Pub Date : 2025-02-05DOI: 10.1016/j.chemgeo.2024.122442
Andrea Agangi , Axel Hofmann , Takuya Echigo , Robert Bolhar , Daisuke Araoka , Vincent Mashoene , Lucia T. Ndhlovu , Ryohei Takahashi , Pearlyn C. Manalo
<div><div>The Mesoarchaean Murchison Greenstone Belt is composed of a strongly deformed volcano-sedimentary succession metamorphosed up to amphibolite facies and surrounded by metaluminous and peraluminous granitoids in the north of the Kaapvaal Craton of southern Africa. A circa 40 km-long shear-zone of strongly carbonatised rocks (the Antimony Line, or Sb-Line) oriented along the main trend of the greenstone belt (WSW–ENE) hosts important Sb deposits with accessory Au. These commodities mostly occur as stibnite and native gold hosted by quartz‑carbonate rocks at the centre of the Sb-Line, underlining the importance of CO<sub>2</sub>-rich fluid flow for mineralisation during deformation and metamorphism.</div><div>In this study, we compare the elemental and stable isotope (C-O-Mg) composition of carbonates from the Sb-Line with regionally distributed carbonates hosted by the volcano-sedimentary succession distal to mineralisation. The carbonates of the Sb-Line and regional rocks have overlapping major element compositions. Both magnesite and dolomite in most Sb-Line samples have marked light-REE-depleted patterns with variable positive Eu anomalies. Carbon isotope ratios define two clusters, with marked δ<sup>13</sup>C peaks at ca. -5 ‰ for Sb-Line rocks and ca. -2 ‰ for regional rocks, implying separate C-sources. The peak at ca. -2 ‰ likely represents early carbonatisation through sea-floor alteration, whereas the first peak at ca. -5 ‰ is indicative of deep CO<sub>2</sub> (mantle, or magma-derived) introduced during tectonic activity of the Sb-Line. Magnesium isotope ratios of regional rocks reveal limited fractionation (bulk δ<sup>26</sup>Mg = −0.27 ± 0.10 ‰) that overlap with mantle values, but some carbonate-bearing veins present <sup>26</sup>Mg-depleted compositions (bulk δ<sup>26</sup>Mg = −1.91 to −0.40 ‰). Sb-Line carbonated rocks have more fractionated Mg isotope compositions (bulk δ<sup>26</sup>Mg = −0.8 to 0.0 ‰) and carbonates display marked negative <sup>26</sup>Mg values (δ<sup>26</sup>Mg from −1.46 to −0.31 ‰). We interpret these results in terms of preferential remobilisation of isotopically light Mg during fluid-rock interaction and dissolution of carbonate in the host-rocks. The lack of correlation between δ<sup>13</sup>C and δ<sup>26</sup>Mg indicates decoupling of these isotopic systems, implying contribution from isotopically distinct sources of C and Mg to the mineralised zone.</div><div>Similar to other structurally controlled Au<img>Sb mineralisation in Archaean greenstone belts, metal transport and ore deposition in the Murchison Greenstone Belt was closely related to the deep cycle of carbon, linking C-draw-down during sea-floor alteration, carbonate re-mobilisation during metamorphism and CO<sub>2</sub> degassing from deep sources along major crustal discontinuities. In contrast to models for orogenic Au<img>Sb deposits invoking a purely intra-crustal, metamorphic origin of mineralising fluids, our results underline
{"title":"The use of combined CMg isotope compositions of carbonates from orogenic SbAu deposits as a tracer of fluid interaction with sea-floor altered crust","authors":"Andrea Agangi , Axel Hofmann , Takuya Echigo , Robert Bolhar , Daisuke Araoka , Vincent Mashoene , Lucia T. Ndhlovu , Ryohei Takahashi , Pearlyn C. Manalo","doi":"10.1016/j.chemgeo.2024.122442","DOIUrl":"10.1016/j.chemgeo.2024.122442","url":null,"abstract":"<div><div>The Mesoarchaean Murchison Greenstone Belt is composed of a strongly deformed volcano-sedimentary succession metamorphosed up to amphibolite facies and surrounded by metaluminous and peraluminous granitoids in the north of the Kaapvaal Craton of southern Africa. A circa 40 km-long shear-zone of strongly carbonatised rocks (the Antimony Line, or Sb-Line) oriented along the main trend of the greenstone belt (WSW–ENE) hosts important Sb deposits with accessory Au. These commodities mostly occur as stibnite and native gold hosted by quartz‑carbonate rocks at the centre of the Sb-Line, underlining the importance of CO<sub>2</sub>-rich fluid flow for mineralisation during deformation and metamorphism.</div><div>In this study, we compare the elemental and stable isotope (C-O-Mg) composition of carbonates from the Sb-Line with regionally distributed carbonates hosted by the volcano-sedimentary succession distal to mineralisation. The carbonates of the Sb-Line and regional rocks have overlapping major element compositions. Both magnesite and dolomite in most Sb-Line samples have marked light-REE-depleted patterns with variable positive Eu anomalies. Carbon isotope ratios define two clusters, with marked δ<sup>13</sup>C peaks at ca. -5 ‰ for Sb-Line rocks and ca. -2 ‰ for regional rocks, implying separate C-sources. The peak at ca. -2 ‰ likely represents early carbonatisation through sea-floor alteration, whereas the first peak at ca. -5 ‰ is indicative of deep CO<sub>2</sub> (mantle, or magma-derived) introduced during tectonic activity of the Sb-Line. Magnesium isotope ratios of regional rocks reveal limited fractionation (bulk δ<sup>26</sup>Mg = −0.27 ± 0.10 ‰) that overlap with mantle values, but some carbonate-bearing veins present <sup>26</sup>Mg-depleted compositions (bulk δ<sup>26</sup>Mg = −1.91 to −0.40 ‰). Sb-Line carbonated rocks have more fractionated Mg isotope compositions (bulk δ<sup>26</sup>Mg = −0.8 to 0.0 ‰) and carbonates display marked negative <sup>26</sup>Mg values (δ<sup>26</sup>Mg from −1.46 to −0.31 ‰). We interpret these results in terms of preferential remobilisation of isotopically light Mg during fluid-rock interaction and dissolution of carbonate in the host-rocks. The lack of correlation between δ<sup>13</sup>C and δ<sup>26</sup>Mg indicates decoupling of these isotopic systems, implying contribution from isotopically distinct sources of C and Mg to the mineralised zone.