Applied Geochemistry最新文献

{"title":"Mercury isotopes from ferromanganese rocks fingerprint metal recycling by intracontinental basinal fluids","authors":"Alexandre Raphael Cabral ,&nbsp;Runsheng Yin ,&nbsp;Di Chen ,&nbsp;Stephanie Lohmeier ,&nbsp;Tiago Henrique DeFerreira ,&nbsp;Francisco Javier Rios ,&nbsp;Bernd Lehmann","doi":"10.1016/j.apgeochem.2025.106583","DOIUrl":"10.1016/j.apgeochem.2025.106583","url":null,"abstract":"<div><div>Mercury isotopes, capable of mass-dependent fractionation (δ²⁰²Hg) and mass-independent fractionation (Δ¹⁹⁹Hg), are particularly useful in tracing ore-forming sources and metallogenic pathways in mineral deposits. Here, we apply Hg isotopes to elucidate the formation of ferromanganese sedimentary rocks in a Cenozoic, graben-like sedimentary basin. The basin was a historically important Mn supplier within the Archaean–Palaeoproterozoic Quadrilátero Ferrífero of Minas Gerais, Brazil. The rocks are enriched in Hg, up to about 9700 ppb, and have negative Δ¹⁹⁹Hg down to −0.39‰. The negative Δ¹⁹⁹Hg signals are consistent with the signature of terrestrial reservoirs, suggesting that the ferromanganese enrichment received Hg from terrestrial sediments, in consonance with the intracontinental setting of the basin. Ferromanganese samples with more than 5% Mn show a positive correlation of Fe/Mn vs. δ²⁰²Hg, which likely represents intracontinental basinal fluids with positive δ²⁰²Hg signals of dissolved Hg(II). Mercury was leached from terrestrial sediments and preferentially sequestered by Fe-oxide precipitates, mostly goethite. The transfer of Hg, traced by its isotopes, to ferromanganese concentrations testifies to metal recycling by Cenozoic basinal fluids within the Archaean–Palaeoproterozoic Quadrilátero Ferrífero.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"194 ","pages":"Article 106583"},"PeriodicalIF":3.4,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145265180","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":"Provenance and geogenic modes of high-fluoride groundwater occurred in various sedimentary environments: constraints of hydrogeology and hydrogeochemstry","authors":"Guojie Feng ,&nbsp;Zhiqin Li ,&nbsp;Chunli Su ,&nbsp;Xianjun Xie ,&nbsp;Weili Ge ,&nbsp;Yiqun Gan ,&nbsp;Zhaohui Luo ,&nbsp;Kunfu Pi ,&nbsp;Hongjie Pan ,&nbsp;Yanhui Gao ,&nbsp;Yanmei Yang","doi":"10.1016/j.apgeochem.2025.106624","DOIUrl":"10.1016/j.apgeochem.2025.106624","url":null,"abstract":"<div><div>Hetao Plain is one of three major agricultural irrigation areas in China, where groundwater salinization and associated high fluoride concentrations (F⁻ &gt;1.5 mg/L) pose serious threats to ecological sustainable development. A total of 487 groundwater samples were collected from the Hetao Plain to explore the spatial variability, sources, and dominant hydrogeochemical processes controlling groundwater F⁻ enrichment. Furthermore, the genetic modes of high F⁻ groundwater occurring in different hydrogeological units were clarified and compared using hydrochemical analysis and factor analysis. The results show groundwater F⁻ concentrations range from &lt;0.05 mg/L (detection limit) to 7.83 mg/L, with 46.6 % and 7.9 % of samples in the Qiantao Plain and Houtao Plain, respectively, having concentrations exceeding 1.5 mg/L. High F- groundwater exhibited high spatial variability and occurred in shallow aquifers with depth less than 60 m, which is mainly regulated by the fluoride sources and hydrogeological conditions. Sediments in the Houtao Plain mainly originate from alluvial deposits of the Yellow River, whereas in the Qiantao Plain originate from fluoride-rich bedrocks/minerals of the eastern Yin Mountains. Different material sources are the primary factor causing spatial variability of groundwater F⁻ concentrations in the two plains. High F⁻ groundwater in the Qiantao Plain is characterized by leaching-enrichment type, while in the Houtao Plain is dominated by leaching-enrichment type in the piedmont alluvial-pluvial