Chemical Geology最新文献

{"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}

{"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}

{"title":"Hydrothermal origin of platinum-group minerals during serpentinization of the podiform chromitites from the Kızıldağ ophiolite in southern Türkiye","authors":"Chen Chen, Christina Yan Wang, Saihong Yang, İbrahim Uysal","doi":"10.1016/j.chemgeo.2024.122563","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122563","url":null,"abstract":"Platinum-group minerals (PGMs) in podiform chromitites usually occur in the interior and/or edge of chromite. However, the origin of PGMs in podiform chromitites has long been a matter of debate. Here we examined sub-micro to nanoscale textural features, morphologies, and compositions of PGMs from the disseminated, banded, massive and nodular chromitites in the Kızıldağ ophiolite in southern Türkiye, and found both primary and secondary PGMs. The aim of this study is to reveal the transformation processes from primary to secondary PGMs, thereby taking a thorough examination of the origin of these PGMs. Primary PGMs include laurite and Os-Ir alloy, which are prevalent in all samples. They are typically enclosed within or located at the edge of chromite, and formed either prior to or contemporaneously with the crystallization of chromite at temperature of 1100–1200 °C and logƒS&lt;ce:inf loc=\"post\"&gt;2&lt;/ce:inf&gt; values of -2 to -1. In contrast, PGE-bearing pentlandite are commonly present at the edge of chromite, corresponding to an increase of &lt;ce:italic&gt;f&lt;/ce:italic&gt;S&lt;ce:inf loc=\"post\"&gt;2&lt;/ce:inf&gt; with the progressive crystallization of chromite. These primary PGMs and PGE-bearing pentlandite in the intergranular space of chromite are susceptible to alter and transform into secondary PGMs and base metal mineral assemblages, which include Os-Ru nanophases (Os-Ru nanoparticle and OsRu&lt;ce:inf loc=\"post\"&gt;3&lt;/ce:inf&gt; nanoalloy) + awaruite (FeNi&lt;ce:inf loc=\"post\"&gt;3&lt;/ce:inf&gt;) + trevorite (Fe&lt;ce:inf loc=\"post\"&gt;2&lt;/ce:inf&gt;NiO&lt;ce:inf loc=\"post\"&gt;4&lt;/ce:inf&gt;) in nodular chromitite, Os-rich laurite + Os-Ir(Ru) alloy/oxide + pentlandite + millerite (NiS) in banded and massive chromitite, and Ru(Ir) oxide + heazlewoodite (Ni&lt;ce:inf loc=\"post\"&gt;3&lt;/ce:inf&gt;S&lt;ce:inf loc=\"post\"&gt;2&lt;/ce:inf&gt;) in disseminated chromitite. The development of these diverse assemblages can be attributed to the degrees of serpentinization of chromitites. The nodular chromitite underwent weak serpentinization and had low water/rock ratios (&lt;∼1), &lt;ce:italic&gt;f&lt;/ce:italic&gt;S&lt;ce:inf loc=\"post\"&gt;2&lt;/ce:inf&gt; and &lt;ce:italic&gt;f&lt;/ce:italic&gt;O&lt;ce:inf loc=\"post\"&gt;2&lt;/ce:inf&gt;, leading to the conversion of IPGE (Os, Ir and Ru)-bearing pentlandite into Os-Ru nanoparticle- and OsRu&lt;ce:inf loc=\"post\"&gt;3&lt;/ce:inf&gt; nanoalloy-bearing awaruite. The massive and disseminated chromitites had high water/rock ratios and high &lt;ce:italic&gt;f&lt;/ce:italic&gt;S&lt;ce:inf loc=\"post\"&gt;2&lt;/ce:inf&gt; and &lt;ce:italic&gt;f&lt;/ce:italic&gt;O&lt;ce:inf loc=\"post\"&gt;2&lt;/ce:inf&gt; relative to those of the nodular chromitite during serpentinization, and consequently the corresponding pentlandite was transformed into heazlewoodite and/or millerite associated with S loss. Meanwhile, Ir, Os and possibly Ru were released from laurite to form Os-Ir(Ru) alloy/oxide at the edge of laurite. Our observation highlights that primary PGMs and pentlandite in the chromitites of the Kızıldağ ophiolite have been modified under different physical-chemical conditions during serpentinization, resu","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"99 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142857929","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}