</div><div>Similar to other structurally controlled Au<img>Sb mineralisation in Archaean greenstone belts, metal transport and ore deposition in the Murchison Greenstone Belt was closely related to the deep cycle of carbon, linking C-draw-down during sea-floor alteration, carbonate re-mobilisation during metamorphism and CO<sub>2</sub> degassing from deep sources along major crustal discontinuities. In contrast to models for orogenic Au<img>Sb deposits invoking a purely intra-crustal, metamorphic origin of mineralising fluids, our results underline ","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"673 ","pages":"Article 122442"},"PeriodicalIF":3.6,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143168553","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-05DOI: 10.1016/j.chemgeo.2024.122560
Xian Chen , Zhengzhe Fan
The role of tectonic setting in new continental crust formation remains enigmatic. A key to solve this issue is to determine which tectonic setting(s) are involved in the generation of new continental crust through time. Modern mantle-derived magmas that formed in intracontinental extension settings (U/Pb = ∼0.28–0.37) and in subduction settings (U/Pb = ∼0.1–0.16) have distinct mean U/Pb ratios. When shifting from subduction to intracontinental extension settings, the mean U/Pb ratios of new crust should define an increasing trend with time, whereas a decreasing trend will be observed when the converse transition is observed. Here we calculate U/Pb ratios of new crust [(U/Pb)jc] of the Songliao Block from East Asia to determine the tectonic settings of new crust formation. Our results show that (U/Pb)jc ratios have a decreasing trend from ∼1.55 to ∼1.2 Ga, followed by an increasing trend from ∼1.2 to ∼0.8 Ga, and changed to a decreasing trend again between ∼0.8 and ∼ 0.6 Ga. This implies that new crust formation of the microcontinent in a subduction setting during the middle-late Mesoproterozoic and the middle-late Neoproterozoic, however, in an intracontinental extension setting in the late Mesoproterozoic-early Neoproterozoic. Our method may provide a potential avenue to explore the regimes of new continental crust formation.
{"title":"Evaluating the role of tectonic setting in new continental crust formation by U/Pb ratios","authors":"Xian Chen , Zhengzhe Fan","doi":"10.1016/j.chemgeo.2024.122560","DOIUrl":"10.1016/j.chemgeo.2024.122560","url":null,"abstract":"<div><div>The role of tectonic setting in new continental crust formation remains enigmatic. A key to solve this issue is to determine which tectonic setting(s) are involved in the generation of new continental crust through time. Modern mantle-derived magmas that formed in intracontinental extension settings (U/Pb = ∼0.28–0.37) and in subduction settings (U/Pb = ∼0.1–0.16) have distinct mean U/Pb ratios. When shifting from subduction to intracontinental extension settings, the mean U/Pb ratios of new crust should define an increasing trend with time, whereas a decreasing trend will be observed when the converse transition is observed. Here we calculate U/Pb ratios of new crust [(U/Pb)<sub>jc</sub>] of the Songliao Block from East Asia to determine the tectonic settings of new crust formation. Our results show that (U/Pb)<sub>jc</sub> ratios have a decreasing trend from ∼1.55 to ∼1.2 Ga, followed by an increasing trend from ∼1.2 to ∼0.8 Ga, and changed to a decreasing trend again between ∼0.8 and ∼ 0.6 Ga. This implies that new crust formation of the microcontinent in a subduction setting during the middle-late Mesoproterozoic and the middle-late Neoproterozoic, however, in an intracontinental extension setting in the late Mesoproterozoic-early Neoproterozoic. Our method may provide a potential avenue to explore the regimes of new continental crust formation.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"673 ","pages":"Article 122560"},"PeriodicalIF":3.6,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142858008","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-05DOI: 10.1016/j.chemgeo.2024.122549
J.A. Vila , G.L. Bia , S. Bengió , C. Balbis , L. Borgnino
During eruption, sulphur dioxide gas interacts with glass shards, favouring the formation of sulphuric acid (H2SO4) aerosols and coatings enriched in hazardous elements such as fluorine (F). This study discusses the formation of F-bearing compounds during acidic weathering of Andean juvenile pyroclastic rock emitted from Puyehue and Lanín volcanoes and their potential to release F into aqueous reservoirs. Surface chemical composition and solid speciation of Si, Al, and O were performed by XPS. Batch experiments were carried out to understand the release of F from S-bearing compounds.
When pyroclastic rocks are partially altered in H2SO4, a mixture of S-bearing compounds precipitates on the surface of the rock grains. These compounds precipitate as a result of the weathering process of pyroclastic rocks after hydrolysis of the aluminate and silicate groups. The composition of the precipitated compounds is influenced by the magmatic source. Consequently, mafic particles exhibit precipitated compounds enriched in Al, Mg, Ca, and Fe and are more altered compared to felsic particles. The hydrolysis process also promotes the release of F, which was originally associated with the aluminosilicate network. Once released, a proportion of the dissolved F either precipitates or re-adsorbed onto S-bearing compounds, eventually being transported into the environment.
