Different Degrees Of Weathering Research Articles

Effect of In Situ Polymerization of Super Absorbent Polymers on the Protection of Earthen Heritage Sites in Semi-Arid Regions

As precious cultural heritage, earthen sites are susceptible to various natural factors, leading to diverse forms of degradation. To protect earthen sites, the effects of super absorbent polymers (SAPs) on soil water retention, physical properties, and color compatibility at different concentrations were studied. After applying SAP treatment to an earthen site with different degrees of weathering, we drew the following conclusions. SAP-2 improved soil water retention capacity, increased soil water content, and slowed down the precipitation of soluble salts. At the same time, SAP-2 had the least effect on soil color difference and reduced the development of cracks by filling soil pores and enhancing the cohesion between soil particles, thus giving the earthen sites better weathering resistance. Therefore, the results provide a useful reference for the surface cracking of earthen sites in semi-arid areas and the degradation caused by flaking and block spalling.

Assessment to locate potential deep aquifer systems using lithological logs, pumping tests and electromagnetic surveys in hard rock terrain of Dodoma urban area, Tanzania

The Dodoma region located in Central Tanzania is a semi-arid area characterised by scarce surface water resources. Because of climate change and dependence on groundwater resources in the Dodoma urban area, there is currently an increased demand for water due to low groundwater recharge and high groundwater withdrawals due to the growing population. There is therefore a need to explore potential deep aquifer systems around the Dodoma urban area to meet the increasing water demand. This study uses lithological logs, pumping tests, and electromagnetic survey data to delineate the subsurface lithologies to locate potential deep aquifer system in the area. Results show that the shallow aquifer system is unconfined in some areas with resistivity values ranging from 11 to 28 Ωm and semi-confined in other areas with resistivity values ranging from 19 to 27 Ωm. The unconfined aquifer extends up to 60 m, while the semi-confined aquifer extends between 50–55 m and 65–120 m. The study found a potential deep aquifer system at a depth of between 200 and 290 m, with resistivity values ranging from 11 to 20 Ωm. Currently, this deep aquifer system has not been exploited as most boreholes in the area are only up to 150 m deep. The main lithology in the study area is weathered and fractured granite, with different degrees of weathering and fracturing, indicating a hard-rock aquifer system. This study adds valuable knowledge on the location of potential deep aquifer systems in the area for proper groundwater utilisation and management.

Investigating advection–dispersion behavior for simulation of HTO and 238Pu transport in argillaceous shale with different varying degrees of weathering

Abstract Exploring the migration behavior of radioactive nuclides in the surrounding rock media of the disposal site is the basis for the safety evaluation of radioactive waste disposal sites. In this study, the column experiment was employed to evaluate the nuclide migration behavior in the surrounding rock medium of a near-surface disposal site in China and to investigate the advection–dispersion behavior of tritium (HTO) and plutonium-238 (238Pu) in highly weathered argillaceous shale with different degree of weathering. A reasonable numerical model was selected to fit the experimental breakthrough curves (BTCs) and obtain relevant migration parameters. The results showed that: (1) the breakthrough curves of HTO and 238Pu in fractured media with varying degrees of weathering exhibited clear “peak forward” and “tail dragging” phenomena; (2) the stream tube model can better fit the BTCs of the nuclides in the highly weathered fractures and obtain the average dispersion coefficient <D>, average distribution coefficient <K d>, and other parameters; (3) the two-region non-equilibrium model can better fit the BTCs of the nuclides in the penetrating fractures and weak weathering fractures and obtain the volumetric water content of the mobile liquid region (θ m), distribution coefficient (K d), and other parameters.

Geological Hazard Susceptibility Analysis and Developmental Characteristics Based on Slope Unit, Using the Xinxian County, Henan Province as an Example.

