Chemical Geology最新文献

{"title":"Increased oxygenation during the peak Cambrian Explosion: Evidence from global carbon isotope records","authors":"Dongping Hu ,&nbsp;Lilin Sun ,&nbsp;Yilun Xu ,&nbsp;Xingliang Zhang ,&nbsp;Xiaolin Zhang ,&nbsp;Yanan Shen","doi":"10.1016/j.chemgeo.2025.122890","DOIUrl":"10.1016/j.chemgeo.2025.122890","url":null,"abstract":"<div><div>The early Cambrian is characterized by the rapid emergence of diverse animal lineages within a relatively short time interval, known as the “Cambrian Explosion”. During this period, ecosystems dominated by metazoans were established, with an increase in morphological and ecological complexity of metazoan phyla. While enhanced oxygenation of subsurface environments has often been suggested as a primary driver of this unprecedented evolutionary event, the relative magnitude and underlying mechanisms of changes in O₂ levels remain elusive. Here, we integrate high-resolution carbonate and organic carbon isotope records (δ¹³C_carb and δ¹³C_org) compiled from 17 globally distributed successions to elucidate carbon‑oxygen cycle dynamics during the Cambrian late Stage 2 to Stage 3, corresponding with the apex of Cambrian Explosion. Our dataset reveals a synchronous positive Δ¹³C (δ¹³C_carb–δ¹³C_org) excursion in phase with the CARE (historically termed as the Cambrian Arthropod Radiation Isotope Excursion), a significant excursion in both δ¹³C_carb and δ¹³C_org records, which is interpreted as indicative of increased organic carbon burial in marine sediments. Numerical modelling based on the O₂-dependent fractionation of C-isotopes during oxygenic photosynthesis suggests that this carbon isotope shift corresponds to a substantial increase in atmospheric O₂ levels. Independent O₂ estimates derived from traditional C-isotope mass balance models and the total organic carbon (TOC) contents of various sedimentary facies further corroborate a rise in atmospheric O₂ caused by enhanced organic matter burial. Our findings reveal a broad temporal correspondence between inferred rising O₂ levels and the acme of Cambrian Explosion, suggesting that increased oxygen availability may have provided a permissive environmental backdrop for the diversification of marine metazoans and the establishment of modern-like marine ecosystems during the early Cambrian.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"690 ","pages":"Article 122890"},"PeriodicalIF":3.6,"publicationDate":"2025-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144189821","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":"Contrasting PGM assemblages in the Verkh-Neivinsk and Alapaevsk chromite deposits: Implications for the source of the HSE in the Urals ophiolite-type massifs","authors":"Kreshimir N. Malitch ,&nbsp;Igor S. Puchtel ,&nbsp;Inna Yu. Badanina ,&nbsp;Valery V. Murzin","doi":"10.1016/j.chemgeo.2025.122881","DOIUrl":"10.1016/j.chemgeo.2025.122881","url":null,"abstract":"<div><div>In order to gain further insights into the origin of platinum-group minerals (PGM) and the source of the highly siderophile elements (HSE: Os, Ir, Ru, Pt, Pd, Re) in the chromite deposits associated with the Urals ophiolite-type massifs, we carried out a mineralogical, HSE abundance, and Pt-<em>Re</em>-Os isotope study of chromitites and PGM from the Verkh-Neivinsk and Alapaevsk dunite-harzburgite massifs in the Middle Urals. The chromitites are characterized by negatively-sloped Bulk Silicate Earth (BSE)-normalized HSE patterns, consistent with the predominance of PGM of the Ir-group platinum-group elements (PGE), i.e., Os-Ru-Ir alloys and Ru<img>Os sulfides, over the PGM of the Pd-group PGE, i.e., stibiopalladinite and geversite. These two groups of PGM are interpreted to represent the primary and secondary mineral assemblages, respectively. The observed HSE patterns in the studied chromitites are typical of those formed in supra-subduction zone (SSZ) settings. The near-chondritic average initial γ¹⁸⁷Os and μ¹⁸⁶Os values in the chromitites and PGM of the Verkh-Neivinsk