在火山爆发过程中，二氧化硫气体与玻璃碎片相互作用，有利于形成硫酸（H2SO4）气溶胶和富含氟（F）等有害元素的涂层。本研究讨论了普耶胡火山和拉宁火山喷出的安第斯幼年火成碎屑岩在酸性风化过程中形成的含氟化合物，以及它们向含水储层释放氟的潜力。利用 XPS 对硅、铝和 O 进行了表面化学成分和固体规格分析。为了解含 S 化合物释放 F 的情况，进行了批量实验。
{"title":"Surface acid alteration of juvenile Andean pyroclastic rocks: effect of glass composition on the development of surface fluoride-bearing minerals","authors":"J.A. Vila , G.L. Bia , S. Bengió , C. Balbis , L. Borgnino","doi":"10.1016/j.chemgeo.2024.122549","DOIUrl":"10.1016/j.chemgeo.2024.122549","url":null,"abstract":"<div><div>During eruption, sulphur dioxide gas interacts with glass shards, favouring the formation of sulphuric acid (H<sub>2</sub>SO<sub>4</sub>) aerosols and coatings enriched in hazardous elements such as fluorine (F). This study discusses the formation of F-bearing compounds during acidic weathering of Andean juvenile pyroclastic rock emitted from Puyehue and Lanín volcanoes and their potential to release F into aqueous reservoirs. Surface chemical composition and solid speciation of Si, Al, and O were performed by XPS. Batch experiments were carried out to understand the release of F from S-bearing compounds.</div><div>When pyroclastic rocks are partially altered in H<sub>2</sub>SO<sub>4</sub>, a mixture of S-bearing compounds precipitates on the surface of the rock grains. These compounds precipitate as a result of the weathering process of pyroclastic rocks after hydrolysis of the aluminate and silicate groups. The composition of the precipitated compounds is influenced by the magmatic source. Consequently, mafic particles exhibit precipitated compounds enriched in Al, Mg, Ca, and Fe and are more altered compared to felsic particles. The hydrolysis process also promotes the release of F, which was originally associated with the aluminosilicate network. Once released, a proportion of the dissolved F either precipitates or re-adsorbed onto S-bearing compounds, eventually being transported into the environment.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"673 ","pages":"Article 122549"},"PeriodicalIF":3.6,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142858010","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-05DOI: 10.1016/j.chemgeo.2024.122550
Oluwatoosin B.A. Agbaje , Qian Huang , Michiel Op De Beeck , Per L. Ambus , Lisbeth G. Thygesen , Bernd R. Schöne , Karina K. Sand
Arctica islandica (Linnaeus, 1767) is a bivalve mollusk with a lifespan of up to 500 years. Its shell is a complex inorganic-organic nanocomposite, which is still not fully characterized. Here, we used Optical Photothermal Infrared (O-PTIR) microspectroscopy to characterize its organic phase, i.e. the hydrophobic insoluble extracts of both modern and fossil A. islandica shells. We compared the spectra from O-PTIR technique with those obtained from microRaman, microFTIR and ATR-FTIR spectroscopies. The structure of the shells was also studied using scanning electron microscope imaging. The spectroscopic techniques confirmed the presence of β-chitin and chitin-binding protein in the hydrophobic insoluble organic matrix. The results of element and light stable isotope analyses (δ13C, δ15N) from the hydrophobic insoluble extracts of both the modern and fossil shells were consistent with a shallow marine environment. The results demonstrate how O-PTIR can be applied in-situ for the study of biomaterials in shells, and points towards how it can be applied for the elucidation of intricate structure-function relationships. Furthermore, the approach of using the hydrophobic insoluble extracts to probe conditions and the nature of organic remains in fossil shells demonstrate an alternative to the use of soft tissues in isotopic studies and hence opens new possibilities for environmental reconstruction using fossil material when soft tissues are unavailable.
{"title":"Molecular signatures of biomacromolecules at micron and submicron scales in Arctica islandica shells","authors":"Oluwatoosin B.A. Agbaje , Qian Huang , Michiel Op De Beeck , Per L. Ambus , Lisbeth G. Thygesen , Bernd R. Schöne , Karina K. Sand","doi":"10.1016/j.chemgeo.2024.122550","DOIUrl":"10.1016/j.chemgeo.2024.122550","url":null,"abstract":"<div><div><em>Arctica islandica</em> (Linnaeus, 1767) is a bivalve mollusk with a lifespan of up to 500 years. Its shell is a complex inorganic-organic nanocomposite, which is still not fully characterized. Here, we used Optical Photothermal Infrared (O-PTIR) microspectroscopy to characterize its organic phase, i.e. the hydrophobic insoluble extracts of both modern and fossil <em>A. islandica</em> shells. We compared the spectra from O-PTIR technique with those obtained from microRaman, microFTIR and ATR-FTIR spectroscopies. The structure of the shells was also studied using scanning electron microscope imaging. The spectroscopic techniques confirmed the presence of <em>β</em>-chitin and chitin-binding protein in the hydrophobic insoluble organic matrix. The results of element and light stable isotope analyses (δ<sup>13</sup>C, δ<sup>15</sup>N) from the hydrophobic insoluble extracts of both the modern and fossil shells were consistent with a shallow marine environment. The results demonstrate how O-PTIR can be applied in-situ for the study of biomaterials in shells, and points towards how it can be applied for the elucidation of intricate structure-function relationships. Furthermore, the approach of using the hydrophobic insoluble extracts to probe conditions and the nature of organic remains in fossil shells demonstrate an alternative to the use of soft tissues in isotopic studies and hence opens new possibilities for environmental reconstruction using fossil material when soft tissues are unavailable.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"673 ","pages":"Article 122550"},"PeriodicalIF":3.6,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142815870","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-05DOI: 10.1016/j.chemgeo.2024.122527
James A. Kidder , Christopher E. Beckett-Brown , Alexandre Voinot , Zhaoping Yang , Pierre Pelchat , Duane C. Petts , Matthew Polivchuk , John B. Chapman , Scott Casselman , Matthew I. Leybourne
