Pub Date : 2024-12-17DOI: 10.1016/j.chemgeo.2024.122573
Zheng Bo Liu, Jing Zhang, Shuo Jiang, Han Su, Jingling Ren, Hang Zhang, Shijian Hu
The concentration data of Gallium (Ga) observed in the Western Pacific section spanning from 2°S to 20°N along 142°E are reported for the first time. The spatial distribution of Ga in the surface, subsurface, intermediate, and deep layers is presented, and its influencing factors are discussed. We find that terrestrial input from Papua New Guinea constitutes a significant source of surface Ga in this region, while the distribution of Ga concentrations is regulated by water mass mixing. The elevated concentrations of dissolved Ga in the subsurface are derived from the North Pacific Subtropical Mode Water, implying that the latter exerts significant influence on the spreading of dissolved Ga. The Ga concentration in intermediate waters is mainly governed by the Antarctic Intermediate Water (AAIW). A strong correlation (R2 > 0.8) is found between Ga concentration and salinity at depths of deep waters, and the non-conservative behavior of Ga in deep waters is difficult to detect in this region. Profile structures of Ga concentration inside the Philippine Sea basin are different from that outside the basin, indicating that the Ga concentration may reflect the upwelling of deep water within the basin. We further compared the concentration data of Ga with those from the GS01, GP16, GP15, IOC2002, and VERTEX cruises in terms of distribution, behavior and potential usage. We suggest that Ga exhibits promising potential as a new tracer for monitoring intermediate and deep water masses, and Ga concentration can serve as a good indicator for the AAIW and Upper Circumpolar Deep Water.
{"title":"Observed dissolved gallium in the tropical and subtropical waters in the Western Pacific Ocean","authors":"Zheng Bo Liu, Jing Zhang, Shuo Jiang, Han Su, Jingling Ren, Hang Zhang, Shijian Hu","doi":"10.1016/j.chemgeo.2024.122573","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122573","url":null,"abstract":"The concentration data of Gallium (Ga) observed in the Western Pacific section spanning from 2°S to 20°N along 142°E are reported for the first time. The spatial distribution of Ga in the surface, subsurface, intermediate, and deep layers is presented, and its influencing factors are discussed. We find that terrestrial input from Papua New Guinea constitutes a significant source of surface Ga in this region, while the distribution of Ga concentrations is regulated by water mass mixing. The elevated concentrations of dissolved Ga in the subsurface are derived from the North Pacific Subtropical Mode Water, implying that the latter exerts significant influence on the spreading of dissolved Ga. The Ga concentration in intermediate waters is mainly governed by the Antarctic Intermediate Water (AAIW). A strong correlation (R<ce:sup loc=\"post\">2</ce:sup> > 0.8) is found between Ga concentration and salinity at depths of deep waters, and the non-conservative behavior of Ga in deep waters is difficult to detect in this region. Profile structures of Ga concentration inside the Philippine Sea basin are different from that outside the basin, indicating that the Ga concentration may reflect the upwelling of deep water within the basin. We further compared the concentration data of Ga with those from the GS01, GP16, GP15, IOC2002, and VERTEX cruises in terms of distribution, behavior and potential usage. We suggest that Ga exhibits promising potential as a new tracer for monitoring intermediate and deep water masses, and Ga concentration can serve as a good indicator for the AAIW and Upper Circumpolar Deep Water.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"25 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142887292","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 : 2024-12-17DOI: 10.1016/j.chemgeo.2024.122576
Sarah E. Smith-Schmitz, Alexander P. Gysi
The rare earth elements (REE) have important applications in green energy technologies. The formation of mineral deposits in geologic systems commonly involves hydrothermal fluids which can mobilize the REE. However, the REE speciation is not well known as a function of pH. The thermodynamic properties of REE hydroxyl complexes used in geochemical models are based on the Helgeson-Kirkham-Flowers (HKF) equation of state parameters which were derived by extrapolation of low temperature experimental and estimated data. In this study, Dy hydroxide solubility experiments are combined with available literature data to improve these models from 25 to 250 °C and optimize the thermodynamic properties of Dy<ce:sup loc="post">3+</ce:sup> and Dy hydroxyl complexes using GEMSFITS. Batch-type solubility experiments were conducted from 150 to 250 °C and at saturated water vapor pressure in perchloric acid solutions with initial pH values of 2 to 5 in 0.5 pH unit increments. The measured solubility of Dy hydroxide is retrograde with temperature and decreases with pH. The logarithm of total dissolved Dy molality ranges from −2.3 to −5.3 at 150 °C (pH 4.7–5.5), from −2.4 to −5.6 at 200 °C (pH 3.9–5.1), and from −3.7 to −6.9 at 250 °C (pH of 3.4 and 5.0). The optimized standard partial molal Gibbs energies of formation (∆<ce:inf loc="post"><ce:italic>f</ce:italic></ce:inf><ce:italic>G</ce:italic>°<ce:inf loc="post"><ce:italic>T</ce:italic></ce:inf>) derived for Dy<ce:sup loc="post">3+</ce:sup> and DyOH<ce:sup loc="post">2+</ce:sup> display a close to linear relationship with temperature, fitting with previous optimizations based on DyPO<ce:inf loc="post">4</ce:inf> solubility data in the literature. A comparison of the optimized ∆<ce:inf loc="post"><ce:italic>f</ce:italic></ce:inf><ce:italic>G</ce:italic>°<ce:inf loc="post"><ce:italic>T</ce:italic></ce:inf> values for aqueous Dy species with predictions from available HKF parameters indicates significant differences ranging from +11 to −26 kJ/mol between 25 and 250 °C. The experimental fits are used to derive the Dy hydroxide solubility products (<ce:italic>K</ce:italic><ce:inf loc="post">s0</ce:inf>) and formation constants for the hydrolysis of Dy (<ce:italic>β</ce:italic><ce:inf loc="post"><ce:italic>n</ce:italic></ce:inf> with <ce:italic>n</ce:italic> = 1 to 3; Dy<ce:sup loc="post">3+</ce:sup> + <ce:italic>n</ce:italic>OH<ce:sup loc="post">−</ce:sup> = DyOH<ce:inf loc="post"><ce:italic>n</ce:italic></ce:inf><ce:sup loc="post">3-<ce:italic>n</ce:italic></ce:sup>) as a function of temperature. The optimization method presented yields accurate thermodynamic properties for the Dy<ce:sup loc="post">3+</ce:sup> aqua ions and the DyOH<ce:sup loc="post">2+</ce:sup> species at the acidic to mildly acidic pH studied whereas more experimental work is needed at near-neutral and alkaline conditions to better constrain the other hydroxyl complexes. The optimized thermodynamic data have a significant impact on geochemical mod