Geological hazards in Xinxian County, Xinyang City, Henan Province, are characterized by their small scale, wide distribution, and significant influence from regional tectonics. This study focuses on collapses and landslide hazards within the area, selecting twelve evaluation factors: aspect, slope shape, normalized difference vegetation index (NDVI), topographic relief, distance from geological structure, slope, distance from roads, land use cover type, area of land change (2012-2022), average annual rainfall (2012-2022), and river network density. Utilizing data from historical disaster sites across the region, the information quantity method and hierarchical analysis method are employed to ascertain the information quantity and weight of each factor. Subsequently, a random forest model is applied to perform susceptibility zoning of geological hazards in Xinxian County and to examine the characteristics of these geological disasters. The results show that in the study area, the primary factors influencing the development of geohazards are the distance from roads, rock groups, and distance from geological structure areas. A comparison of the susceptibility results obtained through two methods, the analytic hierarchy process information quantity method and the random forests model, reveals that the former exhibits a higher accuracy. This model categorizes the geohazard susceptibility in the study area into four levels: low, medium, high, and very high. Notably, the areas of very high and high susceptibility together cover 559.17 km2, constituting 35.99% of the study area's total area, and encompass 57 disaster sites, which represent 72.15% of all disaster sites. Geological hazards in Xinxian County frequently manifest on steep canyon inclines, along the curved and concave banks of mountain rivers, within watershed regions, on gully inclines, atop steep cliffs, and on artificially created slopes, among other sites. Areas with very high and high vulnerability to these hazards are mainly concentrated near the county's geological formations. The gneiss formations are widely exposed in Xinxian County, and the gneisses' strength is significantly changed under weathering, which makes the properties of the different degrees of weathering of the rock and soil bodies play a decisive role in the stability of the slopes. This paper provides a basis for evaluating and preventing geologic hazards in the Dabie mountainous area of the South Henan Province, and the spatial planning of the national territory.

Changes in coal waste DOM chemodiversity and Fe/Al oxides during weathering drive the fraction conversion of heavy metals

The long-term accumulation of coal waste on the surface during natural weathering leads to the inevitable migration of heavy metals contained in the coal waste, which increases the likelihood of environmental contamination and health risks. Dissolved organic matter (DOM) and Fe/Al oxides play crucial roles in the transformation and bioavailability of heavy metals. Thus, we analyzed the Fe/Al oxide content and DOM molecular composition in coal waste with different degrees of weathering and explored the influence of DOM chemical diversity and Fe/Al oxides on the potential mobility of heavy metals. Results showed that weathering-driven decrease in Fe oxides (Fed, FeO, and Fep decreased from 82.4, 37.5, and 3.6 mg∙L−1 to 41.3, 24.7, and 2.3 mg∙L−1, respectively) led to decreases in the reducible fractions of V and Cr. The potential environmental risks of more toxic metals of Cd and As, also increased as a result of the residual fractions decreased to 32.6 % and 41.3 %, respectively. Weathering caused an increase in oxygen-to‑carbon ratio, double-bond equivalent, modified aromaticity index, nominal oxidation state of carbon, and molecular diversity and a decrease in (m/z)w and (H/C)w, suggesting that the DOM of highly weathered coal waste possessed high unsaturation, aromatic structures, hydrophilicity, and strong oxidative characteristics. Additionally, although VMF and CrMF showed significant negative correlations with O/C ratio, polyphenolic, carbohydrates, and condensed aromatics, pH remained a key environmental factor determining the potential environmental risks of V and Cr by changing the residual fractions. The mobilities of Cd and As were significantly negatively correlated with those of Fe/Al oxides, particularly Fed, FeO, Fep, and Alp. Our findings contribute to the understanding of the impact of weathering on the geochemical cycling of different coal waste components, providing priority options for environmental risk prevention and control in coal mining areas.

