Chemical Geology最新文献

{"title":"Widespread chemically oscillating reactions during oxidative organic diagenesis recorded during the Ediacaran","authors":"Dominic Papineau ,&nbsp;Zhenbing She ,&nbsp;Liangxuan Jiao ,&nbsp;Shuzhan Liu ,&nbsp;Deng Liu ,&nbsp;Genming Luo ,&nbsp;Chao Li","doi":"10.1016/j.chemgeo.2025.122753","DOIUrl":"10.1016/j.chemgeo.2025.122753","url":null,"abstract":"<div><div>The Neoproterozoic oxygenation event co-occurred with widespread phosphate deposition in sediments, the formation of concretionary structures, perturbations in stable carbon and sulphur isotope compositions, and possibly with the emergence of animals, all well-recorded in South China. However, the significance of concretionary structures in this context remains enigmatic. Occurrences of fossils inside Ediacaran apatite granules are also poorly explained by rounding through sediment reworking, which is the model usually invoke the origin of granules. The main problem with the reworking model is that it does not predict that granules should contain specific minerals, geometric patterns, or fossils. Here we show that concretionary diagenetic spheroids such as botryoids, rosettes, granules, nodules, and concretions are widespread in the Ediacaran Doushantuo Fm and we compare their patterns and composition to those involved in chemically oscillating reactions (COR). We report that diagenetic spheroids in the Doushantuo Fm have distinct radial, concentric, twinned, and cavity-like patterns and geometries that span several orders of dimension sizes. Their mineral assemblage is documented to be variably dominated by a small range of minerals including apatite, carbonate, chert, and sulphide. Their ubiquitous content of redox sensitive trace elements and halogens shows that they contain some residual reactants from their original sedimentary environments. The organic matter (OM) therein includes more than six different types of crystallinities and disorder, which is interpreted to suggest variable abundance of molecular functional groups from biomass decomposition or low-grade metamorphism. Hence, Doushantuo diagenetic spheroids have self-similar geometric patterns and, combined with their mineralogy, trace elements, and diverse OM, they are comparable to compounds involved in pattern formation during new COR experiments reported here. The COR model therefore points to diagenetic spheroids as a continuum of fractal objects and patterns, which is argued to have formed during the diagenetic decarboxylation of carboxylic acids from biomass, although carboxylic acids on other planetary bodies could also be abiotic in origin. The abiotic COR model is not inconsistent with previous models for the origin of diagenetic spheroids, but it is more specific in explaining their patterns, mineralogy, and content of OM and fossils. Hence, COR should be considered as a major geochemical process involved in the formation of diagenetic spheroids in the Doushantuo Fm, which represents a new model to understand abiotic carbon cycling during diagenesis, and which is also applicable to extraterrestrial settings.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"683 ","pages":"Article 122753"},"PeriodicalIF":3.6,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143760040","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Appearance of SSFs in earliest Cambrian seas of South China linked to salinity conditions","authors":"Zhanhong Liu ,&nbsp;Thomas J. Algeo","doi":"10.1016/j.chemgeo.2025.122761","DOIUrl":"10.1016/j.chemgeo.2025.122761","url":null,"abstract":"<div><div>The Ediacaran-Cambrian (E/C) transition in South China witnessed the evolution of early animals during an epoch of major oceanic environmental changes. Although the relationship of metazoan development to redox conditions has been investigated in many studies, the influence of watermass salinity has remained largely unexamined to date. Here, we report large salinity fluctuations in earliest Cambrian seas of South China based on shale elemental proxies (B/Ga, Sr/Ba, and S/TOC) in