Applied Geochemistry最新文献

{"title":"Uranium enrichment in altered metasedimentary rocks of Jahaz uranium deposit, North Delhi fold belt, Rajasthan, India: Inferences from whole-rock geochemical studies","authors":"Priyanka Mishra ,&nbsp;Rajagopal Krishnamurthi ,&nbsp;Ajit Kumar Sahoo ,&nbsp;Shailendra Kumar Sharma","doi":"10.1016/j.apgeochem.2025.106476","DOIUrl":"10.1016/j.apgeochem.2025.106476","url":null,"abstract":"<div><div>Jahaz deposit is one of the promising Na-metasomatic uranium deposits along the “<em>albitite line</em>” and is hosted in the Meso-Proterozoic metamorphic rocks of the North Delhi Fold Belt, Rajasthan, India. This article presents whole-rock geochemical analyses of major, trace, and rare-earth elements of less to moderately altered and albitized rocks, which are used to quantify the exchange of chemical components during fluid-rock interaction. The alteration box plot indicates the intensity of alterations (albitization, chloritization, calcitization, sericitization, pyritization), and it is inferred that Na-Ca-Mg-K metasomatism was responsible for the formation of albite, chlorite, calcite, and sericite in the altered rocks. Isocon diagrams have been constructed using major and selected trace element concentrations of less to moderately altered and albitized garnetiferous quartz biotite schist/amphibolite to determine the net loss and gain of elements during rock-fluid interaction. The correlation coefficients indicated that elements such as Zr, Nb, Hf, and Ti were less mobile during fluid-rock interaction. Isocon analyses show that the albitized garnetiferous quartz biotite schist is significantly enriched in U, Na, Mg, Fe, Ca, Mo, Cu, Rb, and depleted in K, Pb, Ba, Ni, Zn. Albitized amphibolites are enriched in Na, Cu, Mg, Cu, Y, Cr, Se, Ni, K, LOI and depleted in Ba, Co, Pb, Zn, Ca, P, Mn, Fe. The low Th/U ratio of albitized garnetiferous quartz biotite schist indicates that the albitized rocks are significantly enriched in uranium. Hence, uranium enrichment is positively correlated with Na, Mo, Cu, Th, Zr, LOI, and light rare-earth elements of albitized garnetiferous quartz biotite schist/amphibolite in the Jahaz uranium deposit. These results are similar to Kirovograd and Novoukrainka (Ukraine), Lagoa Real (Brazil), Valhalla (Australia), Longshoushan (China), Aricheng (Guyana) and Coles Hill (USA) Na-metasomatic uranium-deposits.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"190 ","pages":"Article 106476"},"PeriodicalIF":3.1,"publicationDate":"2025-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144535968","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemistry of geothermal well gases from superhot zones of Larderello, Italy","authors":"Fabrizio Gherardi,&nbsp;Gabriella Magro","doi":"10.1016/j.apgeochem.2025.106480","DOIUrl":"10.1016/j.apgeochem.2025.106480","url":null,"abstract":"<div><div>At Larderello, granitic intrusions into a thinned continental crust act as the heat source for the regional thermal anomaly, and a major seismic reflector (K-horizon) extends all over the field at 3–6 km depth. The geological meaning of the K-horizon is still under debate, and some authors believe that the presence of high-P, supercritical fluids may explain this feature. In late 2017, a deep well was deepened at Larderello to search for supercritical fluids. Temperatures more than 500 °C were estimated at the bottom hole, associated with a leak-off pressure of about 30 MPa, though an exploitable reservoir was not proven. The lack of relevant fluid entries in concomitance with the crossing of the local major seismic reflectors, during the deepening of the well, raised fundamental questions about the geothermal significance of these seismic reflectors, as well as their relevance as possible targets for drilling and industrial exploitation of supercritical fluids.