Chemical Geology最新文献

{"title":"Fe(III)-mediated sediment sequestration of phosphate and humic acid: Timing of inputs regulates environmental processes","authors":"FengTing Wu ,&nbsp;ChunYan Luo ,&nbsp;YueHan Lu ,&nbsp;XueYan Li ,&nbsp;KuanYi Li ,&nbsp;YingXun Du","doi":"10.1016/j.chemgeo.2025.122778","DOIUrl":"10.1016/j.chemgeo.2025.122778","url":null,"abstract":"<div><div>The co-precipitation of dissolved organic matter (DOM) and phosphate with Fe(III) at the sediment-water interface plays a crucial role in the biogeochemical cycling of organic carbon (OC) and phosphate (P) in aquatic ecosystems. The fluxes of organic matter and phosphate may occur in a sequential manner. This study investigated how phosphate affected pre-equilibrated Fe(III)-humic acid (HA) co-precipitates and how HA influenced pre-equilibrated Fe(III)-phosphate co-precipitates under varying pH and Fe(III) concentrations. The results revealed that the addition of phosphate to the Fe-HA co-precipitation system generally promoted further precipitation of dissolved Fe(III) with phosphate, resulting in about 9.48–33.15 % of the phosphate being precipitated. This addition had minimal impact on the percentage of pre-immobilized HA but facilitated the release of high-aromaticity HA from the Fe-HA co-precipitate. Conversely, adding HA to the Fe<img>P co-precipitation system increased the concentrations of soluble Fe(III) and phosphate, likely due to the strong complexation ability of HA with Fe(III). The percentage of HA remaining dissolved was lower at lower pH levels and higher initial Fe(III) concentrations. These findings highlight how the timing of phosphate or DOM inputs influences their sequestration. This has important implications for carbon and nutrient storage in aquatic sediments, where fluxes of organic carbon and phosphate may occur in a sequential manner.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"683 ","pages":"Article 122778"},"PeriodicalIF":3.6,"publicationDate":"2025-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143807163","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":"Source-sink process of reactive iron in shelf sediments controlled by Holocene depositional environments and redox states: Insight from the Central Yellow Sea Mud","authors":"Yu Gu ,&nbsp;Xiting Liu ,&nbsp;Qiao Liu ,&nbsp;Fanxing Kong ,&nbsp;Kai Lan ,&nbsp;Xin Chang ,&nbsp;Mingyu Zhang ,&nbsp;Guangchao Zhuang ,&nbsp;Houjie Wang","doi":"10.1016/j.chemgeo.2025.122780","DOIUrl":"10.1016/j.chemgeo.2025.122780","url":null,"abstract":"<div><div>Iron in shelf sediments is crucial in the marine iron cycle, significantly impacting the global C-S-Fe biogeochemical cycles. However, its fate in shelf sediments remains unclear. This study focuses on sediment core YSCW-1 from the Central Yellow Sea Mud, utilizing sediment grain size, redox-sensitive elements U and Mo, and iron speciation to explore the control mechanisms of redox states and sedimentary environments on highly reactive iron since the Holocene. Sediments in core YSCW-1 can be classified into U1, U2, U3, and U4 units based on lithology, grain size, and geochemical characteristics. The results indicate that iron in the Central Yellow Sea Mud is relatively enriched in the mud-depocenter, occurring in fine-grained terrestrial sediments derived from continental chemical weathering, but its fate varies among different units. In U1 (9.3–9.0 ka), iron was mainly sourced from the Yellow River, deposited under oxic–suboxic conditions with pyrite iron as the dominant reactive iron speciation. In U2 (9.0–7.3 ka), an estuarine environment with low salinity and oxidizing conditions contributed to the increase of carbonate iron. In U3 (7.3–3.1 ka), the establishment of modern circulation in the Yellow Sea led to the dominance of Yangtze River-derived sediments, and the stable, low-energy environment promoted the prevalence of pyrite iron. U4 was deposited under oxic–suboxic conditions, with the iron dissimilatory reduction being the dominant process of organic matter mineralization, resulting in a decline in pyrite iron and an increase in magnetic iron. Our findings suggest that sedimentary environments and redox states jointly control the process of iron speciation on the continental shelf.