two sections (i.e., the platform Gunshi'ao and slope Huangye sections), and we examine their relationships to contemporaneous biotic and environmental evolution. Our results show persistently sub-fully-marine salinities on the Yangtze Platform, marked by long-term fluctuations between low-brackish (Units I, III) and high-brackish conditions (Units II, IV), likely due to variations in the relative influences of freshwater runoff from adjacent landmasses and seawater influx from the Nanhua Basin. Furthermore, we show that other environmental factors, e.g., redox, hydrographic restriction, and productivity, covaried strongly with and may have been largely controlled by watermass salinity variation. The low-brackish Units I and III were associated with ferruginous conditions, stronger restriction, and lower productivity, whereas the high-brackish Units II and IV were associated with close-to-euxinic conditions, weaker restriction, and higher productivity, suggesting that seawater influx provided both aqueous sulfate and nutrients to the Yangtze Platform. The appearance of early metazoan faunas was linked to salinity changes: a sponge-acritarch community was dominant under low-brackish conditions, whereas early Cambrian small shelly faunas (SSFs) appeared concurrently with a shift to high-brackish conditions. It is as yet unclear whether the temporal relationship of salinity and faunal changes was purely coincidental or whether it reflects exclusion of the small shelly faunas from the Yangtze Platform under low-brackish conditions. Fully marine conditions were not established until near the top of Unit IV, even in the slope Huangye section. The ultimate control on secular variation in salinity and other environmental parameters in the lower Cambrian of South China was likely eustatic sea level and its influence on the rate of watermass exchange across marginal sills of the Nanhua Basin. Our results highlight the importance of undertaking salinity analysis in epicratonic and marginal-marine settings in the context of exploring controls on early metazoan evolution.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"683 ","pages":"Article 122761"},"PeriodicalIF":3.6,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143759993","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":"Key role of recycled terrigenous sediments in generating continental arc magmatism in the West Qinling orogen, China","authors":"Li-Tao Ma ,&nbsp;Li-Qun Dai ,&nbsp;Hao Liang ,&nbsp;Ye-Dan Hu ,&nbsp;Qing-Cheng Yang ,&nbsp;Zi-Fu Zhao ,&nbsp;Guo-Chao Sun","doi":"10.1016/j.chemgeo.2025.122758","DOIUrl":"10.1016/j.chemgeo.2025.122758","url":null,"abstract":"<div><div>Substantial quantities of heterogeneous sediments are transported into the mantle at subduction zones. However, geochemical signatures linked to recycled terrigenous sediments are almost absent in MORB and are only sporadically observed in some hotspot volcanoes. Therefore, identifying the provenance of the subducting sediments and their fate in the mantle is critical for unraveling the geochemical evolution of the silicate earth. Here we present a comprehensive study of the Triassic ultramafic-mafic igneous rocks from the West Qinling orogen, China. These rocks display arc-like trace element features, weakly enriched Sr–Nd–Hf isotopes, low Ba/Th, Ba/La, Pb/Ce and U/Th ratios, and high Th/La, Th/Yb, Th/Nd and La/Sm ratios. These characteristics suggest that they originate from a mantle source predominantly metasomatized by the subducting sediment-derived hydrous melts. In addition, their high Th/La, Th/Yb and Hf/Sm ratios, paired with low Lu/Hf ratio and significantly low ε_Hf(t) values, closely resemble those of terrigenous sediments, indicating a primarily terrigenous origin. Furthermore, these rocks exhibit lighter Li isotope ratios than MORB, similar to the arc rocks whose mantle sources have incorporated isotopically light terrigenous sediments. By comparing the geochemical features of these ultramafic-mafic igneous rocks with seafloor sediments, we propose the rocks in the