</div><div>To gain some insight into the super-hot horizons of the Larderello geothermal field, we present new geochemical data on gases from productive wells approaching the K-horizon, and/or closely related to granitic bodies in the southern and eastern sectors of the geothermal field. The wells considered here discharge a single gaseous phase, draining a vapor-dominated reservoir at temperatures up to 375 °C. The stable isotope signature of steam is indicative of enhanced water-rock interactions at depth (oxygen-shift), and the C–He isotope systematics allowed the identification of a predominant crustal source for CO₂. The He isotope distribution at the surface mirrored a dynamic balance between crustal- and mantle-derived fluids, as also indicated by the relative abundances of N₂, Ar, He, and Ne.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"190 ","pages":"Article 106480"},"PeriodicalIF":3.1,"publicationDate":"2025-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144298021","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deciphering the magmatic evolution of the northern lesser antilles Arc: Insights from major-trace element and Pb isotopic analyses of submarine tephra","authors":"Zhiyu Han ,&nbsp;Fei Wang ,&nbsp;Liekun Yang ,&nbsp;Wenbei Shi ,&nbsp;Yinzhi Wang","doi":"10.1016/j.apgeochem.2025.106463","DOIUrl":"10.1016/j.apgeochem.2025.106463","url":null,"abstract":"<div><div>The Lesser Antilles Arc (LAA), a subduction-driven volcanic system, exhibits pronounced geochemical and isotopic variations. Montserrat and Guadeloupe serve as key locations for elucidating magmatic processes in the northern LAA region. This study integrates marine tephra records from IODP Expedition 340 borehole U1396A with terrestrial volcanic data to reconstruct the magmatic evolution of the northern LAA over an extended timescale (∼4.5 Ma to present). Through grain morphology analysis, Pb isotopes, and major/trace element compositions of whole rocks and melt inclusions, we demonstrate that the Pb isotopic compositions of samples from Montserrat and Guadeloupe are primarily controlled by magmatic source regions rather than crustal contamination. Based on mixing models involving depleted mantle and subducted slab components, Guadeloupe exhibits greater sediment input compared to Montserrat, and such sediment contributions must be added as melt additions to the Guadeloupe magmatic system to account for its elevated Th/Nd ratios (0.36). Although significant differences in sediment contributions exist between Guadeloupe and Montserrat, fluid inputs show no discernible distinction. Furthermore, the contrasting Eu and Sr signatures between Guadeloupe and Montserrat are likely attributable to plagioclase accumulation rather than fundamental differences in magmatic differentiation processes. This study extends the volcanic activity history of the northern Lesser Antilles Arc back to 4.5 million years ago, filling a critical gap in previous studies that were limited to terrestrial volcanic rocks.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"190 ","pages":"Article 106463"},"PeriodicalIF":3.1,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144270224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Millimeter-scale leaf litter placement modulates carbon dioxide and methane emissions in wetlands","authors":"Hao Liu ,&nbsp;Yining Zhang ,&nbsp;Yu-Jia Cai ,&nbsp;Zi-Yan Liu ,&nbsp;Liang Li ,&nbsp;Ya-Qin Wang ,&nbsp;Xiao Shu ,&nbsp;Royston Goodacre ,&nbsp;Zheng Chen","doi":"10.1016/j.apgeochem.2025.106475","DOIUrl":"10.1016/j.apgeochem.2025.106475","url":null,"abstract":"<div><div>Flooded soils play a crucial role in global carbon cycling, acting as significant reservoirs of soil organic carbon and sources of carbon emissions. Leaf litter, especially from local vegetation, is a key contributor to soil organic carbon formation in these ecosystems, with its decomposition driving the production of carbon dioxide (CO₂) and methane (CH₄). Although numerous studies have examined the factors influencing leaf litter decomposition and associated greenhouse gas emissions, the impact of millimeter-scale variations in leaf litter placement within the soil-water interfaces (SWI) has received little attention. This study hypothesizes that even small changes in burial depth could significantly affect the emission patterns of CO₂ and CH₄. To test this hypothesis, a microcosm experiment was conducted to monitor gas fluxes and physicochemical profiles in treatments with leaf litter placed uncovered at the SWI (LU) or covered by a thin (10 mm) soil layer (LC). The results demonstrated