Trace elements characterization of soils and rocks in Agricultural areas of Labunwa, Near Idanre, Southwestern Nigeria

Trace elements (TE) concentrations of subsoil and the underlying parent rocks of Labunwa – Odele area were determined in other to ascertain the enrichment level, distribution and sources of these TEs in the subsoil in the study area. Twenty-one (21) subsoil (at depth of 30 -100 cm) and thirteen (13) rock samples were collected, pulverised and digested using aqua regia for soil samples and near total digestion of HClO4, HF, HCl and HNO3of different proportions for the rocks. The samples were analysed using Inductively Coupled Plasma- Mass Spectrometry, (ICP-MS). The mean TE concentrations in ppm for subsoil showed Cu (40.0), Pb, (24.2), Zn (56.3), As (0.9) and U (2.7) among other elements as against the mean concentrations of granite gneiss (GGN) with Cu (22.9), Pb (61.4), Zn (64.6), As (1.0), U (2.6) and Pegmatite, (PGM) Cu(128.4), Pb(17.0), Zn(108.8), As (1.1), U (1.3) among other TEs. The relatively low concentrations of the TEs in the subsoil compared to the underlying parent rocks suggests that TEs in the subsoil may have been influenced by geogenic factors, such as weathering of the underlying rocks. TEs source apportionments in the subsoil using Bivariant plots, correlation coefficient, Bi-polar and dendogram analyses showed that these TEs are essentially from the underlying GGN and PGM in the area. Pollution status indices, I-geo, Contamination factor and PLI showed that the study area is practically unpolluted. This suggests that locations with relatively higher concentrations of some TEs are probably due to mineralisation and since most of the subsoil TEs are significantly lower in concentrations compared to the underlying bedrock, the area is safe for agricultural activities.

Geochemistry and tectonic setting for the deposition of IOG siliciclastics at the western margin of Bonai Granite, Singhbhum-Orissa Craton, India

Bagiyabahal and Birtola areas are located in the south-western extension of the Noamundi-Koira Iron Ore Group (IOG) basin. Rock types exposed in the area comprises of siliciclastics and volcanics which occurs unconformably over the basement tonalite-trondhjemite granite-gneiss (Bonai Granite Phase-I). The cover rocks show sheared contact with the porphyritic Bonai Granite Phase-II. The IOG basin margin is suggested to be a part of a ‘volcanic passive margin’ as indicated by the geochemical behaviour of the siliciclastics as well as massive emplacements of mafic intrusives (doleritic sill, dyke and gabbro) and extrusives (basaltic lava flow) along faulted continental blocks. The siliciclastics comprise of U and Au bearing quartz-pebble conglomerate (QPC) and quartzite succession. It was deposited along the western margin of the Bonai granite (phase I) in anoxic conditions as indicated by their low Th/U ratios and presence of detrital uraninite grains. Repeated cycles of sedimentation and volcanism led to the formation of alternate layers of siliciclastics and basic bodies in the area. Major, trace and rare earth elements (REE) geochemical data suggests a semi-humid to humid palaeo-climatic environment of during the deposition in the passive continental margin setting characterized by fault-controlled sedimentation over a rift related faulted continental crust and shelf. Geochemical data suggests chemically weathered provenance dominated by clay minerals. Higher content of U, Th, Au, Cr, REE, platinum group of elements (PGE) and other geochemical ratios suggest a mixed provenance for the deposition of the siliciclastics comprising a predominantly acidic/granitic source possibly from the Bonai Granitic Complex (BGC) along with granite derived reworked quartzose sediments, minor basic and ultrabasic sources of Older Metamorphic Group (OMG). This paper attempts to characterize the geochemical behaviour, tectonic setting and provenance of the siliciclastics of Birtola and Bagiyabahal areas by analyzing drill core and surface samples.