The fate of metals, such as Cu, in stream waters draining porphyry mineralization is commonly controlled by several natural processes such as sorption, microbial processes, and ligand availability. Isotopes of Cu offer a novel approach to understanding these processes and determining metal sources within complicated mineralogical systems. Drainages at the Casino Cu-Au-Mo porphyry deposit, Yukon, Canada exhibit circumneutral (pH > 5) in Casino Creek and natural acid rock drainage (pH < 3.5) in Proctor Gulch with the precipitation of schwertmannite (Fe3+). Isotopic systems δ65Cu and δ34Ssulfate indicate different metal sources, with signatures of both hypogene and supergene mineralization. Waters from Proctor Gulch contain δ65Cu values (< −0.5 ‰) consistent with supergene Cu sources from the leached or oxide portion of the mineralization. Comparatively, drainage in the upper part of Casino Creek contains a δ65Cu composition (> 0.5 ‰) characteristic of Cu sourced from hypogene sulfide mineral oxidation. Variation in metal sources is similarly supported by aqueous δ34Ssulfate values in the stream waters, which suggest mixing of S derived from a sulfide mineral phase and a much heavier sulfate mineral (e.g., gypsum or anhydrite). Isotopic fractionation of Cu in the dissolved (<0.45 μm) phase presents two predominant controls on Cu dispersion. The natural acid conditions in Proctor Gulch favor the preferential co-precipitation of 63Cu with schwertmannite but could be influenced by intracellular assimilation or adsorption by microbes, which also has been shown to preferentially favor 63Cu. Copper isotopic fractionation results in a gradient of increasing δ65Cu values in waters downstream. In Casino Creek, higher pH conditions favor the precipitation of Fe(OH)3 and the preferential adsorption of 65Cu, resulting in decreasing δ65Cu values downstream. Copper concentrations in stream waters remain elevated (up to 4.1 μg/L) above ambient background (1.9 μg/L) levels up to 11 km downstream of the deposit. Given the abundance of surface water in many parts of northern Canada, hydrogeochemical prospecting using broad scale stream water catchment analysis is clearly a viable greenfield exploration methodology.
{"title":"Using δ65Cu and δ34S to determine the fate of copper in stream waters draining porphyry mineralization: Implications for exploration targeting","authors":"James A. Kidder , Christopher E. Beckett-Brown , Alexandre Voinot , Zhaoping Yang , Pierre Pelchat , Duane C. Petts , Matthew Polivchuk , John B. Chapman , Scott Casselman , Matthew I. Leybourne","doi":"10.1016/j.chemgeo.2024.122527","DOIUrl":"10.1016/j.chemgeo.2024.122527","url":null,"abstract":"<div><div>The fate of metals, such as Cu, in stream waters draining porphyry mineralization is commonly controlled by several natural processes such as sorption, microbial processes, and ligand availability. Isotopes of Cu offer a novel approach to understanding these processes and determining metal sources within complicated mineralogical systems. Drainages at the Casino Cu-Au-Mo porphyry deposit, Yukon, Canada exhibit circumneutral (pH > 5) in Casino Creek and natural acid rock drainage (pH < 3.5) in Proctor Gulch with the precipitation of schwertmannite (Fe<sup>3+</sup>). Isotopic systems δ<sup>65</sup>Cu and δ<sup>34</sup>S<sub>sulfate</sub> indicate different metal sources, with signatures of both hypogene and supergene mineralization. Waters from Proctor Gulch contain δ<sup>65</sup>Cu values (< −0.5 ‰) consistent with supergene Cu sources from the leached or oxide portion of the mineralization. Comparatively, drainage in the upper part of Casino Creek contains a δ<sup>65</sup>Cu composition (> 0.5 ‰) characteristic of Cu sourced from hypogene sulfide mineral oxidation. Variation in metal sources is similarly supported by aqueous δ<sup>34</sup>S<sub>sulfate</sub> values in the stream waters, which suggest mixing of S derived from a sulfide mineral phase and a much heavier sulfate mineral (e.g., gypsum or anhydrite). Isotopic fractionation of Cu in the dissolved (<0.45 μm) phase presents two predominant controls on Cu dispersion. The natural acid conditions in Proctor Gulch favor the preferential co-precipitation of <sup>63</sup>Cu with schwertmannite but could be influenced by intracellular assimilation or adsorption by microbes, which also has been shown to preferentially favor <sup>63</sup>Cu. Copper isotopic fractionation results in a gradient of increasing δ<sup>65</sup>Cu values in waters downstream. In Casino Creek, higher pH conditions favor the precipitation of Fe(OH)<sub>3</sub> and the preferential adsorption of <sup>65</sup>Cu, resulting in decreasing δ<sup>65</sup>Cu values downstream. Copper concentrations in stream waters remain elevated (up to 4.1 μg/L) above ambient background (1.9 μg/L) levels up to 11 km downstream of the deposit. Given the abundance of surface water in many parts of northern Canada, hydrogeochemical prospecting using broad scale stream water catchment analysis is clearly a viable greenfield exploration methodology.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"673 ","pages":"Article 122527"},"PeriodicalIF":3.6,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142815876","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-05DOI: 10.1016/j.chemgeo.2024.122552
Guifang Cai , Zhao-Wen Zhan , Zhiguang Song , Yao-Ping Wang , Jia Xia , Ding He
Carbon isotope ratios (δ13C) in plant lipid biomarkers yield insights into historical climates by reflecting plant responses to environmental stressors. Previous research has established a correlation between increased salinity and elevated δ13C in Avicennia marina leaf wax n-alkanes, yet it remains unclear if these isotopic signatures are universally applicable across different species and regions or consistently preserved in sedimentary records. We investigated the influence of a 30 ppt salinity gradient on Aegiceras corniculatum in Zhanjiang, China, examining δ13C values in leaf wax n-alkanes and adjacent sediments. Leaf wax δ13C values ranged from −36.7 ‰ to −31.4 ‰, while sediment n-alkanes ranged from −35.6 ‰ to −28.2 ‰. Sediments consistently exhibited higher δ13C values than leaf wax, and their total lipid and n-alkane δ13C exhibited a positive correlation with salinity, increasing by 0.06 ± 0.02 ‰ and 0.1 ± 0.04 ‰ per ppt respectively. This positive correlation may be attributed to factors such as marine material input, seasonal variations in lipid synthesis, and plant community succession. In contrast, no significant correlation with salinity was observed in A. corniculatum's bulk leaf tissues or total lipids. This lack of correlation can be attributed to the unique physiological conditions and varying salt exclusion mechanisms among mangrove species, which influence water use efficiency. Accordingly, while sediment δ13C values can indicate past vegetation, the variability necessitates caution in using mangrove sediment δ13C for paleoenvironmental reconstruction.
