Applied Geochemistry最新文献

{"title":"Destination of metals transported by hydrocarbon fluids in lead-zinc mineralization of the ediacaran strata in the central Sichuan Basin, China","authors":"Lianqiang Zhu ,&nbsp;Zezhang Song ,&nbsp;Guangdi Liu ,&nbsp;Peng Cheng ,&nbsp;Haifeng Gai ,&nbsp;Hui Tian","doi":"10.1016/j.apgeochem.2025.106319","DOIUrl":"10.1016/j.apgeochem.2025.106319","url":null,"abstract":"<div><div>Hydrocarbon fluids play crucial roles in Pb–Zn mineralization, yet the contribution of metals from hydrocarbon fluids remains a key research topic. Based on petrographic analyses of sulfide minerals and solid bitumen, combined with LA-ICP-MS analysis of sphalerite, this study investigates hydrocarbon-phase evolution during metal mineralization and the composition of trace elements and rare earth elements (REEs) in sphalerite formed in various hydrocarbon phases. The study focuses on the classical lead-zinc mineralization belt of the Yangtze Block, South China. By comparing the composition of trace elements and REEs in solid bitumen and sphalerite across different hydrocarbon phases, the hydrocarbon contribution to metal mineralization is assessed. The results indicate that hydrothermal activity induced oil cracking in the reservoir, leading to the formation of two distinct types of sphalerites before and after oil cracking, reflecting environments with and without crude oil. Sphalerites formed before and after oil cracking exhibit formation temperatures of 132–252 °C and 88–202 °C, respectively. Both sphalerites share identical ore-forming fluid sources with similar sulfur and oxygen fugacity and the weak difference in their trace element compositions was caused by the decreasing fluid temperature, suggesting that crude oil did not significantly contribute to ore-forming metals. Moreover, the compositions of trace elements and REEs in both sphalerites differ from those of solid bitumen from oil cracking, further supporting that the metals for mineralization were not from crude oil. Instead, hydrothermal fluids induced rapid oil cracking, causing metals like Pb and Zn in crude oil to precipitate with solid bitumen without mineralization. This study provides direct evidence that metals transported by hydrocarbons precipitate with solid bitumen during oil cracking and do not contribute to Pb–Zn mineralization in medium-to high-temperature hydrothermal systems, disproving previous assumption that inferred metal involvement in mineralization solely based on high metal concentrations in hydrocarbon fluids.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"182 ","pages":"Article 106319"},"PeriodicalIF":3.1,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143454658","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":"Microbial influence on fast-growing iron oxyhydroxide-based speleothems in the acidic environment of Sitarjevec mine, Slovenia","authors":"Minka Kovač ,&nbsp;Marjan Bele ,&nbsp;Boris Orel ,&nbsp;Anton Meden ,&nbsp;Mohor Mihelčič","doi":"10.1016/j.apgeochem.2025.106313","DOIUrl":"10.1016/j.apgeochem.2025.106313","url":null,"abstract":"<div><div>This study investigates the mineralogical and morphological structure of iron oxide/hydroxide speleothems formed in the acid mine drainage (AMD) of the abandoned Sitarjevec mine near Litija in Slovenia (EU). These speleothems grow in the mine shafts under stable environmental conditions (complete darkness, a constant temperature of 10 °C and water with a pH value of 2.2–3.3), but show rapid growth of up to 5 cm/year. Using ion chromatography (IC) and carbon analysis, we detected phosphates, sulfates and carbon in the water dripping from the ceiling onto the stalagmite, indicating that bacteria can indeed colonize the surface of the stalagmite. SEM measurements provided evidence of the bacterial population and the morphology of the colored mineral (<em>precipitate</em>), closely resembling mineralogy of schwertmannite, which was formed in the mine water stored for several months under conditions normally found in the mine. Comparisons of the morphology, elemental composition and structure determined for different locations on the stalagmite (inner/outer part) with the morphological characteristics of the <em>precipitate</em> obtained by SEM/EDS measurements in combination with the analysis of XRD patterns and ATR-IR spectra showed the presence of bacteria and schwertmannite in the form of a hedge-hog particles. Analysis of the ATR-IR spectra of the outer part of the stalagmite and the mine water precipitate confirmed the presence of schwertmannite and a small amount of goethite. Goethite was predominantly present in the inner part of the stalagmite, but the ATR-IR spectra showed no evidence of schwertmannite or bacteria. From the XRD spectra, using the Rietveld method, it was confirmed that the outer part of the stalagmite contains mainly goethite, while the amount of schwertmannite did not exceed 17 wt%, which is also consistent with the results of the infrared spectra analysis. For the interior of the stalagmite, the Rietveld analysis showed no schwertmannite but only goethite.