{"title":"Hydrothermal solubility of Dy hydroxide as a function of pH and stability of Dy hydroxyl aqueous complexes from 25 to 250 °C","authors":"Sarah E. Smith-Schmitz, Alexander P. Gysi","doi":"10.1016/j.chemgeo.2024.122576","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122576","url":null,"abstract":"The rare earth elements (REE) have important applications in green energy technologies. The formation of mineral deposits in geologic systems commonly involves hydrothermal fluids which can mobilize the REE. However, the REE speciation is not well known as a function of pH. The thermodynamic properties of REE hydroxyl complexes used in geochemical models are based on the Helgeson-Kirkham-Flowers (HKF) equation of state parameters which were derived by extrapolation of low temperature experimental and estimated data. In this study, Dy hydroxide solubility experiments are combined with available literature data to improve these models from 25 to 250 °C and optimize the thermodynamic properties of Dy<ce:sup loc=\"post\">3+</ce:sup> and Dy hydroxyl complexes using GEMSFITS. Batch-type solubility experiments were conducted from 150 to 250 °C and at saturated water vapor pressure in perchloric acid solutions with initial pH values of 2 to 5 in 0.5 pH unit increments. The measured solubility of Dy hydroxide is retrograde with temperature and decreases with pH. The logarithm of total dissolved Dy molality ranges from −2.3 to −5.3 at 150 °C (pH 4.7–5.5), from −2.4 to −5.6 at 200 °C (pH 3.9–5.1), and from −3.7 to −6.9 at 250 °C (pH of 3.4 and 5.0). The optimized standard partial molal Gibbs energies of formation (∆<ce:inf loc=\"post\"><ce:italic>f</ce:italic></ce:inf><ce:italic>G</ce:italic>°<ce:inf loc=\"post\"><ce:italic>T</ce:italic></ce:inf>) derived for Dy<ce:sup loc=\"post\">3+</ce:sup> and DyOH<ce:sup loc=\"post\">2+</ce:sup> display a close to linear relationship with temperature, fitting with previous optimizations based on DyPO<ce:inf loc=\"post\">4</ce:inf> solubility data in the literature. A comparison of the optimized ∆<ce:inf loc=\"post\"><ce:italic>f</ce:italic></ce:inf><ce:italic>G</ce:italic>°<ce:inf loc=\"post\"><ce:italic>T</ce:italic></ce:inf> values for aqueous Dy species with predictions from available HKF parameters indicates significant differences ranging from +11 to −26 kJ/mol between 25 and 250 °C. The experimental fits are used to derive the Dy hydroxide solubility products (<ce:italic>K</ce:italic><ce:inf loc=\"post\">s0</ce:inf>) and formation constants for the hydrolysis of Dy (<ce:italic>β</ce:italic><ce:inf loc=\"post\"><ce:italic>n</ce:italic></ce:inf> with <ce:italic>n</ce:italic> = 1 to 3; Dy<ce:sup loc=\"post\">3+</ce:sup> + <ce:italic>n</ce:italic>OH<ce:sup loc=\"post\">−</ce:sup> = DyOH<ce:inf loc=\"post\"><ce:italic>n</ce:italic></ce:inf><ce:sup loc=\"post\">3-<ce:italic>n</ce:italic></ce:sup>) as a function of temperature. The optimization method presented yields accurate thermodynamic properties for the Dy<ce:sup loc=\"post\">3+</ce:sup> aqua ions and the DyOH<ce:sup loc=\"post\">2+</ce:sup> species at the acidic to mildly acidic pH studied whereas more experimental work is needed at near-neutral and alkaline conditions to better constrain the other hydroxyl complexes. The optimized thermodynamic data have a significant impact on geochemical mod","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"31 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142887303","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 : 2024-12-17DOI: 10.1016/j.chemgeo.2024.122582
Li-Tao Ma, Li-Qun Dai, Ye-Dan Hu, Zi-Fu Zhao
Constraining the origin of the Nb-enriched mafic igneous rocks and associated rock assemblages is critical for understanding the tectonic evolution and geodynamic processes in the subduction zone. In this study, we focus on Early Devonian normal arc gabbros and Nb-enriched gabbros from the Central Tianshan Block (CTB), along with Early Carboniferous Nb-enriched basalts from the southern margin of Yili Block. The Early Devonian arc gabbros display pronounced Nb and Ta troughs, relatively depleted Sr–Nd–Hf isotopes, and low zircon δ18O value. In contrast, the Nb-enriched gabbros show both arc- and OIB-like trace element features, more enriched Sr–Nd–Hf isotopes, higher zircon δ18O value, and elevated Nb and Nb/La ratio. These rocks are coeval with N-MORB, E-MORB and OIB in the South Tianshan Belt and Nb-enriched mafic igneous rocks in the northern Tarim, suggesting their formation during back-arc opening of the South Tianshan Ocean, triggered by the southward subduction of Terskey Ocean beneath the Central Tianshan-Northern Tarim Craton. In such a circumstance, the normal arc gabbros represent mantle melts modified by aqueous solutions derived from subducting slab, while the Nb-enriched gabbros were generated by partial melting of mantle metasomatized by subducting oceanic slab-derived melts with rutile breakdown. The Early Carboniferous Nb-enriched basalts also display arc-like trace element signatures and depleted Sr–Nd–Hf isotope features, as well as high Nb and Nb/La. These basalts, coexisting with adakitic granite porphyry and sanukitic high-Mg andesites. These suggest their formation was primarily related to interactions between a mantle wedge and adakitic melts derived from basaltic oceanic crust, with or without sediment melts, in a back-arc setting developed during the northward subduction of South Tianshan Ocean. Thus, this study provides crucial insights into the origin of Nb-enriched mafic rocks and tectonic transition from Ordovician-Early Devonian subduction of the Terskey Ocean to Late Devonian-Late Carboniferous subduction of the South Tianshan Ocean.