THE WEATHERING PRODUCTS CREATING GOOD VITAL ENVIRONMENT TO BIOTA FOR BETTER DELIVERY SOIL ECOSYSTEM SERVICES

There is little information about the plasmic constituent intimate arrangement of the Phaeozem groundmass. In this respect, a micromorphological investigation of a Vertic Phaeozem (located in Perchiu Hill) was performed.The research results emphasise the presence of many types of striated birefringent fabric (b-fabric) in the groundmass of the pedogenetic horizons, induced by the swell-shrink processes (and representing criteria for the quantification of stress processes in Vertisols and vertic subgroups) as: porostriated and granostriated b-fabric, are rarely and weak developed; and both reticulate and parallel striated b-fabric developed on short distances. Into the pedogenetic horizons, rock fragments also appear in different degrees of weathering and integration into the groundmass, emphasising different evolution steps in the solification process. The linear and cross-linear alteration types of the rock fragments induced optical orientation of the clay domains similar to the different types of the striated b-fabric.It could be concluded, that the b-fabrics, which are generally used as criteria for the quantification of the swell-shrinking processes stress (that disturbed the plant roots development and the soil life environment) also formed in situ from the strong weathered rock fragments. Consequently, the striated b-fabric generated by the weathering process created a friendly environment in soil and underlined a less stress forces (during the swell-shrink processes) in the studied soil.The weathering products enriched the soils in the most precious constituents (the clay and nutrients) responsible for soil fertility, and further creating a good vital environment for biota to better delivery the soil ecosystem services.

Variations in soil nutrient availabilities and foliar nutrient concentrations of trees between temperate monsoon karst and non‐karst forest ecosystems on Mount Ibuki in Japan

AbstractPlants growing on karst soils, which are characterized by high pH (>7.5–8.0) and low phosphorus availability, often exhibit phosphorus deficiency. However, little is known about the soil nutrient availabilities and foliar nutrient concentrations of trees in karst ecosystems with lower soil pH (<7.0). In this study, we analyzed soil properties and nutrient concentrations of leaf litter from two secondary forests in the Asian monsoon temperate region of Japan, one on karst (limestone) soil and the other on non‐karst (sandstone) soil. We also compared the live leaf nutrient concentrations of four dominant tree species (Carpinus tschonoskii, Cornus macrophylla, Neolitsea sericea, and Quercus variabilis) found in both sites. The karst soil had a higher pH (6.5) than the non‐karst soil (5.6), as well as higher phosphorus concentrations and calcium availability, but lower potassium availability. The phosphorus concentrations measured using Truog ([NH4]2SO4) and Olsen (NaHCO3) extraction methods were both higher in the karst soil. The availabilities of ammonium and nitrate in the soil did not differ significantly between the sites. The concentrations of calcium, potassium, and phosphorus in the live leaves and leaf litter reflected their availability in the soil, and the litter nitrogen concentration was higher in the karst forest. Overall, this karst soil with a relatively low pH (6.5) was rich in phosphorus but poor in potassium. Karst soil may provide a large quantity of phosphorus for trees at low pH. Future research should investigate the change in phosphorus availability of karst soils at different degrees of weathering.

Analysis of the composition of ancient glass products based on Spearman's correlation coefficient

Ancient glass stored underground for a long time has undergone different degrees of weathering, which has led to changes in its chemical composition and affected the correct judgment of its category. Based on this, this paper uses various algorithms such as Spearman correlation coefficient, chi-square test and cluster analysis to establish a comprehensive model for glass composition evaluation. The results show that: (1) The surface weathering degree of glass artifacts is significantly correlated with their types; (2) The content of Lead oxide can be used to make a general distinction between high-potassium glass and lead-barium glass; (3) Among the known glass samples, high-potassium glass can be divided into three categories and lead-barium glass can be divided into four categories; (4) According to the reasonableness test, it is known that the model has good reliability and can provide guidance for the study of ancient glass.

Geochemical Provenance, Source Area Weathering, and Tectonic Setting of the Bida Sandstone in the Northern Bida Basin, Northcentral Nigeria

This paper aims to determine the geochemical provenance, source area weathering, and tectonic setting of the Bida sandstone exposed at Doko and Jima in the Northern Bida Basin, Northcentral Nigeria. Geological fieldwork was carried out and sandstone samples were collected and analyzed for major element concentrations using X-Ray Fluorescence (XRF) method. Major element abundance shows that the studied sandstone samples consist of SiO2 (average 71.42%), Al2O3 (average 15.16%), and CaO (average 0.26%) constituting about 90% of the bulk rock composition. While P2O5, Na2O, K2O, MgO, TiO2, MnO, and Fe2O3 constitute about 10% of the composition. The results obtained using the Al2O3/TiO2 ratios show that the sandstones derived from intermediate to felsic igneous rocks. The A-CN-K triangular diagram shows that majority of the analyzed samples plotted on the aluminum zone towards kaolinite shows predominantly intermediate degree of weathering except for one sample which falls towards the CN-K line, indicating the different degree of weathering (perhaps an existence of differential weathering in the area). The source area weathering indices which include CIA (68.6%), CIW (71.20%), and PIA (54.66%) further confirms that the sediments have been subjected to intermediate weathering. The K2O/Na2O versus SiO2 tectonic setting discriminant plot shows that the samples are dominantly deposited in the passive margin setting. It is, therefore, concluded that the Bida sandstone analyzed was sourced from predominantly felsic igneous rocks where the degree of chemical weathering was intermediate and in the passive margin setting.