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"683 ","pages":"Article 122780"},"PeriodicalIF":3.6,"publicationDate":"2025-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143800377","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":"Effects of sulfite on oxidation and immobilization of arsenite during troilite oxygenation: A mechanistic study","authors":"Xianghao Zha ,&nbsp;Guangxia Liu ,&nbsp;Ning Chen ,&nbsp;Yu Zeng ,&nbsp;Juan Wang ,&nbsp;Ziyan Yang ,&nbsp;Huan Tang ,&nbsp;Guodong Fang","doi":"10.1016/j.chemgeo.2025.122779","DOIUrl":"10.1016/j.chemgeo.2025.122779","url":null,"abstract":"<div><div>The iron and sulfur species play key roles in the transformation and immobilization of heavy metals (e.g., As(III)) in soil environments, while the underlying mechanism of these processes was not fully explored. In this study, the effects of sulfite (an important intermediate of sulfur species) on As(III) transformation induced by troilite (FeS) were investigated. Results showed that the presence of sulfite not only greatly enhanced As(III) oxidation by FeS, with <em>k</em>_obs increased by approximated 30 times, but also significantly increased the As(III) immobilization on FeS surface. Further analysis reveal that sulfate radicals (SO₄^•−) and hydroxyl radicals (^•OH), derived from the redox reactions of surface Fe(II)/Fe²⁺ with sulfite, were the main contributors to As(III) oxidation. In addition, As(III) oxidation was significantly enhanced in the sulfite/FeS system over a wide pH range, and oxygen was a prerequisite for the generation of free radicals. Besides, the dissolved As can be efficiently immobilized on FeS surface through co-precipitation with amorphous Fe(OH)₃ phases, which was negligibly affected by the presence of anions and organic matters. This study provides new insights into the mechanism by which sulfur species drive the transformation and immobilization of As(III) during oxygenation of iron-sulfide minerals.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"684 ","pages":"Article 122779"},"PeriodicalIF":3.6,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143808034","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":"Attenuation of pollution risks in sulfidic lead‑zinc tailings through accelerating weathering of sulfides by indigenous Acidithiobacillus consortia","authors":"Yunjia Liu ,&nbsp;Songlin Wu ,&nbsp;Fang You ,&nbsp;Narottam Saha ,&nbsp;Ting-Shan Chan ,&nbsp;Longbin Huang","doi":"10.1016/j.chemgeo.2025.122765","DOIUrl":"10.1016/j.chemgeo.2025.122765","url":null,"abstract":"<div><div>The long-lasting pollution risks from sulfidic and metalliferous tailings are caused by the unpredictable weathering of unstable sulfidic minerals and associated release of potentially toxic soluble metals. The present study aims to investigate whether indigenous <em>Acidithiobacillus</em> consortia containing ferrous iron (Fe) and sulfide (S) oxidizing bacteria could be harnessed to accelerate the weathering of sulfidic minerals (e.g., pyrite, galena) in lead (Pb)‑zinc (Zn) tailings for rapidly attenuating the risks of toxic metal contamination. After a 72-day incubation of the tailings bioaugmented with indigenous Fe oxidizing bacteria (FeOB), sulfur oxidizing bacteria (SOB) and their combination (FeSOB), it was found that sulfidic minerals were significantly weathered to form secondary mineral cements and develop cementation structure. The combined indigenous FeSOB groups exhibited greater functional advantages over the individual groups. According to the synchrotron-based X-ray fluorescence microscopy coupled with X-ray absorption near edge fine structure spectroscopy (XFM-XANES) analysis, the mineral cements were largely composed of secondary Fe oxyhydroxides and jarosite which captured metals (such as Zn) released from the weathered minerals. Furthermore, the in situ formation of cementation structure passivated and encapsulated remnant sulfide particles, presenting a physical barrier against further weathering and toxic metal release. The study has revealed the critical role of indigenous FeSOB in sulfidic mineral weathering and toxic metal immobilization in Pb-Zn tailings, providing important basis for developing in situ field-based technologies towards pollution control of sulfidic and metalliferous tailings.