Aluminum Saturation Research Articles

Ultrahigh‐Temperature Anatexis of Metapelites Generates Near‐Anhydrous Garnet Granitoids

AbstractIt remains unresolved whether extensive granitoids can originate from ultrahigh‐temperature crustal anatexis beyond the stability of fusible hydrous minerals and, if any, how they are generated and characterized. Here we investigate near‐anhydrous garnet granitoids in the Jining Complex, North China, using bulk‐rock and mineral analyses combined with phase equilibria modeling. The Jining garnet granitoids are parautochthonously emplaced within granulite terranes and diagnostically contain perthite, abundant garnet but minor biotite. The rocks exhibit high maficity (FeOT + MgO) of 4–12 wt.%, minimal H2O contents below ∼0.16 wt.% and limited aluminum saturation indexes within 1.1–1.7. Their magmas are scarcely fractionated and have ultrahigh temperatures of 1000–1100°C as revealed by K‐feldspar rich in anorthite (10–13 mol.%) and Ti (175−276 ppm), and garnet rims depleted in heavy rare‐earth elements that crystallize from melts. Besides, these magmas have deficient H2O contents (<∼0.19 wt.%) and high densities and viscosities. The garnet granitoids are generated by metapelite anatexis at ultrahigh‐temperature conditions likely around ∼1100°C, with selective entrainment of 5–40 vol.% residua, and underwent some melt loss during magma crystallization. The melting temperatures are far beyond biotite stability and close to the crustal dry solidus. Garnet‐involved congruent melting reactions are required to produce the maficity‐rich and H2O‐deficient melts with high capability for entraining residua. The ultrahigh‐temperature garnet granitoids differ from ordinary low‐ and high‐temperature garnetiferous granites in both petrologic features and petrogenesis, and represent a new subcategory of S‐type granitoids. They can indicate mantle‐actuated extreme crustal thermal perturbations.

Spatial prediction of lime requirements by adjusting aluminium saturation in Sub-Saharan Africa croplands

Acidic soils cover over 30 % of Sub-Saharan Africa cropland. Acidic soils deprive crops of calcium, magnesium, potassium, molybdenum, and phosphorus due to aluminium (Al), manganese, and iron toxicities. Thus, liming is required to adjust the level of exchangeable Al3+ to the desired level of Al saturation of the crops grown. Lime requirement (LR) was quantified using soil dataset from Africa soil information service (AfSIS). Spatial variations of LR of cereals, pulses and cash crops were predicted using random forest algorithm. Our results revealed that mean of LR Mg CaCO3 (1 Mg = 106 g) ha−1 for cereal crops were 6.34, 6.35, and 4.41 for maize, sorghum, and upland rice, respectively. Mean of LR (Mg ha−1) for pulses were 6.28, 5.19, and 4.90 for common beans, soybeans, and cowpeas, respectively. Mean of LR Mg CaCO3 (1 Mg = 106 g) ha−1 for cash crops were 3.41 and 6.29 for coffee and cotton, respectively. Spatial variation showed that LR in croplands was higher in tropical humid regions than in semi-arid and arid regions and ranged from 0 to 8.8 Mg ha−1. The results of 10-fold cross validation for high model performance of LR for tested crops were coefficient of determination (R2) of 0.61, a root mean square error (RMSE) of 0.5, and a mean absolute error (MAE) of 0.31, maize LR with RMSE = 0.9, MAE = 0.24, and R2 = 0.51, and cotton LR with RMSE = 0.5, MAE = 0.31, and R2 = 0.60. We recommend predicting lime requirement in acidic soils of Sub-Saharan Africa by adjusting Al saturation up to the tolerance of the grown crop, updating soil surveys in Sab Saharan Africa, and using digital soil mapping to monitor soil acidity and lime requirement.