massif indicate that its HSE budget was derived from the convecting upper mantle source that evolved with time-integrated near-chondritic Re/Os and Pt/Os ratios. These features are also typical of the sources of most Archean and Proterozoic mafic-ultramafic rocks worldwide. In contrast to the Verkh-Neivinsk massif rocks, the Alapaevsk massif chromitites show radiogenic initial γ¹⁸⁷Os values indicating evolution of the mantle source of these rocks with a supra-chondritic time-integrated Re/Os ratio. This long-term enrichment in Re relative to Os could be the result of interaction of the source peridotites with ¹⁸⁷Os-enriched melts derived from ancient recycled oceanic crust.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"690 ","pages":"Article 122881"},"PeriodicalIF":3.6,"publicationDate":"2025-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144204610","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 heterogeneity in salinity and redox dynamics during the Ordovician-Silurian transition: Multi-proxy constraints on the Late Ordovician Mass Extinction mechanisms","authors":"Yangbo Lu ,&nbsp;Fang Hao ,&nbsp;Yiquan Ma ,&nbsp;Wei Wei ,&nbsp;Shen Jun ,&nbsp;Yuxuan Wang ,&nbsp;Qiyang Gou","doi":"10.1016/j.chemgeo.2025.122860","DOIUrl":"10.1016/j.chemgeo.2025.122860","url":null,"abstract":"<div><div>The Ordovician-Silurian transition (OST; ∼448–443 Ma) was marked by the Hirnantian glaciation, rapid climatic shifts, and the Late Ordovician Mass Extinction (LOME). While redox changes and ice-sheet dynamics have been widely studied, the role of salinity-pH-redox feedbacks in modulating extinction mechanisms remains poorly constrained. Here, we present a high-resolution multi-proxy dataset (δ¹¹B, Sr/Ba, B/Ga, redox-sensitive trace metals, and iron speciation) from middle- and outer-shelf successions of the Upper Yangtze Sea, South China, to unravel spatial-temporal feedbacks between glacial meltwater, ocean connectivity, and biogeochemical cycles. Our results reveal pronounced salinity stratification in the middle-shelf (brackish to freshwater conditions, B/Ga &lt;4, δ¹¹B &lt; −13 ‰) driven by pulsed meltwater inputs during glacial retreat, which amplified euxinic wedges (Mo &gt; 64 ppm, Fe_Py/Fe_HR &gt; 0.8) through sulfate limitation and pH-driven boron adsorption. In contrast, the outer shelf maintained stable marine salinity (B/Ga ∼6.2, δ¹¹B ∼ −8 ‰) and suboxic conditions (Mo &lt; 25 ppm, Fe_Py/Fe_HR &lt; 0.35), acting as refugia for benthic fauna. Crucially, boron isotopes unveil pH-salinity coupling during icehouse collapse−freshwater dilution of the middle-shelf amplified H₂S toxicity by reducing carbonate buffering capacity, while open-marine connectivity stabilized outer-shelf pH. The first LOME pulse was initiated by glacial expansion-driven cooling and habitat contraction, with its severity amplified by pulsed meltwater-induced mid-shelf euxinia, whereas the second pulse was linked to post-glacial transgressive euxinia amplified by sulfate influx. This study establishes paleosalinity as a critical amplifier of climate-biogeochemical feedbacks, demonstrating how spatial ocean connectivity regulated extinction selectivity through salinity stratification. Our findings provide a novel mechanistic framework linking icehouse dynamics to marine ecosystem collapse, with implications for understanding hypoxia expansion in modern warming oceans.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"690 ","pages":"Article 122860"},"PeriodicalIF":3.6,"publicationDate":"2025-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144148100","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":"Formation of early continental crust by remelting of hydrothermally altered oceanic crust: Evidence from potassium and oxygen isotopes","authors":"Shao-Bing Zhang ,&nbsp;Liang Zhang ,&nbsp;Xing-Yu Yao ,&nbsp;Zhen-Xin Li ,&nbsp;Xiaoqiang Li ,&nbsp;Guilin Han ,&nbsp;Yong-Fei Zheng","doi":"10.1016/j.chemgeo.2025.122888","DOIUrl":"10.1016/j.chemgeo.2025.122888","url":null,"abstract":"<div><div>Early