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"182 ","pages":"Article 106313"},"PeriodicalIF":3.1,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143454611","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":"Thermally-induced release of arsenic from minerals and phases relevant to polluted natural systems affected by wildfires","authors":"Marek Tuhý ,&nbsp;Vojtěch Ettler ,&nbsp;Jan Rohovec ,&nbsp;Kateřina Stonová ,&nbsp;Šárka Matoušková ,&nbsp;Petr Drahota ,&nbsp;Andrew L. Sullivan","doi":"10.1016/j.apgeochem.2025.106318","DOIUrl":"10.1016/j.apgeochem.2025.106318","url":null,"abstract":"<div><div>Fire-induced arsenic (As) emission from contaminated biomass or soil is dependent on its solid-phase speciation. To quantify the nature of this release, environmentally relevant As-bearing compounds (sulfides, sulfosalts, As-oxides, arsenates, As-doped Fe-oxyhydroxides and organic material) were experimentally heated with a linear temperature increase (25–800 °C) and simultaneous detection of As and other emitted elements. Organic As-bearing materials (fungi, dimethylarsinic acid-DMAA) exhibited the peak of As release at the lowest temperatures of 275–350 °C, followed by arsenolite (As₂O₃) with the maximum As emission at ∼400 °C. Realgar (As₄S₄) and orpiment (As₂S₃) exhibited the maximum As release at 425–450 °C, while enargite (Cu₃AsS₄) and arsenopyrite (FeAsS) released As at much higher temperatures with emission peaks at ∼625 and &gt; 725 °C, respectively. Similarly, As-bearing Fe-oxyhydroxides emitted As at temperatures exceeding 650 °C. Arsenic emission from arsenates was rather variable and peaked at ∼700 °C for conichalcite [CaCu(AsO₄)(OH)], and scorodite (FeAsO₄·2H₂O), while for mimetite [Pb₅(AsO₄)₃Cl], it peaked towards the upper limit of the temperature range. These results suggest that typical low intensity wildland fires would affect only organically bound As and arsenolite, while higher intensity wildland fires could cause the redistribution of As from all studied phases, thereby posing a significant environmental risk of As redistribution beyond contaminated sites.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"182 ","pages":"Article 106318"},"PeriodicalIF":3.1,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143454610","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Global sensitivity analysis of reactive transport modelling for the geochemical evolution of a high-level radioactive waste repository","authors":"J. Samper ,&nbsp;C. López-Vázquez ,&nbsp;B. Pisani ,&nbsp;A. Mon ,&nbsp;A.C. Samper-Pilar ,&nbsp;F.J. Samper-Pilar","doi":"10.1016/j.apgeochem.2025.106286","DOIUrl":"10.1016/j.apgeochem.2025.106286","url":null,"abstract":"<div><div>Reactive transport models are used for the performance assessment of high-level radioactive waste repositories (HLW). Quantifying model uncertainty requires the identification of the parameters having the most significant effect on model outputs and the largest impact on prediction uncertainties. Sophisticated sensitivity analysis methods have been developed for numerical models based on the analysis of model results such as the Morris elementary effects and the High Dimensional Model Reduction (HDMR) method proposed by Sobol. VARS (Variogram Analysis of Response Surfaces) is a variance-based method to analyze the structure of a model output. Here we report the application of VARS and HDMR for evaluating the global sensitivities of the predictions of a reactive transport model of the metallic canister and bentonite buffer of a HLW repository in granitic rock. Global sensitivities are analyzed for pH, redox potential and volume of corrosion products at the canister/bentonite interface at t = 1·10⁴, 2.5·10⁴ and 5·10⁴ years. The input parameters include: the corrosion rate of the metallic canister (CR), the bentonite porewater diffusion coefficient (D_e), the groundwater flow through the granitic host rock (Q_gra), the cation exchange selectivity of Fe (K_Fe) and the solubility of