{"title":"Origin of the coeval Nb-enriched and arc mafic igneous rocks: Implications for Paleozoic tectonic evolution of the Southwestern Tianshan","authors":"Li-Tao Ma, Li-Qun Dai, Ye-Dan Hu, Zi-Fu Zhao","doi":"10.1016/j.chemgeo.2024.122582","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122582","url":null,"abstract":"Constraining the origin of the Nb-enriched mafic igneous rocks and associated rock assemblages is critical for understanding the tectonic evolution and geodynamic processes in the subduction zone. In this study, we focus on Early Devonian normal arc gabbros and Nb-enriched gabbros from the Central Tianshan Block (CTB), along with Early Carboniferous Nb-enriched basalts from the southern margin of Yili Block. The Early Devonian arc gabbros display pronounced Nb and Ta troughs, relatively depleted Sr–Nd–Hf isotopes, and low zircon δ<ce:sup loc=\"post\">18</ce:sup>O value. In contrast, the Nb-enriched gabbros show both arc- and OIB-like trace element features, more enriched Sr–Nd–Hf isotopes, higher zircon δ<ce:sup loc=\"post\">18</ce:sup>O value, and elevated Nb and Nb/La ratio. These rocks are coeval with N-MORB, <ce:italic>E</ce:italic>-MORB and OIB in the South Tianshan Belt and Nb-enriched mafic igneous rocks in the northern Tarim, suggesting their formation during back-arc opening of the South Tianshan Ocean, triggered by the southward subduction of Terskey Ocean beneath the Central Tianshan-Northern Tarim Craton. In such a circumstance, the normal arc gabbros represent mantle melts modified by aqueous solutions derived from subducting slab, while the Nb-enriched gabbros were generated by partial melting of mantle metasomatized by subducting oceanic slab-derived melts with rutile breakdown. The Early Carboniferous Nb-enriched basalts also display arc-like trace element signatures and depleted Sr–Nd–Hf isotope features, as well as high Nb and Nb/La. These basalts, coexisting with adakitic granite porphyry and sanukitic high-Mg andesites. These suggest their formation was primarily related to interactions between a mantle wedge and adakitic melts derived from basaltic oceanic crust, with or without sediment melts, in a back-arc setting developed during the northward subduction of South Tianshan Ocean. Thus, this study provides crucial insights into the origin of Nb-enriched mafic rocks and tectonic transition from Ordovician-Early Devonian subduction of the Terskey Ocean to Late Devonian-Late Carboniferous subduction of the South Tianshan Ocean.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"87 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142887290","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 : 2024-12-17DOI: 10.1016/j.chemgeo.2024.122565
Sen Li, Paul B. Wignall, Simon W. Poulton
Numerous approaches have been developed for determining past redox conditions in marine settings (e.g., Fe speciation, redox sensitive trace metal (RSTM) systematics, pyrite morphologies, I/(Ca + Mg) ratios), enabling a broad range of redox conditions, from fully oxic to euxinic, to be potentially identified. However, many points along this spectrum remain difficult to constrain, including dysoxic and highly versus weakly euxinic conditions. This limits the broader scale inferences that can be drawn from paleoredox studies, including links between oxygen availability and biological evolution, and the potential for isotope systems (e.g., Mo) to record water column signals. Here, we develop a new approach using RSTM ratios (Re/Mo, Re/U, Re/V, Mo/U), in combination with modified RSTM enrichment factors (EF<ce:sup loc="post">⁎</ce:sup>) and Mo<ce:inf loc="post">EF</ce:inf><ce:sup loc="post">⁎</ce:sup>-U<ce:inf loc="post">EF</ce:inf><ce:sup loc="post">⁎</ce:sup> cross-plots, that potentially enables a robust, highly resolved reconstruction of ancient water column redox conditions to be achieved. We initially document the differential behaviour of RSTM EF<ce:sup loc="post">⁎</ce:sup> values and ratios in modern settings that range from fully oxygenated, through weakly (30–90 μM O<ce:inf loc="post">2</ce:inf>) and highly (<30 μM O<ce:inf loc="post">2</ce:inf>) dysoxic, to anoxic non-sulfidic and euxinic conditions. This redox behaviour is further resolved when the drawdown mechanisms for Mo are evaluated by Mo<ce:inf loc="post">EF</ce:inf><ce:sup loc="post">⁎</ce:sup>-U<ce:inf loc="post">EF</ce:inf><ce:sup loc="post">⁎</ce:sup> cross-plots. We subsequently ground-truth this approach by considering samples from the Carboniferous Bowland Basin, which have previously been studied for redox conditions via independent geochemical and mineralogical techniques, as well as the Jurassic Kimmeridge Clay Formation, where redox conditions have been defined based on paleoecological characteristics. A strong degree of consistency between RSTM behaviour in modern and ancient settings highlights that weakly to highly dysoxic conditions are characterized by increases in Re/Mo, Re/U and Re/V ratios, accompanied by RSTM EF<ce:sup loc="post">⁎</ce:sup> values that only become notably enriched under highly dysoxic conditions. Non-sulfidic water column anoxia is indicated by increased U<ce:inf loc="post">EF</ce:inf><ce:sup loc="post">⁎</ce:sup> values and low Re/Mo ratios, while euxinia is readily identified by high Mo/U, low Re/U and very low Re/Mo ratios, alongside high Mo<ce:inf loc="post">EF</ce:inf><ce:sup loc="post">⁎</ce:sup> values. In addition, highly euxinic conditions may be distinguished from weak euxinia by particularly high Mo/U ratios and Mo<ce:inf loc="post">EF</ce:inf><ce:sup loc="post">⁎</ce:sup> values. This combined approach has the potential to provide a hitherto unprecedented level of insight into paleodepositional redox conditions, and consequently