Modelling geochemical indices from hyperspectral drill core data from the Eucla Basin basement

Whole rock geochemical analysis of drill core is crucial for rock classification and understanding the evolution of a geological province. This becomes even more important when access to fresh rock samples is hindered by considerable overburden, such as in the case of the basement to the Eucla Basin sediments in Australia. A partial least squares (PLS) regression method was trialled to model geochemical indices, commonly applied for classification of igneous rocks, from hyperspectral visible-near infrared (VNIR; 350 to 1200 nm), shortwave infrared (SWIR; 1200 to 2500 nm) and thermal infrared (TIR; 6000 to 14,500 nm) reflectance spectra of three drill cores intersecting the basement of the Eucla Basin. Modelling of the Mg# (Mg/Mg + Fe) achieved a high correlation between the calculated and predicted values (i.e. R2 > 0.9) at an RMSE of about 10 %. The 2200 to 2400 nm wavelength region of the SWIR was key in modelling the Mg#, with amphibole and chlorite-related absorption features overlapping with the most important input bands in the PLS model. Modelling of the silicon, calcium, iron, magnesium index (SCFM; SiO2/(SiO2 + CaO + FeO + MgO)) required the TIR wavelength range, where diagnostic spectral signatures of silicates are located. PLS-based modelling of the SCFM achieved even a high correlation (i.e. R2 > 0.8) when the model was developed for one drill core but applied to another drill core that intersects the same lithologies. The third geochemical index trialled was the aluminium saturation index (ASI; Al2O3/(Na2O + K2O + CaO), producing high correlation between calculated and predicted ASI when using either, the VNIR-SWIR and the TIR wavelength ranges as input. Our study demonstrates how PLS regression can utilise hyperspectral data to determine geochemical indices, without the cost of full geochemical analysis of every sample in a wide array of rock types. The higher spatial resolution of the modelled geochemistry and the extrapolation of the modelling results to intervals that haven't been sampled for geochemistry supports stratigraphic correlation between drill cores. Furthermore, the combined analysis of geochemical and hyperspectrally-derived mineralogy helps mapping the intensity of weathering of basement as well as mineralogical and physicochemical gradients potentially related to hydrothermal systems.

First assessment of soil mesofauna, microbiota, and humic substances associations in a minesoil revegetated with four grasses in Brazil: An 18-year field study

Moving away from coal protects our environment and soil. However, coal use in 2022 exceeded all previous years, systematically generating minesoils. The reestablishment of vegetation and organisms in minesoils is jeopardized by excessive soil compaction, eventual acidity, and depletion of soil organic matter (SOM), fauna, and microbial communities. Therefore, monitoring the recovery of soil attributes and functions as influenced by revegetation species is crucial to understanding the processes and time of ecological restoration. We aimed to verify if 18 years of revegetation with perennial grasses (Hemarthria altissima, Paspalum notatum, Cynodon dactylon, Urochloa brizantha) transformed the minesoil a habitat for mites, springtails and other invertebrates as well as for soil microorganisms. Moreover, we investigated associations between these biological indicators with soil humic substances (HS) content. The minesoil is located in Candiota (Brazil), and was constructed in 2003, when revegetation with the grasses started. In 2021, soil samples (0.10 m depth) were collected to determine mites and springtails abundance, microbial respiration, carbon and metabolic quotient, soil, HS content, pH, bases, and aluminum saturation. In order to monitor the soil attributes recovery by the perennial grasses, the means of treatments were compared to the control using percentage differences (positive or negative), as the control was not part of the experimental design. The relationship between the biological variables and the soil variables was assessed using Spearman correlation, and the Canonical Correspondence Analysis was used to identify the performance of each grass in relation to the dataset. The associations observed confirm that the minesoil recovery process is still in its initial, mainly between soil biological functions with SOM humification. Positive associations occurred between mites and microbial respiration and accumulation of humin, especially with Urochloa brizantha revegetation.

Identifying appropriate reference ecosystems based on soil indicators to evaluate postmining reclamation: A multivariate framework

ABSTRACTLarge-scale mining operations, such as those associated with iron extraction, disturb soils and vegetation and create the need for effective rehabilitation practices. The Iron Quadrangle region of southeastern Brazil is one of the world’s biodiversity hotspots; however, iron mining activities threaten many natural and seminatural ecosystem types in which many rare/protected species occur. The Iron Quadrangle has four main ecosystem types: Atlantic Forest (AF), ferruginous rupestrian grassland with dense vegetation (FRG-D); ferruginous rupestrian grassland with sparse vegetation (FRG-S); and quartzite rupestrian grassland (QRG). To support rehabilitation and monitoring plans, we evaluated reference areas and identified soil and vegetative attributes that best differentiated between these four ecosystems. We measured thirty-four physical, chemical, and biological soil properties and two vegetation parameters and, using a multivariate analysis, detected: 1) correlations between properties and 2) differences between areas. We identified twelve properties that best differentiated the areas (in order from most to least relevant): nickel content; exchangeable aluminum; clay content; above-ground vegetation volume; aluminum saturation; particle density; bulk density; arsenic content; zinc content; lead content, fine sand plus silt content; and fine sand content. Soil physicochemical properties proved to be more sensitive to differences in ecosystem type, and in particular, parameters related to fertility and the presence of metals and semi-metals differentiated the AF from the FRG-D and FRG-S. Soil physical properties, including fine sand and silt content, were most important for differentiating QRG from the other ecosystems, possibly resulting from the exposure of quartzite material to erosive processes. This study demonstrates the importance of identifying appropriate reference areas for post-mining reclamation.

