Pub Date : 2024-12-31DOI: 10.1016/j.chemgeo.2024.122603
Etienne Skrzypek, Daniela Gallhofer, Christoph Hauzenberger, Isabella Haas, Anh Thi Quynh Nong, Harald Fritz, Milan Kohút, Viljem Podgoršek, Zmago Žorž
Allanite is a REE-bearing, epidote-group mineral that incorporates Th, U, but also initial Pb. This results in UPb isotopic analyses defining a mixing trend between an initial and radiogenic Pb component. So far, only the latter has been given attention because it can reveal the age of various geological events, whereas the significance of the former has been neglected. We explore both the age and initial Pb isotopic composition of nine magmatic samples (volcanic, plutonic, pegmatitic) with emplacement ages that cover nearly the entire Phanerozoic (∼ 540–19 Ma). We first characterize the major-element composition of allanite by EPMA, then measure its (Th–)U–Pb isotopic composition in situ by LA-MC-ICP-MS using zircon as reference material. UPb data are regressed to determine both the crystallization age and initial 207Pb/206Pb0 composition. These results are compared to the UPb age of co-genetic zircon and the 207Pb/206Pb ratio of coexisting feldspar from the same samples or localities, respectively. Their good agreement (mainly less than ∼4 % and 1 % offset, respectively) supports the validity of our analytical protocol. The accuracy of age and 207Pb/206Pb0 results is governed by the proportion of initial Pb, f(206Pb0), especially its minimum (for age)/maximum (for 207Pb/206Pb0) value, while precision is chiefly controlled by the centroid of f(206Pb0) distribution. Calculations using published allanite/melt partition coefficients show that a 230Th disequilibrium correction based on the whole-rock Th/U is not only appropriate for magmatic samples, but also necessary to improve accuracy. In four samples the 207Pb/206Pb0 ratios obtained from allanite are lower than values predicted by terrestrial Pb evolution models at the time of emplacement, showing that anchoring a regression line to a fixed Pb composition is not always valid. Although it does not affect age determination, it overlooks the potential of allanite UPb data for constraining the radiogenic character of crustal magma sources.
{"title":"Investigating the crystallization age and initial lead composition of Phanerozoic magmatic allanites by LA-MC-ICP-MS","authors":"Etienne Skrzypek, Daniela Gallhofer, Christoph Hauzenberger, Isabella Haas, Anh Thi Quynh Nong, Harald Fritz, Milan Kohút, Viljem Podgoršek, Zmago Žorž","doi":"10.1016/j.chemgeo.2024.122603","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122603","url":null,"abstract":"Allanite is a REE-bearing, epidote-group mineral that incorporates Th, U, but also initial Pb. This results in U<ce:glyph name=\"sbnd\"></ce:glyph>Pb isotopic analyses defining a mixing trend between an initial and radiogenic Pb component. So far, only the latter has been given attention because it can reveal the age of various geological events, whereas the significance of the former has been neglected. We explore both the age <ce:italic>and</ce:italic> initial Pb isotopic composition of nine magmatic samples (volcanic, plutonic, pegmatitic) with emplacement ages that cover nearly the entire Phanerozoic (∼ 540–19 Ma). We first characterize the major-element composition of allanite by EPMA, then measure its (Th–)U–Pb isotopic composition in situ by LA-MC-ICP-MS using zircon as reference material. U<ce:glyph name=\"sbnd\"></ce:glyph>Pb data are regressed to determine both the crystallization age and initial <ce:sup loc=\"post\">207</ce:sup>Pb/<ce:sup loc=\"post\">206</ce:sup>Pb<ce:inf loc=\"post\">0</ce:inf> composition. These results are compared to the U<ce:glyph name=\"sbnd\"></ce:glyph>Pb age of co-genetic zircon and the <ce:sup loc=\"post\">207</ce:sup>Pb<ce:sup loc=\"post\">/206</ce:sup>Pb ratio of coexisting feldspar from the same samples or localities, respectively. Their good agreement (mainly less than ∼4 % and 1 % offset, respectively) supports the validity of our analytical protocol. The accuracy of age and <ce:sup loc=\"post\">207</ce:sup>Pb/<ce:sup