{"title":"Pressure sensor based on the Raman shift of the 128-cm−1 band of quartz for pressure measurements in hydrothermal diamond-anvil cells","authors":"Jiankang Li, I-Ming Chou, Xian Wang, Yongchao Liu, Ziheng Han, Jie Gao","doi":"10.1016/j.chemgeo.2024.122558","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122558","url":null,"abstract":"To interpret data collected from high-pressure (<ce:italic>P</ce:italic>)–temperature (<ce:italic>T</ce:italic>) experiments simulating geological processes, pressure information during these experiments is crucial. Traditionally, the Raman shifts of the quartz 464-cm<ce:sup loc=\"post\">−1</ce:sup> band are commonly used as a hydrostatic-pressure calibrant in such experiments, particularly in those performed using hydrothermal diamond-anvil cells (HDACs). In this study, we conducted experiments using HDAC and a Raman spectrometer to investigate the sensitivity of the quartz 128-cm<ce:sup loc=\"post\">−1</ce:sup> Raman band to changes in <ce:italic>P</ce:italic> and <ce:italic>T</ce:italic>. We found that the Raman shift of this band exhibits higher sensitivity to changes in <ce:italic>P</ce:italic> and <ce:italic>T</ce:italic> than the 464-cm<ce:sup loc=\"post\">−1</ce:sup> band at <ce:italic>T</ce:italic>s above 200 °C. Changes in the Raman shift of the 128-cm<ce:sup loc=\"post\">−1</ce:sup> band with <ce:italic>P</ce:italic>s and <ce:italic>T</ce:italic>s are 9–16 cm<ce:sup loc=\"post\">−1</ce:sup>/GPa and ~ (50–40) × 10<ce:sup loc=\"post\">−3</ce:sup> cm<ce:sup loc=\"post\">−1</ce:sup>/°C, respectively, at 200–700 °C and &lt; 1.0 GPa; the corresponding values for the 464-cm<ce:sup loc=\"post\">−1</ce:sup> band are ~9 cm<ce:sup loc=\"post\">−1</ce:sup>/GPa and ~14 × 10<ce:sup loc=\"post\">−3</ce:sup> cm<ce:sup loc=\"post\">−1</ce:sup>/°C, respectively. The experimental data of <ce:italic>P</ce:italic>s, <ce:italic>T</ce:italic>s, and the Raman shifts of the quartz 128 cm<ce:sup loc=\"post\">−1</ce:sup> band relative to that at 0.1 MPa and 23 °C (<ce:italic>∆ω</ce:italic><ce:inf loc=\"post\">128</ce:inf>) were fitted into an equation to express their relation:","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"90 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142858004","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}