Geology and Rare Earth Element Geochemistry of Magnesian Granitoids Within Proterozoic Schist Belt of Southwest Nigeria

Abstract The increased global demand for and price of rare earth elements (REEs) has led to intensive search for them in rocks of the upper continental crust all over the world. This study is aimed at characterising the granitoids at Okeho within Southwestern Nigeria using geochemical data and assessing their potential for REE enrichment. Ten representative rock samples of the Proterozoic intrusives, syenite and granodiorite, were studied for their mineralogical and elemental compositions. Elemental concentrations were analysed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Average major oxide concentrations revealed SiO2 (57.53 wt. %), Al2O3 (13.25 wt. %), CaO (5.05 wt. %), and MgO (5.59 wt. %) for the syenite and SiO2 (62.39 wt. %), Al2O3 (14.98 wt. %), CaO (3.67 wt. %), and MgO (3.25 wt. %) for the granodiorite. Total Alkali–Silica (TAS), Aluminum Saturation Index (ASI), and La/10-Y/15-Nb/8 plots discriminated the granitoids as metaluminous monzonite-syenite and peraluminous diorite-granodiorite. Average total REE concentrations in the syenite (625.06 ppm) and porphyritic-granodiorite (364.51 ppm) were above values reported for the granites in some mines in Jiangxi Province, Southern China.

Could Airborne Geophysical Data Be Used to Improve Predictive Modeling of Agronomic Soil Properties in Tropical Hillslope Area?

Airborne geophysical data (AGD) have great potential to represent soil-forming factors. Because of that, the objective of this study was to evaluate the importance of AGD in predicting soil attributes such as aluminum saturation (ASat), base saturation (BS), cation exchange capacity (CEC), clay, and organic carbon (OC). The AGD predictor variables include total count (μR/h), K (potassium), eU (uranium equivalent), and eTh (thorium equivalent), ratios between these elements (eTh/K, eU/K, and eU/eTh), factor F or F-parameter, anomalous potassium (Kd), anomalous uranium (Ud), anomalous magnetic field (AMF), vertical derivative (GZ), horizontal derivatives (GX and GY), and mafic index (MI). The approach was based on applying predictive modeling techniques using (1) digital elevation model (DEM) covariates and Sentinel-2 images with AGD; and (2) DEM covariates and Sentinel-2 images without the AGD. The study was conducted in Bom Jardim, a county in Rio de Janeiro-Brazil with an area of 382,430 km², with a database of 208 soil samples to a predefined depth (0–30 cm). Non-explanatory covariates for the selected soil attributes were excluded. Through the selected covariables, the random forest (RF) and support vector machine (SVM) models were applied with separate samples for training (75%) and validation (25%). The model’s performance was evaluated through the R-squared (R2), root mean square error (RMSE), and mean absolute error (MAE), as well as null model values and coefficient of variation (CV%). The RF algorithm showed better performance with AGD (R2 values ranging from 0.15 to 0.23), as well as the SVM model (R2 values ranging from 0.08 to 0.23) when compared to RF (R2 values ranging from 0.10 to 0.20) and SVM (R2 values ranging from 0.04 to 0.10) models without AGD. Overall, the results suggest that AGD can be helpful for soil mapping. Nevertheless, it is crucial to acknowledge that the accuracy of AGD in predicting soil properties could vary depending on various common factors in DSM, such as the quality and resolution of the covariates and available soil data. Further research is needed to determine the optimal approach for using AGD in soil mapping.