Occurrence, characteristics, and removal of microplastics in wastewater treatment plants located on the Moroccan Atlantic: The case of Agadir metropolis

Wastewater treatment plants (WWTPs) are some of the main sources of microplastics (MPs) in the environment. However, studies on the occurrence and removal efficiency of MPs in WWTPs are still scarce, especially in African countries. Thus, the aim of this work was to study the abundance of MPs in the influent and effluent of two WWTPs (Aourir and M'zar) from the Agadir metropolis (Moroccan Atlantic). The two WWTPs receive different wastewater inputs (domestic and industrial). In addition, the impacts of seasonality on the fate and removal efficiency were investigated. The results showed that the MPs abundance in the wastewater decreased from 188 MPs/L in the influent to 50 MPs/L in the effluent for Aourir WWTP (domestic inputs); while the abundance was greater in the M'zar WWTP (urban and industrial inputs) recording a mean value of 519 MPs/L and 86 MPs/L in the influent and effluent, respectively. MPs collected in the Aourir WWTP ranged from 290 to 3200 μm, while MPs from the M'zar WWTP, ranged from 330 to 4200 μm. Overall, the size range of 100–500 μm was the most abundant for both WWTPs. Fibers were the highest MPs morphotype found, followed by fragments. MP colors were mainly red, black, blue, and transparent for both treatment plants. Additionally, FTIR spectroscopy showed the presence of eight different polymers, mainly polyethylene (PE), polypropylene (PP), and polystyrene (PS). Seasonal variation analysis showed that MPs abundance in summer was significantly higher compared to other seasons. However, the comparison of the removal efficiency (RE) between the different seasons indicated that the winter season (74 %) recorded the highest RE for Aourir WWTP. Conversely, spring (87 %) recorded the highest RE for M'zar WWTP. SEM/EDX micrographs showed different degrees of weathering and chemical elements adhering to the surface of the MPs. The findings of the current study will serve as a baseline for future considerations about management strategies, wastewater reuse, as well as the understanding of the occurrence of microplastic pollution along the marine ecosystems of Morocco.

Leaching characteristics and stabilization of heavy metals in tin-polymetallic tailings by sodium diethyl dithiocarbamate intercalated montmorillonite (DDTC-Mt)

There are a large number of tailings left over by industrial development the world over and the tailings are harmful to the environment for a long time, so it is very important to study how to reduce environmental pollution from tailings. Here, the acid producing potential of three types of tin polymetallic tailings from the same locality with different degrees of weathering and the forms of heavy metals that exist in these tailings were studied. The effects of pH of simulated acid rain, temperature and time on the leaching of heavy metals from the different tailings were investigated along with their leaching characteristics. In addition, stabilization mechanism of heavy metals was analyzed from the kinetic and microscopic aspects. The potential application of sodium diethyldithiocarbamate intercalated montmorillonite (DDTC-Mt) was studied for stabilizing tin polymetallic tailings. The leaching of heavy metals in tailings is mainly due to the oxidation of tailings, which in turn is closely related to the acid producing potential of tailings and the existing forms of heavy metals in them. The stabilization of heavy metals by DDTC-Mt is mainly due to coordination between DDTC and heavy metals in the interlayer of montmorillonite. DDTC-Mt revealed a superior stabilization property in remediation of heavy metals from tin-polymetallic tailings with high acid producing potential by enhancing the stability of heavy metals in tailings, for example, the stabilization rates of Mn and Zn were 89.11% and 93.89%, respectively.