{"title":"Evaluating the role of tectonic setting in new continental crust formation by U/Pb ratios","authors":"Xian Chen, Zhengzhe Fan","doi":"10.1016/j.chemgeo.2024.122560","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122560","url":null,"abstract":"The role of tectonic setting in new continental crust formation remains enigmatic. A key to solve this issue is to determine which tectonic setting(s) are involved in the generation of new continental crust through time. Modern mantle-derived magmas that formed in intracontinental extension settings (U/Pb = ∼0.28–0.37) and in subduction settings (U/Pb = ∼0.1–0.16) have distinct mean U/Pb ratios. When shifting from subduction to intracontinental extension settings, the mean U/Pb ratios of new crust should define an increasing trend with time, whereas a decreasing trend will be observed when the converse transition is observed. Here we calculate U/Pb ratios of new crust [(U/Pb)<ce:inf loc=\"post\">jc</ce:inf>] of the Songliao Block from East Asia to determine the tectonic settings of new crust formation. Our results show that (U/Pb)<ce:inf loc=\"post\">jc</ce:inf> ratios have a decreasing trend from ∼1.55 to ∼1.2 Ga, followed by an increasing trend from ∼1.2 to ∼0.8 Ga, and changed to a decreasing trend again between ∼0.8 and ∼ 0.6 Ga. This implies that new crust formation of the microcontinent in a subduction setting during the middle-late Mesoproterozoic and the middle-late Neoproterozoic, however, in an intracontinental extension setting in the late Mesoproterozoic-early Neoproterozoic. Our method may provide a potential avenue to explore the regimes of new continental crust formation.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"201 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142858008","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fe-dependent structural evolution of peralkaline soda aluminosilicate glasses: Iron speciation vs. glass transition","authors":"Michele Cassetta, Emanuele De Bona, Alessia Sambugaro, Francesco Enrichi, Nicola Daldosso, Beatrice Giannetta, Claudio Zaccone, Mattia Biesuz, Vincenzo M. Sglavo, Renat Almeev, Luca Nodari, Daniele Giordano, Gino Mariotto","doi":"10.1016/j.chemgeo.2024.122561","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122561","url":null,"abstract":"The incorporation of iron into peralkaline silicate glasses significantly impacts their structural and thermal properties. Here we investigate how addition of iron influences the network connectivity (short- and medium-range order) and glass transition temperature (<ce:italic>T</ce:italic><ce:inf loc=\"post\"><ce:italic>g</ce:italic></ce:inf>) with particular regard to the iron speciation and the Fe<ce:sup loc=\"post\">2+</ce:sup> and Fe<ce:sup loc=\"post\">3+</ce:sup> coordination state. We also found a sort of tipping point in iron concentration beyond which the short-range structures evolve linearly with density while the medium-range structure deviates from linearity. This behavior seems related to a re-enrichment of tetrahedral units triggered by iron self-compensation effect explaining the observed jump in <ce:italic>T</ce:italic><ce:inf loc=\"post\"><ce:italic>g</ce:italic></ce:inf>.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"23 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142858003","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}

{"title":"Redox conditions in a carbonatite-alkaline complex: Deciphering Fe- and S-XANES in melt inclusions with silicate‑carbonate immiscibility","authors":"Céline Baudouin, Hugo Moreira, Charles Le Losq, Max Wilke, Fleurice Parat","doi":"10.1016/j.chemgeo.2024.122559","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122559","url":null,"abstract":"Hanang is a volcano in the southern part of the east branch of the East African Rift (North Tanzania Divergence) and represents volcanism at the early stage of continental break-up. Hanang volcanism is characterized by CO<ce:inf loc=\"post\">2</ce:inf>-alkaline-rich magmas and silicate‑carbonate immiscibility process at crustal level. This study describes microscale iron (Fe) and Sulfur (S) K-edge X-ray absorption near edge structure (μXANES) spectroscopy measurements on nepheline-hosted melt inclusions (MI) preserved in Hanang lavas. For the first time, the μXANES method has been used on melt inclusions composed of both silicate glass and carbonate phase. Silicate glasses from Hanang display relatively high Fe<ce:sup loc=\"post\">3+</ce:sup>/ΣFe ratio (Fe<ce:sup loc=\"post\">3+</ce:sup>/ΣFe = 0.31, indicative of oxidized conditions) and very low S<ce:sup loc=\"post\">6+</ce:sup>/ΣS ratio (S<ce:sup loc=\"post\">6+</ce:sup>/ΣS = 0.05–0.07, indicative of reduced conditions). The discrepancy of the oxidation state measured from iron and sulfur and thus, the redox conditions (<ce:italic>f</ce:italic>O<ce:inf loc=\"post\">2</ce:inf>) inferred from these two values, either suggests that the oxidation state is affected by post entrapment processes, such as re-equilibration with the host-mineral or the immiscibility process with carbonate liquid, or it suggests a significantly different relation of Fe and S oxidation state to <ce:italic>f</ce:italic>O<ce:inf loc=\"post\">2</ce:inf> in this chemical system. The Fe<ce:sup loc=\"post\">3+</ce:sup>/ΣFe in melt inclusions yields magma redox conditions (<ce:italic>f</ce:italic>O<ce:inf loc=\"post\">2</ce:inf>) at around ∆FMQ + 1.4 for phonolitic liquid composition from evolved differentiation and immiscibility process between silicate melt and carbonatite (≤850C°). Sulfur speciation decoupling is attributed to silicate‑carbonate immiscibility, and as such, low S<ce:sup loc=\"post\">6+</ce:sup>/ΣS does not provide primary redox conditions in this system. Hanang lavas at the early stage of East African Rift have one of the most oxidizing conditions, related to the presence of carbonate-rich alkaline magmatic system associated with carbonatites.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"78 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142858005","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}