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"683 ","pages":"Article 122765"},"PeriodicalIF":3.6,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143800378","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":"Astronomically forcing hydrological controls on salinity variations during the late Ordovician-early Silurian in the Upper Yangtze area: Responses to the monsoon climate and HICE","authors":"Min Xiong ,&nbsp;Lei Chen ,&nbsp;Chongjie Liao ,&nbsp;Xin Chen ,&nbsp;Xiucheng Tan ,&nbsp;Jian Cao ,&nbsp;Shuaicai Wu ,&nbsp;Hexing Qin ,&nbsp;Zuyou Zhang ,&nbsp;Gaoxiang Wang ,&nbsp;Dazhong Li ,&nbsp;Jiaxun Lu","doi":"10.1016/j.chemgeo.2025.122772","DOIUrl":"10.1016/j.chemgeo.2025.122772","url":null,"abstract":"<div><div>Salinity, a key indicator of watermass conditions, is crucial for understanding the interactions between watermass conditions and climate change. This study presents novel insights into the paleosalinity variations with astronomically forced hydrological changes in Late Ordovician - Early Silurian marine shales of the Upper Yangtze area, based on high-resolution cyclostratigraphic analysis of the gamma-ray (GR) series. Watermass conditions proxies and organic carbon isotope (δ¹³C_org) are significantly in-phase variations with ∼405 kyr long eccentricity cycles. The astronomically forced climate controls the hydrological conditions by modulating the expansion and shrinkage of ice sheet, resulting in lower paleosalinity in interglacial interval than glacial interval. Specifically, during the eccentricity maxima, increased monsoon precipitation established a positive feedback mechanism between continental runoff and marine water, significantly decreasing salinity. The Kwangsian Orogeny induced tectonic-sedimentary patterns created substantial spatial heterogeneity in salinity distribution across different sedimentary centers. Furthermore, we focused on the Hirnantian Isotopic Curve Excursion (HICE) event during the Ordovician – Silurian (O-S) transition, identified by minimum GR, TOC values, positive excursions in δ¹³C_org with organic–lean shale. Hence, under the regional tectonic-sedimentary setting, the astronomically forcing monsoon system, sea level fluctuations and the dynamic changes in glacier have been the decisive factors for the salinity variations. This study advances our understanding of orbital-scale climate forcing influences salinity dynamics in a restricted marine basin, providing new insights for paleoenvironmental reconstruction in deep-time sedimentary systems.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"683 ","pages":"Article 122772"},"PeriodicalIF":3.6,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143807165","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":"Sedimentation rates control trace element composition of sedimentary phosphorites: Anomalously low uranium and cadmium levels in Paleozoic shelly phosphorites from the Baltica Paleobasin","authors":"Kaarel Lumiste ,&nbsp;Johannes Vind ,&nbsp;Kairi Põldsaar ,&nbsp;Lauri Joosu ,&nbsp;Elina Kuusma ,&nbsp;Päärn Paiste ,&nbsp;Kalle Kirsimäe","doi":"10.1016/j.chemgeo.2025.122776","DOIUrl":"10.1016/j.chemgeo.2025.122776","url":null,"abstract":"<div><div>Phosphorites – made up of chemically precipitated authigenic apatite or composed of bioapatitic fossil remains – become enriched in a variety of trace elements such as Rare Earth Elements (REE), Cd, and U during diagenesis. The Cambrian-Ordovician phosphorites of the Baltica Paleobasin that are almost