continental crust mainly consists of tonalite, trondhjemite, and granodiorite (TTG), yet the origin of TTG rocks has been controversial with respect to the operation of plate tectonics. It is of critical importance, therefore, to resolve whether Archean TTG rocks formed from thick oceanic crust generated at spreading ridges or from oceanic plateaus in intraplate settings. Here, we use K and O isotopes to trace the source of Archean TTG rocks. The rationale is that the hydrothermal alteration of oceanic crust during its growth at mid-ocean ridges would result in correlated changes in their δ⁴¹K and δ¹⁸O values. A series of Archean TTG rocks with zircon U<img>Pb ages of 3.45–2.85 Ga and zircon δ¹⁸O values ranging from 5.3 ‰ to 7.4 ‰ from the Kaapvaal Craton of South Africa and the Yangtze Craton of South China were analyzed for K isotope compositions. These TTG rocks show variable δ⁴¹K values from −0.58 ‰ to −0.19 ‰. The δ⁴¹K values show weakly positive correlations with Na/K, Eu/Eu* and Sr/Y ratios, suggesting that accumulation of plagioclase may lead to the increase of K isotope ratios because plagioclase is enriched in heavier K isotopes. After correcting for the effect of plagioclase accumulation on samples with high Eu/Eu* and Sr/Y ratios, a negative correlation is obtained between whole-rock δ⁴¹K and zircon δ¹⁸O values. This suggests that the source of Archean TTG rocks should be the oceanic crust that had experienced hydrothermal alteration. Given that hydrothermal alteration is pervasive near mid-ocean ridges but minimal in oceanic plateaus, we propose that the source of Archean TTG rocks was thick oceanic crust generated at spreading mid-ocean ridges rather than oceanic plateau basalts in intraplate settings. The most plausible geodynamic setting for the formation of early continental crust, therefore, is at convergent plate margins, where thick seawater-altered oceanic crust would be subducted or stacked and partially melted to produce TTGs.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"690 ","pages":"Article 122888"},"PeriodicalIF":3.6,"publicationDate":"2025-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144204608","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":"Lithium isotopes reveal mantle plume heterogeneity: Insights from the Emeishan Large Igneous Province","authors":"Dong-Bo Tan ,&nbsp;Yilin Xiao ,&nbsp;Song-yue Yu ,&nbsp;He Sun ,&nbsp;Hai-Ou Gu ,&nbsp;Xiangying Ye","doi":"10.1016/j.chemgeo.2025.122889","DOIUrl":"10.1016/j.chemgeo.2025.122889","url":null,"abstract":"<div><div>Mantle plumes, rising from deep within the Earth, provide key insights into the interior heterogeneity. Previous studies of ocean island basalts have demonstrated the role of recycled crustal materials in modifying elemental and isotopic signatures in mantle plume sources in oceanic settings. However, the volume and nature of recycled crustal contributions to plume sources in continental settings remain poorly constrained. The Emeishan Large Igneous Province in southwestern China, widely recognized as the product of a mantle plume in a continental setting, offers an ideal natural laboratory to address this question. Here we report lithium (Li) isotopic data from high-Ti picrites at Ertan and Maoniuping (δ⁷Li = 5.1–9.6 ‰) and low-Ti picrites at Wulongba (δ⁷Li = 4.7–7.2 ‰), all of which exhibit heavier Li isotopic compositions than the typical mantle value (3.5 ± 1.0 ‰). After ruling out the effects of weathering and crustal and lithospheric mantle contamination, we attribute the elevated δ⁷Li values to the source characteristics of the Emeishan plume, which we estimate to contain 10–15 % recycled altered oceanic crust and 0.05–5 % marine silicate sediments. High-Ti picrites exhibit higher δ⁷Li values than the low-Ti picrites, likely reflecting differences in the proportions of pyroxenite and peridotite involved in mantle partial melting. A global comparison further reveals that plume-derived magmas from both continental and oceanic settings systematically display high δ⁷Li values, underscoring the widespread incorporation of recycled crust and the formation of pyroxenite with higher δ⁷Li values in the plume source. The even higher δ⁷Li values in continental settings are attributed to an “overlying lid effect”, whereby suppressed mantle melting enhances the relative contribution of pyroxenite-derived melts. Together, these findings provide isotopic evidence for the presence of recycled crust in mantle plume sources and establish Li isotopes as a robust tracer of deep crustal recycling.