Lithological mapping using remote sensing techniques: A case study of Alagbayan area, Dornogobi province, Mongolia

This study investigated the multispectral remote sensing techniques including ASTER, Landsat 8 OLI, and Sentinel 2A data in order to distinguish different lithological units in the Alagbayan area of Dornogobi province, Mongolia. Therefore, Principal component analysis (PCA), Band ratio (BR), and Support Vector Machine (SVM), which are widely used image enhancement methods, have been applied to the satellite images for lithological mapping. The result of supervised classification shows that Landsat data gives a better classification with an overall accuracy of 93.43% and a kappa coefficient of 0.92 when the former geologic map and thin section analysis were chosen as a reference for training samples. Moreover, band ratios of ((band 7 + band 9)/band 8) obtained from ASTER corresponds well with carbonate rocks. According to PCs, PC4, PC3 and PC2 in the RGB of Landsat, PC3, PC2, PC6 for ASTER data are chosen as a good indicator for different lithological units where Silurian, Carboniferous, Jurassic, and Cretaceous formations are easily distinguished. In terms of Landsat images, the most efficient BR was a ratio where BRs of 5/4 for alluvium, 4/7 for schist and 7/6 to discriminate granite. In addition, as a result of BR as well as PCA, Precambrian Khutag-Uul metamorphic complex and Norovzeeg formation can be identified but granite-gneiss and schist have not given satisfactory results.

Permeability variation in crystalline rocks due to low-grade solution phenomena

Permeability of crystalline rocks depends on parameters such as density and interconnectivity of fractures and pores. While in pristine crystalline rocks porosity is usually considered to be low, low-grade solution phenomena such as the formation of episyenites occur occasionally and may cause a local dramatic increase in porosity and permeability. These solution phenomena can be effective in otherwise unaltered rocks and may result in the preferential removal of certain mineral phases, especially of quartz so that porosities correspond to the spatial distribution of the previously existing mineral phase if no subsequent mineralization occurs (e.g., Pennacchioni et al., 2016). Using light-optical and scanning electron microscopy, X-ray tomography, micro-XRD, as well as digital image analysis, the differences in connectivity and hence permeability between, for example, quartz-depleted granite, gneiss, and schist can be characterized and quantified. We demonstrate that such porosities do not necessarily result in high permeabilities in an undeformed granodiorite from the Central Gneiss unit of the Tauern Window (Lago di Neves area, Italy), since former quartz aggregates are not interconnected due to their relatively late crystallization age and the preservation of the magmatic fabric; however, in the case of moderate mylonitic deformation, quartz as rheologically weak phase forms interconnected aggregates and layers. Its dissolution results in an extremely increased permeability. Therefore, not only the content and grain size but also the distribution, shape and alignment of minerals are crucial for rock permeability and need to be carefully investigated when searching for a final repository of highly radioactive waste in crystalline rocks. Especially since local shear zones may form in otherwise undeformed intrusive bodies, a detailed structural analysis beyond the exclusion of the presence of fractures is required to mitigate the risk of a long-lasting nuclear waste disposal.

Characterization and classification of major coconut growing soils in South Eastern Ghats of Tamil Nadu, India

Six soil series representing major coconut growing soils of the Eastern Ghats in Krishnagiri district of Tamil Nadu State, India, were evolved from granite gneiss and alluvium parent materials. Characterization of different soil properties was done using a detailed soil survey at 1:10000 scale. The soils were neutral to moderately alkaline in reaction (7.31 to 9.19), non-saline, poor to moderately well-drained and moderately shallow (<75 cm) to very deep (>150 cm) in depth. The soils were sandy to clay in texture, sub-angular blocky to crumb in structure, dark reddish-brown to brown, very low to high in OC content (0.06 to 2.70%), low to medium in AWC (3.44 to 22.39%), low to high in CEC (4.70 to 54.0 cmol (p+) kg-1) and having high base saturation (77 to 100%). The soils also had sizable amounts of exchangeable sodium (4.29 to 33.46%), which was maximum in P5, P6 and P1, and high clay content in P5 and P2. The distribution of CaCO3 in different depths was found to be maximum in P4 and P1. The soil orders identified in the coconut area were Inceptisols, Entisols, Alfisols and Vertisols. Assessment of soil resources and identification of yield-limiting soils factors on coconut could be by way of better management and improved productivity.