{"title":"Terrestrial mercury anomalies across the Permian-Triassic transition in North China linked to volcanism","authors":"Peixin Zhang, Minfang Yang, Jing Lu, Zhongfeng Jiang, Lei Wang, Yuanyuan Zhu, Wenjing Guo, Zejing Li, Zhibiao Shi, Pan Wang, Kai Zhou, Xiaotao Xu, Longyi Shao, Jason Hilton","doi":"10.1016/j.chemgeo.2024.122555","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122555","url":null,"abstract":"The Permian-Triassic mass extinction (PTME) is the most severe biological crisis in Earth history and is closely linked to massive contemporaneous volcanism. However, there is currently limited evidence of Mercury (Hg) enrichment directly from volcanic sources in terrestrial strata, necessitating evidence from different regions and latitudes to confirm the relationship between volcanism and changes in terrestrial environments and biotas. To explore this connection, we conducted a comprehensive analysis integrating astronomical cycles to provide a temporal framework, Hg concentrations, and Hg isotopes from terrestrial strata in the Yiyang Coalfield, located in the southern North China Plate (NCP). Our high-resolution astronomical timescale reveals that in the low latitude NCP the PTME commenced on land with the end-Permian Terrestrial Collapse (EPTC) which preceded the marine mass extinction by approximately 270 kyr and was latitudinally diachronous. The EPTC commenced in high-to-mid latitudes (75–30°S), then approximately 100–430 kyr later spread through different mid-to-low latitude regions (60–20°N) into equatorial paleolatitudes (10°N–0°). Hg isotopic results show that the initial Hg enrichment peak during the EPTC originated from terrestrial weathering and wildfire combustion rather than directly from volcanism, whereas the three subsequent Hg enrichment peaks over a 500 kyr interval following the EPTC originated directly from volcanism. This temporal coupling suggests that terrestrial ecosystems exhibited greater sensitivity and a more rapid response to global warming than marine ecosystems. Stratigraphic correlations show the early eruptive phase of the Siberian Traps Large Igneous Province (STLIP) led to gradual collapse of terrestrial ecosystems from high to low latitudes as they responded to increasingly warmer and more stressed conditions. The main eruptive phase of the STLIP, potentially augmented by contemporaneous widespread volcanism, may have ultimately led to the final collapse of terrestrial ecosystems and marine extinctions.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"23 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142858006","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}