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"691 ","pages":"Article 122889"},"PeriodicalIF":3.6,"publicationDate":"2025-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144261962","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":"Early diagenetic versus hydrothermal signals in pyrite from ancient metamorphic sediment-hosted massive sulfides – implications for the stability of sulfur and iron isotope records in deep time","authors":"Eric Runge ,&nbsp;Muammar Mansor ,&nbsp;Virgil Pasquier ,&nbsp;Thomas Bovay ,&nbsp;Johanna Marin-Carbonne ,&nbsp;Vanessa Fichtner ,&nbsp;Andreas Kappler ,&nbsp;Jan-Peter Duda","doi":"10.1016/j.chemgeo.2025.122885","DOIUrl":"10.1016/j.chemgeo.2025.122885","url":null,"abstract":"<div><div>Stable isotope compositions in pyrite are widely employed for tracing microbial sulfur and iron cycling through geological time. In hydrothermal sulfide systems, however, sulfur and iron pools can be affected by both microbial and abiotic processes, limiting the applicability of the respective stable isotopes as biosignatures. Moreover, the diagenetic and metamorphic stability of sulfur and iron isotope signatures in pyrite under hydrothermal conditions is insufficiently understood. Here, we employed coupled in-situ Secondary Ion Mass Spectrometry (SIMS) triple sulfur (δ³⁴S and Δ³³S) and iron (δ⁵⁶Fe) isotope analysis on morphologically diverse pyrite in ∼390 Ma sediment-hosted massive sulfides to better understand biosignature preservation in hydrothermal systems. Petrographic analysis reveals recrystallized or cemented framboid-like pyrite that was locally overgrown by a secondary generation of subhedral pyrite. δ³⁴S and Δ³³S signatures of the pyrites (−15.13 to +18.77 ‰ and − 0.21 to +0.26 ‰, respectively) can be explained by either microbial or thermochemical sulfate reduction. However, the isotopically lightest δ³⁴S value in framboid-like pyrite (−15.13 ‰) most likely represents a mixed signal of early diagenetic microbial sulfur cycling and later sulfidic hydrothermal fluids driving recrystallization or cementation. The same pyrites show highly variable δ⁵⁶Fe compositions (−1.30 to +2.19 ‰), indicating precipitation from hydrothermal Fe(II) at varying rates and/or pyritization of a diagenetically fractionated iron pool. The lower median δ⁵⁶Fe value in framboid-like versus subhedral pyrite points to a greater expression of kinetic and equilibrium fractionation in the former. This may reflect differences in precipitation rates between early diagenetic (microbial) processes and hydrothermal overprint of the system, consistent with textural evidence for framboid recrystallization or cementation, and overgrowth. Nevertheless, the likely presence of microbially formed pyrite and the incomplete equilibration with hydrothermal fluids highlight that signatures of early diagenetic redox cycling can be preserved in hydrothermal sulfides despite alteration by sulfidic fluids or greenschist metamorphism. Our study stresses the challenges and potentials of coupled textural and in-situ stable isotope analysis for tracing microbial sulfur and iron cycling in hydrothermal sulfide systems through Earth's history.