Utilizing Coal ash and Lignite Enriched-Compost to Improve Chemical Properties of Ultisols

Continuous monoculture activities can cause soil degradation, leading to low pH, organic matter content, and nutrient deficiencies in Ultisols. Compost has been used to improve soil fertility. Unfortunately, its effectiveness has been limited due to rapid decomposition in the humid tropic area. This study investigated the effect of adding coal ash (fly ash and bottom ash or abbr. as FABA) and lignite to compost on the chemical properties of degraded Ultisols planted with pineapple. The study was conducted at Pineapple plantation in Central Lampung using a split-plot design. The application technique (row or spread) was the main plot and three treatments as subplots were 100% compost (K), 75% compost + 25% FABA (KF), and 70% compost + 20% FABA + 10% lignite (KFL). Each treatment was applied at a dose of 50 Mg ha-1. The results showed that adding FABA and lignite to compost effectively increased the organic carbon, pH, base saturation, exchangeable calcium, -magnesium, -sodium, and zinc, decreasing the aluminum saturation of Ultisols. The application of ameliorants in rows technique was more effective than those of spreading. These findings suggest that FABA and lignite-enriched compost in row application can effectively improve the chemical properties of degraded Ultisols.

Petrogenesis of the Yunling Sn-rich magma in the Baoshan Block, SW China: Constraints from mineral and whole-rock geochemistry

Southwest Yunnan is one of the most important tin (Sn) metallogenic belts in China. The Sn mineralization is mainly linked with the Cretaceous and Cenozoic magmatism. Triassic granitoids are also widely developed in this region, where the Yunling granitoids are considered to represent an essential target for the localization of Sn mineralization. However, the source characteristics of these ore-related granitoids are still unclear. Here we present geochronology, petrology, and mineral geochemistry to reveal the petrogenesis of Sn-rich magma. Zircon U-Pb dating indicates that the Yunling samples were emplaced at 220–209 Ma, suggesting that the Late Triassic magmatism in the Yunling district along the S–N trending Changning-Menglian suture zone (CMSZ) was generated at the post-collisional stage. Samples from the Yunling pluton exhibit a variable SiO2 content of 54.8–68.5 wt% and are characterized by a high normative corundum content (>1 wt%) and aluminum saturation index (A/CNK = 0.84–1.17). Systemic zircon geochemistry suggests that these samples belong to S-type granite. Moreover, the granitoids have extremely enriched Nd-Hf isotopic signatures with εNd(t) values of −11.5 to −10.7 and εHf(t) values of −21.6 to −10.6. These findings, together with the elevated Ba/Pb ratios and high zircon Ti temperatures (≥800 °C), indicate that the Yunling S-type granitoids were likely to have been derived from the dehydrating partial melting of biotite in the metasedimentary rocks at high temperatures. In addition, the magmatic oxygen fugacity obtained from the magmatic accessory minerals suggests that the ore-related granitic magmas are highly reduced, with the estimated ΔFMQ (fayalite-magnetite-quartz buffer) generally ranging from −5.45 to −0.22 (-3.48 on average). Based on these results, we conclude that the decomposition of biotite in the source effectively extracted Sn, thus forming initial Sn-rich melts which crystallized and differentiated at a low oxygen fugacity and were eventually deposited in the shallow crust to form the Yunling Sn-bearing granitoids.

Soil attributes and their interralationships in Rio Grande do Sul

The present study aimed to highlight and understand the dynamics of interaction of the levels of soil parameters that are determinant for the expression of crop productivity. The study took place in seven municipalities in the northwest of the state of Rio Grande do Sul (Barra do Guarita, Braga, Derrubadas, Miraguaí, Redentora, Tenente Portela, and Vista Gaúcha), in the year 2017/2018. Soil samples were collected in these environments, with a total of 67 soil samples. Most of the studied soils presented pH above 5,5 with 79% of the samples with CEC between 12 and 18. The values of base saturation in 82% of the soils presented values of 80%, while, for of aluminum saturation, in 87% of the samples the values were 0. As for the contents of organic matter, 60% of the soils presented contents above 2,5% with high and low levels of potassium and phosphorus, respectively. When the levels of potential acidity increase, consequently, there is a reduction in the availability of the main nutrients, micronutrients and the Ca:K ratio. On the other hand, when there is an increase in pH levels, there is a greater availability of nutrients and a reduction in potential acidity and aluminum levels.