{"title":"n-Alkanes δ13C and salinity correlation in mangrove Aegiceras corniculatum leaves and surface sediments from Zhanjiang estuaries, China","authors":"Guifang Cai , Zhao-Wen Zhan , Zhiguang Song , Yao-Ping Wang , Jia Xia , Ding He","doi":"10.1016/j.chemgeo.2024.122552","DOIUrl":"10.1016/j.chemgeo.2024.122552","url":null,"abstract":"<div><div>Carbon isotope ratios (δ<sup>13</sup>C) in plant lipid biomarkers yield insights into historical climates by reflecting plant responses to environmental stressors. Previous research has established a correlation between increased salinity and elevated δ<sup>13</sup>C in <em>Avicennia marina</em> leaf wax <em>n</em>-alkanes, yet it remains unclear if these isotopic signatures are universally applicable across different species and regions or consistently preserved in sedimentary records. We investigated the influence of a 30 ppt salinity gradient on <em>Aegiceras corniculatum</em> in Zhanjiang, China, examining δ<sup>13</sup>C values in leaf wax <em>n</em>-alkanes and adjacent sediments. Leaf wax δ<sup>13</sup>C values ranged from −36.7 ‰ to −31.4 ‰, while sediment <em>n</em>-alkanes ranged from −35.6 ‰ to −28.2 ‰. Sediments consistently exhibited higher δ<sup>13</sup>C values than leaf wax, and their total lipid and <em>n</em>-alkane δ<sup>13</sup>C exhibited a positive correlation with salinity, increasing by 0.06 ± 0.02 ‰ and 0.1 ± 0.04 ‰ per ppt respectively. This positive correlation may be attributed to factors such as marine material input, seasonal variations in lipid synthesis, and plant community succession. In contrast, no significant correlation with salinity was observed in <em>A. corniculatum</em>'s bulk leaf tissues or total lipids. This lack of correlation can be attributed to the unique physiological conditions and varying salt exclusion mechanisms among mangrove species, which influence water use efficiency. Accordingly, while sediment δ<sup>13</sup>C values can indicate past vegetation, the variability necessitates caution in using mangrove sediment δ<sup>13</sup>C for paleoenvironmental reconstruction.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"673 ","pages":"Article 122552"},"PeriodicalIF":3.6,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142815867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-05DOI: 10.1016/j.chemgeo.2024.122548
Henrique Albuquerque Fernandes , Paulo César Boggiani , Jesper Allan Frederiksen , Marcelo Da Roz Campos , Vinicius Cardoso-Lucas , Bernardo Tavares Freitas , Robert Frei
Early Ediacaran cap dolostones are distinctive strata deposited directly above glaciogenic rocks from the Marinoan Glaciation (650–635 Ma), one of the most dramatic ice ages in Earth's history. These cap dolostones were rapidly deposited during global synchronous deglaciation, being a superb depositional window into the immediate glaciation aftermath and suitable for investigating the icehouse-hothouse transition in this period. However, some aspects of this transition are still unclear, such as the timing of primary productivity recovery. Aiming to explore this question, we present new sedimentological, trace element, and Sr-Cr-Cd isotope data for the Puga cap dolostone in the Southern Paraguay Belt (Brazil), here termed Morraria do Sul Formation. The cap dolostone overlies diamictites, siltstones with outsized clasts, and basement rocks. It is divided into a basal dolograinstone and an upper tubestone-microbialite succession, with abundant vertical tube-like structures. The diamictites and siltstones were formed in a glaciomarine setting, within the range of ice-rafted debris. The basal dolograinstone facies of the cap dolostone was formed under high-energy post-glacial conditions, and the overlying tubestone-microbialite facies was deposited in a low-energy, well-lit environment. Rare earth elements and yttrium (REY) preserved the original seawater-like pattern, displaying true negative Ce anomalies down to 0.84, indicating oxygenated shallow waters. The cap dolostone displays relatively high 87Sr/86Sr ratios, up to 0.7123, above the assumed value for the Early Ediacaran seawater, suggesting the influence of meltwater plumes in a salinity-stratified setting. Authigenic Cr isotope values (δ53Crauth) are within the range of Bulk Silicate Earth (BSE) to slightly positive in the basal dolograinstone and negatively fractionated below BSE values in the tubestone-microbialite facies, implying that microbial-influenced Cr reduction progressively increased upwards, controlling the isotopic fractionation. A rise upwards in δ114Cd, from −0.11 to 0.17 ‰, reveals a substantial increase in Cd-uptake by biomass, and maximum estimates for seawater δ114Cd show values within the range of present-day surface seawater. The data presented herein suggest that significant primary productivity recovery occurred in the immediate aftermath of the Marinoan Glaciation. This study also shows the efficiency of combined trace elements and Sr-Cr-Cd isotope analyses on reconstructing past seawater chemistry and productivity levels.