substantial shifts in emissions: cumulative CH₄ emissions were more than doubled in the LC group (115.3 μgC) compared to the LU group (42.5 μgC), while cumulative CO₂ emissions were reduced by 25 % in the LC group (77 mgC) versus the LU group (103 mgC). Consequently, the overall global warming potential over a 20-year horizon (GWP20) was 13.2 % lower for the LC treatment (280.7 mgCO₂e) compared to the LU treatment (323.3 mgCO₂e). These findings advance our understanding of wetland carbon dynamics by revealing that a millimeter-scale change in leaf litter placement significantly alters the spatiotemporal patterns and partitioning of CO₂ and CH₄ emissions, highlighting the critical role of micro-scale heterogeneity in regulating greenhouse gas fluxes. Moreover, our results demonstrate a decoupling of CO₂ and CH₄ responses to this small-scale environmental variation, ultimately leading to a reduction in overall global warming potential despite increased methane release.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"190 ","pages":"Article 106475"},"PeriodicalIF":3.1,"publicationDate":"2025-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144322514","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrogenesis and prospecting implications of early Permian Daqishan plutons in the Beishan region, southern Central Asian Orogenic Belt, NW China: constraints from zircon U–Pb geochronology and petrogeochemistry","authors":"Yu Liu ,&nbsp;Biao Jiang ,&nbsp;Jichang Zhao ,&nbsp;Peibin Xu ,&nbsp;zongfu Fan ,&nbsp;Yinding Zhang ,&nbsp;Xudong Zhu","doi":"10.1016/j.apgeochem.2025.106461","DOIUrl":"10.1016/j.apgeochem.2025.106461","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The Beishan Orogenic Belt, as a critical component of the Central Asian Orogenic Belt (CAOB), holds pivotal significance for understanding the tectonic evolution of the CAOB. The Beishan region records multiphase tectono-magmatic events spanning from the Proterozoic to the Mesozoic. Magmatic flux peaked during the Early Paleozoic and Early Mesozoic, accompanied by the formation of numerous Cu–Ni and Cu–Au deposits. Early Permian magmatic rocks in the Beishan region exhibit restricted spatial distribution and have a relatively lower degree of research. This study integrates geochronological, petrochemical, and zircon geochemical analyses of Permian plutons exposed in the Daqishan area, Beishan, Gansu Province. Research on the monzogranite (274.1–279.6 Ma), quartz diorite (271.8 Ma), and dacite porphyry (273.2–274.1 Ma) from the Yin'aoxia and Luotofang areas in the Daqishan region has revealed that the zircon U–Pb ages of these rocks are relatively concentrated. This indicates that there was a relatively intense magmatic activity in the Daqishan area during the Early Permian (between 270 and 280 Ma), with an emplacement sequence of monzogranite → dacite porphyry → quartz diorite. The monzogranite exhibits high SiO&lt;sub&gt;2&lt;/sub&gt; (69.5–78.1 wt%), Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; enrichment (11.9–14.3 %), and low CaO (0.6–3.7 %) and TiO&lt;sub&gt;2&lt;/sub&gt; (0.1–0.4 %), classifying as calc-alkaline to high-K calc-alkaline series. The dacite porphyry shows moderate SiO&lt;sub&gt;2&lt;/sub&gt; (69.0–71.0 wt%), low K&lt;sub&gt;2&lt;/sub&gt;O (0.7–2.8 wt%), elevated Na&lt;sub&gt;2&lt;/sub&gt;O (4.9–5.3 wt%) and Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; (14.4–15.0 wt%), belonging to tholeiitic to calc-alkaline series. The quartz diorite displays lower SiO&lt;sub&gt;2&lt;/sub&gt; (63.9–69.0 wt%) but higher Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; (14.5–17.3 wt%), TFe&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; (3.5–4.1 wt%), MgO (1.1–1.6 wt%), and CaO (2.7–2.9 wt%), characterized by Na-enrichment and classified as tholeiitic-calc-alkaline series. Together with the monzogranite, both are classified as I-type granites. All three rock types have A/CNK &gt;1.1 and A/NK &gt; 1.1, indicating their peraluminous nature. These rocks exhibit volcanic arc signatures and are interpreted as post-collisional products derived from deep crustal melting maybe with mantle contribution and subduction-related fluid metasomatism. Zircon crystallization