West Qinling orogen are derived from a mantle wedge predominantly enriched by subducting terrigenous sediments. Their geochemical features are similar to those of modern continental arcs, suggesting the contribution of different sediment types largely depends on the location of the island arc (oceanic vs. continental). Moreover, much of the subducting sediments may rapidly return to the surface during continental arc magmatism. Therefore, this study provides new insights into the origin and fate of subducting terrigenous sediments in the mantle, as well as their role in generating mafic magmatism in continental arc systems.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"683 ","pages":"Article 122758"},"PeriodicalIF":3.6,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143735207","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":"Retraction notice to “Distribution of 3-hydroxy fatty acids in South China Sea since the last deglaciation: Applicability of 3-hydroxy fatty acid-based palaeothermometry” [Chem. Geol. 652 / 122024]","authors":"Yinwei Xi,&nbsp;Liuyan Wang,&nbsp;Yasong Wang,&nbsp;Huangmin Ge,&nbsp;Mingxing Zhang,&nbsp;Shengjie Ye,&nbsp;Xueqin Zhao,&nbsp;Yunping Xu","doi":"10.1016/j.chemgeo.2025.122723","DOIUrl":"10.1016/j.chemgeo.2025.122723","url":null,"abstract":"","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"682 ","pages":"Article 122723"},"PeriodicalIF":3.6,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143697924","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A novel method for correlating/predicting the thermodynamic properties of aqueous ions at high T and P","authors":"Andrey V. Plyasunov","doi":"10.1016/j.chemgeo.2025.122756","DOIUrl":"10.1016/j.chemgeo.2025.122756","url":null,"abstract":"<div><div>Calculation of the molar standard state Gibbs energies of aqueous ions, <span><math><msubsup><mi>G</mi><mn>2</mn><mi>o</mi></msubsup></math></span>, at supercritical temperatures and pressures is a prerequisite for thermodynamic modeling of hydrothermal processes. Currently, such calculation is performed only with the well-known HKF model, and the development of alternative methods is highly desirable to avoid any possible bias. As a step in this direction, the author presents a novel “isochoric” method for predicting the Gibbs energies of aqueous ions up to high temperatures and pressures. The method is based on the analysis of the temperature dependence of the partial molar isochoric heat capacity of aqueous ions, <span><math><msubsup><mi>C</mi><mrow><mi>v</mi><mo>,</mo><mn>2</mn></mrow><mi>o</mi></msubsup></math></span>. Knowing <span><math><msubsup><mi>C</mi><mrow><mi>v</mi><mo>,</mo><mn>2</mn></mrow><mi>o</mi></msubsup></math></span>, one can compute the partial molar isobaric heat capacity <span><math><msubsup><mi>C</mi><mrow><mi>p</mi><mo>,</mo><mn>2</mn></mrow><mi>o</mi></msubsup></math></span>, provided that <span><math><msubsup><mi>V</mi><mn>2</mn><mi>o</mi></msubsup></math></span> is known as a function of <em>T</em> and <em>P</em>. Then the calculation of <span><math><msubsup><mi>G</mi><mn>2</mn><mi>o</mi></msubsup></math></span> can be performed by the traditional methods. The test of this method was performed using two literature formulations (Arcis et al., 2024; Marshall and Franck, 1981) for the ionization constant of water over wide ranges of temperature (273–1273 K) and water density ρ (up to ρ = 1.25 g cm⁻³), which allow computing all thermodynamic properties of a hypothetical HOH electrolyte. Using 4 parameters at most, it is possible to reproduce the water ionization constants recommended by either Arcis et al. (2024) or Marshall and Franck (1981) formulations at supercritical temperatures with deviations less than those of these formulations. It is expected that the proposed “isochoric” method deserves further investigation.