埃迪卡拉纪早期的帽状白云岩是一种独特的地层，直接沉积在马里诺冰期（650-635 Ma）的冰川岩石上，这是地球历史上最戏剧性的冰期之一。这些盖层白云岩是在全球同步消冰期间快速沉积的，是研究冰川直接后果的极好沉积窗口，适合研究这一时期的冰-温室过渡。然而，这种转变的一些方面仍然不清楚，比如初级生产力恢复的时间。为了探索这个问题，我们提出了巴西南巴拉圭带（此处称为Morraria do Sul组）Puga盖层白云岩的新的沉积学、微量元素和Sr-Cr-Cd同位素数据。盖层白云岩覆盖在双晶岩、带有超大碎屑的粉砂岩和基底岩上。分为基底白云岩和上部管状-微生物岩序列，具有丰富的垂直管状构造。二晶岩和粉砂岩形成于冰川期海洋环境，在浮冰碎屑的范围内。盖层白云岩的基底白云岩相形成于高能量的后冰期条件下，上覆的管状岩-微生物岩相沉积于低能、光照良好的环境中。稀土元素和钇（REY）保持了原始的海水样模式，Ce真负异常低至0.84，表明含氧浅水。盖层白云岩87Sr/86Sr比值较高，达到0.7123，高于早埃迪卡拉纪海水的假设值，表明在盐度分层环境中受到融水羽流的影响。自生Cr同位素值（δ53Crauth）在基底白云岩的体积硅酸盐土（BSE）范围内至微正，在管状岩-微生物岩相的BSE值以下呈负分馏，表明微生物影响的Cr还原逐渐向上增加，控制了同位素分馏。δ114Cd从- 0.11‰上升到0.17‰，表明生物质对cd的吸收显著增加，海水δ114Cd的最大估计值在现今表层海水的范围内。本文提供的数据表明，显著的初级生产力恢复发生在马里诺冰期之后。该研究还显示了微量元素组合和Sr-Cr-Cd同位素分析在重建过去海水化学和生产力水平方面的有效性。
{"title":"Rapid bioproductivity recovery following the Marinoan glaciation: Evidence from Sr-Cr-Cd isotopes and trace elements in the Morraria do Sul cap dolostone, Brazil","authors":"Henrique Albuquerque Fernandes , Paulo César Boggiani , Jesper Allan Frederiksen , Marcelo Da Roz Campos , Vinicius Cardoso-Lucas , Bernardo Tavares Freitas , Robert Frei","doi":"10.1016/j.chemgeo.2024.122548","DOIUrl":"10.1016/j.chemgeo.2024.122548","url":null,"abstract":"<div><div>Early Ediacaran cap dolostones are distinctive strata deposited directly above glaciogenic rocks from the Marinoan Glaciation (650–635 Ma), one of the most dramatic ice ages in Earth's history. These cap dolostones were rapidly deposited during global synchronous deglaciation, being a superb depositional window into the immediate glaciation aftermath and suitable for investigating the icehouse-hothouse transition in this period. However, some aspects of this transition are still unclear, such as the timing of primary productivity recovery. Aiming to explore this question, we present new sedimentological, trace element, and Sr-Cr-Cd isotope data for the Puga cap dolostone in the Southern Paraguay Belt (Brazil), here termed Morraria do Sul Formation. The cap dolostone overlies diamictites, siltstones with outsized clasts, and basement rocks. It is divided into a basal dolograinstone and an upper tubestone-microbialite succession, with abundant vertical tube-like structures. The diamictites and siltstones were formed in a glaciomarine setting, within the range of ice-rafted debris. The basal dolograinstone facies of the cap dolostone was formed under high-energy post-glacial conditions, and the overlying tubestone-microbialite facies was deposited in a low-energy, well-lit environment. Rare earth elements and yttrium (REY) preserved the original seawater-like pattern, displaying true negative Ce anomalies down to 0.84, indicating oxygenated shallow waters. The cap dolostone displays relatively high <sup>87</sup>Sr/<sup>86</sup>Sr ratios, up to 0.7123, above the assumed value for the Early Ediacaran seawater, suggesting the influence of meltwater plumes in a salinity-stratified setting. Authigenic Cr isotope values (δ<sup>53</sup>Cr<sub>auth</sub>) are within the range of Bulk Silicate Earth (BSE) to slightly positive in the basal dolograinstone and negatively fractionated below BSE values in the tubestone-microbialite facies, implying that microbial-influenced Cr reduction progressively increased upwards, controlling the isotopic fractionation. A rise upwards in δ<sup>114</sup>Cd, from −0.11 to 0.17 ‰, reveals a substantial increase in Cd-uptake by biomass, and maximum estimates for seawater δ<sup>114</sup>Cd show values within the range of present-day surface seawater. The data presented herein suggest that significant primary productivity recovery occurred in the immediate aftermath of the Marinoan Glaciation. This study also shows the efficiency of combined trace elements and Sr-Cr-Cd isotope analyses on reconstructing past seawater chemistry and productivity levels.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"673 ","pages":"Article 122548"},"PeriodicalIF":3.6,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142815871","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-05DOI: 10.1016/j.chemgeo.2024.122526
Rakesh K. Tiwari , Tarun K. Dalai , Rupak Samadder , Waliur Rahaman , Sunil K. Singh
This study is focussed on understanding of molybdenum (Mo) cycling in the mesotidal to macrotidal estuary of the Ganga (Hooghly) River in India. Our investigation encompasses the composition of water and suspended particulate matter (SPM) samples collected in three separate periods (pre-monsoon: PrM, monsoon: M and post-monsoon: PoM) over two consecutive years, surface sediments, exchangeable phases of surface and suspended sediments, one sediment core, urban and industrial effluent waters and ground waters. The observed dissolved Mo concentrations in the estuary are in excess of those expected from conservative mixing of seawater and river water. The “excess” Mo values, observed in the mid-to-high salinity regions (4–27 ‰) for four out of the six study periods, are the highest in the monsoon samples. The bulk and exchangeable phase compositions are supportive of release of Mo from the Fe-Mn oxyhydroxide phases of the SPM and surface sediments in the estuary. Mass balance calculations indicate that Mo release from the SPM and surface sediments can account for up to 40 % of the median value of the “excess” Mo in the estuary. The compositions of the sediment core provide evidence for the mobilization of Mo and its release to porewater due to reductive dissolution of Fe-Mn oxyhydroxides. The tidally induced sediment resuspension likely facilitates the transport of porewater Mo to the overlying water. Mass balance calculations indicate that Mo loss from the sediment column can account for the bulk of the “excess” Mo in the estuary waters. This study further demonstrates that industrial effluents, urban waste waters and groundwaters do not constitute significant sources of dissolved Mo in the estuary.