Geochemical and paleomagnetic characteristics of Vestfold Hills mafic dykes in Prydz Bay region: implications on the Paleoproterozoic connection between East Antarctica and proto-India

The Archean age granite gneiss basement along the Prydz Bay coastline in East Antarctica hosts N-S, E-W, NE-SW, and NW-SE trending mafic dyke swarms in the Vestfold Hills region that intruded between 2420 and 1250 Ma. The dyke trends do not show a direct correlation with the dyke geochemistry but can be broadly discriminated into high-Mg and Fe-rich tholeiites. The former type being more siliceous, LILE, HFSE, and LREE enriched, crystallized from a fractionated melt with a notable crustal component or fluid enrichment through the previous subduction process. The Fe-rich tholeiites are less siliceous, have lower abundances of LILE and REE, and were derived from an undifferentiated, primitive melt. The geochemical characteristics of both types underline a shallow level and a high degree of melting in the majority of cases, and a broadly Island Arc Basalt (IAB) affinity. Paleomagnetic analysis of hand samples shows directional groups consistent with geochemical groupings. The Vestfold Hills dykes show a possible linkage with the coeval mafic dykes in Eastern Dharwar and Bastar cratons of the South Indian Block, based on the similarity in the Paleoproterozoic paleolatitudes.

Inhomogeneities of the earth’s crust of the Aldan-Stanovoy shield along the 3-DV profile (Eastern Siberia, Russia

Profile 3-DV (Skovorodino-Tommot) crosses in the sublatitudinal direction the Stanovoy and Aldan megablocks of the Aldan-Stanovoy shield. As the basic elements of the Earth’s crust section along the profile 3-DV, a technique was adopted for identifying regional inhomogeneities of the lithosphere based on the results of the analysis of seismic and gravimetric data with subsequent typification of their nature. According to the SRM-CMP data, in the upper part of the section (up to 35 km) of the Aldan megablock, the Yakokut and Chulman heterogeneities are distinguished, and the Stanovoy megablock — the Kalara-Dzhugdzhur heterogeneity. The Yakokut and Chulman seismic inhomogeneities in the gravitational field correspond to minima with an the amplitude of up to 25 mGal. The gravitational field of the Kalara-Dzhugdzhur heterogeneity is mosaic and reflects its block structure. It is shown that the deep structure of the Aldan megablock in the area of the 3-DV profile is determined by the Yakokut granite-gneiss dome and Chulman sublateral decompaction zone, and the upper part (0—25 km) of the Stanovoy megablock is represented by the Kalar-Dzhugdzhur structure, composed of the Stanovoy complex of rocks and blocks of highpressure granulites. A significant (up to 10 km) increase in the thickness of the earth’s crust of the Aldan megablock is explained by the presence of the upper layer juvenile crust formed in the Paleoproterozoic as a result of regional metamorphism of igneous rocks. The Earth’s crust of the Stanovoy megablock is tectonically rebuilt for almost the entire thickness of up to 40 km during the Mesozoic collision of the Precambrian North Asian and Sino-Korean cratons. The Yakokut granite-gneiss dome, in accordance with the proposed model of the structure of the Earth’s crust of the Aldan megablock, is the ore-controlling structure of the Central Aldan gold-bearing region, and highpressure granulites of the Zverevsky block of the Kalara-Dzhugdzhur heterogeneity of the Stanovoy megablock served as a source of gold in the Chako-Berkakit ore cluster.

Integration of geophysical, hydrogeological and geospatial analysis for groundwater assessment in Chotanagpur Granite-Gneiss Complex, Ranchi

Integrated study combining electrical resistivity tomography, geology, hydrogeomorphology, and weighted overlay analysis of various surface and subsurface thematic layers proved to be a very useful tool for evaluating the heterogeneous hard aquifer systems for groundwater assessment and development. A comprehensive study was carried out at representative and varied geological settings viz., Chotanagpur Granite-Gneiss Complex (CGGC), Ranchi has been accomplished from geology and geophysical datasets. The electrical resistivity tomography results revealed potential target zones at three sites in the study area up to a maximum of 170 m depth with a large variation in aquifer resistivity ranging from 80 to 800 Ω.m. These significant findings depicted a good correlation and are validated with the lithology in the surrounding of the resistivity tomography results. Nevertheless, the weighted overlay technique act as an essential tool for spatial analysis and interpretation of potential groundwater zones in the study area as well as validated the geophysical depth models whereas in-depth study on geology and hydrogeomorphology provides a detailed hydrogeological scenario throughout the study area for the long-term sustainability of the groundwater resources both at a local and in regional scale in the typical hard rock aquifer system.