{"title":"Multistage formation and geochemical response of pipe-morphology cold seep carbonate in the Qiongdongnan Basin, northern South China Sea","authors":"Jing Zhao, Xuewan Wu, Wei Zhang, Zhifeng Wan, Yifei Dong, Xi Xiao, Yang Wu, Xiaoyu Wu, Junxi Feng, Qianyong Liang","doi":"10.1016/j.chemgeo.2024.122524","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122524","url":null,"abstract":"Cold seep carbonates are commonly used to record the nature of seepage, including fluid sources, diagenetic environments, and variations in seepage activity. However, the relationship between diagenetic environments and trace element enrichment in dynamic environments is poorly understood. Pipe-morphology cold seep carbonates form from outside to inside in methane seeps and record variations in elements and isotopes over time, which can be used to reconstruct diagenetic environments and fluid dynamics. In this work, we analysed the mineral compositions, carbon and oxygen (C<ce:glyph name=\"sbnd\"></ce:glyph>O) isotopes and major and trace element contents in different areas of pipe-morphology cold seep carbonate collected from the Qiongdongnan Basin in different growth directions. The cold seep carbonate exhibits changes from high-magnesian calcite (HMC) to aragonite and then to HMC, indicating that it has undergone changes in the sedimentary environment inside the fluid migration pathway. On the basis of these findings, the formation of this pipe-morphology cold seep carbonate is divided into three stages. The low δ<ce:sup loc=\"post\">13</ce:sup>C values (from −36.13 ‰ to −32.18 ‰) indicate anaerobic oxidation of methane during carbonate formation. The response of δ<ce:sup loc=\"post\">13</ce:sup>C to changes in the methane flux is not obvious. The gradual increase in δ<ce:sup loc=\"post\">18</ce:sup>O from the outer to the inner portions suggests that the methane flux affected δ<ce:sup loc=\"post\">18</ce:sup>O. The samples have relatively high enrichment factors (EFs) of molybdenum (Mo) and high molybdenum/uranium (Mo/U) ratios. The U<ce:inf loc=\"post\">EF</ce:inf> values show an increasing trend from the outer to the inner portions, whereas the changes in Mo<ce:inf loc=\"post\">EF</ce:inf>, Cd<ce:inf loc=\"post\">EF</ce:inf> and V<ce:inf loc=\"post\">EF</ce:inf> are not obvious. However, Mo<ce:inf loc=\"post\">EF</ce:inf>, Cd<ce:inf loc=\"post\">EF</ce:inf>, and V<ce:inf loc=\"post\">EF</ce:inf> all have good correlations with Mn/Al and Fe/Al, indicating that the particulate shuttle process significantly impacts the enrichment of Mo, Cd, and V. We concluded that the enrichment of U is influenced by the methane flux, whereas the enrichment of Mo, Cd and V is unrelated to methane dynamics. This study provides insights into the behaviour of the methane flux and seawater, redox-sensitive trace element contents and changes in the sedimentary environment and plays an essential role in understanding the activities of cold seeps in dynamic environments.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"22 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142815919","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}

{"title":"Prediction of organic geochemical parameters from inorganic geochemical data in the Cretaceous-Danian Moreno Formation, San Joaquin Basin, California","authors":"Hunter C. Olson, Allegra Hosford Scheirer, Samantha R. Ritzer, Erik A. Sperling","doi":"10.1016/j.chemgeo.2024.122551","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2024.122551","url":null,"abstract":"Accurately reconstructing original Total Organic Carbon (TOC) in thermally mature rocks is essential for the correct application of geochemical proxies and understanding organic carbon burial through time. To reconstruct original TOC using empirical methods, it is vital to have an accurate estimate of the original Hydrogen Index (HI). The two most common methods are estimating original HI using kerogen type or using average HI values from immature rocks elsewhere in the basin. This study tests the ability to use inorganic geochemical data to reconstruct original HI using the Upper Cretaceous-Paleogene Moreno Formation from the San Joaquin Basin, California, USA as a case study. The study utilized cores from the Moreno Formation that are thermally immature, thus preserving original HI values, and that span a range in initial HI. First, inorganic geochemical data were produced (elemental abundances and iron speciation) for samples previously analyzed for organic geochemistry. These data suggest that bottom water conditions during deposition of the Moreno Formation were ferruginous (anoxic and non-sulfidic), without development of sustained euxinia (anoxic and sulfidic). Next, a random forest machine learning analysis was implemented to analyze which inorganic geochemical variables best predict HI in the Moreno Formation. The most important proxies were those for detrital input (Ti, Th), marine export productivity (Cu, Ni), and redox proxies for suboxic conditions (Se, Cr, iron speciation). Finally, the random forest framework was used to predict HI values for three main study cores based on their inorganic geochemistry. These predictions were compared stratigraphically and statistically against the measured values and the kerogen type and average HI methods for reconstructing HI and show this new method has better predictive power than approaches based on single values. This indicates strong promise for using inorganic geochemistry, which is relatively immune to thermal maturation, to reconstruct organic geochemical parameters that are modified during burial and diagenetic process.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"54 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142858007","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}