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K‐feldspar, which constitutes about 60%$\%$ of the Earth's crust, is crucial for understanding electrical conductivity in porous rocks. Its electrical properties are vital for applications in ceramics, electrical insulation and conductive polymers. In this work, we study the time evolution of electrical conductivity of K‐feldspar‐rich rocks with varying temperatures, at high and low pH, which has been studied through simulation using time domain random walk. Random walkers, mimicking ions in transport, move in accordance with appropriate hydrodynamic equations, dissolution and precipitation kinetics. Electrical conductivity has been calculated considering variations in the parameters of temperature, fluid pH and the abundance of K‐feldspar in rocks. Electrical conductivity is found to increase with temperature up to a critical value, after which it decreases. The sharpness of the rise and fall in electrical conductivity is quantified through a measure defined as the conductivity quality factor Qσ$Q_{\sigma }$. We find that Qσ$Q_{\sigma }$ increases with a decrease in the availability of K‐feldspar mineral. Our simulated results of electrical conductivity show a good match with the experimental trends reported. [ABSTRACT FROM AUTHOR]

Phosphorus is a key element for identifying past human activity. Recently, phosphorus analyses have been extended to archaeological objects, aiming at distinguishing how depositional contexts contribute to its enrichment. In archaeological pottery, phosphorus might depend on several manufacturing and postdepositional processes (i.e., addition of organic temper, pigments, diagenetic incorporation). We analyzed by XRD, XRF, and mid-infrared (FTIR-ATR) spectroscopy 178 pots from eight NW Spain archaeological sites. These sites encompass different chronologies, contexts, and local geology. The phosphorus content was highly variable (224–27,722 mg kg−1) overall but also between archeological sites (1644 ± 487 to 13,635 ± 6623 mg kg−1) and within archaeological sites (4–36, max/min ratio). No phosphate minerals were identified by XRD nor FTIR-ATR, but correlations between phosphorus content and MIR absorbances showed maxima at 1515 and 980 cm−1, suggesting the presence of two sources: one organic (i.e., phosphorylated aromatic compounds) and another inorganic (i.e., albite and K-feldspar). Phosphorylated aromatics were most likely formed during pottery firing and were preserved due to their high resistance to temperature and oxidation. Meanwhile, albite and K-feldspar are among the P-bearing minerals with higher P concentrations. Our results suggest that P content is related to intentional and non-intentional actions taken in the pottery production process. [ABSTRACT FROM AUTHOR]

Controlling factors of potassium (K) isotopic fractionation in K-feldspar remain poorly constrained. In this study, we analyzed the K isotopic compositions of 11 K-feldspar samples from diverse lithological compositions. The degree of Al/Si order ranged from 0.22 to 0.94 (1.0 = completely ordered). Analyzed samples are mixtures of K-feldspar (>70 wt%) and coexisting albite. The relative contribution of K2O from the K-feldspar phase of the sample was over 98%, indicating that the K isotopic composition (δ41K) derives mainly from K-feldspar and hence reflects its behavior. The δ41K values of these samples range from –0.710 to –0.075‰, which are slightly correlated with the degree of Al/Si order. The correlations of δ41K with SiO2 and Al2O3 contents and the corresponding Al/Si mole ratios reveal that Al and Si play a significant role in the K isotopic behavior of K-feldspar. The correlations of δ41K with SiO2 and Al2O3 contents are attributed to the difference in K-O bond strengths. Compared to K-feldspar, the K content could be a better proxy for constraining the δ41K of plagioclase. Our results demonstrate that the δ41K of K-feldspar is dependent on its mineral chemistry, and its K isotopic composition may be insensitive to other factors, such as the source heterogeneity. The inference is further confirmed by comparing the δ41K values in this study with published δ41K values of K-feldspar from different sources. [ABSTRACT FROM AUTHOR]

An improved hydrothermal method was proposed to rapidly synthesize zeolite W from alkali fusion‐activated K‐feldspar. The effects of m (KOH)/m (K‐feldspar), n (SiO2)/n (Al2O3), n (H2O)/n (SiO2), crystallization time, and crystallization temperature on the synthesis of the zeolite W were investigated. The optimal synthesis conditions were m (KOH)/m (K‐feldspar) ratio of 1.5:1, the activation time of 2 h, and the activation temperature of 500°C, n (H2O)/n (SiO2) ratios of 42, n (K2O)/n (SiO2) of 0.90, n (SiO2)/n (Al2O3) of 5, crystallization time of 6 h, and crystallization temperature of 150°C. The mechanism for rapid synthesis of zeolite W was illustrated. In this process, Na2SiO3·9H2O and Al2(SO4)3·18H2O were first dissolved rapidly in the synthesis system to form an amorphous gel, which contributes to the accelerated crystallization process. Compared with the state‐of‐the‐art synthesis method, this method remarkably decreases the water content to be added in the synthesis process and crystallization time, avoids the pre‐preparation process of the xerogel, and enhances the utilization rate of K‐feldspar. This work provides an industrial‐friendly synthesis process of zeolite W and could realize the highly efficient utilization of K‐feldspar. [ABSTRACT FROM AUTHOR]

Potassium-containing feldspars provide a high potential for producing potash, a product with widespread use in agriculture. The present work assesses applying the anti-solvent crystallization method for the purification and recovery of high-purity muriate of potash (KCl) from feldspar leaching solutions. Initially, screening experiments were carried out on a synthetic leaching solution with the aim of analyzing the crystallization behavior of key components. Screening experiments were performed using five anti-solvents, namely methanol, ethanol, acetone, 2-propanol, and ethylene glycol. Acetone and 2-propanol were viable options for crystallization of potassium chloride. Then, the effects of anti-solvent ratio (O/A), time, and anti-solvent addition rate on potassium-chloride crystallization were further investigated using acetone and 2-propanol. A recovery of 83% of potassium was achieved when using acetone at the O/A of 5 with the addition rate of 10 mL/min, at room temperature with a hold time of 180 min. The optimum conditions for 2-propanol were determined to be similar, except for using a 5 mL/min addition rate for 79% recovery. The final muriate of potash products had a purity of over 99.9% using either of the anti-solvent. However, differences in morphology and crystal size of products were observed. Acetone-formed potash crystals were aggregates of cubic crystals with an average size of 3 microns, while 2-propanol-formed potash crystals were 20 microns in size as cubic particles with a hollow core. Despite having almost the same performance in potassium recovery, acetone was found to be a more feasible anti-solvent for potash recovery due to simpler downstream solvent recovery. [ABSTRACT FROM AUTHOR]