Supergene mobilization and redistribution of platinum-group elements in the Merensky Reef, eastern Bushveld Complex, South Africa

ABSTRACT Near-surface supergene ores of the Merensky Reef in the Bushveld Complex, South Africa, contain economic grades of platinum-group elements, however, these are currently uneconomic due to low recovery rates. This is the first study that investigates the variation in platinum-group elements in pristine and supergene samples of the Merensky Reef from five drill cores from the eastern Bushveld. The samples from the Richmond and Twickenham farms show different degrees of weathering. The whole-rock platinum-group element distribution was studied by inductively coupled plasma-mass spectrometry and the platinum-group minerals were investigated by reflected-light microscopy, scanning electron microscopy, and electron microprobe analysis. In pristine (“fresh”) Merensky Reef samples, platinum-group elements occur mainly as discrete platinum-group minerals, such as platinum-group element-sulfides (cooperite–braggite) and laurite as well as subordinate platinum-group element-bismuthotellurides and platinum-group element-arsenides, and also in solid solution in sulfides (especially Pd in pentlandite). During weathering, Pd and S were removed, resulting in a platinum-group mineral mineralogy in the supergene Merensky Reef that mainly consists of relict platinum-group minerals, Pt-Fe alloys, and Pt-oxides/hydroxides. Additional proportions of platinum-group elements are hosted by Fe-hydroxides and secondary hydrosilicates (e.g., serpentine group minerals and chlorite). In supergene ores, only low recovery rates (ca. 40%) are achieved due to the polymodal and complex platinum-group element distribution. To achieve higher recovery rates for the platinum-group elements, hydrometallurgical or pyrometallurgical processing of the bulk ore would be required, which is not economically viable with existing technology.

Investigation on cement-improved phyllite based on the vertical vibration compaction method.

The vertical vibration compaction method (VVCM), heavy compaction method and static pressure method were used to form phyllite specimens with different degrees of weathering. The influence of cement content, compactness, and compaction method on the mechanical properties of phyllite was studied. The mechanical properties of phyllite was evaluated in terms of unconfined compressive strength (Rc) and modulus of resilience (Ec). Further, test roads were paved along an expressway in China to demonstrate the feasibility of the highly weathered phyllite improvement technology. Results show that unweathered phyllite can be used as subgrade filler. In spite of increasing compactness, phyllite with a higher degree of weathering cannot meet the requirements for subgrade filler. With increasing cement content, Rc and Ec of the improved phyllite increases linearly. Rc and Ec increase by at least 15% and 17%, respectively, for every 1% increase in cement content and by at least 10% and 6%, respectively, for every 1% increase in compactness. The higher the degree of weathering of phyllite, the greater the degree of improvement of its mechanical properties.

Morphological and mineralogical characterization of weathering zones in tropical climates: A basis for understanding the weathering process on granitic rocks in southeastern Brazil

Weathering zones of granitic rock masses are of particular interest in tropical climate regions because of their morphologies and mineralogical properties. To address the lack of studies on weathering profiles of granitic rocks in Brazil, this research aimed to perform a complete morphological and mineralogical characterization of weathering profiles of a syenogranite developed in tropical southeastern Brazil. Fieldwork was performed, resulting in the identification and investigation of five weathering profiles. The morphological description included the spatial distribution of the different layers, the weathering features and the mechanisms responsible for the transformation of rock masses. At the rock matrix scale, the mineralogical characterization was based on petrographic thin sections made from samples of each of the different degrees of weathering. Petrographic indices such as the micropetrographic index (Imp) and microfracturing index (Imf) were determined and compared with data obtained in the literature. The results indicated that the weathering in the profiles studied was facilitated by a network of joints and fractures, which allowed water access, causing chemical decomposition at a certain depth and then resulted in relatively thick weathered profiles characterized by the presence of corestones. On a microscopic scale, changes in unweathered rock are controlled by the opening of pre-existing microcracks and the development of new cracks in the early stages of weathering, as well as chemical decomposition through the transformation of primary minerals into secondary minerals from medium-weathered rock. It is clear that physical weathering controls the initial changes and chemical weathering controls the later stages of syenogranite alterations. The increase in the microfracturing index from 3.2 to 7.7 had a larger influence on the control of physical weathering in the early stage. The micropetrographic index decreases to 2.1 at the most advanced stage of weathering, demonstrating the dominance of chemical weathering of the matrix in the final stages of rock weathering.