The average annual Mo flux from the estuary is (∼2–3) × 106 mol, of which ∼30–50 % of Mo is due to estuarine addition. More significantly, Mo contribution from the Hooghly River estuary, accounting for ∼0.7–1.0 % of the global riverine Mo flux, is ∼3–4 folds higher than its water contribution (∼0.25 %) to the global river water flux. Our study highlights the role of interactions between oxyhydroxide phases and estuarine water, diagenetic mobilization of elements in the sediment column and porewater transport in the cycling of Mo in a monsoon-dominated tropical estuary with high sediment loads. We also demonstrate that the mobilization of Mo through chemical weathering is driven by physical weathering in the catchments of the South Asian Rivers.
{"title":"Non-conservative behaviour of molybdenum in the Ganga (Hooghly) River estuary, India: Role of solute-particle interaction and sediment diagenesis","authors":"Rakesh K. Tiwari , Tarun K. Dalai , Rupak Samadder , Waliur Rahaman , Sunil K. Singh","doi":"10.1016/j.chemgeo.2024.122526","DOIUrl":"10.1016/j.chemgeo.2024.122526","url":null,"abstract":"<div><div>This study is focussed on understanding of molybdenum (Mo) cycling in the mesotidal to macrotidal estuary of the Ganga (Hooghly) River in India. Our investigation encompasses the composition of water and suspended particulate matter (SPM) samples collected in three separate periods (pre-monsoon: PrM, monsoon: M and post-monsoon: PoM) over two consecutive years, surface sediments, exchangeable phases of surface and suspended sediments, one sediment core, urban and industrial effluent waters and ground waters. The observed dissolved Mo concentrations in the estuary are in excess of those expected from conservative mixing of seawater and river water. The “excess” Mo values, observed in the mid-to-high salinity regions (4–27 ‰) for four out of the six study periods, are the highest in the monsoon samples. The bulk and exchangeable phase compositions are supportive of release of Mo from the Fe-Mn oxyhydroxide phases of the SPM and surface sediments in the estuary. Mass balance calculations indicate that Mo release from the SPM and surface sediments can account for up to 40 % of the median value of the “excess” Mo in the estuary. The compositions of the sediment core provide evidence for the mobilization of Mo and its release to porewater due to reductive dissolution of Fe-Mn oxyhydroxides. The tidally induced sediment resuspension likely facilitates the transport of porewater Mo to the overlying water. Mass balance calculations indicate that Mo loss from the sediment column can account for the bulk of the “excess” Mo in the estuary waters. This study further demonstrates that industrial effluents, urban waste waters and groundwaters do not constitute significant sources of dissolved Mo in the estuary.</div><div>The average annual Mo flux from the estuary is (∼2–3) × 10<sup>6</sup> mol, of which ∼30–50 % of Mo is due to estuarine addition. More significantly, Mo contribution from the Hooghly River estuary, accounting for ∼0.7–1.0 % of the global riverine Mo flux, is ∼3–4 folds higher than its water contribution (∼0.25 %) to the global river water flux. Our study highlights the role of interactions between oxyhydroxide phases and estuarine water, diagenetic mobilization of elements in the sediment column and porewater transport in the cycling of Mo in a monsoon-dominated tropical estuary with high sediment loads. We also demonstrate that the mobilization of Mo through chemical weathering is driven by physical weathering in the catchments of the South Asian Rivers.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"673 ","pages":"Article 122526"},"PeriodicalIF":3.6,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142815873","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-05DOI: 10.1016/j.chemgeo.2024.122529
A. Entrena , L.F. Auqué , M.J. Gimeno , J.J. Fornós
Calcite-aragonite bimineralic rafts and related waters from hypogenic lakes in the coastal cave of “Cova dets Ases”, Mallorca, have been analyzed for mineralogy and geochemistry (including stable isotopes). The main objective has been the evaluation of the factors that control the chemical and mineralogical composition of the precipitates as they are another natural example of the classical problem of aragonite vs calcite precipitation.
The hydrochemistry of the lakes in these coastal caves is mainly conditioned by the mixture of fresh and marine waters. The percentage of mixing, together with the CO2 degasification from the lakes water, seems to play a fundamental role in the precipitation of the carbonate rafts. However, their presence in the studied lakes does not show a homogeneous distribution in space and time and no clear relation has been found between that distribution and the evolution of any of the monitored environmental variables. With respect to their mineralogy, the main factor that seems to control the dominant bimineralic composition of the rafts studied here is the Mg/Ca ratio in the waters, which means the percentage of marine component in those waters. The variations of this ratio, in combination with changes in the degasification rate and in the oversaturation with respect to calcite and aragonite will condition the presence of one or the other polymorph. Even small microenvironmental variations seem to affect the order of precipitation of these bimineralic rafts.