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The increasing global demand for potassic fertilizer, due to the population growth, indirectly forces many countries to search for an alternative source of potassium. The present study reports the recovery of potassium from K-feldspar (K2O 12.5 wt. %) through the chlorination roasting—water leaching process applying a mixture of CaCl2 and NaCl. Individual use of NaCl and CaCl2 results in the extraction of ∼50% and 92% of potassium, respectively. Though the K-extraction is very high via CaCl2 roasting process, it adds an extra cost to the process as compared with NaCl. However, the use of salt mixture CaCl2: NaCl (40:60 wt. %) recovers potassium to the tune of ∼98% at optimum conditions (850 °C, 60 min roasting period, salt mixture: feldspar 1:1). Various experimental parameters such as temperature, time, and salt to feldspar ratio were optimized to recover maximum potassium from the complex structure of K-feldspar. The experimental results are explained using a theoretical extraction model, further supported by characterizations of the samples using XRD, SEM-EDX and FTIR studies.NOVELTY STATEMENTS Potassium extracted from K-feldspar applying a mixture of CaCl2 and NaCl. The chlorination-roasting temperature (using salt mixture) was lesser (by 50 °C) as compared with the use of individual salts. The extraction process (using salt mixture) was less expensive as compared with the use of independent salts. The K-extraction mechanism has been discussed considering the experimental results. Characterization studies support the proposed extraction mechanism. [ABSTRACT FROM AUTHOR]

Ceramic sanitaryware products are produced using inorganic and non-metallic raw materials such as clay, kaolin, quartz and feldspar at certain rates. After mixing and grounding process, the slip is obtained. The products are shaped in gypsum or synthetic resin moulds. Green bodies are fired at 1250 °C for 16–18 h, and their water absorption values are less than 0.5%. Nowadays the most important issues are raw materials and energy costs. In this study, the sintering behaviour of Na-feldspar and K-feldspar, which are widely used in ceramic sanitaryware, is analysed by reducing to different grain sizes. The grain sizes of the samples containing Na-feldspar were reduced under 63 µm. It was found that the decrease in grain size of Na-feldspar contributed to the decrease in sintering temperature. Potassium feldspar was also added instead of Na-feldspar in order to develop deformation behaviour at higher temperature. The increase in the amount of K-feldspar contributed to the decrease in deformation values. However, the flexural strength of the bodies decreased. A decrease in grain size of Na-feldspar resulted in a reduction of 10 °C at the sintering temperature. The decrease in sintering temperature will provide a cost advantage of around 3%. It was also found that technical properties such as firing shrinkage, bulk density, and flexure strength increased as the grain size of Na-feldspar decreased. [ABSTRACT FROM AUTHOR]

Lead isotopes are a powerful and versatile tool to elucidate fundamental geological problems related to the formation and evolution of continental crust. K‐feldspar is a popular target for Pb isotope measurement as it is prevalent in many rock types and tends to capture the initial Pb isotope composition of its parental magma. We present data for a new Pb isotope reference material: Albany K‐feldspar; as well as updated data for Shap K‐feldspar. Results of Pb double‐spike TIMS for Albany K‐feldspar are 206Pb/204Pb = 16.7872 ± 0.0062, 207Pb/204Pb = 15.5640 ± 0.0056, and 208Pb/204Pb = 36.6600 ± 0.0168 (2s). TIMS measurement results for Shap K‐feldspar indicate two isotopically distinct Pb populations. LA‐MC‐ICP‐MS, with a spatial resolution as high as 15 μm, indicates a homogeneous Pb isotopic composition in Albany K‐feldspar. In accord with previous studies, our results show that scatter in the measured Pb isotope ratios, related to the low natural isotopic abundance of 204Pb, along with the effect of isobaric 204Hg‐204Pb interference, increases at lower count rates. However, the mean Pb isotope ratios measured via LA‐MC‐ICP‐MS using a range of spot sizes are in excellent agreement with TIMS results thus highlighting the feasibility of Pb isotope determination via LA‐MC‐ICP‐MS to access geological information preserved in small crystals, including mineral inclusions. [ABSTRACT FROM AUTHOR]

In this study, effects of mechanical activation in the chlorination roasting and water leaching route known as CaCl2 process and developed for the production of potassium chloride (KCl) from potassium feldspar ores were studied. A microcline containing K-feldspar ore with 10.89% K2O was first intensively dry milled by a planetary ball mill and mixed with calcium chloride (CaCl2) and then roasted at temperatures up to 1000 °C to obtain KCl that will be finally dissolved by the water leaching. Potassium recovery by water leaching increased rapidly up to 800 °C. At higher temperatures, the recovery decreased fast due to the evaporation of KCl. According to the K recovery values per unit energy consumed, the optimum roasting temperature was determined as 750 °C and the milling time was 15 min. It was concluded that intensive milling causes mechanical activation of the microcline to reduce the chlorination roasting temperature, which triggers a rise in the K recovery by the water leaching. [ABSTRACT FROM AUTHOR]

Microbial endolithic communities are ubiquitous in many deserts around the globe. They have been found in many different lithologies, including quartz, plagioclase and calcite. The use of culture methods in geomicrobiology is important because most bacteria are non-cultivable, which makes it very difficult to characterize and describe them. In this study, endolithic bacteria and yeast were cultured in three rock-forming minerals (quartz, K-feldspar and calcite) with standard culture methodologies. It was demonstrated that these endolithic microorganisms could grow in noble agar enriched with a mineral different from the one they were extracted. Microbes were also cultured in a nutritive broth under some physicochemical factors (sugar, salt, pH and temperature) to study their possible tolerance to different ecological conditions. These results were combined with Multiple Factorial Analysis to identify statistical trends between their morphologies (pigment, size and Gram stain), chemical elements and their tolerance to physicochemical factors. Our results show that it might exist a relationship between pigments in microbial colonies,their tolerance to pH9, salinity and temperature conditions; and that Gram-negative bacillus might have a high adaptive ability to different enriched minimum media. Characterizing microbial communities associated with lithic substrates in the laboratory could be helpful for future planning in the search for life on Mars.

Previous studies have demonstrated that quartz optically stimulated luminescence (OSL) dating has limitations for samples older than the last glaciation. However, infrared stimulated luminescence (IRSL) from K-feldspar can be applied beyond this limit if the problem of anomalous fading can be overcome. Elevated temperature stimulated IRSL signals (pIRIR) have shown great potential for minimizing the underestimation. In this study, we compared three commonly applied protocols (pIR 50 IR 290 , pIR 200 IR 290 , MET-pIRIR) for the same set of loess samples from the Tianshan Mountains in arid central Asia (ACA). For loess samples in the 70–130 ka age range (i.e., D e values in the range of 200–400 Gy), pIR 200 IR 290 and MET-pIRIR could both be used for dating, while a varying degree of underestimation occurred for the pIR 50 IR 290 dating protocol. For samples older than 130 ka (i.e., D e values in the range of 400–700 Gy), the MET-pIRIR 250 signal was the most suitable. [ABSTRACT FROM AUTHOR]