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"682 ","pages":"Article 122756"},"PeriodicalIF":3.6,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143715143","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":"Corrigendum to “Ca-Sr-Nd isotopic signatures of mid-ocean ridge basalts from the Central Indian Ridge and implications for recycled materials in the Indian Ocean mantle domain” [Chemical Geology 673 (2025) 122546]","authors":"Hongli Zhu ,&nbsp;Yujie Shan ,&nbsp;Renqiang Liao ,&nbsp;Lipeng Zhang ,&nbsp;Jianghong Deng ,&nbsp;Congying Li ,&nbsp;Long Du ,&nbsp;Zhaofeng Zhang ,&nbsp;Weidong Sun","doi":"10.1016/j.chemgeo.2025.122750","DOIUrl":"10.1016/j.chemgeo.2025.122750","url":null,"abstract":"","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"682 ","pages":"Article 122750"},"PeriodicalIF":3.6,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143679206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Time constraints for the Lomagundi excursion and the earliest known Paleoproterozoic macroscopic organisms from the Francevillian Group, Gabon","authors":"Frantz Ossa Ossa ,&nbsp;Jan D. Kramers ,&nbsp;Axel Hofmann ,&nbsp;Ronny Schoenberg ,&nbsp;Andrea Agangi ,&nbsp;Georgy Belyanin ,&nbsp;Marlina A. Elburg ,&nbsp;Dan Gregory ,&nbsp;Igor M. Villa ,&nbsp;Andrey Bekker","doi":"10.1016/j.chemgeo.2025.122749","DOIUrl":"10.1016/j.chemgeo.2025.122749","url":null,"abstract":"<div><div>The Francevillian Group, deposited during the Lomagundi carbon isotope excursion (LE), recently revealed evidence for complex and diverse Paleoproterozoic biota. This biota is preserved as pyritized and non-pyritized macrofossil structures hosted in black shale deposited in an oxygenated, open-marine environment. However, the timing of the LE, and the time when these macroscopic organisms evolved is still poorly constrained. Here, we present U-Pb ages for zircons separated from coeval volcaniclastic sandstone, ²⁰⁷Pb/²⁰⁶Pb model ages for pyrite preserving the macrofossils, and ⁴⁰Ar/³⁹Ar dates for K-rich clay minerals from the fossiliferous black shales. The youngest group of zircons yields a weighted average ²⁰⁷Pb/²⁰⁶Pb age of 2132 ± 4 Ma, which is considered as a maximum depositional age for the strata that record the LE and host the earliest known, macroscopic multicellular organisms. By contrast, the ²⁰⁷Pb/²⁰⁶Pb dates of pyritized fossils, scattering between ca. 2085 and 2070 Ma, with a weighted average of 2077 ± 17 Ma, reflect early diagenesis in the Francevillian basin and thus provide a minimum age for fossiliferous strata. This range of ages overlaps with reproducible ⁴⁰Ar/³⁹Ar dates and the ages for other open-marine sedimentary successions that record the LE in both shallow- and deep-marine environments. Taken together, the data demonstrate that the synchronicity of the record of the Lomagundi carbon isotope excursion in shallow- and deep-marine carbonates worldwide is consistent with a global biogeochemical signature of the Paleoproterozoic oceans, with its latest stage, between ca. 2.13 and 2.08 Ga, being preserved in the fossiliferous Francevillian Group strata. Further, the results also suggest that ⁴⁰Ar/³⁹Ar dating of K-rich clay minerals extracted from black shale can be used to constrain the depositional and/or early diagenetic age of more than 2-billion-years old sedimentary strata not affected by high-temperature hydrothermal and metamorphic overprint.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"682 ","pages":"Article 122749"},"PeriodicalIF":3.6,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143697923","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Phosphate oxygen isotope insights into the coupled distribution of phosphorus, iron, and manganese in lake sediments","authors":"Takuya Ishida ,&nbsp;Noboru Okuda ,&nbsp;Shin-ichi Onodera ,&nbsp;Mitsuyo Saito ,&nbsp;Yusuke Tomozawa ,&nbsp;Xin Liu ,&nbsp;Naoshige Goto ,&nbsp;Ken'ichi Osaka ,&nbsp;Masahiro Maruo ,&nbsp;Ichiro Tayasu ,&nbsp;Syuhei Ban","doi":"10.1016/j.chemgeo.2025.122754","DOIUrl":"10.1016/j.chemgeo.2025.122754","url":null,"abstract":"<div><div>Understanding phosphorus (P) dynamics in lake and marine sediments is critical for predicting P re-release into water bodies and its stable accumulation through burial. The distribution of