fan (Zone C) and a combination of leaching-enrichment type and evaporation-concentration type in the riparian zone of the Yellow River and north margin of the Ordos Plateau (Zone E), respectively. The vital factors responsible for F⁻ enrichment are abundant sources, favorable hydrogeological conditions, alkaline soda water type, and strong evaporation. The study clearly distinguished the difference in sediment material sources between the two adjacent plains, achieving a deepening understanding of the genetic models from the basin to specific hydrogeological units. These findings can provide a theoretical basis for safe groundwater supply in arid regions.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"195 ","pages":"Article 106624"},"PeriodicalIF":3.4,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145518707","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":"Geochemical evaluation of fluid-rock interactions between high-pH hydraulic fracturing fluid and carbonate-rich reservoirs: A case study of the Niobrara Formation, Denver-Julesburg Basin, Colorado, USA","authors":"Olivia Terry ,&nbsp;Derek Caro ,&nbsp;Tianxiao Shen ,&nbsp;Shaina Kelly ,&nbsp;Janet Dewey ,&nbsp;John P. Kaszuba","doi":"10.1016/j.apgeochem.2025.106613","DOIUrl":"10.1016/j.apgeochem.2025.106613","url":null,"abstract":"<div><div>Unconventional hydrocarbon reservoirs are commonly hydraulically fractured with acidified fresh water. Most development of unconventional reservoirs occurs in rural environments with little surface water, meaning fresh water is transported from other regions or is extracted from local groundwater and aquifers. Use of formation fluid extracted from active or depleted reservoirs has been proposed, however formation fluid is notoriously high in total dissolved solids, which is thought to be unfavorable for subsurface geochemical reactions. Additionally, some fluid stabilizers, which alter fluid viscosity, are less effective in fluid with high total dissolved solids. Gel-based fluid stabilizers, such as crosslink, are effective in high ionic strength fluids, however viscosity is best maintained at high pH (&gt;8). High-pH fracturing fluid interactions with reservoir rock have not been well studied compared to acidic fluids. Field studies can provide long-term insight into efficiency of high-pH fracturing fluid in reservoir rock, however geochemical reactions between reservoir rock and injected fluid are known to occur on the order of a few days, during well shut-in (days to weeks). Two laboratory experiments were performed to analyze the potential for geochemical reactions between reservoir rock and high-pH fracturing fluid within the shut-in timescale. Core from the Niobrara Formation (marl and chalk), a productive unconventional reservoir in the Denver-Julesburg Basin, Colorado, USA, and high-pH hydraulic fracturing fluid (pH = 10.1) were reacted at reservoir conditions (113 °C, 27.5 MPa) for ∼35 days. Temporal evolution of aqueous geochemistry and thermodynamic analysis of both experiments indicates 1) fluid accesses nanopores; 2) pH decreases to circumneutral values as geochemical reactions shift from fluid-to rock-dominated; and 3) no significant secondary precipitation is observed. The absence of secondary mineralization indicates limited reaction between high-pH hydraulic fracturing fluid and Niobrara Formation marl and chalk and suggests that geochemical fluid-rock interactions will not impact matrix porosity and permeability during extraction of fluids from unconventional reservoirs under similar conditions. Additionally, results are compared to acidic fracturing fluid studies to assess the response of carbonate-bearing reservoir rock to pH and relative concentrations of calcium and magnesium.