Reactivity of two acidity correctives in a medium texture soil

For crops to have good productivity, it is necessary to adopt agricultural practices that ensure an adequate supply of water and nutrients, and neutralize toxic elements in the soil, especially exchangeable aluminum, both in the arable layer and in the subsurface. One of these agricultural practices usually employed in both small and medium and large rural properties is the correction of soil acidity, which aims, in addition to neutralizing exchangeable aluminum, to provide calcium and magnesium for plants. Several materials have been used to correct soil acidity, with carbonates, oxides, hydroxides or silicates as neutralizing components. In the present work, the reactivity of two acidity correctives was evaluated in a soil of medium texture, with high aluminum saturation: 72.96%. The correctives used were a steel slag (calcium silicate), and a dolomitic limestone, applied in doses equivalent to one, one and a half, two, and two and a half times the analytically predicted amount, to raise the base saturation to 60%, using calcium acetate with H+ + Al3+ extractor. The study also included a control treatment, which did not receive acidity correction. The method used to evaluate the reactivity of the two correctives was soil incubation. The block design was used, with six repetitions per concealer dose. The experimental units were plastic bags with 3.0 kg of soil. After mixing the correctives with the soil, in the doses corresponding to each treatment, they were transferred to plastic bags and incubated at 70% of the maximum water retention capacity for ninety days. After the incubation period, the soil was analyzed for pH in CaCl2, pH in H2O, exchangeable aluminum (Al+3), and base saturation (V %). Steel slag and dolomitic limestone had the same efficiency to neutralize aluminum and increase base saturation. The pH in CaCl2 and pH in H2O were highly correlated, with the average pH in H2O being 0.50 units greater than the pH in CaCl2. The equation to relate pH in CaCl2 to pH in H2O was Y= 1.0273 x + 0.4716, with R2 = 0.9730. Complete neutralization of Al+3 occurred when the soil pH was raised to 5.03 (pH in CaCl2) or pH 5.50 (pH in H2O). The extraction of H+ + Al3+ with calcium acetate resulted in an underestimation of the cation exchange capacity at pH 7.0 (CTC T), and consequently of the corrective dose to be applied. On average, there was a need to double the amount of concealer predicted analytically to reach the desired base saturation. The equation to relate base saturation with corrective doses, in CaCO3 equivalents, was Y= 9.1476x + 3.8439, with R2 of 0.9449.

Ameliorative effect of calcium poly(aspartic acid) (PASP-Ca) and calcium poly-γ-glutamic acid (γ-PGA-Ca) on soil acidity in different horizons.

Soil acidification is a worldwide eco-environmental problem detrimental to plant growth and threatening food security. In this study, calcium poly(aspartic acid) (PASP-Ca) and calcium poly-γ-glutamic acid (γ-PGA-Ca) were obtained through cation exchange and used to mitigate soil acidity owing to high solubility and complexing capability. Three rates at 6.7, 13.4, and 20.1gkg-1, denoted as PASP-Ca1, PASP-Ca2, and PASP-Ca3, and γ-PGA-Ca (7.4gkg-1) were surface-applied and compared with conventional lime (CaCO3, 2.5gkg-1) along with control in two soil layers (top soil 0-10cm, subsoil 10-20cm). After leaching, various soil properties and aluminum fractions were measured to assess their ameliorative performance and mechanisms. Although lime achieved the highest soil pH (6.91) in the topsoil followed by PASP-Ca and γ-PGA-Ca (pH: 5.57-6.33), it had less effect on subsoil increase (5.3) vs. PASP-Ca and γ-PGA-Ca (pH: 5.44-5.74). Surface-applied PASP-Ca demonstrated efficiency in elevating soil pH and reducing exchangeable acidity, mainly as exchangeable Al3+, whereas γ-PGA-Ca addition superiorly improved soil pH buffering capacity (pHBC). Moreover, PASP-Ca and γ-PGA-Ca addition improved organic carbon by 34.4-44.9%, available P by 4.80-20.71%, and cation exchange capacity (CEC) by 6.19-29.2%, thus greatly enhanced soil fertility. Ca2+ from polyAA-Ca promoted the displacement of exchangeable Al3+ or H+ from soil colloid, which were subsequently complexed or protonated and facilitated leaching. Additionally, the transformation into stable organo-aluminum fractions via complexation inhibited further hydrolysis. Under PASP-Ca or γ-PGA-Ca addition, the saturation of aluminum in cation exchange complex was reduced 2.91-7.81% compared to the control without addition amendments. Thus, PASP-Ca and γ-PGA-Ca can serve as potent ameliorants to alleviate soil acidity and aluminum toxicity for sustainable agricultural development.

