amounts up to 63.46 - 75.03 %, Al2O3 sesquioxide content is 13.16 - 17.14 %, Fe2O3 content is 4.25 - 6.83 %. Molecular ratios in cambisols located beneath the beech virgin forests postulate the removal of sesquioxides out from a soil profile. For instance, the ratios of SiO2/Fe2O3 in beech virgin forests cambisols are 42.8 - 44.61 and they decrease sharply at the soil profile bottom to 26.35, i.e. the removal of Fe2O3 sesquioxide out from a soil profile is observed. The molar ratio of SiO2/R2O3 in cambisols located beneath coniferous virgin forests is narrower than in beech virgin forest cambisols and amounts up to 5.64 - 5.81, which is due to the lower content of SiO2 oxide and higher number of Fe2O3 and Al2O3 sesquioxides. The analysis of leach factor indices shows that leaching of Calcium and Magnesium oxides is observed in these soils. However, leaching in cambisols located beneath the beech virgin forests is less intense than in cambisols located beneath the coniferous virgin forests. Leaching of Sodium and Potassium oxides in cambisols located beneath the beech virgin forests is minor, and in cambisols located beneath the coniferous virgin forests is weakly expressed.

Mineralogická charakteristika fosforitové konkrece s rodochrozitem z lokality Tabarky, severní Chřiby

The second occurrence of phosphorite in the Chřiby Mts. was found in a secondary position (pebble from stream gravel) in the northern part of the mountain massif at the Tabarky site. Its original host rock environment were Cretaceous-to-Palaeocene flysch sediments of the Soláň Formation, belonging to the Rača Unit of the flysch belt of the Outer Western Carpathians. Based on bulk chemical composition, the studied phosphorite concretion is formed by ca. 47 wt. % of carbonate-fluorapatite, 31 wt. % of carbonate (rhodochrosite to Fe-rich rhodochrosite), and 21 wt. % of detritic admixture. The grains of carbonate are zoned with increasing Fe/Mn ratio from core to rim. Accessory pyrite with elevated contents (0.X wt. %) of Mn, Ni, Co, Cu, As and Pb as well as very rare sphalerite were also found. Phosphorite is product of early diagenetic processes operating in unconsolidated host deep-sea sediments. The material source of this mineralization was in unstable components of host sediments, which were remobilized by pore fluids under reducing conditions associated with shallow burial. The geochemical signature suggests that material resembling oceanic manganese nodules could have participate during formation of the studied authigenic mineralization.

Chemical variation, modal composition and classification of granitoids

Granites (sensu lato) come in many types and flavours, defining distinct magmatic series/suites/types. A good classification not only gives generally accepted and understandable names to similar rocks but also links the bulk chemical composition to the stoichiometry of the constituent minerals and, potentially, also to the likely source, magmatic evolution and tectonic setting.The ‘ideal’ granitoid classification should be based on chemical criteria amenable to an objective treatment. Statistical analysis helps to identify the most discriminant variables. The key properties are (1) acidity/maficity, (2) alkalinity (balance of Na + K v. Ca), (3) aluminosity (balance of Al v. Ca, Na and K), (4) Fe/Mg balance and (5) Na/K balance and K contents at the given SiO2 level. These are used by successful classifications, e.g. the I/S dichotomy is based mainly on aluminosity, while the Frost et al. (2001; ‘A geochemical classification for granitic rocks', Journal of Petrology, 42, 2033–2048, https://doi.org/10.1093/petrology/42.11.2033) classification includes all but Na/K. Even though it is commonplace to use weight percentages of oxides, we suggest that a better strategy is to employ simple atomic parameters (e.g. millications-based) that can be directly linked to modal proportions and compositions/crystal structure of individual rock-forming minerals. This facilitates a petrological interpretation, which, in turn, can be related to petrogenesis and, ultimately, to likely tectonic setting(s).

Synrift sandstones and clayey rocks: bulk chemical composition and location on a number of discriminant paleogeodynamic diagrams

The bulk chemical composition of synrift sandstones and associated clayey rocks has been analized, and the distribution of the fields they form has been studied on discriminant paleogeodynamic SiO2K2O/Na2O [Roser, Korsch, 1986] and DF1DF2 [Verma, Armstrong-Altrin, 2013] diagrams. The studied sandstones in terms of bulk chemical composition mainly correspond to greywacke, lititic, arkose and subarkose psammites; Sublitites and quartz arenites are also found. A significant part in the analyzed data massif consists of psammites, in which log(Na2O/K2O)-1.0; missing on the Pettijohn classification chart. This confirms our conclusion, based on the results of mineralogical and petrographic studies, that the sedimentary infill of rift structures unites immature sandstones, the detrital framework of which was formed due to erosion of local sources, represented by various magmatic and sedimentary formations. Synrift clayey rocks, compared with sandstones, are composed of more mature fine-grained siliciclastics. As follows from the distribution of figurative data points of clayey rocks on the F1F2 diagram [Roser, Korsch, 1988], its sources were mainly sedimentary deposits. The content of most of the main rock-forming oxides in the synrift sandstones is almost the same as in silt-sandstone rocks present in the Upper Precambrian-Phanerozoic sedimentary mega-complex of the East European Plate, but at the same time differs significantly from the Proterozoic and Phanerozoic cratonic sediments, as well as from the average composition upper continental crust. It is shown that the distribution of the fields of syntift sandstones and clayey rocks on the SiO2K2O/Na2O diagram does not have any distinct features, and their figurative data points are localized in the areas of terrigenous rocks of passive and active continental margins. On the DF1DF2 diagram, the fields of the studied psammites and clayey rocks are located in areas of riftogenous and collisional environments. We have proposed a different position of the border between these areas in the diagram, which will require further verification.

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

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.