exclusively made up of fossilized remains of phosphatic brachiopod shells are, however, exceptional in this regard, showing abnormally low levels of trace elements. In this study, we examined the depositional environment and the trace elemental composition of the Baltic Paleobasin shelly phosphorites. We show that hydrodynamic conditions during deposition exert control on the trace elemental composition of shelly phosphorites. A combination of high sedimentation rates, redox conditions, and the biogenic origin of the shells led to the depletion of bio-toxic Cd and U relative to other similar phosphorite deposits. Similarly, the concentrations of REE are below the global phosphorites average; however, the shelly phosphorites show a higher degree of Middle Rare Earth Element (MREE) enrichment. These findings have further implications for exploration — phosphorites that contain abundant bioapatite and/or were deposited in areas with high sedimentation rates and oxic conditions are likely less enriched in trace elements.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"684 ","pages":"Article 122776"},"PeriodicalIF":3.6,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143815600","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":"Origins of rodingite-forming fluids from the seafloor to exhumed terranes: Insights from calcium, strontium, and oxygen isotopes","authors":"E. Hostettler ,&nbsp;J.D. Barnes ,&nbsp;J.C. Lassiter ,&nbsp;B. Dragovic ,&nbsp;A. Satkoski","doi":"10.1016/j.chemgeo.2025.122775","DOIUrl":"10.1016/j.chemgeo.2025.122775","url":null,"abstract":"<div><div>Rodingites are metasomatic Ca-rich, Si-poor rocks typically formed on the seafloor during interaction of a gabbroic dike with seawater. However, rodingites are also common in exhumed metamorphic terranes, in which their formation and tectonic history are more complex. Here we measure the O, Ca, and Sr isotope compositions of seafloor and Alpine rodingites from various tectonic settings (obducted oceanic lithosphere, subducted oceanic lithosphere, fossil rifted margins). We focus on andradite-grossular garnet, one of the first phases to crystallize during rodingitization, and clinopyroxene to discern the origins of rodingite-forming fluids and thus the tectonic setting of rodingitization. δ^44/40Ca values of plagioclase (pl), clinopyroxene (cpx), and calculated whole rock (WR) from altered gabbro (i.e., rodingite protoliths) from the Mid-Atlantic Ridge span a range of ∼0.2 ‰ (1.24 to 1.40 ‰ for pl, <em>n</em> = 2; 1.30 ‰ for cpx, <em>n</em> = 1; 1.29 ‰ for WR, n = 1), whereas, garnet (grt), cpx, and WR from the Western and Central Alpine rodingites span ∼2.8 ‰ (0.01 to 2.52 ‰ for grt, <em>n</em> = 9; −0.32 to 1.58 ‰ for cpx, n = 9; −0.22 to 1.92 ‰ for WR, n = 9). ⁸⁷Sr/⁸⁶Sr ratios of mineral separates from the seafloor span from 0.702606 to 0.703700 (0.703516 to 0.703700 for pl, <em>n</em> = 2; 0.702606 for cpx, <em>n</em> = 1) and 0.70330 to 0.710559 for Alpines rodingites (0.704756 to 0.710559 for grt, <em>n</em> = 9; 0.70330 to 0.707080 cpx, n = 9). Lastly, δ¹⁸O values span ∼1.6 ‰ for the seafloor (5.7 to 6.4 ‰ for pl, <em>n</em> = 2; 4.8 ‰ for cpx. n = 2) and ∼ 6.4 ‰ for Alpine rodingites (−0.4 to 4.5 ‰ for grt, <em>n</em> = 9; 1.7 to 6.0 ‰ for cpx, <em>n</em> = 8). Isotope mass balance modeling shows that these data are overall consistent with rodingitization of a gabbroic dike via seawater on the seafloor and subsequent recrystallization with limited isotopic modification during subduction. A few Alpine rodingites with distinctly high or low δ^44/40Ca values compared to mantle values (e.g., δ^44/40Ca_WR = 1.92 ‰ at Erro-Tobbio and δ^44/40Ca_WR = −0.22 ‰ at Lago di Cigana) cannot be explained via metasomatism by seawater using the model presented here, requiring either evolution of the fluid source during rodingitization and associated serpentinization and/or Ca isotope disequilibrium.