Tracing black shales in the source of a porphyry Mo deposit using molybdenum isotopes

Abstract Porphyry Mo deposits are important suppliers of molybdenum for industrial applications, but the origin and source of metals in these deposits remain debated. Here, we present Mo isotope data for Miocene mineralized porphyritic monzogranites (MPMs) and Paleocene barren biotite monzogranites and tuffs (BMTs) from the Bangpu porphyry Mo (Cu) deposit in the Gangdese metallogenic belt. The results show that the MPMs display radiogenic Sr and Pb isotopes and elevated δ98/95Mo (relative to NIST SRM 3134; +0.07‰–1.2‰) and Mo contents, which exceed the range of the depleted mantle. These characteristics cannot be attributed to surface weathering, hydrothermal alteration, magmatic differentiation, or partial melting but rather reflect the incorporation of Mo from black shales into their magma sources, as evidenced by the significant correlations between δ98/95Mo and εNd(t) and aluminum saturation index (ASI) values. In contrast, the BMTs display lower Mo and δ98/95Mo values than the mineralized samples, and their δ98/95Mo values display no correlations with radiogenic isotopes or ASI values. The contrasting characteristics of mineralized and barren samples provide strong evidence that the addition of black shales played an important role in the formation of the Bangpu porphyry Mo deposit. Our study thus establishes a possible link between porphyry Mo deposits and organic-rich sediments and highlights the great potential of Mo isotopes in studying porphyry Mo deposits.

Removal of nutrients and bromatological quality of corn in high productivity crops

Corn has been the most used plant for the production of silage of high bromatological value, aiming at feeding dairy cows of medium to high productivity. Several techniques have been proposed to increase the productivity of crops and the bromatological quality of silages, including new agricultural practices in the implantation and management of crops and also new procedures during cutting and ensiling. In the present work, soil fertility, nutritional status, dry matter production, nutrient removal and chemical quality of maize destined for silage were evaluated in four high productivity crops. The evaluations were carried out in rural properties in the Zona da Mata Mineira, which intensively use the production of corn silage to feed dairy cows. Samplings for the evaluation of soil fertility, nutritional status and production and accumulation of nutrients were carried out systematically. In the female inflorescence emission phase, the leaf blade was analyzed for N, P, K, Ca, Mg, S, B, Cu, Fe, Mn and Zn contents, systematically sampling seven areas of 3, 5 m2 each. When the aerial biomass of the plants presented an average of 33% of dry matter, the forage production of the crop was evaluated, sampling again, in the same areas used to evaluate the soil fertility and the nutritional status of the plants. The corn was cut at about 20 cm above the ground and the plant material was weighed and passed through a forage chopper. Subsamples of this material were analyzed for N, P, K, Ca, Mg and S contents. Soil fertility in the crops of the small rural properties assessed was medium to high, with phosphorus contents ranging from 10 to 20 mg dm- 3, while for potassium this variation ranged from 40 to 89 mg dm-3. In the soils of the four analyzed crops, there was no exchangeable aluminum in the 0 to 20 cm layer, and in the 20 to 40 cm layer, aluminum saturation in crops 1 and 3 was also small, less than 5%. It was found that all crops had adequate mineral nutrition for both macros and micronutrients. The production of dry matter and nutrient accumulation in the aerial biomass of maize in the crops were high. The average value of dry matter accumulation was close to 20.0 t per hectare, and the average removal of nutrients, by harvesting the aerial part of the corn for silage, was 247, 34, 245, 34, 23 and 22 kg per hectare for N, P, K, Ca, Mg and sulfur, respectively. The average values of crude protein, NDF, ADF, lignin and starch were, respectively, in g kg-1, 78; 460; 258; 40 and 277, characterizing forage of good bromatological quality.