Reservoir quality of sandstones can be controlled by the dissolution of minerals such as K‐feldspar. The present work investigates the impact of dissolution of K‐feldspar (Orthoclase) on the resulting porosity and permeability of sandstones using a thermodynamically consistent multiphase‐field model. Two novel aspects of this research are: (a) identification and calibration of interfacial surface energy and kinetics related model parameters based on existing literature, to account for the formation and growth of diamond‐shaped etch‐pits during dissolution, and (b) the workflow for three‐dimensional modeling of dissolution at sub‐micrometer scale within individual feldspar grains, followed by up‐scaling the phenomenon to a multigrain pack analogous to sandstone. The simulated dissolution, when visualized in the relevant planes, show clear similarities with microphotographs of natural samples and previous numerical works, in terms of facet‐formation and merging of the etch‐pit morphologies. For the computation of permeability, computational fluid dynamics analysis was performed for grain packs at different stages of dissolution. Finally, the generated data‐sets were analyzed to study the impact of rock properties including a fraction of feldspar grains and their crystallographic orientation on the porosity, permeability and their correlations, for sandstones undergoing K‐feldspar dissolution. At the same porosity, sandstones containing a greater proportion of K‐feldspar grains are expected to have greater permeabilities. The devised workflow for model calibration and up‐scaling complimented by the innovative post‐processing and visualization techniques can be adapted to study dissolution of other minerals in different rocks. Plain Language Summary: The dissolution of minerals like K‐feldspar controls how well sandstones act as a storage sites for fluids. In this work, we use a multi‐physics modeling approach and perform simulations to study how K‐feldspar grain dissolution impacts the overall porous and permeable characteristics of natural sandstones. The calibration of a simulation model helped us to capture the shape and growth characteristics of etch‐pits, which are responsible for the dissolution of K‐feldspar grains. Additionally, we perform pre‐ and post‐processing techniques which allow the up‐scaling of this phenomenon to a multigrain pack analogous to sandstone, while also reducing the computational costs. When comparing the simulation result with natural samples, the etch‐pit's morphology evolution showcases great resemblance. Furthermore, for computation of the permeability evolution during K‐feldspar grain dissolution, we performed computational fluid dynamics analysis. The fluid‐flow analysis allows us to analyze the effect of the volume of K‐feldspar grains and their respective cleavage plane (weaker plane, where etch‐pits form) orientations on the overall porosity‐permeability evolution within the sandstone. This work showcases new modeling techniques, which can be used in future work, for handling large‐scale dissolution processes with different minerals and rock types. Key Points: A phase‐field investigation illuminating the etch‐pitting behavior on the surface of K‐feldspar and its impact on reservoir qualityA novel simulation‐based workflow for capturing the etch‐pitting phenomena in sandstone up to three orders of magnitude largerOrientation of etch‐pits and volume percentage of K‐feldspar substantially affect porosity‐permeability correlation in sandstone [ABSTRACT FROM AUTHOR]

This study's aim is to investigate the wet and dry grindability of K-feldspar in a narrow grain size range in a stirred ball mill. In the evaluation of the grinding process, a full factorial design was used to observe the effects of the selected parameters on the dependent variable. On a narrow grain size range grinding, the parameter effects such as ball diameter, stirring speed, grinding time, and interstitial filling ratio were investigated. Experimental results showed that K-feldspar can be efficiently milled with a stirred ball mill in a narrow grain size range (1-10 microns).

The relevance of selecting an appropriate bed material in fluidized bed gasification is a crucial aspect that is often underestimated. The ideal material should be economical, resistant to high temperatures and have small chemical interaction with biomass. However, often only the first of such three aspects is considered, neglecting the biomass–bed interaction effects that develop at high temperatures. In this work, olivine and K-feldspar were upscale-tested in a prototype fluidized bed gasifier (FBG) using arboreal biomass (almond shells). The produced syngas in the two different tests was characterized and compared in terms of composition (H2, CH4, CO, CO2, O2) and fate of contaminants such as volatile organic compounds (VOCs), tar and metals.. Moreover, the composition of olivine and K-feldspar before and after the biomass gasification process has been characterized. The aim of this work is to show which advantages and disadvantages there are in choosing the most suitable material and to optimize the biomass gasification process by reducing the undesirable effects, such as heavy metal production, bed agglomeration and tar production, which are harmful when syngas is used in internal combustion engines (ICE). It has been observed that metals, such as Ni, Cu, Zn, Cd, Sn, Ba and Pb, have higher concentrations in the syngas produced by using olivine as bed material rather than K-feldspar. In particular, heavy metals, such as Pb, Cu, Cd, Ni and Zn, show concentrations of 61.06 mg/Nm3, 15.29 mg/Nm3, 17.97 mg/Nm3, 37.29 mg/Nm3 and 116.39 mg/Nm3, respectively, compared to 23.26 mg/Nm3, 11.82 mg/Nm3, 2.76 mg/Nm3, 24.46 mg/Nm3 and 53.07 mg/Nm3 detected with K-feldspar. Moreover, a more hydrogen-rich syngas when using K-feldspar was produced (46% compared to 39% with olivine). [ABSTRACT FROM AUTHOR]

Potassium feldspar is a typical insoluble potassium ore with enormous deposits in China. Its industrial utilization has not been developed yet because of high costs and technological difficulties. One of the problems is related to a low potassium extraction ratio. To address this, the KAS6-chloride salts-CaCO3 system has been studied with a focus on the influence of calcination temperature, type, and the portion of additives. The results demonstrate that the extraction ratio of potassium appeared to be typically extremely low because of the nature of CaCO3 additive. The extraction ratio can be notably raised by increasing the content of chloride salts. The potassium extraction has been shown to reach 85% in the KAS6-MgCl2-CaCO3 and KAS6-CaCl2-CaCO3 systems, whereas the leaching rate was only 60% in the KAS6-NaCl-CaCO3 system at 800°C. Extraction in the KAS6-NaCl-CaCO3 system increased as the roasting temperature raised to 900°C. With the mass ratio of KAS6:NaCl:CaCO3 = 1:2:4, the extraction of potassium constitutes to 97.29% at 900°C. A method of improving the extraction of potassium in the KAS6-chloride salts-CaCO3 system with manganese ions as an additive has been investigated. The results indicate that adding 5 wt% anhydrous manganese sulfates enables to increase the leaching rate of potassium in the KAS6-chloride salts-CaCO3 system. [ABSTRACT FROM AUTHOR]

Zeolite W with the spindle morphology has been rapidly synthesized from alkali fusion activated K‐feldspar via gel‐like‐solid phase method after supplementing a small amount of silica‐aluminum xerogel. The effects of n(H2O)/n (SiO2), m (activation product)/m (xerogel), and crystallization time on the synthesis of zeolite W were investigated. The optimal synthesis conditions were m (activation product)/m (xerogel) of 3.92, n(H2O)/n (SiO2) of 25.8, and crystallization time of 12 h. The synthesized zeolite W was used to extract K+ ion from the simulated seawater. The synthesized zeolite W with the fluffier spindle morphology exhibited a higher K+ extraction capacity. The maximum exchange capacity of zeolite W for K+ ion reached 49.57 mg·g−1. The zeolite W synthesized by the gel‐like‐solid phase method possessed a superior K+ extraction capacity than that synthesized by the hydrothermal method when K‐feldspar was used as the raw material and an approximate K+ extraction capacity with that synthesized from chemical reagents. In addition, the recycling process of the mother liquor was designed. This work provides an effective way for the zeolite W synthesis and the resource utilization of K‐feldspar with advantages of high raw material utilization, low water content in the synthesis system, short crystallization time, and recyclable mother liquor after synthesis of zeolite W. [ABSTRACT FROM AUTHOR]