magnetite (Log K). VARS and HDMR results show that the most influential input parameters for pH are CR, Q_gra and K_Fe. The sensitivity indexes of pH for parameters CR and K_Fe increase with time while that of log K of magnetite decreases. The sensitivity index of D_e, however, remains constant in time. Similar to pH, the most influential parameters for Eh are CR and Q_gra. The sensitivity indexes of Eh for CR and log K of magnetite decrease with time while that of Q_gra increases with time. The main interactions between parameters computed with HDMR indexes for pH and Eh at t = 5·10⁴ years occur between CR and Q_gra. Similar to pH and Eh, CR is the most influential parameter for the volume of corrosion products while D_e is the second most relevant. All the sensitivity indexes for the volume of corrosion products increase with time except for CR. Parameter rankings of Sobol and VARS are nearly identical.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"180 ","pages":"Article 106286"},"PeriodicalIF":3.1,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143177854","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Predicting salinity and alkalinity fluxes of U.S. freshwater in a changing climate: Integrating anthropogenic and natural influences using data-driven models","authors":"Beibei E ,&nbsp;Shuang Zhang ,&nbsp;Elizabeth Carter ,&nbsp;Tasmeem Jahan Meem ,&nbsp;Tao Wen","doi":"10.1016/j.apgeochem.2025.106285","DOIUrl":"10.1016/j.apgeochem.2025.106285","url":null,"abstract":"<div><div>Climate change is an ongoing and intensifying threat. Previous studies indicate that U.S. rivers are undergoing salinization and alkalinization driven by both natural (e.g., temperature and precipitation) and anthropogenic (e.g., population density) factors. In this study, random forest models were developed to predict how the salinity (i.e., sodium) and alkalinity fluxes from 226 U.S. rivers will vary with changing population density and climatic forcings (i.e., temperature and precipitation) from 2040 to 2100 for three socioeconomic development pathways. The models predicted a lower future sodium flux in the northern U.S., likely due to reduced winter road salting under projected warmer winter. In the southern and western U.S., where road salting is uncommon, the models predicted little or no change in future sodium flux, however, a projected warmer and drier climate might exacerbate soil salinization in these regions. The models also indicated that carbonate weathering rates are inhibited when temperatures exceed 10 °C, leading to a lower future alkalinity flux in carbonate-rich watersheds at high temperatures. In siliciclastic-dominated or organic carbon-rich watersheds, rising temperatures are associated with increased riverine alkalinity flux, likely through the acceleration of silicate weathering and decomposition of soil organic carbon. Higher precipitation and enhanced transport capacity were generally deemed to contribute to higher solute fluxes before reaching a plateau. This study underscores the urgency for policymakers and scientists to adapt strategies for managing rivers, focusing on mitigating the impacts of river salinization and shifts in riverine alkalinity driven by global warming.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"180 ","pages":"Article 106285"},"PeriodicalIF":3.1,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143178805","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Behavior of rare earth elements during the chemical weathering of two granite profiles in different climatic regions of southern China","authors":"Zihan Xia,&nbsp;Junwen Zhang,&nbsp;Na Wu,&nbsp;Meili He,&nbsp;Qi Liu,&nbsp;Zhiqi Zhao","doi":"10.1016/j.apgeochem.2025.106303","DOIUrl":"10.1016/j.apgeochem.2025.106303","url":null,"abstract":"<div><div>Granite saprolites are important hosts of rare earth elements (REE), especially in southern China. The elucidation of REE's migration and fractionation mechanisms during granite weathering allows researchers to thoroughly investigate REE deposits efficiently. This study comprehensively analyzed REE contents and distribution patterns in bulk samples obtained from two granite profiles, exposed to different climatic conditions. In both profiles, REE concentrations increased with depth, indicating downward migration (facilitated by the acidic conditions near the surface) and significant enrichment of REEs at the bottom. The distribution of REEs in the weathering profiles is highly related to mineralogical compositions (such as the role of clay minerals and