Dynamic Response and Time-Frequency Characteristic of Dangerous Rocks under the Combined Action of Rock Cavity Weathering and Earthquake

In order to further reveal the failure mode and dynamic response law of dangerous rocks with different degree of weathering in the rock cavity under the action of earthquake and to provide early warning and forecast for steep slope of dangerous rocks in similar earthquake areas, a typical steep slope of dangerous rock in earthquake area of Sichuan, China, was taken as the research object, after detailed geological survey, and according to the chain development law of dangerous rock, the steep slope of dangerous rock before the earthquake was restored. Based on the 3D particle flow software PFC3D, the dangerous rock was divided into 3 modes according to the degree of weathering of the mudstone rock cavity, and the three-dimensional discrete element dangerous rock model under different modes was established. By introducing the horizontal and vertical two-way coupled seismic waves in Wenchuan, Sichuan, in 2008, the failure evolution process of steep slope of dangerous rock under the action of the horizontal and vertical coupled seismic waves was dynamically simulated, which proved the rationality of the simulation. The frequency spectrum of velocity-time history signal of each rock block in the dangerous rock model was analyzed by MATLAB programming, and the time-frequency characteristics of each dangerous rock model under the action of coupled seismic wave were studied. The research results have important scientific guiding significance and practical value for the dynamic stability evaluation and prediction of such steep slope of dangerous rocks under the combined action of rock cavity weathering and earthquake.

Potential mobilizable Fe from secondary phases of differentially altered subsurface basaltic rock– a sequential extraction study on ICDP site Hawaii

The potential for the mobilization of Fe from secondary phases within subsurface basaltic rocks of the Hawaii Scientific Drilling Project Phase2 (HSDP2) drill core was investigated to elucidate the possible contribution of volcanic islands to the Fe budget of nearby ocean surface waters. Rock specific parameters governing Fe mobilization, such as Fe redox state, specific surface area (SSA), and connected porosity were determined. A four-step sequential extraction procedure using solutions with increasing strength of the extractants was applied to characterize different states of chemical bonding of Fe in secondary phases of the basaltic rocks, a controlling parameter for its release to oceanic water. The sequential extraction results were then used as a measure for the reactivity of secondary Fe-bearing phases and the mobilizable Fe from these rocks. Basaltic rocks with different degrees of weathering showed elevated Fe(III) contents up to 58% total Fe as Fe(III), compared to 11–18% in fresh basalts. SSAs increased with depth, with maximum values of 70 m2/g observed for hyaloclastites. Both parameters depended mainly on the alteration state of the basalt, which was more strongly affected by the fluid chemistry (freshwater ↔ seawater) than by the age of the rocks. The sequential extractions revealed the presence of highly reactive secondary Fe-bearing phases in submarine rocks exposed to seawater whereas observations for rocks altered in freshwater point to better crystallized phases with lower mobilizable Fe contents. In seawater, aging of secondary Fe-bearing phases was most probably suppressed by the adsorption of silica and multivalent anions. Comparing different types of rock, hyaloclastites and pillow basalts showed the highest mobilizable Fe with up to 19% and 16%, respectively, of the total Fe of the bulk rock. The potential for high amounts of mobilizable Fe from basaltic rocks altered under seawater dominated conditions suggests that the submarine part of volcanic ocean islands represent an underestimated source of Fe supply to ocean surface waters.

Effect of void ratio to the strength parameters of sedimentary rocks

This paper is to study the influence of void ratio on the compressive and shear strength of sedimentary rocks at different degree of weathering. As void ratio is related to porosity therefore the present of void ratio should influence the mechanical properties of the porous sedimentary rocks such as sandstone and limestone. In order to determine the microstructures including pores and cracks of the samples, sandstone and limestone from different weathering grades were analyzed using photomicrograph analysis method. From the image of photomicrograph, the void ratio of the sample was calculated using image processing technique. The uniaxial compression and triaxial tests were carried out to determine the compressive and shear strength of the same samples by using GCTS Testing System. Results for void ratio, compressive and shear strength of the four different weathering grades of rocks were correlated to see the trend of relationships between the void ratio and the mechanical properties. In relation to weathering grades, the void ratio of the sedimentary rocks increases as the degree of weathering increases. The results also show that the void ratio and mechanical properties of sandstone are closely related. With the increase of void ratio, the compressive strength and shear strength decrease.