loc=\"post\">206</ce:sup>Pb<ce:inf loc=\"post\">0</ce:inf> results is governed by the proportion of initial Pb, <ce:italic>f(</ce:italic><ce:sup loc=\"post\">206</ce:sup>Pb<ce:inf loc=\"post\">0</ce:inf>), especially its minimum (for age)/maximum (for <ce:sup loc=\"post\">207</ce:sup>Pb/<ce:sup loc=\"post\">206</ce:sup>Pb<ce:inf loc=\"post\">0</ce:inf>) value, while precision is chiefly controlled by the centroid of <ce:italic>f(</ce:italic><ce:sup loc=\"post\">206</ce:sup>Pb<ce:inf loc=\"post\">0</ce:inf>) distribution. Calculations using published allanite/melt partition coefficients show that a <ce:sup loc=\"post\">230</ce:sup>Th disequilibrium correction based on the whole-rock Th/U is not only appropriate for magmatic samples, but also necessary to improve accuracy. In four samples the <ce:sup loc=\"post\">207</ce:sup>Pb/<ce:sup loc=\"post\">206</ce:sup>Pb<ce:inf loc=\"post\">0</ce:inf> ratios obtained from allanite are lower than values predicted by terrestrial Pb evolution models at the time of emplacement, showing that anchoring a regression line to a fixed Pb composition is not always valid. Although it does not affect age determination, it overlooks the potential of allanite U<ce:glyph name=\"sbnd\"></ce:glyph>Pb data for constraining the radiogenic character of crustal magma sources.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"15 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142940014","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 : 2024-12-31DOI: 10.1016/j.chemgeo.2024.122606
Cristian Abraham Rivera Armendariz, Antonio Cardona Benavides, Andre Banning
Fluoride (F), arsenic (As) and uranium (U) are naturally occurring trace elements that cause adverse health effects when ingested by humans. The groundwater in the cities of Chihuahua, Zacatecas and Salinas, Mexico, have elevated concentrations of these elements that are linked to felsic magmatic sequences (rhyolites, ignimbrites and granites; comprising the Sierra Madre Occidental and Mesa Central) and sediments derived from these rocks. Recent studies have identified that these elements´ host phases are fluorapatite, biotite, fluorite and glassy matrix. However, the remobilization mechanisms and efficiency of the different bearing phases from the rocks and/or sediments to groundwater are rarely characterized. In a multi-method approach that combines the analysis of groundwater geochemistry, different degrees of rock alteration, and sequential extractions procedure (SEP), the mechanisms of mobilization, as well as the fractions that contribute higher concentrations of As, F and U to the environment are proposed. Based on the present study the presence and distribution of As, F and U in groundwater are associated with fault zones in rhyolitic and ignimbrite volcanic rocks, and basin fill sediments derived from this type of rocks, deposited in the central parts of basins. The concentration of F and As exceed the drinking water limits set by both the World Health Organization (WHO) and Mexican standards by several orders of magnitude in numerous wells (>60 %), which indicates a substantial and general water quality problem. Weathering has been identified as one of the main mechanisms favoring F, As and U mobilization from the bearing phases to groundwater. This process is controlled and benefited by the different bearing phases of F, As and U (F-apatite, biotite and glassy matrix), oxidizing conditions (Eh ≈340), neutral pH (≈7.7), high temperatures (>27 °C) and regional flows. The solid phase F, As, and U fractionations were characterized by means of a modified SEP. The results showed that F is mainly linked to F-apatite and the silicate portion (biotite and glassy matrix), while As and U are strongly related to the silicate fraction associated with the glassy matrix. This research gives insight into F, As and U geochemistry and mobilization processes that can be used to further guide research needs in this area for the protection of groundwater resources. In addition, methodologies and results obtained can be transferred to geogenically impacted zones in Latin America and other parts of the world.