{"title":"Co-application of rhenium, vanadium, uranium and molybdenum as paleo-redox proxies: Insight from modern and ancient environments","authors":"Sen Li, Paul B. Wignall, Simon W. Poulton","doi":"10.1016/j.chemgeo.2024.122565","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122565","url":null,"abstract":"Numerous approaches have been developed for determining past redox conditions in marine settings (e.g., Fe speciation, redox sensitive trace metal (RSTM) systematics, pyrite morphologies, I/(Ca + Mg) ratios), enabling a broad range of redox conditions, from fully oxic to euxinic, to be potentially identified. However, many points along this spectrum remain difficult to constrain, including dysoxic and highly versus weakly euxinic conditions. This limits the broader scale inferences that can be drawn from paleoredox studies, including links between oxygen availability and biological evolution, and the potential for isotope systems (e.g., Mo) to record water column signals. Here, we develop a new approach using RSTM ratios (Re/Mo, Re/U, Re/V, Mo/U), in combination with modified RSTM enrichment factors (EF<ce:sup loc=\"post\">⁎</ce:sup>) and Mo<ce:inf loc=\"post\">EF</ce:inf><ce:sup loc=\"post\">⁎</ce:sup>-U<ce:inf loc=\"post\">EF</ce:inf><ce:sup loc=\"post\">⁎</ce:sup> cross-plots, that potentially enables a robust, highly resolved reconstruction of ancient water column redox conditions to be achieved. We initially document the differential behaviour of RSTM EF<ce:sup loc=\"post\">⁎</ce:sup> values and ratios in modern settings that range from fully oxygenated, through weakly (30–90 μM O<ce:inf loc=\"post\">2</ce:inf>) and highly (<30 μM O<ce:inf loc=\"post\">2</ce:inf>) dysoxic, to anoxic non-sulfidic and euxinic conditions. This redox behaviour is further resolved when the drawdown mechanisms for Mo are evaluated by Mo<ce:inf loc=\"post\">EF</ce:inf><ce:sup loc=\"post\">⁎</ce:sup>-U<ce:inf loc=\"post\">EF</ce:inf><ce:sup loc=\"post\">⁎</ce:sup> cross-plots. We subsequently ground-truth this approach by considering samples from the Carboniferous Bowland Basin, which have previously been studied for redox conditions via independent geochemical and mineralogical techniques, as well as the Jurassic Kimmeridge Clay Formation, where redox conditions have been defined based on paleoecological characteristics. A strong degree of consistency between RSTM behaviour in modern and ancient settings highlights that weakly to highly dysoxic conditions are characterized by increases in Re/Mo, Re/U and Re/V ratios, accompanied by RSTM EF<ce:sup loc=\"post\">⁎</ce:sup> values that only become notably enriched under highly dysoxic conditions. Non-sulfidic water column anoxia is indicated by increased U<ce:inf loc=\"post\">EF</ce:inf><ce:sup loc=\"post\">⁎</ce:sup> values and low Re/Mo ratios, while euxinia is readily identified by high Mo/U, low Re/U and very low Re/Mo ratios, alongside high Mo<ce:inf loc=\"post\">EF</ce:inf><ce:sup loc=\"post\">⁎</ce:sup> values. In addition, highly euxinic conditions may be distinguished from weak euxinia by particularly high Mo/U ratios and Mo<ce:inf loc=\"post\">EF</ce:inf><ce:sup loc=\"post\">⁎</ce:sup> values. This combined approach has the potential to provide a hitherto unprecedented level of insight into paleodepositional redox conditions, and consequently ","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"2 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142887304","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 : 2024-12-17DOI: 10.1016/j.chemgeo.2024.122574
J. Ahmadi, E. Widom, S.M. Straub, R. Sanchez, D.C. Kuentz, A. Gómez-Tuena, R. Espinasa-Perena, I.N. Bindeman, F.M. Stuart
We have integrated Os isotope systematics in olivine phenocrysts with published O and He isotope data from a suite of well-characterized high-Mg olivine-phyric basalts to andesites across the Trans-Mexican Volcanic Belt (TMVB) to address the relative roles of subduction-related crustal input to the mantle source versus shallow fractional crystallization and/or crustal assimilation. Osmium concentrations in the olivines across all the samples range from 7.3 to 2200 pg/g and, with the exception of one anomalous sample with <ce:sup loc="post">187</ce:sup>Os/<ce:sup loc="post">188</ce:sup>Os<ce:inf loc="post">(ol)</ce:inf> = 0.532, <ce:sup loc="post">187</ce:sup>Os/<ce:sup loc="post">188</ce:sup>Os<ce:inf loc="post">(ol)</ce:inf> ranges from 0.125 to 0.259. Olivines from the rear-arc samples are relatively unradiogenic in Os (<ce:sup loc="post">187</ce:sup>Os/<ce:sup loc="post">188</ce:sup>Os = 0.122 to 0.136) compared to the arc front olivines (<ce:sup loc="post">187</ce:sup>Os/<ce:sup loc="post">188</ce:sup>Os ≥ 0.130), which are more radiogenic than primitive upper mantle and largely overlap with mantle xenoliths from arc settings. The arc front olivines exhibit distinctly heavier δ<ce:sup loc="post">18</ce:sup>O than those of the rear-arc, but a significant role for crustal assimilation in the evolution of most TMVB magmas can be precluded due to the lack of correlation between <ce:sup loc="post">187</ce:sup>Os/<ce:sup loc="post">188</ce:sup>Os<ce:inf loc="post">(ol)</ce:inf> or δ<ce:sup loc="post">18</ce:sup>O<ce:inf loc="post">(ol)</ce:inf> with indices of fractionation (e.g., Fo#, Ni<ce:inf loc="post">(ol)</ce:inf>, and Mg#<ce:inf loc="post">(WR)</ce:inf>), as