Fe oxides in hosting REEs). Moreover, mineralogy also plays a crucial role in modulating REE fractionation while others affect secondarily. Substantial amounts of kaolinite and illite preferentially adsorb HREEs and LREEs, respectively; thus, the intensively weathered HZ profile, developing in a warm and humid climate, presents elevating (La/Yb)_N toward the bottom. In contrast, considering its distinct mineralogical compositions, the similar patterns of (La/Yb)_N of the WMS profile in dry and cold conditions, result from preferential retention of HREEs by chlorite or OM and significant LREEs release via epigenetic denudation. In addition, both profiles exhibited significantly positive Ce and Eu anomalies near the surface, with those in the HZ profile being more severe. The HZ profile, being exposed to warm and humid conditions, was characterized by more pronounced REE migration (61% losses of REEs during weathering) and significant (La/Yb)_N (1.24 ± 1.15, n = 15, 1sd) than the WMS profile (28% losses, 1.06 ± 30, n = 19, 1sd), which were predominantly controlled by massive clay minerals formed during extreme weathering; correspondingly, the WMS profile, with different mineralogical compositions, experienced less complete chemical weathering, wherein REE behavior would be affected by multiple factors.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"181 ","pages":"Article 106303"},"PeriodicalIF":3.1,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143403187","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":"Hydrochemical characteristics and evolution of geothermal waters in western Yunnan, China based on self-organizing map and hydrogeochemical simulation","authors":"Bo Li ,&nbsp;Guangcai Wang ,&nbsp;Fei Liu ,&nbsp;Zheming Shi ,&nbsp;Qingmin Kong ,&nbsp;Shouchuan Zhang ,&nbsp;Xin Yan ,&nbsp;Fu Liao ,&nbsp;Liang Guo ,&nbsp;Chenglong Liu","doi":"10.1016/j.apgeochem.2025.106291","DOIUrl":"10.1016/j.apgeochem.2025.106291","url":null,"abstract":"<div><div>Ascertaining the hydrochemical features of geothermal waters and their spatial distribution and the associated hydrogeochemical regimes in complex geothermal areas with intense tectonic and hydrothermal activities is important for hydrothermal resource management, but still remains difficult. Western Yunnan, located in the Mediterranean–Himalayan geothermal zone and collision zone between the Indian and Eurasian plates with diverse hydrothermal activities and temperatures, is an ideal area for such study, which was realized by utilizing self-organizing map method (SOM), hydrogeochemical simulations and solute geothermometers in this study. The combined results show that four geothermal water groups with different hydrogeochemical features were discerned. The Group 1 geothermal waters are HCO₃–Na type, and they have relatively high reservoir temperatures ranging from 170 to 200 °C and moderate d-excess (d-excess = δ²H-8∗δ¹⁸O), whose major components originate from alkaline feldspar dissolution during the deep circulation. The hydrogeochemical type of Group 2 is HCO₃–Ca–Mg with the largest d-excess and the lowest reservoir temperatures ranging from 50 to 100 °C, and carbonate mineral dissolutions are the source of their major components. Group 3 is characterized by high acidity and abundant SO₄, which is from shallow groundwaters heated by high-temperature steam comprising H₂S, with the smallest d-excess due to strong hydrothermal alteration. Group 4 (Cl–HCO₃–Na/HCO₃–Cl–Na type) possesses a smaller d-excess and the highest reservoir temperatures ranging from 160 to 240 °C, resulting from deep NaCl-type parent fluid replenishment under the influence of magmatic input. During the upward migration, alkaline feldspar dissolution followed by extensive steam loss induces elevated concentrations. Furthermore, CO₂ degassing is another vital process that affects geothermal waters evolution at high temperatures. In this study, coupling SOM network clustering and hydrogeochemical simulation sheds new light on the extraction of hydrogeochemical characteristics and evolution information.