temperatures decrease sequentially from quartz diorite to dacite porphyry to monzogranite. The Ce&lt;sup&gt;4+&lt;/sup&gt;/Ce&lt;sup&gt;3+&lt;/sup&gt; ratios (monzogranite: 57.17; quartz diorite: 47.42; dacite porphyry: 75.25) suggest low oxygen fugacity (&lt;em&gt;f&lt;/em&gt;O&lt;sub&gt;2&lt;/sub&gt;) conditions for all three rock types. The Early Permian magmas in Daqishan are highly differentiated (whole-rock SiO&lt;sub&gt;2&lt;/sub&gt; &gt;70 wt%) with low &lt;em&gt;f&lt;/em&gt;O&lt;sub&gt;2&lt;/sub&gt;, water-poor signatures (V/Sc &lt; 9). Minor sphalerite grains observed in thin sections suggest that the intrusions underwent post-magmatic processes. These characteristics indicate that the Early Permian ","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"190 ","pages":"Article 106461"},"PeriodicalIF":3.1,"publicationDate":"2025-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144262397","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Isotopic signaling and environmental significance of cave waters in a heavily rocky desertification area","authors":"Ju Ni ,&nbsp;Yurong Mu ,&nbsp;Dayun Zhu ,&nbsp;Jialu Wang ,&nbsp;Yurong Han ,&nbsp;Yingshan Zhao ,&nbsp;Ning Yang ,&nbsp;Juanfang Du","doi":"10.1016/j.apgeochem.2025.106468","DOIUrl":"10.1016/j.apgeochem.2025.106468","url":null,"abstract":"<div><div>Cave systems are important tools for inversion of rock desertification. However, the complexity of the climate system, the long-term nature of cave sediment accumulation and the spatial and temporal heterogeneity of karst geologic processes allow the original signals to be altered during transmission. In this work, the isotopic values and environmental parameters of atmospheric precipitation, plant water, soil water, cave drip water and underground river outflow water in the Guizhou karst cave system are monitored in situ on a monthly scale, and the processes of water migration and change are explored in detail. The results showed that precipitation has a significant regulatory effect on the physicochemical properties of the cave microenvironment, and cave drip water exhibits a Ca²⁺•Mg²⁺-HCO₃^- hydrochemical type. Atmospheric precipitation is the main water source in the study area, except for plant water isotopes, the remaining water bodies are characterized by seasonal changes. The lag times of the water bodies in the cave system significantly differ during the transmission process, ranging from 2 d to 1 year, which is closely related to the mechanism of water accumulation and release in typical karst landscape areas. The spatial and temporal distributions of water vapor sources, as well as seasonal variations in temperature and precipitation, significantly influence the isotopic changes in water bodies in the study area. Overall, this study provides a systematic study on the migration and transformation process of water bodies in Guizhou karst caves, which provides a new approach and perspective for an improved understanding of hydrological processes and climate change in karst areas.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"190 ","pages":"Article 106468"},"PeriodicalIF":3.1,"publicationDate":"2025-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144270223","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tracing organic matter sources in upland lakes of southeastern Amazonia: Insights from a Bayesian mixing model","authors":"Luiza Santos Reis ,&nbsp;José Tasso Felix Guimarães ,&nbsp;Prafulla Kumar Sahoo ,&nbsp;Alessandro Sabá Leite ,&nbsp;Lourival Tyski ,&nbsp;Markus Gastauer","doi":"10.1016/j.apgeochem.2025.106464","DOIUrl":"10.1016/j.apgeochem.2025.106464","url":null,"abstract":"<div><div>This study investigates organic matter (OM) sources in upland lakes within the Carajás and Araguaia regions, in the southeastern Amazonia. Focusing on lakes developed on lateritic crusts, the research encompasses different types of lake basins to better understand variations in OM sources, using a Bayesian mixing model (MixSIAR), based on a dataset of carbon isotopes (δ¹³C) and C:N ratio from sediment cores. Our results underscore the influence of local vegetation and lake basin evolution on OM composition, revealing some similarities between the two regions. For