Ultrahigh-Temperature Anatexis of Greywackic Granulites Generates Peraluminous Charnockites in the Jining Complex, North China Craton

Abstract Charnockites form an important component of the lower continental crust. Quantitative investigation on the properties of magmas that can stabilize orthopyroxene at solidi is crucial to understanding the petrogenesis of igneous charnockites. This study has performed detailed petrologic analyses and thermodynamic constraints on the Paleoproterozoic high-maficity (FeOT + MgO = 5–14 wt%) and peraluminous charnockites from the Jining Complex in the North China Craton. These charnockites occur as intrusions in granulite facies terranes and contain the mineral assemblages including prevalent perthitic/antiperthitic feldspars and garnet with minor biotite (usually less than ~5 vol%) beside orthopyroxene. The Jining charnockitic magmas were ascertained to have ultrahigh temperatures up to 1050–1100°C, poor H2O contents around 0.14–0.42 wt% and limited aluminum saturation indexes (ASIs) of 1.0–1.3. The stabilization of orthopyroxene at the solidus is attributed to low magmatic H2O contents and ASIs, which have maxima of 1.2 wt% and 1.5, respectively, and are positively correlated to bulk-rock maficity. Such charnockitic magmas could not release H2O-rich fluids near solidi, as the H2O is buffered by the orthopyroxene–biotite pair. Moreover, combined geochemical discrimination and progressive melting modelling reveal that the Jining charnockites were generated by partial melting of a greywackic granulite source, with about 15%–40% entrainment of solid phases in mushy magmas. The melting occurs at temperatures as high as 1050–1100°C, obviously beyond biotite stabilities, and involves quartz, feldspars and garnet as melting reactants, which differs from the previous proposition that peraluminous charnockites are related to biotite dehydration melting. The resultant magmas are substantially enriched in maficity and depleted in H2O due to both the melt compositions per se and the high entraining capability. Such peraluminous charnockite plutons massively emplaced in granulite facies terranes indicate post-orogenic ultrahigh-temperature anatexis of metasedimentary rocks in conditions close to the crustal dry solidus.

Soil compaction in skid trails still affects topsoil recovery 28 years after logging in Central Amazonia

The use of heavy machinery in logging operations leads to soil compaction, especially in highly used skid trails. In Amazonia, recovery of topsoil physical properties has been reported in skid trails. So, the present study sought to determine if this was a full recovery by investigating additional attributes, such as soil chemical properties and fine root biomass (FRB). In addition, forest floor litter was investigated to present a more complete view of soil recovery dynamics. To accomplish this, litter above sampling locations was collected, as well as soil samples below this in two depths. These depths represented the recovered topsoil layer (0–5 cm) and the still compacted soil layer (5–10 cm) below. Three areas were compared: control, middle of the skid trails, and skid trail ruts. Dry mass, C%, N% were determined for litter and FRB. Foliar nutrients (P, K, Ca, Mg, Fe, Zn, Mn) were also determined. Soil chemical properties such as pH, cation exchange capacity, base saturation, aluminum saturation, soil organic C and nutrients (total N, available P, exchangeable Ca, Mg, K, Na, Fe, Zn, Mn) were also assessed. The primary objective was to determine if there was a full recovery of properties evaluated in the topsoil, but also to determine if the compacted soil below acted as an effective hardpan that potentially exerted influence on the recovered topsoil. In the skid trail ruts, results revealed no significant differences with the controls in the recovered topsoil for FRB and all but one soil nutrient, Mn which was elevated. Additionally, the base saturation and volumetric water content of the ruts topsoil was significantly higher than the controls indicating a potential hardpan condition below. So, even though a topsoil may be considered fully recovered, the compacted soil below may still exert influence in the form of increased soil moisture and nutrient accumulation. Therefore, the key finding of this research is that for the first time a recovered topsoil in skid trails was demonstrated to be affected and influenced by the compacted soil below. This influence in the very clayey soils of Amazonia was observed after nearly-three decades.

Functional analysis of soil chemical attributes using Geographic Information Systems to assess nutrient deficiencies

Information on soil fertility is essential to determine the need for correcting measures. However, the use of appropriate techniques to provide information on the specific potential of each soil in many agricultural areas is scarce. Soil fertility in an area with family farming was evaluated based on spatialization of soil chemical attributes to indicate their usage limitations. The study area was on the water basin of the Natuba River, in the Mata Centro Zone, Pernambuco state, Brazil. Samples were taken from soils under the most representative agricultural uses and under native vegetation following a slope gradient (top, middle and bottom). Samples were analyzed for their base saturation, cation exchange capacity, aluminum saturation and phosphorus concentration. These parameters were used to indicate their degree of limitation to agricultural use in order to create a georeferenced database and were mapped using a Geographic Information System (GIS). The cultivated Rhodic Acrisol and Eutric Gleisol had the highest fertility, while the Xanthic Acrisol, Chromic Acrisol and Xanthic Ferralsol had the highest usage limitations. Areas used to grow vegetables had higher nutrient availability than those cropped to sugarcane. Spatialization in the GIS system contributed to the overall fertility analysis, allowing a clear visualization of areas that need soil improvement.