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"181 ","pages":"Article 106291"},"PeriodicalIF":3.1,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143241658","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":"Chemodiversity of coastal seawater dissolved organic matter shaped by wastewater treatment plant effluent in Tokyo Bay, Japan","authors":"Yanhui Cheng ,&nbsp;Jibao Liu ,&nbsp;Manabu Fujii ,&nbsp;Qing-Long Fu","doi":"10.1016/j.apgeochem.2025.106292","DOIUrl":"10.1016/j.apgeochem.2025.106292","url":null,"abstract":"<div><div>The wastewater treatment plants (WWTPs) effluent can affect the chemodiversity of dissolved organic matter (DOM) in the aquatic systems. In this study, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was employed to reveal the effluence of WWTPs on the chemodiversity of coastal seawater DOM in Tokyo Bay, Japan. The average number of compounds identified in the background group with minor anthropogenic perturbation was 63.9% for the coastal seawater samples. Compared with the background samples, CHOS compounds were the predominant fraction of DOM in some coastal seawater receiving vast effluent from WWTPs. Additionally, the artificial sweetener sucralose was identified in coastal seawater samples. The intensity percentages of CHOS molecules in the coastal seawater linearly increased with the number of received WWTPs (<em>R</em>² = 0.786, <em>P</em> &lt; 0.05). These findings suggested that DOM molecular composition in Tokyo Bay coastal seawater had been highly influenced by upstream WWTPs effluents and highlighted the great potential of FT-ICR MS in tracing anthropogenically derived molecular signatures in the environments.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"180 ","pages":"Article 106292"},"PeriodicalIF":3.1,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143177926","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":"Chemostratigraphy of the Cretaceous Hue Shale in Arctic Alaska: Exploring paleoceanographic controls on trace element enrichment, organic matter accumulation, and source-rock evolution","authors":"Palma J. Botterell ,&nbsp;Margaret M. Sanders ,&nbsp;David W. Houseknecht ,&nbsp;Richard O. Lease ,&nbsp;William A. Rouse ,&nbsp;Katherine J. Whidden ,&nbsp;Julie A. Dumoulin ,&nbsp;Rebecca A. Smith ,&nbsp;Christina A. DeVera ,&nbsp;Brett J. Valentine","doi":"10.1016/j.apgeochem.2024.106277","DOIUrl":"10.1016/j.apgeochem.2024.106277","url":null,"abstract":"&lt;div&gt;&lt;div&gt;We document chemostratigraphy in an outcrop of late Albian to early Campanian (∼103–82 Ma) marine source rocks to better understand paleoenvironmental controls on trace element (TE) enrichment and organic matter accumulation in the distal Colville foreland basin of Arctic Alaska and how those drivers are linked to arc volcanism and successions of Cretaceous oceanographic and climatic biogeochemical events. This unique, 113-m-thick section of Cretaceous Hue Shale deposited during a series of previously undocumented Arctic Cretaceous oceanic anoxic events (Lease et al., 2024) is the only known exposure of thermally immature (0.48–0.52% R&lt;sub&gt;o&lt;/sub&gt;, random vitrinite reflectance) Hue Shale in Arctic Alaska. Strata comprise mainly clay-rich mudstone with elevated total organic carbon (TOC) and hydrogen index values reaching 26.3 wt% (mean = 7.5 wt%) and 689 mg hydrocarbon (HC)/g TOC (mean = 385 mg HC/g TOC), respectively. Maceral composition consists predominantly of fluorescent amorphous organic matter, with abundant brightly fluorescent alginite, including &lt;em&gt;Tasmanites&lt;/em&gt;, acritarchs, and &lt;em&gt;Leiosphaeridia&lt;/em&gt;. Discrete layers of volcanic ash (preserved as bentonite) are present throughout the section and provide quantitative age control based on U–Pb dates.&lt;/div&gt;&lt;div&gt;Chemostratigraphic trends are investigated to advance our understanding of local oceanographic conditions and controls on stratigraphic and temporal heterogeneity of Brookian source rocks. Concurrent sedimentary enrichment in Mo, U, V, Pb, and Cu across the Albian–Cenomanian boundary of the exposed basal gamma-ray zone, may reflect anoxic to euxinic benthic redox conditions favoring organic matter accumulation and preservation. Fluctuating degrees of anoxia-euxinia are inferred throughout the overlying Hue Shale succession, reflected by varying patterns of TE enrichment and TE–TOC covariation. Elevated C&lt;sub&gt;org&lt;/sub&gt;/P molar ratios (&gt;250) across most of the section, with several values exceeding 690, signify that enhanced biological productivity is sustained throughout deposition. Enhanced productivity, recorded by both C&lt;sub&gt;org&lt;/sub&gt;/P and excess Ba, also parallels increases in source rock richness (elevated TOC and S&lt;sub&gt;2&lt;/sub&gt; values) during the late Albian–early Cenomanian and late Cenomanian&lt;em&gt;–&lt;/em&gt;Turonian.