{"title":"Origin and fate control of F, As and U in groundwater flow systems of the Sierra Madre Occidental and Mesa Central, Mexico","authors":"Cristian Abraham Rivera Armendariz, Antonio Cardona Benavides, Andre Banning","doi":"10.1016/j.chemgeo.2024.122606","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122606","url":null,"abstract":"Fluoride (F), arsenic (As) and uranium (U) are naturally occurring trace elements that cause adverse health effects when ingested by humans. The groundwater in the cities of Chihuahua, Zacatecas and Salinas, Mexico, have elevated concentrations of these elements that are linked to felsic magmatic sequences (rhyolites, ignimbrites and granites; comprising the Sierra Madre Occidental and Mesa Central) and sediments derived from these rocks. Recent studies have identified that these elements´ host phases are fluorapatite, biotite, fluorite and glassy matrix. However, the remobilization mechanisms and efficiency of the different bearing phases from the rocks and/or sediments to groundwater are rarely characterized. In a multi-method approach that combines the analysis of groundwater geochemistry, different degrees of rock alteration, and sequential extractions procedure (SEP), the mechanisms of mobilization, as well as the fractions that contribute higher concentrations of As, F and U to the environment are proposed. Based on the present study the presence and distribution of As, F and U in groundwater are associated with fault zones in rhyolitic and ignimbrite volcanic rocks, and basin fill sediments derived from this type of rocks, deposited in the central parts of basins. The concentration of F and As exceed the drinking water limits set by both the World Health Organization (WHO) and Mexican standards by several orders of magnitude in numerous wells (>60 %), which indicates a substantial and general water quality problem. Weathering has been identified as one of the main mechanisms favoring F, As and U mobilization from the bearing phases to groundwater. This process is controlled and benefited by the different bearing phases of F, As and U (F-apatite, biotite and glassy matrix), oxidizing conditions (Eh ≈340), neutral pH (≈7.7), high temperatures (>27 °C) and regional flows. The solid phase F, As, and U fractionations were characterized by means of a modified SEP. The results showed that F is mainly linked to F-apatite and the silicate portion (biotite and glassy matrix), while As and U are strongly related to the silicate fraction associated with the glassy matrix. This research gives insight into F, As and U geochemistry and mobilization processes that can be used to further guide research needs in this area for the protection of groundwater resources. In addition, methodologies and results obtained can be transferred to geogenically impacted zones in Latin America and other parts of the world.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"67 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142939819","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 : 2024-12-30DOI: 10.1016/j.chemgeo.2024.122590
Boriana Kalderon-Asael, Jiuyuan Wang, Noah J. Planavsky, Amanda M. Oehlert, Brooke E. Vitek, R. Pamela Reid, Lidya G. Tarhan
Lithium (δ7Li) and stable strontium isotope (δ88/86Sr) ratios of shallow marine carbonate sediments serve as valuable proxies for reconstructing both seawater δ7Li and δ88/86Sr behavior and diverse geological processes. However, interpretations of these isotope values can be complicated by diagenesis. We conducted mineralogical, petrographic, and geochemical analyses of different sediment size fractions from two cores collected from distinct shallow marine depositional settings in the Bahamas, with the aim of evaluating the impact of early diagenetic processes on shallow water carbonate δ7Li and δ88/86Sr values. We found that the finest grain size fraction (i.e., < 63 μm or mud) is particularly vulnerable to recrystallization, leading to notable alteration of both δ7Li and δ88/86Sr values of mud-sized sediments relative to bulk sediment composition and expected fractionations from seawater. We interpret these data to reflect greater extents of recrystallization and secondary carbonate formation in the mud-sized fraction, linked to higher surface area to volume ratios. Although the alteration of the mud fraction appears to have minimally impacted bulk-sediment δ88/86Sr or δ7Li values, these findings expand the framework for interpreting the δ7Li and δ88/86Sr values of carbonate sediments.
{"title":"Evaluation of early diagenetic signatures of lithium and stable strontium isotopes in shallow marine carbonate sediments","authors":"Boriana Kalderon-Asael, Jiuyuan Wang, Noah J. Planavsky, Amanda M. Oehlert, Brooke E. Vitek, R. Pamela Reid, Lidya G. Tarhan","doi":"10.1016/j.chemgeo.2024.122590","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122590","url":null,"abstract":"Lithium (δ<ce:sup loc=\"post\">7</ce:sup>Li) and stable strontium isotope (δ<ce:sup loc=\"post\">88/86</ce:sup>Sr) ratios of shallow marine carbonate sediments serve as valuable proxies for reconstructing both seawater δ<ce:sup loc=\"post\">7</ce:sup>Li and δ<ce:sup loc=\"post\">88/86</ce:sup>Sr behavior and diverse geological processes. However, interpretations of these isotope values can be complicated by diagenesis. We conducted mineralogical, petrographic, and geochemical analyses of different sediment size fractions from two cores collected from distinct shallow marine depositional settings in the Bahamas, with the aim of evaluating the impact of early diagenetic processes on shallow water carbonate δ<ce:sup loc=\"post\">7</ce:sup>Li and δ<ce:sup loc=\"post\">88/86</ce:sup>Sr values. We found that the finest grain size fraction (i.e., < 63 μm or mud) is particularly vulnerable to recrystallization, leading to notable alteration of both δ<ce:sup loc=\"post\">7</ce:sup>Li and δ<ce:sup loc=\"post\">88/86</ce:sup>Sr values of mud-sized sediments relative to bulk sediment composition and expected fractionations from seawater. We interpret these data to reflect greater extents of recrystallization and secondary carbonate formation in the mud-sized fraction, linked to higher surface area to volume ratios. Although the alteration of the mud fraction appears to have minimally impacted bulk-sediment δ<ce:sup loc=\"post\">88/86</ce:sup>Sr or δ<ce:sup loc=\"post\">7</ce:sup>Li values, these findings expand the framework for interpreting the δ<ce:sup loc=\"post\">7</ce:sup>Li and δ<ce:sup loc=\"post\">88/86</ce:sup>Sr values of carbonate sediments.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"51 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143021233","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 : 2024-12-30DOI: 10.1016/j.chemgeo.2024.122609