Here we present in situ Rb Sr and Pb isotopic analysis of K-feldspar from the Shap Granite, (Cumbria, UK) and detrital K-feldspar from the associated Shap Wells Conglomerate Formation, to investigate the potential of the detrital K-feldspar record as an archive of crustal composition. We use a unique, collision cell – multi collector inductively coupled plasma tandem mass spectrometer to make the in situ isotope measurements, using 'chemical resolution' of 87Rb+ and 204Hg+ isobaric interferences on 87Sr+ and 204Pb+, achieved with SF 6 and NH 3 reaction gases, respectively. Using this technique, we successfully demonstrate that the majority of detrital K-feldspar Rb Sr ages, as well as initial Sr and Pb isotope ratios, from the Shap Wells Conglomerate are within uncertainty of those for parental Shap Granite K-feldspar (398 ± 1 Ma, n = 6). Some detrital K-feldspar grains record perturbed Rb Sr ages, reflecting post depositional alteration events. The majority of samples with disturbed Rb Sr ages carry distinct petrographic features evident in SEM imaging, prior to in situ dating, which indicates a means to help screen for reliable ages. We further illustrate the potential value of combined Rb Sr and Pb isotopic information preserved in K-feldspar to estimate the timing and chemical composition of juvenile continental crust formed in the past. Where U Pb has been fractionated during juvenile crust formation, the initial Pb isotope ratio provided by the K-feldspar yields model crustal U/Pb (diagnostic of tectonic setting) and extraction age. The contrast in the U/Pb composition of juvenile crust formed in intraplate or subduction settings allows the model U/Pb ratios of the detrital K-feldspars to be used to constrain the style of juvenile crust formation. Additionally, the initial 87Sr/86Sr isotope ratio measured in detrital K-feldspar can be combined with the calculated crustal extraction age and Rb Sr K-feldspar age to model the Rb/Sr of the juvenile crustal protolith. • Magmatic Rb Sr age and initial Pb isotopic compositions can be preserved in detrital K-feldspars. • Model age and U/Pb composition of crustal protolith determined from coupled Rb Sr and Pb analysis of K-feldspars. • U/Pb composition of crustal protolith can be used to infer tectonic setting of its formation. • Protolith age and K-feldspar initial 87Sr/86Sr ratios used to model protolith 87Rb/86Sr and degree of differentiation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel collector LDEA is synthesized on dodecylamine (DDA) molecular structure. • LDEA has a better selectivity in flotation separation of apatite/quartz/K-feldspar. • LDEA and DDA exhibit comparable adsorption levels on apatite surfaces. • The adsorption configurations of LDEA and DDA on apatite surfaces markedly differ. • LDEA adsorption structure on apatite surface dictates its weak collecting ability. In the reverse flotation separation of apatite and its associated siliceous gangue minerals, the common collector dodecylamine (DDA) exhibits a poor selectivity. To remedy this issue, this study implements a change to DDA molecular structure by integrating two 2-hydroxyethyl groups at the N atom position, ultimately producing a freshly developed collector, lauryldiethanolamine (LDEA). Micro-flotation experiments reveal that, relative to DDA, LDEA showcases an enhanced selectivity in separating apatite from its associated siliceous gangue minerals quartz and K-feldspar through reverse flotation. This difference primarily stems from the weaker collecting ability of LDEA for apatite particles relative to DDA. Nevertheless, zeta potential measurements and X-ray photoelectron spectroscopic tests consistently show that, under identical dosage conditions, LDEA and DDA exhibit similar adsorption quantities on apatite surfaces. This observation implies that factors beyond its adsorption quantities inevitably influence the collecting ability of LDEA for apatite particles. First-principles calculations unveil markedly different adsorption configurations of LDEA and DDA on apatite surfaces, suggesting that the difference in the adsorption configurations of LDEA and DDA accounts for the significant variance in their collecting abilities for apatite particles. [ABSTRACT FROM AUTHOR]

Scanning electron microscope, cathodoluminescence (CL) imaging and laser ablation–inductively coupled plasma–mass spectrometry analyses were conducted on coexisting pairs of quartz and K-feldspar from 14 samples of various types of felsic igneous rocks. Difference of the concentration of trace elements in quartz and K-feldspar among plutonic, pegmatitic and volcanic rocks is closely related to the rock-forming process and P–T condition. In general, a decreasing Ti concentration and increasing Al, Li, and Ge concentrations from plutonic to pegmatitic quartz suggest a higher degree of magmatic fractionation and lower crystallization temperature. Sensitive elements to magma differentiation in K-feldspar such as Ba, Sr, and LREE show a decreasing trend from various granitic rocks to pegmatite, while Rb, Cs, Li, Ge, and P exhibit increasing trends. The K-feldspar from various types of felsic igneous rocks typically shows similar CL textures but relatively higher luminescence intensity compared with coexisting quartz. Both quartz and K-feldspar phenocrysts in the volcanic rhyolite have a bright rim and a dark core in CL images, corresponding to bimodal Ti concentrations. Among all samples, Ti concentrations in both quartz and coexisting K-feldspar positively correlate with their CL intensities, suggesting the activation of Ti-impurity in these minerals leads to increased CL intensity. Meanwhile, there is a good positive correlation between Ti concentrations in quartz and those in K-feldspar with an R 2 value of 0.86. It is considered that Ti concentrations in the both minerals are mainly temperature dependent at relatively constant pressure on basis of a fair a TiO2 restriction. Here, for the first time, we calculated a titanium-in-K-feldspar (TitaniKfs) thermometer in the form of log (X Ti, kfs/ a TiO2) = −(3430 ± 268)/ T (K) + (5.081 ± 0.298) for natural felsic magma systems. The Ti contents of K-feldspar (in ppm by weight) increase exponentially with reciprocal T at temperatures ranging from 500°C to 800°C, at 200–300 MPa. An application of this thermometer to granitic rocks from Xinjiang and Inner Mongolia in China fits well with other geothermometers. In addition, the present TitaniKfs thermometer is expected to be particularly useful in determining the temperature condition of K-feldspar-bearing extraterrestrial materials such as lunar rocks. [ABSTRACT FROM AUTHOR]

The Yichang area located at the exit of the Three Gorges is covered with a set of thick Quaternary gravel layers, recording the evolution of the paleoenvironment and the formation of the Yangtze River. However, there has been a great dispute over the time when the Yangtze River materials in the upper reaches entered the western margin of the Jianghan Basin. K-feldspar is a common mineral in fluvial sediments, and its geochemical element compositions are significantly different in different regions, making it an ideal mineral for the fluvial provenance study. In this case, we utilized the laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to analyze the elementary compositions of detrital K-feldspar grains (n=340) on the gravel layers of the Yichang area and the upper reaches of the Yangtze River. In combination of principal component analysis (PCA) with formation sedimentary ages of gravel layers, we discussed the time when they established the provenance connection. The results show that the provenance connection has been established since 1.15 Ma and a new provenance area appeared at 0.75 Ma, suggesting that the Yangtze River drainage was strongly influenced by the East and South Asian summer monsoon during the period of 1.2~0.7 Ma.