SUGARCANE BAGASSE ASH DOSES AFFECT SOIL CHEMICAL ATTRIBUTES AND PIGEON PEA INITIAL PERFORMANCE

Brazil stands out in the international scenario as the largest producer of sugarcane, processing billions of tons. Thus, this activity generates residues, such as ashes from bagasse burning and straw from sugarcane cleaning and from the production of sugar, alcohol and thermal energy. Therefore, the objective was to evaluate the initial performance and chlorophyll content of pigeon pea and the chemical attributes of the soil after application of ash doses. The experiment was conducted in 2021, in a greenhouse located in southwestern Goiás, Brazil. The design used was completely randomized, composed of five ash doses: 10, 20, 30, 40 and 50 Mg ha-1 and a control treatment, with four replicates, totaling 24 experimental units. The use of only ash as a fertilizer source causes linear increases in the initial growth of pigeon pea and in the contents of total chlorophyll and chlorophyll b, reaching the maximum increments with the estimated ash doses of 35.9 and 38.9 Mg ha-1. Applications of high ash doses promoted improvements in soil fertility, with increase in pH, P, K and base saturation as well as reduction in aluminum content and aluminum saturation. Calcium and magnesium contents reached the maximum increments with the estimated ash doses of 39.5 and 66.7 Mg ha-1, respectively.

Cation Exchange Properties of Subsurface Soil in Mid-Subtropical China: Variations, Correlation with Soil-Forming Factors, and Prediction

Soil cation exchange property (SCEP) is important in soil development and environmental buffering. However, the variations in SCEP and its correlation with soil-forming factors in subsurface soil are not fully understood. In this study, we quantified the surface and subsurface SCEP variations as a function of parent material, vegetation, hillslope position, and soil type. Fifty upland soil profiles from mid-subtropical China were selected. The cation exchange capacity (CEC) and effective CEC (ECEC) of subsurface soil were significantly higher in soils derived from slate, Quaternary red clay (QRC), and limestone than in soils derived from granite and sandstone. The subsurface soils derived from limestone had the highest base saturation (BS) and the sum of base cations, and the lowest aluminum (Al) saturation. The SCEP in surface soil significantly varied with vegetation and hillslope position. The surface soil CEC was the highest in mixed-forest vegetation, whereas the ECEC and exchangeable acidity (EA) were the highest in arable vegetation. Exchangeable potassium (K+) was lowest and the EA was highest in soil orders at the strong development phase. Exchangeable calcium (Ca2+), magnesium (Mg2+), CEC, and BS were the highest in soil orders at the intermediate development phase. The prediction accuracy of soil CEC using the random forest model was higher than that obtained using multiple stepwise regression, with the best results (R2 = 0.92) obtained in the surface soil. Our study indicated that the SCEP in surface and subsurface soils was controlled by different soil-forming factors and could be effectively predicted by soil properties in subtropical China.

Spatial variability of soil fertility under agroforestry system and native forest in eastern Amazonia, Brazil

The usage of spatial tools might be helpful in the optimization of decision-making regarding soil management, with technologies that assist in the interpretation of information related to soil fertility. Therefore, the present study evaluated the spatial variability of chemical attributes of the soil under an agroforestry system compared to a native forest in the municipality of Tomé-açu, Eastern Amazon, Brazil. Soil samples were performed at 36 points arranged in a 55 x 55 m grid. The soils were prepared and submitted to analysis in order to determine pH in H2O, exchangeable calcium, magnesium, potassium and aluminium, available phosphorus, potential acidity, organic matter, bases saturation and aluminium saturation. For each soil attribute, the spherical, gaussian and exponential models were adjusted. After the semivariograms fitting, data interpolation for assessment of spatial variability of the variables was performed through ordinary kriging. The spherical and gaussian models were the most efficient models in estimation of soil attributes spatial variability, in most cases. Most of variables presented a regular spatial variability in their respective kriging maps, with some exceptions. In general, the kriging maps can be used, and we can take them as logistical maps for management and intervention practices in order to improve the soil fertility in the study areas. The results principal components indicate the need for integrated management of soil chemical attributes, with localized application of acidity correctors, fertilizers and other types of incomes, using the spatial variability of these fertility variables.