Urszula Solecka, Bartosz Puzio, Michael Kersten, Justyna Topolska, Maciej Manecki, Tomasz Bajda
Ternary isomorphic lead apatite system comprises mimetite (Pb5(AsO4)3Cl, Mim), vanadinite (Pb5(VO4)3Cl, Vna), and pyromorphite (Pb5(PO4)3Cl, Pym). These phases are frequently studied for environmental applications, such as immobilization of trace metals and metalloids. Despite extensive knowledge of the endmembers, thermodynamic data for the intermediate phases in the Mim–Vna series and their temperature-dependent stability are lacking. This gap was addressed by studying the effect of vanadate substitution on the solubility of the Mim–Vna series, the effect of temperature on dissolution mechanisms and secondary phase formation, and by quantifying the solubility constants (Ksp) at different temperatures (5–65 °C). The Ksp for Mim–Vna phases decreases linearly with V content, showing progressive dissolution with temperature. Dissolution in the Mim–Vna series transitions from congruent to non-congruent as the V content increases, leading to the precipitation of chervetite (Pb2V2O7), particularly at higher temperatures (45–65 °C). Therefore, the concentration of Pb2+ in solution is controlled by chervetite precipitation, unlike the Mim–Pym system, in which Pym controls lead solubility. These findings enhance our understanding of the behavior of lead apatites in contaminated environments. The new solubility constants can be directly implemented into existing thermodynamic databases for geochemical modeling, aiding in the prediction of lead and metalloid behavior in aqueous systems for optimization of remediation strategies.
{"title":"Solubility of mimetite Pb5(AsO4)3Cl – Vanadinite Pb5(VO4)3Cl solid solution series at 5–65 °C","authors":"Urszula Solecka, Bartosz Puzio, Michael Kersten, Justyna Topolska, Maciej Manecki, Tomasz Bajda","doi":"10.1016/j.chemgeo.2024.122609","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122609","url":null,"abstract":"Ternary isomorphic lead apatite system comprises mimetite (Pb<ce:inf loc=\"post\">5</ce:inf>(AsO<ce:inf loc=\"post\">4</ce:inf>)<ce:inf loc=\"post\">3</ce:inf>Cl, Mim), vanadinite (Pb<ce:inf loc=\"post\">5</ce:inf>(VO<ce:inf loc=\"post\">4</ce:inf>)<ce:inf loc=\"post\">3</ce:inf>Cl, Vna), and pyromorphite (Pb<ce:inf loc=\"post\">5</ce:inf>(PO<ce:inf loc=\"post\">4</ce:inf>)<ce:inf loc=\"post\">3</ce:inf>Cl, Pym). These phases are frequently studied for environmental applications, such as immobilization of trace metals and metalloids. Despite extensive knowledge of the endmembers, thermodynamic data for the intermediate phases in the Mim–Vna series and their temperature-dependent stability are lacking. This gap was addressed by studying the effect of vanadate substitution on the solubility of the Mim–Vna series, the effect of temperature on dissolution mechanisms and secondary phase formation, and by quantifying the solubility constants (<ce:italic>K</ce:italic><ce:inf loc=\"post\">sp</ce:inf>) at different temperatures (5–65 °C). The <ce:italic>K</ce:italic><ce:inf loc=\"post\">sp</ce:inf> for Mim–Vna phases decreases linearly with V content, showing progressive dissolution with temperature. Dissolution in the Mim–Vna series transitions from congruent to non-congruent as the V content increases, leading to the precipitation of chervetite (Pb<ce:inf loc=\"post\">2</ce:inf>V<ce:inf loc=\"post\">2</ce:inf>O<ce:inf loc=\"post\">7</ce:inf>), particularly at higher temperatures (45–65 °C). Therefore, the concentration of Pb<ce:sup loc=\"post\">2+</ce:sup> in solution is controlled by chervetite precipitation, unlike the Mim–Pym system, in which Pym controls lead solubility. These findings enhance our understanding of the behavior of lead apatites in contaminated environments. The new solubility constants can be directly implemented into existing thermodynamic databases for geochemical modeling, aiding in the prediction of lead and metalloid behavior in aqueous systems for optimization of remediation strategies.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"72 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142912315","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}
Hidaka Trough, a marine hydrate reservoir in the northwestern Pacific, is characterized by its gas chimney structures, faults, methane plumes, and degassing structures, providing pathways for the upward migration of free hydrocarbon gases from deep sediments to the seabed. A comprehensive understanding of methane emissions from Hidaka Trough sediments in the past and present holds the key to predicting future scenarios of methane emission. This study applied a multi-proxy approach to three sediment cores (PC1609, PC1611, and PC1727) from cold seep regions of the Hidaka Trough in the northwestern Pacific to reconstruct the local history of methane emissions. The chronostratigraphic framework of the cores was established using accelerator mass spectrometry (AMS) radiocarbon dates and δ18O profiles of benthic foraminifera, indicating that the cores were deposited during the Holocene. The geochemical composition of hydrocarbon gases within the sediments suggested a microbial origin or a mixture of microbial and thermogenic gases.