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"195 ","pages":"Article 106613"},"PeriodicalIF":3.4,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145518708","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":"Biased selection and incomplete characterization of feedstock materials in enhanced rock weathering experiments","authors":"Benjamin Möller ,&nbsp;Xavier Dupla","doi":"10.1016/j.apgeochem.2025.106630","DOIUrl":"10.1016/j.apgeochem.2025.106630","url":null,"abstract":"<div><div>Terrestrial Enhanced Rock Weathering (ERW) – the application of crushed rocks to soils to accelerate CO₂ removal – has emerged as a promising climate mitigation strategy to complement emission reduction efforts. One of the key factors controlling the efficacy of ERW is the composition of the utilized rock powder, ultimately constraining the achievable CO₂ removal potential and rate in a given environment. In this article, we highlight that experimental research on ERW is dominated by a narrow range of commercially available rock powders, arguably often selected more for convenience than for relevance. These materials are often poorly characterized, neglecting core methods and principles of petrography. In combination, these shortcomings are detrimental to our understanding of ERW's potential and our ability to guide its successful implementation. We call for a systematic and detailed evaluation of all potential feedstocks, going beyond readily available products. In doing so, we hope to better constrain experimental results and inform on ERW's overall CO₂ removal capacity.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"195 ","pages":"Article 106630"},"PeriodicalIF":3.4,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145518711","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":"A geochemical gene of pollution risk (PRG01) for assessing heavy metal pollution based on the relative relationship between elements","authors":"Jiaxin Huang ,&nbsp;Shengchao Xu ,&nbsp;Ningqiang Liu ,&nbsp;Taotao Yan ,&nbsp;Qingjie Gong","doi":"10.1016/j.apgeochem.2025.106634","DOIUrl":"10.1016/j.apgeochem.2025.106634","url":null,"abstract":"<div><div>Traditional assessments of heavy metal pollution in soils are often carried out on pollution indices and national standards. However, these methods focus on only elemental concentrations, without considering the relative relationship among elements. Here, we propose a geochemical gene of pollution risk (PRG01) and its risk similarity (<em>R</em>_Risk), which are based on the relative relationship between concentrations of heavy metals (Hg, Pb, Cd, Cr, and As) and their contrast elements (Ti, La, Zr, Th, U, and Nb). Through risk similarity, the pollution risk of heavy metals of samples can be classified into six levels, including the safety level (<em>R</em>_Risk&lt;20 %) and the risk level 1 to 5 (corresponding <em>R</em>_Risk values range from 20 % to 100 %). The geochemical gene of PRG01 and its risk similarity were applied in the Dashanbao area of Yunnan province of China and compared with the national standard GB15618-2018 on the pollution risk assessment of heavy metals in agricultural soils. The results indicate that samples with <em>R</em>_Risk&lt;20 % (or in safety level) belong to the non-intervention level (background or screening levels), while samples with <em>R</em>_Risk≥40 % are at the non-background level (screening or intervention levels). Therefore, the PRG01 technique can be used as a novel approach and its risk similarity can be viewed as an integrated index for assessing the pollution risk of heavy metals (i.e., Hg, Pb, Cd, Cr, and As) in agricultural soils. The assessment index of risk similarity of PRG01 can not only circumvent the limitation of a one-size-fits-all approach but also compensate for the limitation of GB15618-2018 in assessing soil samples when agricultural land use type and pH data are missing.