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"683 ","pages":"Article 122775"},"PeriodicalIF":3.6,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143807162","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":"The role of silicate alteration in regulating marine carbon cycling","authors":"Wei-Li Hong ,&nbsp;Xiaole Sun ,&nbsp;Marta E. Torres ,&nbsp;Tzu-Hao Huang ,&nbsp;Rebecca A. Pickering","doi":"10.1016/j.chemgeo.2025.122769","DOIUrl":"10.1016/j.chemgeo.2025.122769","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Alteration of silicate phases in marine sediments is important for the global budget of carbon, silicon, and many other elements. Despite the growing recognition of in-situ marine silicate alteration (dissolution and formation), its global significance and controlling factors are still poorly understood. By compiling data from scientific drilling and applying numerical modelling, we investigate the interactions between two connected feedback loops: the particulate organic-inorganic carbon loop and the forward-reverse silicate weathering loop. By simulating early diagenetic sequences in the top tens of meters of sediments, we examined the saturation state and interactions of a wide range of silicate minerals. When organic matter is degraded at moderate rates, iron- and sulfate-reduction elevate porewater pH and create a condition that favours reverse weathering driven by the formation of smectite-group clay phases. Our simulations estimate an up to 10 % increase in DIC flux towards the oxic surface sediments with no substantial change in the alkalinity flux. On the other hand, fast organic matter degradation acidifies pore fluids in extended methanogenic zones and induces dissolution of silicates. Dissolution of several reactive silicate phases (mica, amphibole, and pyroxene groups) buffers porewater pH by effectively converting dissolved CO&lt;sub&gt;2&lt;/sub&gt; to carbonate alkalinity and results in marine silicate weathering. Consequently, the total alkalinity flux towards oxic sediments increases by as much as 11 % under this condition. The analyses of a global database of pore fluid composition suggest dominant weathering of K- and Mg-containing silicate minerals that can be identified visually. Higher-than-seawater Mg concentrations were observed in almost all sites where total alkalinity is &gt;56 meq/L, with Mg accounting for up to 40 % of the measured alkalinity. Modelling of this data compilation points to dissolution of Mg- and K-rich mica-group silicates as the primary cause for the elevated total alkalinity. The degree of TA excess seems to increase at sites with greater burial thermal history below the sulfate reduction zone with two trends observed among different continental margins. Such a relationship is however not always statistically significant due to the limited number of study sites in certain margins.&lt;/div&gt;&lt;div&gt;Organic matter degradation determines the overall level and flux of DIC as well as dissolved CO&lt;sub&gt;2&lt;/sub&gt; in pore fluids, with DIC speciation is modulated through silicate alteration and carbonate authigenesis. As demonstrated by our numerical modelling, increasing organic matter degradation rate four-fold leads to 6.1 times higher fluxes of DIC and total alkalinity towards the oxic sediments, with marine silicate alteration contributing ca. 10-11 % of the changes in DIC fluxes (for reverse weathering) and total alkalinity fluxes (for silicate weathering). We further show that the amounts of DIC sequestered as aut","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"684 ","pages":"Article 122769"},"PeriodicalIF":3.6,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143858305","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":"Hydrological regulation of seasonal Mg isotopic variation in the upper Jinsha River draining the eastern Tibetan Plateau","authors":"Chenzi Li ,&nbsp;Zhangdong Jin ,&nbsp;Long-Fei Gou ,&nbsp;Yang Xu ,&nbsp;Li Deng","doi":"10.1016/j.chemgeo.2025.122773","DOIUrl":"10.1016/j.chemgeo.2025.122773","url":null,"abstract":"<div><div>The compositions of magnesium