{"title":"Records of past methane discharges from Holocene cold seeps of Hidaka Trough based on carbon isotope values of benthic foraminifera","authors":"Mahsa Saeidi Ortakand, Hitoshi Tomaru, Ryo Matsumoto","doi":"10.1016/j.chemgeo.2024.122608","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122608","url":null,"abstract":"Hidaka Trough, a marine hydrate reservoir in the northwestern Pacific, is characterized by its gas chimney structures, faults, methane plumes, and degassing structures, providing pathways for the upward migration of free hydrocarbon gases from deep sediments to the seabed. A comprehensive understanding of methane emissions from Hidaka Trough sediments in the past and present holds the key to predicting future scenarios of methane emission. This study applied a multi-proxy approach to three sediment cores (PC1609, PC1611, and PC1727) from cold seep regions of the Hidaka Trough in the northwestern Pacific to reconstruct the local history of methane emissions. The chronostratigraphic framework of the cores was established using accelerator mass spectrometry (AMS) radiocarbon dates and δ<ce:sup loc=\"post\">18</ce:sup>O profiles of benthic foraminifera, indicating that the cores were deposited during the Holocene. The geochemical composition of hydrocarbon gases within the sediments suggested a microbial origin or a mixture of microbial and thermogenic gases.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"39 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142940011","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 : 2024-12-27DOI: 10.1016/j.chemgeo.2024.122601
Wen-Xuan Sun, Mao-Xu Zhu, Gui-Peng Yang, Tie Li, Qing-Qing Li, Zhen Xu, Ying-Jian Han
Dissolved iron (DFe) and manganese (DMn) diffusive/benthic fluxes and DFe species in sediments of marginal seas not dominated by major upwelling or riverine inputs have not been well documented. Here, solid-phase and porewater chemistry of sediments was used to quantify diffusive/benthic fluxes of DFe and DMn, and to elucidate the factors governing the fluxes from muddy sediments of the South Yellow Sea (SYS), a representative semi-enclosed shelf sea remote to major rivers. Results show that porewater DFe is produced mainly by dissimilatory iron reduction coupled to organic carbon (OC) mineralization, while DMn is produced dominantly by Mn-oxide reduction coupled to Fe2+ oxidation. Most upwardly diffusing Fe2+ is oxidized in the oxic sediment layer, while organic-Fe(III) complexes is mainly responsible for benthic DFe release, with its relative contributions from 63 % to nearly 100 %. Unlike DFe, DMn is expected to effectively diffuse upward into the overlying water, indicated by nearly 1:1 ratios of its diffusive fluxes to depth-integrated rates of production. Benthic fluxes of DFe (0.98–5.8 μmol/m2/d) and DMn (1.3–249 μmol/m2/d) from the SYS muddy sediments exhibit a high spatial heterogeneity, with a “sweet spot” at the western area, which is controlled largely by local/regional depositional settings and, to a less extent, by local diagenetic regimes. Overall, the semi-enclosed SYS sediment is not a hotspot of benthic DFe release, compared to other marginal seas under various depositional settings, which is attributable to low availability of labile OC and reactive Fe due to its remoteness to major rivers. Unlike DFe, benthic DMn fluxes in the SYS are comparable to those in other marginal seas including river-dominated areas, which is ascribable to refluxing-induced Mn enrichment in surface sediments as a common mechanism to sustain Mn redox cycling and benthic release.