P in sediments is influenced by inputs from rivers and groundwater, as well as post-depositional redistribution processes, such as sink switching and geochemical focusing. Although P, iron (Fe), and manganese (Mn) dynamics are expected to be coupled under reductive conditions, the effects of terrestrial inputs and these redistribution processes on their behavior remain unclear. To assess P, Fe and Mn transport and accumulation in lake sediments, this study applied phosphate oxygen isotope (δ¹⁸O_PO4) analysis to track P sources and redistribution, along with sequential extractions of sedimentary P, Fe, and Mn. The study was conducted in Lake Biwa, Japan's largest lake. We collected the samples of potential P sources (groundwater and river water) and sediments from nearshore to offshore areas. The δ¹⁸O_PO4 values of Fe-bound P and concentrations of Fe-bound P, and reactive Fe and Mn in the sediments increased from nearshore to offshore. Such spatial trends can be explained by groundwater discharge with a high δ¹⁸O_PO4 value and/or geochemical focusing with biological recycling (P uptake and release by organisms). Sedimentary P, Fe, and Mn concentrations were significantly correlated to organic matter concentrations in the sediments, suggesting that organic matter is crucial in their coupled dynamics. This study highlights the utility of δ¹⁸O_PO4 for evaluating P sources and redistribution processes and the importance of the factors contributing to spatial heterogeneity for understanding lake biogeochemistry.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"683 ","pages":"Article 122754"},"PeriodicalIF":3.6,"publicationDate":"2025-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143714440","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":"Zinc mineralisation in marine ooidal ironstones of Western Siberia: Origin and palaeoenvironmental significance","authors":"Maxim Rudmin ,&nbsp;Edward J. Matheson ,&nbsp;Andre Baldermann ,&nbsp;Natalia Maximova ,&nbsp;Evan Dasi ,&nbsp;Sultan R. Tazhiev ,&nbsp;Alexey Ruban","doi":"10.1016/j.chemgeo.2025.122755","DOIUrl":"10.1016/j.chemgeo.2025.122755","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The intricate nature and evolution of the zinc (Zn) biogeochemical cycle in modern and ancient sedimentary basins is a captivating scientific issue with regard to the complexity of Zn sources, diffusion paths and immobilisation processes. This article delves into assessing the sources, migration pathways, and concentration mechanisms of Zn in marine ooidal ironstone deposits of Western Siberia. The study focused on the Cretaceous-Paleogene ironstone strata of the ∼80 m thick Bakchar deposit. The study is based on SEM-EDS, XRF, ICP-MS, and Rock-Eval pyrolysis analyses. In this deposit, Zn minerals frequently form inclusions in the carbonate cement and clay matrix, including micro-impregnations at the contact between siderite spar and the clay matrix, or less common in the cortex of iron-rich ooids. Authigenic Zn mineralisation is predominantly represented by wurtzite ((Zn, Fe)S), while Zn nuggets, zincite (ZnO), tongxinite (Cu&lt;sub&gt;2&lt;/sub&gt;Zn) and Zn-bearing sulphides occur less frequently. They are observed across all major ironstone-bearing Formations of the Bakchar deposit, which span from the Turonian-Coniacian to the Paleocene-Eocene. The inclusions in some layers form clusters that are more commonly associated with carbonate (siderite) cements. This is explained by intense seepage of hydrothermally sourced (reducing and acidic) fluids, likely linked to fault-controlled fluid migration within the bored rift zones of the West Siberian basin. Migration of Zn-bearing low-temperature hydrothermal fluids occurred into weakly lithified or well lithified marine sediments after the formation of iron-rich ooids and primary clay matrix, as reflected in the composition of wurtzite framboids and fracture forms with carbonate-filled ooids and quartz (epigenetic mineralisation). This epigenetic zinc mineralisation may have overprinted the earlier diagenetic