isotopes (δ²⁶Mg) in the river systems are primarily controlled by the sources of Mg²⁺ and the processes of fractionation. However, how these factors govern the riverine δ²⁶Mg values under different seasons remains unclear. To better understand the influences of weathering and hydrology on water chemistry, a systematic investigation was conducted on the seasonal variation of the riverine Mg and Sr isotopes, using water samples collected weekly throughout the year 2021 in the upper Jinsha River draining the eastern Tibetan Plateau. The result showed that both δ²⁶Mg and ⁸⁷Sr/⁸⁶Sr exhibited a significant sensitivity to seasonally hydrological conditions linked to the monsoon climate. A forward model was used to partition riverine Mg²⁺ sources and confirmed that the riverine Mg budget was dominated by carbonate weathering, followed by evaporite dissolution and silicate weathering. However, the conservative mixing of different endmembers could not fully explain riverine δ²⁶Mg in the upper Jinsha River, thus the role of secondary carbonate precipitation associated with hydrological changes was proposed here for the observed variations in riverine δ²⁶Mg values. It showed that higher water discharge triggered by monsoonal rainfall reduced Mg isotope fractionation owing to a shorter water residence time, leading to low riverine δ²⁶Mg values. Conversely, during the dry seasons and the less rainy periods both with lower water discharge, longer water residence time would result in high riverine δ²⁶Mg values that is subjected to increased Mg isotope fractionation. This study provides new insights into the potential influence of hydrological variations on the riverine δ²⁶Mg values.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"684 ","pages":"Article 122773"},"PeriodicalIF":3.6,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143820232","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":"Geochemical evidence of paleo-pacific slab melting in the big mantle wedge beneath Northeast China during the Early Cretaceous","authors":"Chao-Yang Liu ,&nbsp;Hong-Yan Li ,&nbsp;Yi-Gang Xu ,&nbsp;Qiang Ma ,&nbsp;Chun Yang ,&nbsp;Wan-Feng Zhang","doi":"10.1016/j.chemgeo.2025.122771","DOIUrl":"10.1016/j.chemgeo.2025.122771","url":null,"abstract":"<div><div>The ‘big mantle wedge’ (BMW) beneath East Asia extends ∼1800 km inland from the trench, yet its formation time and mechanism remain enigmatic. A key challenge is linking subducted slabs to intraplate basaltic volcanism. Here, we present high-precision Ar-Ar dating and Sr-Nd-Hf-Pb isotopic analyses of Mesozoic basalt drill cores (2000–4500 m depth) from the Songliao Basin, NE China. Together with published data, all the Early Cretaceous basalts show transitional character from MORB to basalts derived from sources containing subducted materials, with variable ⁸⁷Sr/⁸⁶Sr_i (0.70311–0.70750), εNd_i (+5.06 to −6.90), ²⁰⁶Pb/²⁰⁴Pb_i (18.10–18.44) and εHf_i (+7.39 to −4.58). For the first time, we identify an Indian-type oceanic crustal signature to the source of Songliao OIB-like basalts (Δ8/4 = 37–58), linked to the subducted Paleo-Pacific (Izanagi) plate. On the other hand, the arc-type basalts across NE China incorporate sedimentary components in their mantle sources, particularly in the Greater Khingan Range, farthest from the paleo-trench but with the earliest age (∼140 Ma). These findings support a flat subduction-rollback model: sediments accumulate ahead during flat subduction while slab rollback induces asthenospheric welling, driving eastward migration of IAB-like magmatism. In contrast, the Ar-Ar dating suggests that the Songliao OIB-like basalts (107–104 Ma) erupted at the terminal stage of IAB-like magmatism (∼140–100 Ma), coinciding with the full development of the BMW and reflecting melts from the stagnant slab.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"683 ","pages":"Article 122771"},"PeriodicalIF":3.6,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143799855","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}