instance, in the Carajás region, active lakes (AM, LV2, LTI, and LSL) exhibit higher proportions of OM sourced from C3 plants, macrophytes, and soils compared to filled lakes (R5, ST02, LB3, LB4, and LTM). While, filled lakes in the Araguaia region demonstrate greater contributions of OM from C3 plants, phytoplankton, and soils. The Bayesian mixing model effectively estimates OM contributions and tracks historical changes in sediment profiles, offering a robust framework for similar studies in tropical lake ecosystems. Overall, this research enhances our understanding of OM dynamics in tropical upland lakes and lays the groundwork for future investigations into environmental change and management strategies in these distinct regions of the Amazon ecosystem.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"190 ","pages":"Article 106464"},"PeriodicalIF":3.1,"publicationDate":"2025-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144254173","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deposition and early diagenesis of terrestrial plant-derived terpenoids in deep-sea sediments in the northwestern Pacific ocean off Japan","authors":"Ken Sawada ,&nbsp;Madoka Kobayashi","doi":"10.1016/j.apgeochem.2025.106462","DOIUrl":"10.1016/j.apgeochem.2025.106462","url":null,"abstract":"<div><div>Terrestrial plant-derived terpenoids (TPTs) in deep-sea surface to subsurface sediments of the northwestern Pacific were investigated at two sites along the Kuroshio Current and in the gyre over the Nishishichitou Ridge following a latitudinal transect at 138°36′E (Sites LM3 and LM5P), as well as the Japan Trench off the Sanriku coast of northeastern Japan (Site LM8). Cadalene, oleanene, and retene were detected as geoterpenoids in all cores. Possible sources of these geoterpenoids are soil materials, which were attached to clay minerals with or without early diagenetic alteration of precursor bioterpenoids. Friedelin and dehydroabietic acid (DAA) were identified as major functionalized TPTs, or bioterpenoids, in all core samples. Concentrations of TPTs in the core-top samples from all study sites varied with distance from land, sediment lithology, and upland vegetation. Bioterpenoids in the TPTs are relatively abundant at all sites. These results suggest that TPT biomarkers are mainly transported to the open ocean as bioterpenoids. The ratio of friedelin to DAA in core-top samples clearly varied (2.53 in LM3, 1.12 in LM5P, and 0.95 in LM8) depending on upland vegetation, and therefore the bioterpenoid ratio is proposed to be a (paleo)vegetation indicator. Vertical profiles of TPT concentrations showed pronounced variability. The concentrations of oleanene and retene generally decreased with depth in all cores, indicating that these compounds are labile in surface to subsurface sediments. However, the cadalene concentration increased or decreased slightly with depth in cores from the Nishishichitou Ridge, indicating that cadalene is a refractory compound. The DAA concentration decreased markedly with depth, and the gradients were similar in all cores. Thus, DAA was effectively decomposed and behaved as a typical labile compound. On the other hand, the friedelin concentration increased slightly with depth in the core collected off the Sanriku coast. Thus, friedelin appeared to behave as a refractory compound in surface to subsurface sediments despite being a bioterpenoid.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"190 ","pages":"Article 106462"},"PeriodicalIF":3.1,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144240745","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Complexation of Cm(III) with monosilicic acid in chloride media","authors":"Sema Özyagan ,&nbsp;Kim J. Warth ,&nbsp;Thomas Sittel ,&nbsp;Petra J. Panak","doi":"10.1016/j.apgeochem.2025.106465","DOIUrl":"10.1016/j.apgeochem.2025.106465","url":null,"abstract":"<div><div>In this work, we present a detailed complexation study of Cm(III) with monosilicic acid in a NaCl medium at low to medium ionic strengths (I_m = 0.01–3.00 m). The complexation has been monitored using time-resolved laser fluorescence spectroscopy (TRLFS) in the pH_m range of 4–6. The results show that the formation of the monosilicate