Provenance and paleogeography of the Southern Paraná Basin: Geochemistry and U[sbnd]Pb zircon geochronology of the Carboniferous-Permian transition

The Carboniferous-Permian transition of the intracratonic Paraná Basin (S Brazil) includes important evidence of the climate change, tectonics, and paleogeographic configuration of SW Gondwana. During this period, the Late Paleozoic Ice Age (LPIA) was in its final phase in the Paraná Basin, producing a temperate-tropical climate through the transition to the Permian. UPb laser ablation ICP-MS detrital zircon dates and whole-rock geochemistry of rocks from the upper Itararé Group (Carboniferous) and the lowermost Rio Bonito Formation (Early Permian) in the southern Paraná Basin are determined to characterize the sedimentary-dispersal patterns of the source area and glacial paleoflow. Geochemistry proxies suggest that the studied units experienced different degrees of weathering, with the Itararé Group's units forming in an arid environment. The overlying Rio Bonito Formation's units were deposited under hotter and more humid climate conditions. The Late Carboniferous to Early Permian units showed similar zircon-age distribution patterns, with a Neoproterozoic main peak from the Uruguayan Sul-Riograndese Shield. A lack of Mesoproterozoic sources in the studied samples indicates that this area of the Paraná Basin probably did not receive sediments from the African side during the Late Carboniferous as previously described. This result suggests a more complex system in which ice caps and small ice sheets dominated the glacial environment during the Late Carboniferous in this segment of SW Gondwana.

Study on Permeability Characteristics of Granites with Different Degrees of Weathering

In Guangzhou Metro line 21 tunnel construction process, weathered granite shows diversification in strength, deformation characteristics and permeability characteristics. The rock mass permeability coefficient is the core parameter necessary in the construction, and the definition of its value directly affects the accuracy of the calculation in design of tunnel anti-drainage structure and the negative effect evaluation of groundwater environment. With on-site and indoor tests, theoretical calculations, microstructure observations and mineral analysis, the permeability characteristics of granites in different degrees of weathering is studied. The variation of the final permeability characteristics is described. The permeability of granite does not increase unidirectionally as the degree of weathering deepens.

Tropical Soil Toposequence Characterization via pXRF Spectrometry

Variability of elemental composition in a toposequence of quartzite‐derived soils in a tropical environment was evaluated via portable x‐ray fluorescence (pXRF) spectrometry. The toposequence featured different degrees of weathering and variable soil formation processes. Specifically, this study aimed to: (i) use elemental composition obtained through pXRF as a tool to investigate the degrees of weathering–leaching and pedogenic processes; and (ii) correlate elemental data with physicochemical properties of soils. Four soil profiles (Lithic Ustorthent, Typic Ustorthent, Typic Dystrudept, and Xanthic Hapludox) were described and sampled. Laboratory analysis for soil physicochemical characterization and pXRF were performed. Soils featured high contents of SiO2 due to the predominance of quartz in the rock. However, pXRF analysis revealed that the soils showed a decrease in such content with depth. Potassium contents tended to be greater in the C horizons since they are less weathered and retained greater amounts of K‐bearing minerals, such as muscovite. Al, Fe, Ca, Ti, Cu, and Sr increased their contents with increasing clay content in soils, while Zr generally remained stable. Ba was leached out of soils during weathering. Both CaO and Sr were positively correlated with exchangeable contents of Ca2+ and Mg2+, base saturation, pH, and cation exchange capacity, while inversely correlated to Al3+ saturation. Fe, Al, Ti, Ca, K, Cu, Rb, and Zr accumulated in soil in comparison with the parent material. Variability of elemental contents in soils with differential degrees of weathering–leaching can be easily accessed with pXRF and such data correlate well with several soil physicochemical properties.Core Ideas Toposequence of quartzite‐derived soils variability assessed by pXRF. Soils presented varying weathering degrees, from Entisols to Oxisols. pXRF elemental data correlated well with soil physical and chemical properties. Soil mineralogy and pXRF data elucidated soils variability with weathering. Al, Fe, Ca, Ti, Cu, and Sr increased with increasing clay content.