well as the mantle-like He isotope signatures of the olivines. This suggests that the radiogenic Os and heavy δ<ce:sup loc="post">18</ce:sup>O are inherited from the mantle source region. A mixing model between mantle and sediment-rich slab-derived components, as proposed previously for other areas of the TMVB, can explain the <ce:sup loc="post">87</ce:sup>Sr/<ce:sup loc="post">86</ce:sup>Sr<ce:inf loc="post">(wr)</ce:inf> - <ce:sup loc="post">206</ce:sup>Pb/<ce:sup loc="post">204</ce:sup>Pb<ce:inf loc="post">(wr)</ce:inf> - δ<ce:sup loc="post">18</ce:sup>O<ce:inf loc="post">(ol)</ce:inf> systematics. However, the radiogenic <ce:sup loc="post">187</ce:sup>Os/<ce:sup loc="post">188</ce:sup>Os<ce:inf loc="post">(ol)</ce:inf> requires an unexpectedly high degree of fluid mobility for Os in this model. Instead, the Os data suggest that serial subduction fluxing and melting of the mantle wedge result in an accumulation of radiogenic Os in the mantle wedge through progressive slab flux, consistent with models from earlier studies based on olivine chemistry and the positive correlation of δ<ce:sup loc="post">18</ce:sup>O<ce:inf loc="post">(ol)</ce:inf> with mantle depletion proxies. The decoupling of <ce:sup loc="post">187</ce:sup>Os/<ce:sup loc="post">188</ce:sup>Os<ce:inf loc="post">(ol)</ce:
{"title":"Source versus crustal processing and the evolution of the mantle wedge in the Trans-Mexican Volcanic Belt: Constraints from Os-O-He isotope systematics in olivine","authors":"J. Ahmadi, E. Widom, S.M. Straub, R. Sanchez, D.C. Kuentz, A. Gómez-Tuena, R. Espinasa-Perena, I.N. Bindeman, F.M. Stuart","doi":"10.1016/j.chemgeo.2024.122574","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122574","url":null,"abstract":"We have integrated Os isotope systematics in olivine phenocrysts with published O and He isotope data from a suite of well-characterized high-Mg olivine-phyric basalts to andesites across the Trans-Mexican Volcanic Belt (TMVB) to address the relative roles of subduction-related crustal input to the mantle source versus shallow fractional crystallization and/or crustal assimilation. Osmium concentrations in the olivines across all the samples range from 7.3 to 2200 pg/g and, with the exception of one anomalous sample with <ce:sup loc=\"post\">187</ce:sup>Os/<ce:sup loc=\"post\">188</ce:sup>Os<ce:inf loc=\"post\">(ol)</ce:inf> = 0.532, <ce:sup loc=\"post\">187</ce:sup>Os/<ce:sup loc=\"post\">188</ce:sup>Os<ce:inf loc=\"post\">(ol)</ce:inf> ranges from 0.125 to 0.259. Olivines from the rear-arc samples are relatively unradiogenic in Os (<ce:sup loc=\"post\">187</ce:sup>Os/<ce:sup loc=\"post\">188</ce:sup>Os = 0.122 to 0.136) compared to the arc front olivines (<ce:sup loc=\"post\">187</ce:sup>Os/<ce:sup loc=\"post\">188</ce:sup>Os ≥ 0.130), which are more radiogenic than primitive upper mantle and largely overlap with mantle xenoliths from arc settings. The arc front olivines exhibit distinctly heavier δ<ce:sup loc=\"post\">18</ce:sup>O than those of the rear-arc, but a significant role for crustal assimilation in the evolution of most TMVB magmas can be precluded due to the lack of correlation between <ce:sup loc=\"post\">187</ce:sup>Os/<ce:sup loc=\"post\">188</ce:sup>Os<ce:inf loc=\"post\">(ol)</ce:inf> or δ<ce:sup loc=\"post\">18</ce:sup>O<ce:inf loc=\"post\">(ol)</ce:inf> with indices of fractionation (e.g., Fo#, Ni<ce:inf loc=\"post\">(ol)</ce:inf>, and Mg#<ce:inf loc=\"post\">(WR)</ce:inf>), as well as the mantle-like He isotope signatures of the olivines. This suggests that the radiogenic Os and heavy δ<ce:sup loc=\"post\">18</ce:sup>O are inherited from the mantle source region. A mixing model between mantle and sediment-rich slab-derived components, as proposed previously for other areas of the TMVB, can explain the <ce:sup loc=\"post\">87</ce:sup>Sr/<ce:sup loc=\"post\">86</ce:sup>Sr<ce:inf loc=\"post\">(wr)</ce:inf> - <ce:sup loc=\"post\">206</ce:sup>Pb/<ce:sup loc=\"post\">204</ce:sup>Pb<ce:inf loc=\"post\">(wr)</ce:inf> - δ<ce:sup loc=\"post\">18</ce:sup>O<ce:inf loc=\"post\">(ol)</ce:inf> systematics. However, the radiogenic <ce:sup loc=\"post\">187</ce:sup>Os/<ce:sup loc=\"post\">188</ce:sup>Os<ce:inf loc=\"post\">(ol)</ce:inf> requires an unexpectedly high degree of fluid mobility for Os in this model. Instead, the Os data suggest that serial subduction fluxing and melting of the mantle wedge result in an accumulation of radiogenic Os in the mantle wedge through progressive slab flux, consistent with models from earlier studies based on olivine chemistry and the positive correlation of δ<ce:sup loc=\"post\">18</ce:sup>O<ce:inf loc=\"post\">(ol)</ce:inf> with mantle depletion proxies. The decoupling of <ce:sup loc=\"post\">187</ce:sup>Os/<ce:sup loc=\"post\">188</ce:sup>Os<ce:inf loc=\"post\">(ol)</ce:","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"11 1 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142887291","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 : 2024-12-16DOI: 10.1016/j.chemgeo.2024.122567
Yiqing Wang, Mengchang He, Chunye Lin, Wei Ouyang, Xitao Liu