phases, reflecting the complex multi-stage history of the deposit. At moderate or prolonged fluid diffusion rates (distal to the exhalation centre), wurtzite crystallised in a smectite matrix near siderite aggregates or immediately at the smectite-siderite grain boundary. Under such conditions, wurtzite often replaced pyrite framboids. During intense fluid-rock interactions, wurtzite and other Zn sulphides crystallised in siderite micro-veins, which altogether replaced and overprinted previously formed ooids and detrital quartz. A more enigmatic form of wurtzite is an ‘almond-shaped’ variety that grew within the pores of detrital organic matter. In rare cases, native Zn and tongxinite formed in micro-pores between clay microparticles. Within the deposits, Zn is positively correlated with hydrothermal and anoxic metals, such as Co, Pb, REE, Y, U, Sb, Mo, As, Th, Fe and Ni, but negatively or barely correlated with K, Si, Ba, Ge, Al and TOC. This distinct geochemical association suggests a hydrothermal origin of the Zn mineralisations. Based on the mineralogical and geochemical results obtained, we","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"682 ","pages":"Article 122755"},"PeriodicalIF":3.6,"publicationDate":"2025-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143706469","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":"Spatial and temporal heterogeneity of the marine nitrogen cycle during the end-Triassic mass extinction","authors":"Jing Li ,&nbsp;Huyue Song ,&nbsp;Yong Du ,&nbsp;Paul B. Wignall ,&nbsp;David P.G. Bond ,&nbsp;Stephen E. Grasby ,&nbsp;Haijun Song ,&nbsp;Jacopo Dal Corso ,&nbsp;Li Tian ,&nbsp;Daoliang Chu","doi":"10.1016/j.chemgeo.2025.122752","DOIUrl":"10.1016/j.chemgeo.2025.122752","url":null,"abstract":"<div><div>The end-Triassic mass extinction (ETME) marks a pivotal event in Earth's history, characterized by major environmental changes in both marine and terrestrial settings and significant perturbations in the carbon and nitrogen biogeochemical cycles alongside extinction events. Here we employ high-resolution organic carbon isotopes (δ¹³C_org), nitrogen isotopes from bulk samples (δ¹⁵N_bulk), total organic carbon (TOC) and nitrogen content (TN), complemented by carbon (δ¹³C_kerogen) and nitrogen isotopes (δ¹⁵N_kerogen) of kerogen extracts from the Kuhjoch section in Austria in order to investigate the interplay between marine redox state, nitrogen cycling, and the biotic crisis across the Triassic–Jurassic boundary. Our results reveal a significant positive shift (∼3 ‰) in δ¹⁵N_bulk values, indicating a perturbed marine nitrogen cycle and expansion of the oxygen minimum zone prior to the ETME. The δ¹⁵N profiles suggest a transition from a nitrate-limited ocean dominated by nitrogen fixation to a post-extinction ocean with increased proportion of assimilation of NO₃⁻ undergoing non-quantitative denitrification. We also examine the spatial and temporal heterogeneity of the marine nitrogen cycle from different paleoenvironmental settings across the Triassic–Jurassic transition. Bioavailable nitrogen (NO₃⁻ and NH₄⁺) limitation prevailed at some localities before and during the ETME. However, the development of N limitation was not synchronous across different locations: it emerged before the ETME in some European basins and intensified after the ETME on Panthalassan shelves. The early Hettangian saw an expansion of euxinic waters into the photic zone and shoaling of the chemocline. Enhanced continental weathering and deep-water upwelling increased nutrient supply, thereby alleviating N limitation. Our new observations point to an unstable and stratified marine environment during the Triassic–Jurassic transition, and suggest that nitrogen bioavailability and redox conditions may be key factors for the devastation of marine ecosystems.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"682 ","pages":"Article 122752"},"PeriodicalIF":3.6,"publicationDate":"2025-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143697922","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}