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"195 ","pages":"Article 106634"},"PeriodicalIF":3.4,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145577394","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":"A sub-liter pretreatment method for Orbitrap–based freshwater phosphate oxygen isotope measurement","authors":"Zhao Wei ,&nbsp;Baoying Wang ,&nbsp;Longchen Zhu ,&nbsp;Yihang Hong ,&nbsp;Zhenfei Wang ,&nbsp;Hao Yan ,&nbsp;Yongbo Peng ,&nbsp;Shohei Hattori ,&nbsp;Huiming Bao","doi":"10.1016/j.apgeochem.2025.106610","DOIUrl":"10.1016/j.apgeochem.2025.106610","url":null,"abstract":"<div><div>Phosphate oxygen isotope composition (<em>δ</em>¹⁸O(PO₄³⁻)) provides critical insights into the sources and transformation processes of phosphorus in aquatic environments. However, the low PO₄³⁻ concentration (&lt;1 μM) in natural freshwater necessitates large sample volumes (25–100 L) and tedious procedures in the conventional <em>δ</em>¹⁸O(PO₄³⁻) analysis method that uses thermal conversion/elemental analysis linked to a gas–source isotope-ratio mass spectrometer (TC/EA–IRMS). Here, we report a method for analyzing <em>δ</em>¹⁸O(PO₄³⁻) using sub-liter volumes (∼1 L) of freshwater. The approach uses a well-established zirconium-oxide-gel method to adsorb dissolved PO₄³⁻, followed by purification of PO₄³⁻ via anion exchange resin and isotope measurement by Electrospray Ionization Orbitrap Mass Spectrometry (ESI–Orbitrap–MS). The whole pretreatment procedure results in a <em>δ</em>¹⁸O(PO₄³⁻) accuracy of ±0.8 ‰, within the analytical uncertainty of the ESI–Orbitrap–MS measurement. Calibration with TC/EA–IRMS produced nearly a 1:1 regression (slope 0.96, residual &lt;0.9 ‰). Tests on freshwater samples from a natural lake achieved an accuracy of ±0.3 ‰. The method reduces sample volume by three orders of magnitude compared to the TC/EA–IRMS method, opening up opportunities to trace PO₄³⁻ cycling and source apportionment in an unprecedented temporal and spatial resolution.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"194 ","pages":"Article 106610"},"PeriodicalIF":3.4,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145463422","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":"Long-term emission of methane and ethane to the atmosphere from hybrid natural seepage and well leakage in the Sărmăşel gas field (Romania)","authors":"Eduard Ghiorghiu ,&nbsp;Iulia Ajtai ,&nbsp;Ildiko M. Martonos ,&nbsp;Mustafa Hmoudah ,&nbsp;Alexandra Orban ,&nbsp;Alexandru Lupulescu ,&nbsp;Liana Spulber ,&nbsp;Alexandra I. Cozma ,&nbsp;Ștefan Șfabu ,&nbsp;Roxana Moga ,&nbsp;Călin Baciu ,&nbsp;Giuseppe Etiope","doi":"10.1016/j.apgeochem.2025.106614","DOIUrl":"10.1016/j.apgeochem.2025.106614","url":null,"abstract":"<div><div>Fossil methane and ethane, produced and accumulated in sedimentary basins, enter the atmosphere through both artificial leakage during gas-oil production activity (fugitive emissions) and natural seepage (gas naturally migrating to the surface). Well leaks, such as accidental blowouts during or after drilling, can be easily recognized by direct ground-based observations, and prompt remedial actions render them as short-term gas emission events, with no significant atmospheric impact. We report a complex case of long-term fugitive emission that developed away from the drilling site, with gas exhaling from the ground together with natural gas seepage. The site refers to the first producing gas well in Transylvania, drilled in 1909 in the Sărmăşel microbial gas field. We combined (a) a historical reconstruction of the events, based on early documents of that period, (b) geological setting analysis (stratigraphy and fault locations), and (c) present-day observation of the surface gas manifestations, through measurements of methane and ethane flux from the ground, and their concentration in the soil, shallow aquifer and surface waters. We deduce that after the closure of the well in 1911, due to gas pressure increase, the gas leaked from the well bottom, penetrated anticlinal strata and entered a natural seepage system along a fault. The leaked, stray gas mixed with the gas naturally migrating to the surface from the underlying reservoirs, producing surface craters with burning vents, still active today. It is