Abiotic Fe(II) oxygenation to form secondary Fe (oxyhydr)oxides commonly occurs in natural environments and critically affects the mobility and fate of metalloids such as antimony (Sb). However, the Sb(V) immobilization process and mechanism during Fe(II) oxygenation are not well understood, and the interactions between Sb(V) and formed Fe (oxyhydr)oxides need further study. This study comprehensively investigated Sb(V) immobilization and secondary Fe (oxyhydr)oxides formation during Fe(II) oxygenation for 10 h in the presence of Sb(V). The results indicated that Sb(V) was immobilized by secondary Fe (oxyhydr)oxides mainly via coprecipitation rather than adsorption. Extended X-ray absorption fine structure (EXAFS) analysis further verified that Sb(V) was structurally incorporated into the formed lepidocrocite mainly via edge-sharing linkage and into goethite via edge-sharing and double corner-sharing linkages between SbO6 and FeO6 octahedra, thus resulting in the formation of various secondary Fe (oxyhydr)oxides. Additionally, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and X-ray diffraction (XRD) characterization demonstrated that Sb(V) incorporation inhibited lepidocrocite formation and favored goethite formation at pH 6 and 7 with initial Sb(V)/Fe(II) molar ratios above 0.01 and 0.04, respectively, and it also hindered magnetite formation at pH 8. Transmission electron microscopy (TEM) suggested that Sb(V) incorporation affected the morphologies of formed Fe (oxyhydr)oxides. Overall, our findings provide valuable insights into Sb(V) immobilization and Fe (oxyhydr)oxides formation during Fe(II) oxygenation, and are conducive to clarifying the geochemical behavior of Sb(V) coupled with Fe(II) at dynamic redox interfaces in Sb(V)-contaminated environments.
{"title":"Immobilization of Sb(V) by secondary Fe (oxyhydr)oxides during Fe(II) oxygenation: Insights into Sb(V) incorporation and Fe(II) mineralization mechanisms","authors":"Yiqing Wang, Mengchang He, Chunye Lin, Wei Ouyang, Xitao Liu","doi":"10.1016/j.chemgeo.2024.122567","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122567","url":null,"abstract":"Abiotic Fe(II) oxygenation to form secondary Fe (oxyhydr)oxides commonly occurs in natural environments and critically affects the mobility and fate of metalloids such as antimony (Sb). However, the Sb(V) immobilization process and mechanism during Fe(II) oxygenation are not well understood, and the interactions between Sb(V) and formed Fe (oxyhydr)oxides need further study. This study comprehensively investigated Sb(V) immobilization and secondary Fe (oxyhydr)oxides formation during Fe(II) oxygenation for 10 h in the presence of Sb(V). The results indicated that Sb(V) was immobilized by secondary Fe (oxyhydr)oxides mainly via coprecipitation rather than adsorption. Extended X-ray absorption fine structure (EXAFS) analysis further verified that Sb(V) was structurally incorporated into the formed lepidocrocite mainly via edge-sharing linkage and into goethite via edge-sharing and double corner-sharing linkages between SbO<ce:inf loc=\"post\">6</ce:inf> and FeO<ce:inf loc=\"post\">6</ce:inf> octahedra, thus resulting in the formation of various secondary Fe (oxyhydr)oxides. Additionally, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and X-ray diffraction (XRD) characterization demonstrated that Sb(V) incorporation inhibited lepidocrocite formation and favored goethite formation at pH 6 and 7 with initial Sb(V)/Fe(II) molar ratios above 0.01 and 0.04, respectively, and it also hindered magnetite formation at pH 8. Transmission electron microscopy (TEM) suggested that Sb(V) incorporation affected the morphologies of formed Fe (oxyhydr)oxides. Overall, our findings provide valuable insights into Sb(V) immobilization and Fe (oxyhydr)oxides formation during Fe(II) oxygenation, and are conducive to clarifying the geochemical behavior of Sb(V) coupled with Fe(II) at dynamic redox interfaces in Sb(V)-contaminated environments.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"64 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142857734","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}
Occurrence and transformation of schwertmannite (Sch) widely influence the speciation and distributions of iron and sulfur as well as pollutants in acid mine drainage (AMD)-impacted ecosystems. Despite extensive research on the biogeochemical fate of Sch in terrestrial systems, the mechanisms underlying its phase transformation mediated by redox processes in acidic waters remain inadequately understood. This study investigates how the intrinsic activity of naturally abundant organic acids in AMD-impacted waters affects the photochemical behavior and transformation of Sch under oxic and anoxic conditions through comprehensive characterizations. Solid product characterization results showed that the addition of oxalic acid (OA) and tartaric acid (TA), rather than formic acid (FA), significantly accelerated photochemical transformation of Sch into goethite (Gt) and magnetite (Mt), increasing by 29%–−47% and 35% under anoxic condition, respectively. Comparison analyses suggested the photoactivated interfacial electron transfer could be accelerated by the organic acids with the stronger complexing and electron-donating abilities, further enhancing photoreductive dissolution of structural Fe(III) to initiate Fe(II)-catalyzed transformation of Sch. Such transformation pathway of Sch was inhibited due to oxygenation of Fe(II) and only 21% Gt newly formed in the Sch/TA system under oxic conditions. It is further found that carbon-centered radicals (CCR•), derived from organic acids containing electron-withdrawing groups with lower dissociation enthalpy, efficiently protected Fe(II) from oxygenation by competing with oxidants, thus enhancing Sch transformation. The study provides new insights into the expanded transformation pathways of Sch, advancing the understanding of iron cycling and reactive species production in the euphotic zone of acidic waters.