Abstract A recently discovered the rare-earth-rich site in Capacsaya, located at 123 km northwest of Cusco, at the south of Peru, contains significant quantities of light and heavy rare-earth elements such as neodymium, lanthanum, cerium, europium, and yttrium. This work reports the identification of rare-earth elements and their associated minerals using scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction analyses. Five (5) samples extracted from different locations at the Capacsaya site were characterized and identified K-feldspar as the mineral associated with the rare-earth elements in a representative sample with a high concentration of lanthanum and cerium. The results showed rare-earth elements contained within the mineral phase monazite, being cerium the dominant element in the phase (La, Ce, Nd)PO $$_4$$ 4 . Finally, through the electrostatic separation process we demonstrate that it was possible to achieve an efficient separation of the K-feldspar phase in the particle size range 75–150 $$\upmu$$ μ m.

For the first time, cathodoluminescence (CL) was used to show oscillatory zoning in perthitic K‑feldspars from the equigranular Toki granite, central Japan. Based on the CL patterns, two types of zoning are identified: single core oscillatory zoning (SCOZ) and multiple core oscillatory zoning (MCOZ). The SCOZ is defined by oscillatory zoning around a single-crystal core within the K‑feldspar crystal, whereas the MCOZ depicts two or more such crystal cores. The crystal cores displayed in CL images reflect the nucleation parts of magmatic K‑feldspar. The existence of MCOZ patterns in K‑feldspars indicates multiple nuclei. CL patterns reveal crystal growth behavior of magmatic K‑feldspar in the equigranular Toki granite. CL intensities are positively correlated with titanium and barium concentrations, indicating that the CL variations depend on two factors: (1) titanium concentration as a CL activator and (2) density of Al-O−-Al structural defects. The analysis of CL images revealed that albite-rich phases in microperthite and patchperthite with low-luminescence intensities cut across the CL bands of the oscillatory zoning, indicating that the oscillatory zoning in the orthoclase-rich host phase of K‑feldspar was not perturbed by the formation of microperthite and patchperthite in the post-crystallization stage. The luminescence intensities of albite-rich phases in patchperthite are lower than those in microperthite, which is due to the diferences in titanium and barium concentrations between them. In the post-crystallization stage, the mass transfer of titanium and barium occurred during the formation of microperthite and patchperthite. Therefore, the diference in the luminescence intensities between microperthite and patchperthite lamellae reflects their diferent formation mechanisms between exsolution coarsening and dissolution-precipitation coarsening. In summary, CL analyses can be used for the evaluation of the nucleation and growth not only of anhedral K‑feldspar crystals in equigranular granite but also of K‑feldspar phenocrysts/megacrysts in porphyritic granite. It can reveal the spatial extent of element partitioning between the melt and crystal, along with that of mass transfer from the melt into crystals during the magma evolution. Moreover, the CL analyses can also be used for the interpretation of K‑feldspar textural development during the post-crystallization stage. [ABSTRACT FROM AUTHOR]

Arid degraded soils have a coarse texture and poor organic matter content, which reduces the activity of microorganisms and soil enzymes, and thus the soil quality, plant yield and quality decrease. Potassium solubilizing bacteria (KSB) have been suggested to increase the activity of soil enzymes and increase the release of potassium from natural K-feldspar in the arid degraded soil, and thus potentially reduce the rates of the application of chemical fertilizers. Field studies were conducted for three successive growing seasons in an organic farming system to investigate the effects of K-feldspar and KSB (Bacillus cereus) on K release, soil fertility, and fruit yield of mango plants (Mangifera indica L.). The maximum growth of mango plants was found in the treatments inoculated with KSB. KSB increased soil available N, P, K, and the activity of dehydrogenase and alkaline phosphatase enzymes by 10, 7, 18, 54, and 52%, respectively. KSB increased the fruit yield of mango by 23, 27, and 23% in the first, second, and third growing seasons, respectively. The partial (up to 50%) substitution of chemical K-fertilizer with K-feldspar gave fruit yield and quality very close to that fertilized with the full chemical K-fertilizer. The release rate of K (over all the treatments) varied between 0.18 and 0.64 mg kg−1 of soil per day. KSB significantly increased the K release rate. The application of chemical K-fertilizer gave the highest K release, while substitution with K-feldspar reduced the release of K. Natural K-feldspar contains 8.2% K but is poorly soluble when applied alone. KSB increased the soil quality parameters and enhanced the growth and quality of mango fruit. The fruit yield of mango, under KSB inoculation and fertilization with different K sources, ranged between 9.14 to 17.14 t ha−1. The replacement of 50% of chemical K-fertilizer with natural K-feldspar caused a decrease in the fruit yield by 17, 8, and 2.7% in the first, second, and third years, respectively. The substitution of chemical K-fertilizer with K-feldspar up to 50% with KSB is a good strategy to reduce the excessive use of chemical K-fertilizer. B. cereus and natural K-feldspar have the potential to improve soil health and mango plant productivity in low fertile arid soils. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Agricultural Science & Technology (1008-0864) is the property of Journal of Agricultural Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As part of the “generalized Nihewan Basin”, the Huailai basin has recently attracted archaeologists’ attention. Ten Paleolithic sites were found in this basin in 2014; among these, the Zhuwobu site is the oldest―dated to 504 ± 76 ka using the electron spin resonance (ESR) dating method. This study redated the Zhuwobu site using the multiple elevated temperatures (MET) post infrared (pIR) infrared stimulated luminescence (IRSL) procedure (MET-pIRIR) on both multi-grained single and multiple aliquots of potassium-rich feldspars (K-feldspars). The consistency of the De results obtained from the single- and multiple-aliquot procedures mutually supported the reliability of our age results. Our results suggest that the cultural layer at this site was deposited about 280 ± 13 ka (MIS 8) ago, ∼220 ka younger than the previous ESR age. Considering the region’s tectonic history and the characteristics of the sedimentary facies for the ZWB site, we suggested that the previous ESR age results for the bottom three samples from the sediment profile might be overestimated due to poor bleaching before burial. In contrast, the ESR age of 346 ± 32 ka (MIS 10) for one cultural-layer collected sample might be more reliable due to higher-quality bleaching before burial. Further archaeological, geological, and chronological studies are needed to explore the ancient hominins’ survival conditions in the “generalized Nihewan Basin” and possible connections with the renowned Zhoukoudian sites.

The Cenozoic sedimentary rocks on the island of Taiwan hold significant implications for understanding tectonic and drainage evolutions in SE China, but the provenance of these rocks remains controversial. Here we derived Pb isotopes in detrital K-feldspars from the drainage systems in western Taiwan to evaluate the provenance of sediments and reveal the evolution of Cenozoic sedimentary. Our findings indicate that the fluvial sediments eroded from the Cenozoic sedimentary rocks were primarily derived from the eastern Cathaysia Block (91%), with minor contributions from the Yangtze River catchment. Spatially, the northern part of Taiwan contains more sediments derived from the Yangtze River catchment than the southern part. The Cathaysia Block has been crucial in supplying detritus to Taiwan since the Eocene, whereas the contribution of the Yangtze Block varies greatly at different sedimentary periods. Two major shifts in provenance occur at the boundaries between Eocene, Oligocene, and Miocene, which may be related to the changes in drainage systems and landscapes in eastern China. • Pb isotopes in detrital K-feldspar were examined in SE China and western Taiwan. • The sedimentary rocks were primarily derived from the eastern Cathaysia Block. • Northern Taiwan was more influenced by the Yangtze River catchment than the south. • Cenozoic provenance evolution related to changes in landscapes and drainage systems. [ABSTRACT FROM AUTHOR]