complex, [Cm(H₃SiO₄)]²⁺, is decreased with increasing ionic strength, leading to vast changes in the complex stability constant. Using the Specific Ion Interaction Theory (SIT), we were able to determine the complex stability constant at ionic strength I_m = 0 with <span><math><mrow><mi>log</mi><mspace></mspace><msubsup><mi>K</mi><mi>m</mi><mn>0</mn></msubsup></mrow></math></span> = 8.1 ± 0.8 and the binary ion-ion interaction coefficient ε ([Cm(H₃SiO₄)]²⁺,Cl⁻) = 0.40 ± 0.04. Additionally, we studied the complexation at elevated temperatures at low to medium ionic strength. Using the van't Hoff equation, <span><math><mrow><msub><mo>Δ</mo><mi>r</mi></msub><msubsup><mi>H</mi><mi>m</mi><mn>0</mn></msubsup></mrow></math></span> = 16.4 ± 0.5 kJ mol⁻¹, <span><math><mrow><msub><mo>Δ</mo><mi>r</mi></msub><msubsup><mi>S</mi><mi>m</mi><mn>0</mn></msubsup></mrow></math></span> = 210 ± 21 J K⁻¹ mol⁻¹ and the free Gibbs Energy <span><math><mrow><msub><mo>Δ</mo><mi>r</mi></msub><msubsup><mi>G</mi><mi>m</mi><mn>0</mn></msubsup></mrow></math></span> = − 46.2 ± 5 kJ mol⁻¹ have been determined. These results show that the complexation reaction is endothermic and driven by an increase of entropy. These novel results obtained in a wide range of various ionic strengths are very important for the modeling of actinide behavior under near-field conditions of a nuclear waste repository in clay formations containing pore and formation waters with increased ionic strength.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"190 ","pages":"Article 106465"},"PeriodicalIF":3.1,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144240744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"CAFM: a freeware for geochemical data processing and concentration–area fractal modeling and its application for identifying uranium anomalies of different genesis","authors":"Jun-Ting Qiu ,&nbsp;Jiang-Kun Li ,&nbsp;Hong-Xu Mu ,&nbsp;Xin-Min Rui ,&nbsp;Yun-Han Yang ,&nbsp;Liang Qiu","doi":"10.1016/j.apgeochem.2025.106445","DOIUrl":"10.1016/j.apgeochem.2025.106445","url":null,"abstract":"<div><div>We present a freeware named CAFM, which is specifically designed for geochemical data interpolation, computation, and concentration-area (C-A) fractal modeling. Additionally, we propose a Fixed Scale Moving Average Error (FSMAE) method to achieve rapid and automatic classification of C-A fractal populations. This freeware has been successfully applied to identify U anomalies and distinguish their genesis based on surface concentrations of U, Th, and K derived from airborne gamma data. The Yingen area in the southeastern part of the Bayingobi Basin serves as the research focus of our study. In this area, we utilized the breakpoints between adjacent straight-line segments on Log-Log plots of C-A relationships for U, Th, and K to differentiate elemental populations. These separated datasets were subsequently analyzed using the C-A fractal method, and the results were compared with geological observations. The comparison reveals that U populations are highly effective in identifying U enrichment anomalies, particularly surface mineralization anomalies. In contrast, Th populations can indicate the presence of intrusive rocks and hydrothermal activities. However, K populations provide limited geological information due to their susceptibility to surface sediment influences. Furthermore, with the aid of CAFM, we proposed a U/Th bimetal index, which has been demonstrated to effectively distinguish between magmatic, hydrothermal, and sedimentary –hosted U enrichment anomalies. Utilizing this index, we discovered a new area with sedimentary-related U anomalies in the southeastern part of the Yingen area, highlighting its potential value for future exploration efforts. Our study has shown that integrating airborne gamma data with C-A fractal modeling can effectively identify U anomalies and determine their genesis. The CAFM software and the FSMAE method offer valuable tools for U exploration.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"189 ","pages":"Article 106445"},"PeriodicalIF":3.1,"publicationDate":"2025-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144221475","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}