Another important issue in this work is that the data obtained in this natural system have been used to check the most suitable δ18O isotope fractionation equations for the paleotemperature calculations from rafts precipitated in the past under similar conditions.
对马略卡岛“Cova dets Ases”沿海洞穴中方解石-文石双矿物筏体及相关水体进行了矿物学和地球化学（包括稳定同位素）分析。主要目的是评价控制沉淀物的化学和矿物学组成的因素，因为它们是文石与方解石沉淀的经典问题的另一个自然例子。
{"title":"Bimineralic calcite-aragonite rafts in the hypogeous lakes of Cova dets Ases (Mallorca): Controls on precipitation and polymorphism","authors":"A. Entrena , L.F. Auqué , M.J. Gimeno , J.J. Fornós","doi":"10.1016/j.chemgeo.2024.122529","DOIUrl":"10.1016/j.chemgeo.2024.122529","url":null,"abstract":"<div><div>Calcite-aragonite bimineralic rafts and related waters from hypogenic lakes in the coastal cave of “Cova dets Ases”, Mallorca, have been analyzed for mineralogy and geochemistry (including stable isotopes). The main objective has been the evaluation of the factors that control the chemical and mineralogical composition of the precipitates as they are another natural example of the classical problem of aragonite vs calcite precipitation.</div><div>The hydrochemistry of the lakes in these coastal caves is mainly conditioned by the mixture of fresh and marine waters. The percentage of mixing, together with the CO<sub>2</sub> degasification from the lakes water, seems to play a fundamental role in the precipitation of the carbonate rafts. However, their presence in the studied lakes does not show a homogeneous distribution in space and time and no clear relation has been found between that distribution and the evolution of any of the monitored environmental variables. With respect to their mineralogy, the main factor that seems to control the dominant bimineralic composition of the rafts studied here is the Mg/Ca ratio in the waters, which means the percentage of marine component in those waters. The variations of this ratio, in combination with changes in the degasification rate and in the oversaturation with respect to calcite and aragonite will condition the presence of one or the other polymorph. Even small microenvironmental variations seem to affect the order of precipitation of these bimineralic rafts.</div><div>Another important issue in this work is that the data obtained in this natural system have been used to check the most suitable δ<sup>18</sup>O isotope fractionation equations for the paleotemperature calculations from rafts precipitated in the past under similar conditions.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"673 ","pages":"Article 122529"},"PeriodicalIF":3.6,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142857728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-05DOI: 10.1016/j.chemgeo.2024.122554
Vladimír Strunga , Vladimír Havránek , Jan Lorinčík , Kristína Sihelská , Pavel Krist , Martina Havelcová , Bohuslava Čejková , Jiří Mizera
Advanced analytical methods including SEM/EDX and μ-PIXE/RBS microanalyses were used to investigate chemical alterations around uraniferous inclusions in a Cenomanian fossil resin (resinite). Studied alterations related to several types of discontinuities in resinite matrix are a model example of the phase interface between solid polymeric hydrocarbon and aqueous fluids exposed to long-term irradiation by heavy energetic ions resulting mostly from the natural decay of uranium. Computational models of ion ranges correspond well with the observed range of alterations about 35 μm from uraniferous inclusions. The major alteration is found within a 20 μm inner zone. It is characterized by distinct sulfur enrichment and an increase in the O/C ratio. No sulfur enrichment in the resinite matrix occurs apart from the uraniferous phases. Proton beam-induced alterations of the resinite were investigated and compared with the natural ones. The differences indicate the importance of aqueous fluids in the natural radiation-induced alteration process. It is concluded that radiation-enhanced mass transfer and reactions occur at solid-fluid interfaces during the long-term energy deposition by alphas, alpha recoils, and fission fragments combined. The role of thermal effects and and formation of radical species by radiolysis of aqueous fluids on a microscale is discussed.
{"title":"Radiation-enhanced fluid diffusion and alteration around uraniferous inclusions in Cenomanian resinite from North Bohemia","authors":"Vladimír Strunga , Vladimír Havránek , Jan Lorinčík , Kristína Sihelská , Pavel Krist , Martina Havelcová , Bohuslava Čejková , Jiří Mizera","doi":"10.1016/j.chemgeo.2024.122554","DOIUrl":"10.1016/j.chemgeo.2024.122554","url":null,"abstract":"<div><div>Advanced analytical methods including SEM/EDX and μ-PIXE/RBS microanalyses were used to investigate chemical alterations around uraniferous inclusions in a Cenomanian fossil resin (resinite). Studied alterations related to several types of discontinuities in resinite matrix are a model example of the phase interface between solid polymeric hydrocarbon and aqueous fluids exposed to long-term irradiation by heavy energetic ions resulting mostly from the natural decay of uranium. Computational models of ion ranges correspond well with the observed range of alterations about 35 μm from uraniferous inclusions. The major alteration is found within a 20 μm inner zone. It is characterized by distinct sulfur enrichment and an increase in the O/C ratio. No sulfur enrichment in the resinite matrix occurs apart from the uraniferous phases. Proton beam-induced alterations of the resinite were investigated and compared with the natural ones. The differences indicate the importance of aqueous fluids in the natural radiation-induced alteration process. It is concluded that radiation-enhanced mass transfer and reactions occur at solid-fluid interfaces during the long-term energy deposition by alphas, alpha recoils, and fission fragments combined. The role of thermal effects and and formation of radical species by radiolysis of aqueous fluids on a microscale is discussed.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"673 ","pages":"Article 122554"},"PeriodicalIF":3.6,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142858009","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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