Alluvial river in the piedmont area deposits and incises cyclically, in response to both exogenetic and endogenetic forcing across a range of timescales. The paces of these processes unveil the mechanisms governing the evolution of alluvial fan-river system and affect the policy for river management. Numerical simulation suggests that the incision of alluvial river is much faster than the deposition process. However, the field observations are rare. Alluvial rivers entrench up to 300 m into the alluvial fans built pre-Holocene on the northern piedmont of Chinese Tianshan, which provide ideal sites to unveil the pace of alluvial fan-river evolution. Jingou River is one of these rivers, with four levels of terraces identified at the downstream area. These terrace deposits are characterized by a complex of upper very coarse gravels and cobble (VCGC) unit and lower medium and coarse gravels (MCG) unit. In this study, potassium-feldspar (K-feldspar) single grain pIR 110 IR 170 luminescence dating procedure was employed to date the samples taken from sandy lens of both upper VCGC and lower MCG units, for which the depositional ages are supposed to be associated with the fan-building and river incision processes, respectively. The luminescence ages of the lower MCG unit suggests a gradual fan building phase between 16 ± 1.9 ka and 8.1 ± 0.9 ka, while the ages of the upper VCGC unit cluster around ∼5.2 ka rather than a monotonic decrease towards low level terraces. Several scenarios are discussed with respect to the attained age sequences to unravel the pace of deposition and incision of Jingou River, of which the asymmetric aggradation and incision is more preferred and echoes to the finding of previous numerical investigation. [ABSTRACT FROM AUTHOR]

As a vital component of the "Asian water tower", lakes on the Tibetan Plateau (TP) significantly influence the regional ecosystems and economies and they are also an effective sentinel of climate change. However, the temporal and spatial patterns of lakes and the related hydroclimatic evolution on the northwestern TP (NWTP) remain unclear. We reconstructed the lake level variations of a non-glacier-fed lake, Longjue Co, on the NWTP, using optical dating of paleo-shorelines. The optically stimulated luminescence signals of quartz grains were unsuitable for dating due to high contributions of the medium component, and thus the post-infrared infrared stimulated luminescence signals (pIR 50 IR 170 , pIR 50 IR 225) of K-feldspar single grains were used. Internal checks including dose recovery tests, residual dose tests, and anomalous fading tests showed that the pIR 50 IR 170 signal was suitable for paleo-shoreline dating in Longjue Co. However, some of the samples were affected by the incomplete bleaching of pIRIR signals before deposition, and in this case the Minimum Age Model was used to constrain the ages. We also examined the dependence of the K-feldspar equivalent dose (D e) on grain brightness and explored the possible mechanisms, and the brightest grains were then used for D e calculations. The results show that Longjue Co reached its maximum Holocene level (+34 m) during the early Holocene (10.06 ± 1.39 ka), and then after ∼5 ka it commenced a shrinking trend, punctuated by two rapid lake level decreases. Reference to independent paleoclimate records suggests that the Holocene lake level variations of Longjue Co and the regional hydroclimate were mainly controlled by the Indian summer monsoon. [ABSTRACT FROM AUTHOR]

The hydrothermal dissolution of a Brazilian glauconitic siltstone, known as Verdete, in the presence of calcium hydroxide was studied using conventional and rotary furnaces. The objective was to assess the behaviour of Verdete, a mixture of micas and K-feldspar, in response to reaction with calcium hydroxide to recover potassium-bearing soluble species. The hydrothermal procedure generated Ca-, Si- and Al-bearing insoluble products with defined crystalline structure (hydrogrossular and tobermorite), resulting from the breakdown of K-feldspar. The use of citric acid as extracting agent led to potassium recoveries up to 300% greater than in cases where the extracting agent was water, due to the formation of an insoluble and amorphous layer (containing mostly K, Mg and Fe) between Verdete and the alkaline solution. Altered feldspar, as well as possibly potassium-substituted tobermorites, may have the potential to release potassium (and other elements) in the long term, while the amorphous layer is responsible for faster release in the short term. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering & Architectural Faculty of Eskisehir Osmangazi University / Eskişehir Osmangazi Üniversitesi Mühendislik ve Mimarlık Fakültesi Dergisi is the property of Eskisehir Osmangazi University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Sedimentologica Sinica is the property of Acta Sedimentologica Sinica Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Microbial endolithic communities are ubiquitous in many deserts around the globe. They have been found in many different lithologies, including quartz, plagioclase and calcite. The use of culture methods in geomicrobiology is important because most bacteria are non-cultivable, which makes it very difficult to characterize and describe them. In this study, endolithic bacteria and yeast were cultured in three rock-forming minerals (quartz, K-feldspar and calcite) with standard culture methodologies. It was demonstrated that these endolithic microorganisms could grow in noble agar enriched with a mineral different from the one they were extracted. Microbes were also cultured in a nutritive broth under some physicochemical factors (sugar, salt, pH and temperature) to study their possible tolerance to different ecological conditions. These results were combined with Multiple Factorial Analysis to identify statistical trends between their morphologies (pigment, size and Gram stain), chemical elements and their tolerance to physicochemical factors. Our results show that it might exist a relationship between pigments in microbial colonies, their tolerance to pH9, salinity and temperature conditions; and that Gram-negative bacillus might have a high adaptive ability to different enriched minimum media. Characterizing microbial communities associated with lithic substrates in the laboratory could be helpful for future planning in the search for life on Mars. [ABSTRACT FROM AUTHOR]

The K/Cs ratios of K-feldspars from granitic pegmatites are compared to models derived from the Rayleigh equation. The K/Cs and K/Rb ratios of K-feldspars and micas exhibit decreasing values when plotted against their Cs or Rb contents across cogenetic suites of granites and pegmatites and from margin to core of individual bodies. The trends in elemental ratios conform to Rayleigh fractionation for the crystallization of feldspars and micas from a silicate melt. Within two individual pegmatite bodies, the K/Cs ratio of K-feldspar initially falls more rapidly than the Rayleigh model predicts. That might reflect a local increase in the concentration of Cs relative to K due to the pile-up of incompatible elements in a boundary layer of melt adjacent to the crystal growth front. The addition of an aqueous solution to the Rayleigh model (i.e., the simultaneous crystallization of K-feldspars from melt and from aqueous solution) predicts high and increasing K/Cs ratios of K-feldspars that are not observed in natural rock suites, except when K-feldspars crystallize in miarolitic cavities or when primary K-feldspar recrystallizes to microcline perthite in an open hydrothermal system. In those cases, the Cs content of K-feldspars falls to nil because of the high solubility of Cs in aqueous solution and low compatibility of Cs in K-feldspar. Otherwise, the observed patterns of K/Rb or K/Cs in K-feldspar and micas in pegmatites conform to crystal-melt fractionation in which an aqueous solution plays no part. From the viewpoint of the geochemistry of Cs in pegmatites, these observations give support to the model proposed by Cameron et al. (1949) and endorsed by Jahns (1953a, 1953b). [ABSTRACT FROM AUTHOR]

Abstract Silicate rock Verdete, collected in the central region of Minas Gerais state (Brazil) and composed mostly of micas (glauconite and muscovite) and tectosilicates (K-feldspar and quartz), was hydrothermally treated with several reactants in order to release and recover potassium. The hydrothermal products were characterized by flame photometry, XRD, XRF, SEM and EDS. Treatment with sulfuric acid was effective to break the crystal lattice of micas before 1 h of reaction and recovered 24% of potassium in the form of sulfates. The K-feldspar appears to have remained intact during the process. Treatment with a Ca(OH)2 (86 wt.%) - CaCO3 (14 wt.%) mixture did not consume the micas, but K-feldspar was gradually consumed over the 24 h reaction period. The K recovery was probably due to a concurrent hydrolytic framework dissolution of K-feldspar mediated by OH− ions and by the exchange of K+ with Ca2+. The K-bearing species are carbonaceous materials with variable K+/Ca2+ ratios, such as K2Ca(CO3)2.