{"title":"Diagenetic cycling and diffusive/benthic fluxes of iron and manganese in sediments of a large semi-enclosed sea remote to major rivers","authors":"Wen-Xuan Sun, Mao-Xu Zhu, Gui-Peng Yang, Tie Li, Qing-Qing Li, Zhen Xu, Ying-Jian Han","doi":"10.1016/j.chemgeo.2024.122601","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122601","url":null,"abstract":"Dissolved iron (DFe) and manganese (DMn) diffusive/benthic fluxes and DFe species in sediments of marginal seas not dominated by major upwelling or riverine inputs have not been well documented. Here, solid-phase and porewater chemistry of sediments was used to quantify diffusive/benthic fluxes of DFe and DMn, and to elucidate the factors governing the fluxes from muddy sediments of the South Yellow Sea (SYS), a representative semi-enclosed shelf sea remote to major rivers. Results show that porewater DFe is produced mainly by dissimilatory iron reduction coupled to organic carbon (OC) mineralization, while DMn is produced dominantly by Mn-oxide reduction coupled to Fe<ce:sup loc=\"post\">2+</ce:sup> oxidation. Most upwardly diffusing Fe<ce:sup loc=\"post\">2+</ce:sup> is oxidized in the oxic sediment layer, while organic-Fe(III) complexes is mainly responsible for benthic DFe release, with its relative contributions from 63 % to nearly 100 %. Unlike DFe, DMn is expected to effectively diffuse upward into the overlying water, indicated by nearly 1:1 ratios of its diffusive fluxes to depth-integrated rates of production. Benthic fluxes of DFe (0.98–5.8 μmol/m<ce:sup loc=\"post\">2</ce:sup>/d) and DMn (1.3–249 μmol/m<ce:sup loc=\"post\">2</ce:sup>/d) from the SYS muddy sediments exhibit a high spatial heterogeneity, with a “sweet spot” at the western area, which is controlled largely by local/regional depositional settings and, to a less extent, by local diagenetic regimes. Overall, the semi-enclosed SYS sediment is not a hotspot of benthic DFe release, compared to other marginal seas under various depositional settings, which is attributable to low availability of labile OC and reactive Fe due to its remoteness to major rivers. Unlike DFe, benthic DMn fluxes in the SYS are comparable to those in other marginal seas including river-dominated areas, which is ascribable to refluxing-induced Mn enrichment in surface sediments as a common mechanism to sustain Mn redox cycling and benthic release.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"27 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142912313","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 : 2024-12-24DOI: 10.1016/j.chemgeo.2024.122589
Leonardo Corecco, Matthew J. Kohn, Vitor P. Pereira, Linda M. Reynard, Cesar L. Schultz
Bones and teeth incorporate stable isotopes of C and O from an animal's food and water sources that can provide paleoecological and paleoenvironmental information. In this study, thirty-six samples of fossil bones and teeth were collected from two Triassic allostratigraphic units of the Rio Grande do Sul State, Brazil, and analyzed for δ13C and δ18O values. Specific strata include Pinheiros-Chiniquá Sequence (Late Ladinian/Early Carnian) which includes the Dinodontosaurus Assemblage Zone (15 specimens analyzed) and the basal portion of the Candelária Sequence (Late Carnian) in which the Hyperodapedon Assemblage Zone occurs (21 specimens analyzed). The latter assemblage zone was deposited during the Carnian Pluvial Episode, generally characterized by warmer and wetter conditions. Specimens of tooth enamel from the Dinodontosaurus Assemblage Zone have δ13C values ranging from −10.8 to −7.0 ‰ (VPDB) and δ18O values from 16.3 to 23.5 ‰ (VSMOW). In contrast, specimens from the Hyperodapedon Assemblage Zone have overlapping but generally higher δ13C values ranging from −9.0 to −4.8 ‰ and overlapping but higher δ18O values from 19.7 to 27.4 ‰. Evidently, the Carnian Pluvial Episode coincided with higher δ13C and δ18O values, which could represent warmer (higher δ18O) conditions in this region. Although higher δ13C values can indicate greater aridity, atmospheric δ13C compositions were dramatically (2–3 ‰) higher during the Carnian than the earlier Middle Triassic epoch. Within uncertainties, the 2 ‰ increases to fossil δ13C values could be consistent with either constant or increased precipitation. Climate change during the Late Triassic could have helped drive profound faunal turnover during this episode, including dinosaur evolution and diversification.