likely that the natural seepage system amplified and is still sustaining the post-drilling leak. We estimated that, since 1911, the total amounts of methane and ethane injected from the ground to the atmosphere are at least in the order of 10⁴ t and one t, respectively. Sărmăşel gas manifestation, today leaking &gt;20 kg CH₄ h⁻¹, is a super-emitter according to the definition used for fugitive emissions in Romania. This study represents an example of the risk of uncontrolled, persistent and elusive fugitive emissions that may occur when drilling is executed within a natural seepage system. The presence of ethane in the aquifer and soil supports the hypothesis that the Transylvanian Basin may host a deep thermogenic system.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"195 ","pages":"Article 106614"},"PeriodicalIF":3.4,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145465127","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":"A combined 228Ra/226Ra and 87Sr/86Sr approach to identify the production of out-of-zone formation fluid from Marcellus shale gas wells","authors":"L.J. Molofsky ,&nbsp;M.A. Engle ,&nbsp;T.W. Wagner ,&nbsp;A.S. Wylie ,&nbsp;D.P. Fernandez","doi":"10.1016/j.apgeochem.2025.106570","DOIUrl":"10.1016/j.apgeochem.2025.106570","url":null,"abstract":"<div><div>The Marcellus shale is generally characterized by low to irreducible water saturation, and gas wells in this formation typically produce small volumes of produced water compared to the volume of fracturing fluids injected. However, some Marcellus wells produce larger volumes of high-salinity fluids months or years into production, pointing to the possibility of out-of-zone water production. To identify the origin of these high-salinity fluids, we utilize a combination of ²²⁸Ra/²²⁶Ra activity and ⁸⁷Sr/⁸⁶Sr ratios measured in Marcellus produced water samples. Key findings show that: i) bulk rock Th/U and Rb/Sr mass ratios, in concert with fresh water ⁸⁷Sr/⁸⁶Sr leachates, can be used to develop predicted ²²⁸Ra/²²⁶Ra and ⁸⁷Sr/⁸⁶Sr ratios of pore waters within different formations, ii) the ²²⁸Ra/²²⁶Ra and ⁸⁷Sr/⁸⁶Sr ratios of Marcellus produced water are dominated by the Ra²⁺ and Sr²⁺ content of downhole formation fluids and water-accessible fractions, and iii) Marcellus wells with higher water-to-gas production ratios (e.g. &gt;1 bbl water/10⁶ ft³ gas, or &gt;5.6 m³ water/10⁶ m³ gas) and elevated TDS (&gt;100,000 mg/L) exhibit lower ⁸⁷Sr/⁸⁶Sr ratios, consistent with a significant contribution from exogenous Onondaga pore fluids. The approach developed here has potential utility for identifying out-of-zone water sources in other oil and gas basins.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"194 ","pages":"Article 106570"},"PeriodicalIF":3.4,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145326435","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":"Strontium isotopes and Rb/Sr tracers in surface soils for locating subsurface lithium pegmatites","authors":"Grace A. Hall ,&nbsp;Gordon D.Z. Williams ,&nbsp;Mona-Liza C. Sirbescu ,&nbsp;P. Louis Lu ,&nbsp;Gary S. Dwyer ,&nbsp;Daniel D. Richter ,&nbsp;Avner Vengosh","doi":"10.1016/j.apgeochem.2025.106631","DOIUrl":"10.1016/j.apgeochem.2025.106631","url":null,"abstract":"<div><div>Lithium-cesium-tantalum (LCT) pegmatites are a major source of global Li production. They typically occur as dike swarms intruded into metamorphic country rocks. The subsurface locations of these dikes can be difficult to identify from the surface. One common approach is to investigate geochemical anomalies in overlying soils and use these as indicators for the occurrence of subsurface pegmatite dikes. However, even with these methods, economically valuable pegmatites can be difficult to identify, and additional techniques can be beneficial for optimizing geological exploration. Here we present a new methodology for detecting subsurface pegmatites through the analysis of Rb/Sr and strontium isotope (⁸⁷Sr/⁸⁶Sr) variations in relatively shallow soils overlying LCT pegmatites. During their formation, pegmatites become enriched in Rb and depleted in Sr, resulting in distinctly high Rb/Sr ratios (typically ≫10), and with time, the decay of ⁸⁷Rb leads to high ⁸⁷Sr/⁸⁶Sr ratios (typically ≫1.0) far exceeding those of common regional host rocks (typically with Rb/Sr &lt; 10 and ⁸⁷Sr/⁸⁶Sr &lt; ∼0.75). Since soils primarily inherit the ⁸⁷Sr/⁸⁶Sr values of their underlying parent rocks, we propose using these distinctive geochemical fingerprints in site-specific soil geochemical surveys to detect subsurface LCT pegmatites. We demonstrate the potential and utility of this methodology using surface soils around and overlying buried LCT pegmatites in the Late Paleozoic Tin Spodumene Belt in North Carolina and the Proterozoic Animikie Red Ace in Wisconsin, USA. Soils directly overlying the LCT pegmatites inherit distinctly elevated Rb/Sr (∼10–120) and ⁸⁷Sr/⁸⁶Sr (∼1.0–6.8) ratios compared to background soils away from the buried LCT pegmatites (⁸⁷Sr/⁸⁶Sr ∼0.74–0.77, Rb/Sr ∼0.76–3.9), which can be used to identify and reconstruct the location of subsurface LCT pegmatite dikes. The common and uniquely elevated Rb/Sr and ⁸⁷Sr/⁸⁶Sr signatures of global pegmatites suggest that this method can be widely and globally applied to soils derived from LCT pegmatites.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"195 ","pages":"Article 106631"},"PeriodicalIF":3.4,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145577392","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":"Reconstructing coalbed methane accumulation history in the Qinshui Basin using noble gas isotopes","authors":"Zhelin Zhang ,&nbsp;Biying Chen ,&nbsp;Yi Liu ,&nbsp;Zhanjie Xu ,&nbsp;Finlay M. Stuart ,&nbsp;Sheng Xu","doi":"10.1016/j.apgeochem.2025.106629","DOIUrl":"10.1016/j.apgeochem.2025.106629","url":null,"abstract":"<div><div>Coalbed methane (CBM) is an unconventional natural gas resource that supports low-carbon energy demand and mitigates greenhouse gas emissions during coal mining. It is a key natural gas resource in China. Understanding how CBM is produced and accumulates is critical for exploration. Qinshui Basin is the largest and most productive CBM basin in China. This study uses the light noble gas compositions (He, Ne and Ar) of CBM from five blocks in the Qinshui Basin to provide a comprehensive view of gas accumulation history. The noble gases are derived from air and deep crustal sources. Gases from these sources were mixed in formation water prior to methane extraction. Subsequent degassing followed open-system Rayleigh fractionation, enabling the crustal ⁴He and ⁴⁰Ar accumulation ages and the gas-water interaction volume to be determined, as well as the proportion of desorbed methane released during production. The coal seams have incorporated the flux of ⁴He and ⁴⁰Ar from the deep crust. Despite this, the crustal ⁴He and ⁴⁰Ar accumulation ages are considerably younger than the Permo-Carboniferous coal deposition age, revealing widespread gas loss. Adsorbed methane was released during gas extraction. The proportion of desorbed methane in the produced gas shows a strong relationship with crustal ⁴⁰Ar accumulation ages, indicating that the noble gases serve as a proxy for the preservation of adsorbed methane. The interacted gas/water ratios derived from air-sourced noble gases reflect the extent of gas extraction. Low extraction efficiency is indicated by low gas/water ratios, high dilution ratios and low gas production rates, while prolonged high extraction rates lead to a decline in the dilution ratio. These findings demonstrate the value of measuring trace noble gases for understanding gas accumulation and guiding CBM production strategies.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"195 ","pages":"Article 106629"},"PeriodicalIF":3.4,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145518740","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}