&lt;/div&gt;&lt;div&gt;Enhanced productivity and variations in oceanic circulation/stratification likely both drove changes in benthic redox conditions that favored organic carbon accumulation and preservation. Increased continental arc volcanism (e.g., Okhotsk–Chukotka volcanic belt) and High Arctic Large Igneous Province magmatic eruptions throughout the Cretaceous, inferred to have influenced nutrient cycling and local aqueous nutrient availability, also have been invoked as potential drivers of organic carbon burial and source-rock development across the sedimentary sequence. Results presented here document the organic-rich and oil-prone source-rock quality of","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"180 ","pages":"Article 106277"},"PeriodicalIF":3.1,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143177853","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Origin of bentonite deposits in the Eastern Rif Belt (Morocco): Constraints from new mineralogical, geochemical and stable isotopic data","authors":"Othmane Lamrani ,&nbsp;Abdellah Boushaba ,&nbsp;Mohammed Belkasmi ,&nbsp;Mohamed Akouibaa ,&nbsp;Ömer Bozkaya ,&nbsp;Ali Azdimousa ,&nbsp;Fouad Taous ,&nbsp;Mimoun Aalaoul ,&nbsp;Samir Samaoui","doi":"10.1016/j.apgeochem.2025.106287","DOIUrl":"10.1016/j.apgeochem.2025.106287","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The eastern Rif Belt in Morocco represents an important economic region in North Africa due to its extensive bentonite deposits. This study aimed to elucidate the formation processes and mechanisms of Providencia bentonite deposits, classified as yellow and white bentonites, surrounding the Upper Miocene rhyolitic Tidiennit Massif. Multidisciplinary approaches, integrating structural, lithostratigraphic, mineralogical, petrographical and geochemical analyses have been utilized to examine the properties of the bentonites and precursor (host) rocks. The X-ray diffraction analyses of the tuffs, perlites and rhyolites show that the presence of smectite, feldspar, amorphous silica (Opal-A and Opal-CT) and biotite in tuffs, feldspar, quartz, cristobalite and pyroxene in rhyolites, and amorphous silica, pyroxene, feldspar in perlites. The clay fraction patterns of yellow and white bentonites indicate the bentonites are composed of pure or nearly pure dioctahedral (Al-rich) smectite minerals. The characteristic bands observed in Fourier transform infrared spectroscopic analyses were also confirmed the presence of Al-rich smectites in the bentonites. The thermogravimetric and differential thermal analysis data show a total mass loss of 15.7% and 18.13%, and endothermic peaks of 698 °C and 678 °C representing the smectite from white and yellow bentonite, respectively. The major element concentrations indicate the sub-alkaline series, and the composition of dacite to rhyolite for tuffs, whereas rhyolite for perlites and rhyolites. The alteration index (AI) and the chlorite-carbonate-pyrite index (CCPI) data suggest a clear trend towards argillization of the volcanic tuffs surrounding the Tidiennit Massif. The chemical compositions of bentonites and precursor (host) rocks show an increase in Fe&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;, MgO, Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;, TiO&lt;sub&gt;2&lt;/sub&gt;, P&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt;, Nb, Y, Zn, Zr, total &lt;em&gt;REE&lt;/em&gt; from rhyolites-perlites via tuffs to bentonites. The immobile element (Zr, Ti, Nb, Y in ppm) compositions of the bentonites represent a subduction zone (syn-collision and volcanic arc granites) environment. Bentonites and host rocks exhibit a negative Eu anomaly with respect to the chondrite and upper continental crust composition indicating the chemical fractionation from the rhyolitic/rhyodacitic source rocks through removal of Eu by plagioclase fractionation in a reducing environment. The structural formulas of smectites in yellow and white bentonites indicate the montmorillonite-beidellite series of smectite composition. The δ&lt;sup&gt;18&lt;/sup&gt;O and δD isotope data of the smectites show that bentonitization was formed as a result of hydrothermal alteration (hypogene origin) of tuffs interacting with hydrothermal fluids at temperature conditions of 127–165 °C for yellow bentonites and 153–174 °C for white bentonites. Oxygen and hydrogen isotope compositions of smectite-forming fluids indicated that yellow bentonites formed ","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"180 ","pages":"Article 106287"},"PeriodicalIF":3.1,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143179332","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}