{"title":"Intrinsic activity of organic acids controlling photochemical behavior and transformation of schwertmannite in acid mine drainage","authors":"Shishu Zhu, Xiaokang Hou, Huanxin Ma, Hengyi Fu, Jeng-Lung Chen, Tsung-Yi Chen, Zhi Dang, Chunhua Feng","doi":"10.1016/j.chemgeo.2024.122569","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122569","url":null,"abstract":"Occurrence and transformation of schwertmannite (Sch) widely influence the speciation and distributions of iron and sulfur as well as pollutants in acid mine drainage (AMD)-impacted ecosystems. Despite extensive research on the biogeochemical fate of Sch in terrestrial systems, the mechanisms underlying its phase transformation mediated by redox processes in acidic waters remain inadequately understood. This study investigates how the intrinsic activity of naturally abundant organic acids in AMD-impacted waters affects the photochemical behavior and transformation of Sch under oxic and anoxic conditions through comprehensive characterizations. Solid product characterization results showed that the addition of oxalic acid (OA) and tartaric acid (TA), rather than formic acid (FA), significantly accelerated photochemical transformation of Sch into goethite (Gt) and magnetite (Mt), increasing by 29%–−47% and 35% under anoxic condition, respectively. Comparison analyses suggested the photoactivated interfacial electron transfer could be accelerated by the organic acids with the stronger complexing and electron-donating abilities, further enhancing photoreductive dissolution of structural Fe(III) to initiate Fe(II)-catalyzed transformation of Sch. Such transformation pathway of Sch was inhibited due to oxygenation of Fe(II) and only 21% Gt newly formed in the Sch/TA system under oxic conditions. It is further found that carbon-centered radicals (CCR<ce:sup loc=\"post\">•</ce:sup>), derived from organic acids containing electron-withdrawing groups with lower dissociation enthalpy, efficiently protected Fe(II) from oxygenation by competing with oxidants, thus enhancing Sch transformation. The study provides new insights into the expanded transformation pathways of Sch, advancing the understanding of iron cycling and reactive species production in the euphotic zone of acidic waters.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"15 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142912323","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}
The purpose of our study was to test the hypothesis that apatite provides a detailed record of the evolution of carbonatitic magmas. To this end, we investigated the chemistry and textures of apatite in the various rock units (banded carbonatite, biotitised syenite, biotitite, magnetite-biotite rock and massive carbonatite) of the St Honoré carbonatite using a combination of micro-analytical and imaging techniques. Subtle changes in the uptake of a variety of trace elements during growth led to corresponding changes in the cathodoluminescence response that are recorded as distinct zones in the apatite. In the banded carbonatite, the first apatite to crystallise was fluid/mineral inclusion-bearing and was followed by apatite displaying oscillatory zoning and, in turn, by apatite that replaced the earlier apatite through dissolution-reprecipitation. In contrast, the earliest apatite in the biotitised syenite displays oscillatory zoning and was variably replaced by later apatite. The subsequent crystallisation stages duplicate those of apatite in the banded carbonatite. Apatite crystallisation in the magnetite-biotite rock duplicated the stages recorded by apatite in the banded carbonatite. Finally, the apatite of the massive carbonatite contains representatives of all the apatite types mentioned above.
{"title":"Carbonatite evolution at St Honoré (Canada), the apatite record","authors":"O.V. Vasyukova, A.E. Williams-Jones, D.C. Petts, B.A. Kjarsgaard","doi":"10.1016/j.chemgeo.2024.122568","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122568","url":null,"abstract":"The purpose of our study was to test the hypothesis that apatite provides a detailed record of the evolution of carbonatitic magmas. To this end, we investigated the chemistry and textures of apatite in the various rock units (banded carbonatite, biotitised syenite, biotitite, magnetite-biotite rock and massive carbonatite) of the St Honoré carbonatite using a combination of micro-analytical and imaging techniques. Subtle changes in the uptake of a variety of trace elements during growth led to corresponding changes in the cathodoluminescence response that are recorded as distinct zones in the apatite. In the banded carbonatite, the first apatite to crystallise was fluid/mineral inclusion-bearing and was followed by apatite displaying oscillatory zoning and, in turn, by apatite that replaced the earlier apatite through dissolution-reprecipitation. In contrast, the earliest apatite in the biotitised syenite displays oscillatory zoning and was variably replaced by later apatite. The subsequent crystallisation stages duplicate those of apatite in the banded carbonatite. Apatite crystallisation in the magnetite-biotite rock duplicated the stages recorded by apatite in the banded carbonatite. Finally, the apatite of the massive carbonatite contains representatives of all the apatite types mentioned above.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"15 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142887293","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}
Formation of carbonate minerals during alteration of seafloor lavas serves as a significant global CO2 sink. Understanding the timing of carbonate formation is critical for evaluating the role of low-temperature seafloor alteration as a negative feedback on the global carbon cycle. However, whether carbonate mineral formation largely occurs soon after crustal accretion, or continues throughout the entire lifespan of the ocean crust, remains debated. In this study, we use in situ U-Pb dating techniques to investigate the formation ages of carbonate veins and vesicles in ∼120 Ma ocean crust at Deep Sea Drilling Project (DSDP) Sites 417A and 417D, located in the western Atlantic. Our results show that carbonate mineral U concentrations differ between these cores, which we interpret as reflecting a strong dependence of U uptake into calcite on the redox conditions of the aquifer during carbonate growth. The more oxidizing alteration conditions at Site 417A led to growth of carbonate minerals with much lower U concentrations than those formed at Site 417D, which was altered under more reducing conditions. Importantly, through a thorough evaluation of both published and our new carbonate U-Pb age data, we confirm that more than 90 % of carbonate mineral formation during seafloor alteration occurs within <20 m.y. after crustal accretion. Simple models based on this refined timescale of basalt alteration and carbonate mineral formation show that variation in bottom water temperature within the first 10 m.y. after crustal accretion can affect the final carbon content of the upper oceanic crust. Our study provides valuable insights for carbon cycle models and highlights the importance of seafloor alteration in regulating Earth's climate.