{"title":"Paleoenvironmental and Paleoecological reconstruction of Santa Maria Supersequence units (Middle to Late Triassic, Brazil) based on stable isotope data: Influence of the Carnian Pluvial Episode","authors":"Leonardo Corecco, Matthew J. Kohn, Vitor P. Pereira, Linda M. Reynard, Cesar L. Schultz","doi":"10.1016/j.chemgeo.2024.122589","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122589","url":null,"abstract":"Bones and teeth incorporate stable isotopes of C and O from an animal's food and water sources that can provide paleoecological and paleoenvironmental information. In this study, thirty-six samples of fossil bones and teeth were collected from two Triassic allostratigraphic units of the Rio Grande do Sul State, Brazil, and analyzed for δ<ce:sup loc=\"post\">13</ce:sup>C and δ<ce:sup loc=\"post\">18</ce:sup>O values. Specific strata include Pinheiros-Chiniquá Sequence (Late Ladinian/Early Carnian) which includes the <ce:italic>Dinodontosaurus</ce:italic> Assemblage Zone (15 specimens analyzed) and the basal portion of the Candelária Sequence (Late Carnian) in which the <ce:italic>Hyperodapedon</ce:italic> Assemblage Zone occurs (21 specimens analyzed). The latter assemblage zone was deposited during the Carnian Pluvial Episode, generally characterized by warmer and wetter conditions. Specimens of tooth enamel from the <ce:italic>Dinodontosaurus</ce:italic> Assemblage Zone have δ<ce:sup loc=\"post\">13</ce:sup>C values ranging from −10.8 to −7.0 ‰ (VPDB) and δ<ce:sup loc=\"post\">18</ce:sup>O values from 16.3 to 23.5 ‰ (VSMOW). In contrast, specimens from the <ce:italic>Hyperodapedon</ce:italic> Assemblage Zone have overlapping but generally higher δ<ce:sup loc=\"post\">13</ce:sup>C values ranging from −9.0 to −4.8 ‰ and overlapping but higher δ<ce:sup loc=\"post\">18</ce:sup>O values from 19.7 to 27.4 ‰. Evidently, the Carnian Pluvial Episode coincided with higher δ<ce:sup loc=\"post\">13</ce:sup>C and δ<ce:sup loc=\"post\">18</ce:sup>O values, which could represent warmer (higher δ<ce:sup loc=\"post\">18</ce:sup>O) conditions in this region. Although higher δ<ce:sup loc=\"post\">13</ce:sup>C values can indicate greater aridity, atmospheric δ<ce:sup loc=\"post\">13</ce:sup>C compositions were dramatically (2–3 ‰) higher during the Carnian than the earlier Middle Triassic epoch. Within uncertainties, the 2 ‰ increases to fossil δ<ce:sup loc=\"post\">13</ce:sup>C values could be consistent with either constant or increased precipitation. Climate change during the Late Triassic could have helped drive profound faunal turnover during this episode, including dinosaur evolution and diversification.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"19 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142912314","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}
Phosphate rocks are the most important natural source of phosphorus. While a large literature discusses the conditions of their formation in marine environments, few document their formation in a terrestrial context. The Quercy phosphate mines in south-west France, known as phosphatières, are notable for their exceptional Cenozoic palaeontological content and represent a rare example of phosphate precipitation in a non-marine environment. Using the Dams ‘phosphatière’ as an example, this paper reconstructs the conditions under which these terrestrial phosphorites formed during the Eocene-Oligocene interval by analysing karstic sediments (sedimentology, grain size, mineralogy, and geochemistry). It discusses the origin of the karst infills and the processes involved in the genesis of phosphate minerals. The site shows three phases of infill that frame the Eocene-Oligocene transition (EOT). Each deposit contains both a detrital fraction and a phosphate-bearing neo‐formed fraction. The detrital input results from the mass transport of Eocene-Oligocene “siderolithic” sediments (formation of reddish clays with ferruginous concretions) derived from the reworking of lateritic paleosols. This siderolithic material was formed at the surface directly from fresh detrital sediments resulting from the mechanical alteration of the crystalline parent rock, located to the east in the French Massif Central.