Copyright of Journal of Geomechanics is the property of Journal of Geomechanics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Potassium is one of the most important elements in plant growth and development. Most of the potassium reserves on Earth are in insoluble mineral form, which represents a limitation for the absorption of this nutrient by plants. Some microorganisms can solubilize the mineral forms of potassium. This study aimed to isolate and identify potassium solubilizing bacteria resident in corn rhizoplane. To do this, bacteria that formed a solubilization halo around the colony on solid Aleksandrov culture medium were selected. These bacteria were then characterized considering the appearance of the colonies and cell morphology and were identified by partial 16S rDNA sequencing. Their solubilizing and potassium-releasing capacity was determined under different conditions of temperature, pH, and salinity, using potassium feldspar and muscovite as insoluble sources of potassium. Eight strains identified within the genera Paenibacillus, Lysinibacillus, Arthrobacter, Bacillus, Pseudomonas, and Stenotrophomonas were obtained. The release of potassium from feldspar was favored at 28 and 30°C, pH 7.5 and a saline concentration of 4 g L-1, while in the presence of muscovite the best conditions were 30 and 37°C, pH 5.5 and 7.5, and 4 g L-1 of NaCl. The most efficient strains were Bacillus sp. INCA-FRc7 and Bacillus sp. INCA-FRc19x with yields of up to 2.095 mg L-1. These strains could become alternatives to the use of potassium fertilizers and contribute to the ecological sanitation of the agroecosystems.

Copyright of Agronomía Colombiana is the property of Universidad Nacional de Colombia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Soil salinity is one of the major limiting factors for poor crop yield in the world. Increasing salinity in the soil is a challenge for agriculture. In the recent past, plant growth-promoting rhizobacteria (PGPR) are being used to enhance plant growth in various conditions. However, the saline-tolerant PGPR are of great use for plant growth under saline condition. In the present study, saline-tolerant E. hormaechei(MF957335) was isolated from saline water. E. hormaechei(MF957335) was tested for its potassium and calcium solubilizing efficiency using Scanning Electron Microscopy–Energy Dispersive X-Ray (SEM–EDX). E. hormaechei(MF957335) and K-Feldspar treatments significantly increased plant growth as compared to untreated plants (negative control). E. hormaechei(MF957335) significantly increased fresh biomass, shoot and root length of tomato plants. Among all the NaCl treatments, maximum fruits (9.66) were achieved in 250 mM NaCl + E. hormaechei treatment. Similar results with increased fruit numbers were obtained in K-Feldspar-treated plants. Apart from the plant growth, fresh biomass and fruit numbers, tomatoes from K-Feldspar-treated plants were large, fleshy and deep red colored. The study could demonstrate bioavailability of potassium from K-feldspar for tomato cultivation. Control plants tomato were small, non-fleshy, yellowish red, and infected with calcium deficiency disease blossom-end rot. The present study demonstrates the role of E. hormaechei(MF957335) in plant growth, yield promotion and disease tolerance by potassium and calcium solubilization, respectively. The study showed that E. hormaechei(MF957335) could be applied to saline and non-saline soils to enhance tomato yield. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Plant Production is the property of Egyptian National Agricultural Library (ENAL) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Optically stimulated luminescence (OSL) dating technique has increasingly been employed to establish chronologies for coastal deposits since the Late Pleistocene. However, the commonly used single-aliquot quartz OSL dating method may yield inaccurate ages due to factors such as partial bleaching, luminescence characteristics, and the age limit of quartz. In this study, taking the Yangtze River Delta (YRD) as an example, single-aliquot and single-grain OSL dating using varying grain-sized quartz and K-feldspar were cross-checked to establish appropriate dating method for Late-Pleistocene sediments in coastal areas. The quartz OSL signals of the upper 24 m Holocene sediments were dominated by the fast component, and the ages obtained through OSL and AMS 14C ages agree. Conversely, the lower 24–91 m section, representing the last glacial-interglacial cycle, reveals a notable underestimation of quartz OSL ages, with a maximum underestimation of 250%, attributed to the influence of signal components. For samples within the dating limit of quartz (less than 70 ka), the single-grain method effectively mitigates the issue associated with the signal component. Single-grain K-feldspar technique proves valuable for accurately determining the age of those older sediments exceeding 70 ka. Through cross-checking between different OSL dating methods, sediments initially attributed to marine isotope stage (MIS) 3 (36–60 ka) are re-identified as deposited during MIS 5 (80–130 ka). This study highlights the necessity of assessing the variability in luminescence characteristics before applying a single OSL dating protocol to all samples from different sedimentary facies within a single core. • The reliability of single-aliquot quartz OSL ages depends on the composition of signal components. • Single-aliquot quartz OSL ages for Late Pleistocene sediments can be underestimated by 250% due to the medium OSL component. • Understanding sediment provenance and luminescence characteristics is key to reliable OSL ages in coastal area. [ABSTRACT FROM AUTHOR]

• Geothermal alteration of K-spar at acid pH results in Al-rich coating formation. • Weak impact of coatings on K-spar reactivity observed for week-long experiments. • Modeling suggests an order of magnitude decrease in rate for month-long durations. • Acid stimulation on site suggested to remain effective despite enhanced K-spar reactivity. Heat transfer fluid mining represents a thermodynamic perturbation for geothermal reservoirs: The pumping of hot water coupled with the re-injection of colder water at depth favors the dissolution of some rock-forming minerals of the deep reservoir (e.g. feldspars), while promoting the precipitation of secondary phases, resulting in a possible change in the permeability and porosity of the reservoir. Such an impact is even greater when one considers the acid stimulations aimed at increasing the injectivity of the geothermal system. In that respect, no consensus exists in the literature regarding the impact of secondary phases on the dissolution rate of primary phases and therefore, on the sustained modification of pore structure. The present study aimed at shedding new light on these questions. Hydrothermal experiments of K-feldspar alteration were conducted at conditions relevant for the geothermal reservoir of Soultz-sous-Forêts (T = 180 °C, acidic pH domain). Measurements of cation release rates were combined with characterizations of secondary coatings (mineralogy, extent of coverage, thickness and porosity) to determine the reactivity of submillimeter K-feldspar powders with and without secondary precipitates. The formation of µm-thick boehmite coatings on K-feldspar grains was found to result in a modest decrease in its reactivity, which might be better explained by the presence of dissolved Al in the bulk solution. This result was independently confirmed by reactive transport simulations, which revealed that the impact of secondary coatings may become significant only when their thickness exceeds a few tens of microns, or if the dissolution rate of the primary phase is significantly greater (106 times) than that of orthoclase. Taken together, this study offers new constraints on the intricate interplay between dissolution and precipitation reactions, of prime importance for modeling more accurately the impact of mass transfer and porosity generation resulting from fluid circulation in geothermal reservoirs. [ABSTRACT FROM AUTHOR]