{"title":"Timing of carbon uptake during seafloor alteration: Insight from in situ U-Pb dating at DSDP sites 417A and 417D","authors":"Zhichao Liu, Shuo Chen, Yanhong Chen, Lifeng Zhong, Renbiao Tao, Yaoling Niu, Zhaojie Yu, Laurence A. Coogan","doi":"10.1016/j.chemgeo.2024.122571","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122571","url":null,"abstract":"Formation of carbonate minerals during alteration of seafloor lavas serves as a significant global CO<ce:inf loc=\"post\">2</ce:inf> sink. Understanding the timing of carbonate formation is critical for evaluating the role of low-temperature seafloor alteration as a negative feedback on the global carbon cycle. However, whether carbonate mineral formation largely occurs soon after crustal accretion, or continues throughout the entire lifespan of the ocean crust, remains debated. In this study, we use <ce:italic>in situ</ce:italic> U-Pb dating techniques to investigate the formation ages of carbonate veins and vesicles in ∼120 Ma ocean crust at Deep Sea Drilling Project (DSDP) Sites 417A and 417D, located in the western Atlantic. Our results show that carbonate mineral U concentrations differ between these cores, which we interpret as reflecting a strong dependence of U uptake into calcite on the redox conditions of the aquifer during carbonate growth. The more oxidizing alteration conditions at Site 417A led to growth of carbonate minerals with much lower U concentrations than those formed at Site 417D, which was altered under more reducing conditions. Importantly, through a thorough evaluation of both published and our new carbonate U-Pb age data, we confirm that more than 90 % of carbonate mineral formation during seafloor alteration occurs within <20 m.y. after crustal accretion. Simple models based on this refined timescale of basalt alteration and carbonate mineral formation show that variation in bottom water temperature within the first 10 m.y. after crustal accretion can affect the final carbon content of the upper oceanic crust. Our study provides valuable insights for carbon cycle models and highlights the importance of seafloor alteration in regulating Earth's climate.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"56 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142887311","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}
Volcanism has been proposed as the trigger for the environmental perturbations and associated mass extinction during the Ordovician–Silurian (OS) transition. However, the timing, duration, and intensity of volcanic eruptions during this critical period and their relationships to environmental perturbations and biotic changes remain unresolved. In this study, we use mercury (Hg) concentrations and isotopes from marine sediments in South China to reconstruct the evolution of volcanism from the Late Ordovician to early Silurian. Our results show that strong Hg enrichment coupled with generally near-zero to slightly positive Δ199Hg values occurred before, during, and after the classically defined Late Ordovician Mass Extinction (LOME), suggesting a significant influx of volcanogenic Hg. The Hg enrichment intervals coincided with global warming, oceanic anoxia, and negative excursions in carbon and sulfur isotopes, suggesting that volcanism drove the environmental perturbations during the OS transition. The coincidence of Hg enrichment with extinction horizons supports the hypothesis that volcanism may have contributed to LOME. Our study also suggests that volcanism persisted for approximately 3 million years after mass extinction and may have delayed the recovery of marine ecosystems during early Silurian.
{"title":"Mercury evidence for volcanism driving environmental changes during the protracted Late Ordovician mass extinction and early Silurian recovery","authors":"Yanfang Li, Hui Tian, Tongwei Zhang, Baojian Shen, Deyong Shao","doi":"10.1016/j.chemgeo.2024.122566","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122566","url":null,"abstract":"Volcanism has been proposed as the trigger for the environmental perturbations and associated mass extinction during the Ordovician–Silurian (O<ce:glyph name=\"sbnd\"></ce:glyph>S) transition. However, the timing, duration, and intensity of volcanic eruptions during this critical period and their relationships to environmental perturbations and biotic changes remain unresolved. In this study, we use mercury (Hg) concentrations and isotopes from marine sediments in South China to reconstruct the evolution of volcanism from the Late Ordovician to early Silurian. Our results show that strong Hg enrichment coupled with generally near-zero to slightly positive Δ<ce:sup loc=\"post\">199</ce:sup>Hg values occurred before, during, and after the classically defined Late Ordovician Mass Extinction (LOME), suggesting a significant influx of volcanogenic Hg. The Hg enrichment intervals coincided with global warming, oceanic anoxia, and negative excursions in carbon and sulfur isotopes, suggesting that volcanism drove the environmental perturbations during the O<ce:glyph name=\"sbnd\"></ce:glyph>S transition. The coincidence of Hg enrichment with extinction horizons supports the hypothesis that volcanism may have contributed to LOME. Our study also suggests that volcanism persisted for approximately 3 million years after mass extinction and may have delayed the recovery of marine ecosystems during early Silurian.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"14 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142858002","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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