{"title":"Phosphate precipitation, phosphatisation and detrital filling dynamics in karstic contexts: The example of the Dams ‘phosphatière’, Quercy (SW France)","authors":"Carine Lézin, Kévin Moreau, Sébastien Fabre, Christian Dupuis, Thierry Pelissié, Patrick Sorriaux, Gilles Escarguel, Maeva Orliac, Pierre-Olivier Antoine, Monique Vianey-Liaud, Romain Weppe","doi":"10.1016/j.chemgeo.2024.122586","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122586","url":null,"abstract":"Phosphate rocks are the most important natural source of phosphorus. While a large literature discusses the conditions of their formation in marine environments, few document their formation in a terrestrial context. The Quercy phosphate mines in south-west France, known as <ce:italic>phosphatières</ce:italic>, are notable for their exceptional Cenozoic palaeontological content and represent a rare example of phosphate precipitation in a non-marine environment. Using the Dams ‘phosphatière’ as an example, this paper reconstructs the conditions under which these terrestrial phosphorites formed during the Eocene-Oligocene interval by analysing karstic sediments (sedimentology, grain size, mineralogy, and geochemistry). It discusses the origin of the karst infills and the processes involved in the genesis of phosphate minerals. The site shows three phases of infill that frame the Eocene-Oligocene transition (EOT). Each deposit contains both a detrital fraction and a phosphate-bearing neo‐formed fraction. The detrital input results from the mass transport of Eocene-Oligocene “siderolithic” sediments (formation of reddish clays with ferruginous concretions) derived from the reworking of lateritic paleosols. This siderolithic material was formed at the surface directly from fresh detrital sediments resulting from the mechanical alteration of the crystalline parent rock, located to the east in the French Massif Central.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"204 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142940013","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 : 2024-12-22DOI: 10.1016/j.chemgeo.2024.122588
Joan Gutiérrez-León, Sergio Carrero, Devis Di Tommaso, Dimitrios Toroz, Alejandro Fernandez-Martinez, Antonio Aguilar, Alba Lozano, Rafael Pérez-López, Josep M. Soler, Jordi Cama
Schwertmannite as a sink for rare earth elements (REEs) in environments affected by acid mine drainage (AMD) plays a significant role in the fate of these elements. The conditions to precipitate schwertmannite (i.e., sulfate-rich water and pH between 2.5 and 3.5) are not suitable for this Fe-oxyhydroxysulfate (Fe8O8(OH)6SO4) to adsorb REEs. In estuaries where AMD-impacted rivers meet (e.g. the Odiel and the Tinto rivers in the Ría de Huelva estuary in SW Spain), AMD mixes with seawater raising the pH between 4.5 and 8, thereby enabling REE adsorption on schwertmannite at circumneutral pH. However, the estuarine tidal dynamics exposes REE-enriched schwertmannite to more acidic water, inducing REE desorption, which has yet to be studied.
在酸性矿山水环境中，Schwertmannite作为稀土元素（ree）的汇，在稀土元素的去向中起着重要的作用。施魏锰矿的沉淀条件（即富硫酸盐水，pH值在2.5 ~ 3.5之间）不适合这种羟基氧化铁（Fe8O8(OH)6SO4）吸附稀土。在受AMD影响的河流汇合处的河口（如西班牙西南部Ría de Huelva河口的Odiel河和Tinto河），AMD与海水混合，使pH值在4.5 - 8之间升高，从而使稀土元素在pH值为环中性的施wertmannite上吸附。然而，河口潮汐动力学使富含稀土元素的施wertmannite暴露在酸性更强的水中，从而导致稀土元素的解吸，这一点尚有待研究。
{"title":"Desorption of rare earth elements (REEs) from schwertmannite under acid mine drainage (AMD) and AMD-seawater conditions","authors":"Joan Gutiérrez-León, Sergio Carrero, Devis Di Tommaso, Dimitrios Toroz, Alejandro Fernandez-Martinez, Antonio Aguilar, Alba Lozano, Rafael Pérez-López, Josep M. Soler, Jordi Cama","doi":"10.1016/j.chemgeo.2024.122588","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122588","url":null,"abstract":"Schwertmannite as a sink for rare earth elements (REEs) in environments affected by acid mine drainage (AMD) plays a significant role in the fate of these elements. The conditions to precipitate schwertmannite (i.e., sulfate-rich water and pH between 2.5 and 3.5) are not suitable for this Fe-oxyhydroxysulfate (Fe<ce:inf loc=\"post\">8</ce:inf>O<ce:inf loc=\"post\">8</ce:inf>(OH)<ce:inf loc=\"post\">6</ce:inf>SO<ce:inf loc=\"post\">4</ce:inf>) to adsorb REEs. In estuaries where AMD-impacted rivers meet (e.g. the Odiel and the Tinto rivers in the Ría de Huelva estuary in SW Spain), AMD mixes with seawater raising the pH between 4.5 and 8, thereby enabling REE adsorption on schwertmannite at circumneutral pH. However, the estuarine tidal dynamics exposes REE-enriched schwertmannite to more acidic water, inducing REE desorption, which has yet to be studied.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"27 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142912316","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 : 2024-12-22DOI: 10.1016/j.chemgeo.2024.122585
José F. Molina, Aitor Cambeses, Antonio García-Casco, Pilar Montero
{"title":"Key accessory minerals for understanding igneous petrogenesis and crustal evolution: A celebration of the contributions by Fernando Bea","authors":"José F. Molina, Aitor Cambeses, Antonio García-Casco, Pilar Montero","doi":"10.1016/j.chemgeo.2024.122585","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122585","url":null,"abstract":"","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"344 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142912317","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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