Well-preserved shorelines, situated at elevations ranging from tens to hundreds of meters above the current lake levels, are commonly found in the lake basins across the Tibetan Plateau (TP). These shorelines offer a valuable opportunity to reconstruct past hydroclimate changes, contingent upon precise age determination of palaeoshorelines. While single-aliquot luminescence methods have been extensively employed for dating palaeoshoreline sediments, both quartz and K-feldspar fractions, the application of single-grain (SG) dating techniques has been relatively limited, particularly in the case of water-lain sediments where partial bleaching must be taken into account. In this study, we applied the single-grain K-feldspar dating technique using the post-IR IRSL (pIRIR) protocol to a selection of palaeoshorelines from Qinghai Lake, the largest lake on the TP. Our primary objectives were to investigate the behavior of single-grain K-feldspar pIRIR signals and to establish precise timing for late Quaternary lake level fluctuations based on SG data. Our findings reveal a clear correlation between the D e (equivalent dose) values of single grains and their fading rates. The higher fading rates observed in dim grains constitute the primary reason for the underestimation of D e values. However, it appears that the internal K content of the grains cannot explain the relationship between fading rates and grain brightness. Finally, we utilized the 30% brightest grains for SG pIRIR D e determinations, allowing us to reconstruct the historical water level fluctuations of Qinghai Lake. Our results indicate a pronounced decline in lake levels during the last interglacial-glacial transition, approximately 90,000 to 75,000 years ago. This decline can be attributed to the response of regional hydroclimate patterns to global environmental changes. • Single-grain K-feldspar dating is applied to palaeoshorelines from Qinghai Lake. • Equivalent dose values of single grains depend on their brightness and fading rates. • There is no dependence of fading rates on intrinsic K content in individual grains. • The 30% brightest grains are used to constrain the timing of palaeoshoreline formation. • Results show an abrupt decline in the lake levels during around 90–75 ka. [ABSTRACT FROM AUTHOR]

[Display omitted] The mobility of heavy metal contaminants and radionuclides in the environment is directly controlled by their interactions with charged mineral surfaces, hence an assessment of their potential toxicity, e.g. in the context of radioactive waste disposal sites, requires understanding of sorption processes on the molecular level. Here, we investigate the sorption of a variety of rare earth elements (REE) and trivalent actinides (Am, Cm) on K-feldspar using batch sorption, time-resolved laser-induced fluorescence spectroscopy (TRLFS), and a surface complexation model. Initially, a reliable pK a for K-feldspar's surface deprotonation reaction was determined as 2.5 ± 0.02 by column titration experiments, in excellent agreement with a measured pH IEP of 2.8. Batch sorption experiments over a broad range of experimental conditions in terms of mineral grain size, pH, [M3+], ionic radius, solid/liquid ratio, ionic strength, and equilibration procedures were carried out to quantify macroscopic retention. The trivalent d-block element Y, early, mid, and late lanthanides (La, Eu, Nd, Lu), as well as two minor actinides (Am, Cm) were used for batch sorption experiments and showed similar pH dependent uptake behavior, underlining their chemical analogy. In parallel, spectroscopic investigations provided insight into surface speciation. Cm TRLFS spectra indicate the formation of three inner-sphere sorption complexes with increasing hydrolysis. Additionally, a ternary K-feldspar/Cm/silicate complex was found for pH > 10, and batch and spectroscopic data at low pH (<4) point to small amounts of outer sphere sorption complexes. Based on TRLFS data, batch sorption, and titration data, a generic geochemical sorption model was developed, that describes sorption edges for all investigated M3+/K-feldspar systems satisfactorily. The derived stability constants for the binary sorption complexes (logK 1-4 = −3.6, −7.7, −11.5, and −17.4, respectively) could successfully be used to reproduce literature data. The stability constants obtained for the surface complexes were included into the database for the Smart K d -concept, which will further improve the safety assessment of potential repositories for radioactive waste. [ABSTRACT FROM AUTHOR]

Afield experiment was carried out during 2018 growing season in Ismailia Governorate, Egypt. The experiment aimed to study the effect of different sources from sediment i.e., Nasser Lake (NLS) and El Shabab Canal (ECS) solely or in combination with natural fertilizers i.e., rock phosphate (RP) and potassium feldspar (KF) + vermicompost (Ver) on availability of P and K, yield and nutrient uptake by maize plants under sandy soil conditions. Application of Nasser Lake sediment mixed with RP+ KF in the presence of Ver. gave the highest vales of stover, grains, ear yield, biological yield and N,P and K-uptake by maize plants compared to different treatments. The application of nature fertilizers i.e., RP, KF and RP+ KF to Nasser Lake sediment and El Shabab Canal sediment increased available P and K in soil after harvest as compared to the untreated ones under application of vermicompost. [ABSTRACT FROM AUTHOR]

A bstract: The geochemical character of detrital mineral grains carries information that can be used to track sediment generation and transport within the broader context of basin development and crustal evolution. Many provenance studies focus on single minerals, which, as a consequence of different source fertility, survivorship and sediment sample representativeness, generate bias and consequently potentially skew geological interpretations. While a range of approaches has been proposed to either quantify or mitigate some of these biases, a significant limitation associated with the most commonly employed provenance proxy – zircon – remains that the grains are remarkably robust and capable of surviving numerous cycles of erosion, deposition and uplift. Here, same‐sample integration of zircon and feldspar provenance information is used to propose a sediment recycling metric 'R'. This metric quantifies the degree of relative recycling of distinctive source components through comparison of provenance proxies with similar source region fertilities but different survivorship potential. This approach is applied to a case study of several thousand new zircon U‐Pb ages and K‐feldspar Pb‐isotope ratios from 25 Carboniferous to Palaeogene clastic samples from the poorly studied Wollaston Forland–Clavering Ø region in hydrocarbon prospective north‐east Greenland. Concordant detrital zircon populations are dominated by Palaeoproterozoic (ca 1.9 to 1.8 Ga) grains (>60%), with more minor Palaeozoic, Neo‐Mesoproterozoic and Archean subpopulations. Feldspar grain Pb‐isotope ratios almost entirely (>>60%) correspond to Caledonian granites (ca 0.4 Ga). Zircon and feldspar provenance proxies appear decoupled as a consequence of: (i) limited resolvable growth of zircon within Caledonian granites, and more importantly; (ii) significant upgrading of recycled zircon components via rift flanking sedimentary basins. Collectively, the integration of detrital mineral proxies with disparate survivorship potentials through sediment cycles (labile first cycle feldspar versus potentially polycyclic zircon) is essential to facilitate more nuanced definition of sediment source regions, routing pathways and basin evolution. [ABSTRACT FROM AUTHOR]