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"690 ","pages":"Article 122885"},"PeriodicalIF":3.6,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144167135","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":"Hydrous minerals are sinks for first row transition elements in the mantle: An experimental partitioning study","authors":"Isra S. Ezad ,&nbsp;Joshua J. Shea ,&nbsp;Stephen F. Foley","doi":"10.1016/j.chemgeo.2025.122883","DOIUrl":"10.1016/j.chemgeo.2025.122883","url":null,"abstract":"<div><div>Pyroxenites containing hydrous phases are increasingly recognised as contributing significant melt fractions to many primitive melts such as alkaline basalts, basanites, and lamproites. Although hydrous ultramafic rocks are minor components in the mantle, their low-temperature solidi compared to other mantle lithologies drives high melt productivity, making them significant contributors during fractional melting of heterogenous mantle domains. These hydrous ultramafic rocks contain phlogopite, amphibole, and apatite, and upon partial melting they produce distinct alkaline melts enriched in rare earth and high field strength elements when compared to basalts derived from peridotites. First row transition elements (FRTEs) are widely used indicators for identifying dry pyroxenite mantle lithologies in mantle sources, yet the partitioning behaviour of FRTEs between hydrous phases and alkaline melts remains poorly constrained. We present the first complete set of experimentally constrained partition coefficients for FRTEs between phlogopite, amphibole, and apatite and alkaline melts. Our results demonstrate that several FRTEs, Cr and Ni are compatible to highly compatible in phlogopite whilst Sc, Cr, Co and Ni are highly compatible in amphibole. We further demonstrate that coupling rare earth element concentrations with first-row transition elements is a powerful tool for discerning the mantle sources for basanites and lamproites globally.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"690 ","pages":"Article 122883"},"PeriodicalIF":3.6,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144167133","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":"Fast phase transformation of 2-line ferrihydrite to hematite as induced by the injection of photoelectrons","authors":"Lixia Yan ,&nbsp;Jing Liu ,&nbsp;Zihe Ren ,&nbsp;Qingze Chen ,&nbsp;Hongyan Wei ,&nbsp;Jianxi Zhu ,&nbsp;Runliang Zhu","doi":"10.1016/j.chemgeo.2025.122887","DOIUrl":"10.1016/j.chemgeo.2025.122887","url":null,"abstract":"<div><div>The phase transformation of 2-line ferrihydrite (Fh) to more thermodynamically stable iron (oxyhydr)oxides plays a crucial role in regulating the element cycling and energy transfer in Earth's near-surface environments. Redox transformation has been identified as a significant pathway in the phase transformation of Fh. As typical electron-donors, semiconducting minerals can induce the redox transformation of Fh and also serve as heterogeneous surfaces, influencing the aggregation and crystallization processes. In this work, we investigated the rate and product type of Fh transformation in the presence of nanosized TiO₂, a natural semiconductor, under light irradiation. Our findings demonstrate that light irradiation and the coexistence of both TiO₂ and small organic molecules (methanol) are essential for the rapid phase transformation of Fh (within 3 h), primarily to Hem. Higher methanol content and lower O₂ content facilitate the formation of Hem, as evidenced by the faster transformation rate and the higher Hem content in the products. Analysis of the solid phase during the reaction reveals the presence of Fe(II), indicating the reduction of Fh by photoelectrons from TiO₂. Surprisingly, unlike the commonly recognized transformation of Fh to goethite under reduction conditions at room temperature, Hem is identified as the primary product in this study, regardless of the solution pH (pH 4, 7, and 12). This phenomenon can be attributed to the solid-to-solid electron transfer and the facilitated aggregation of Fh in the presence of TiO₂, both of which promote the structural rearrangement of Fh leading to the formation of hematite while inhibiting its dissolution-recrystallization into lepidocrocite and goethite. This study highlights the role of photoelectrons in accelerating the phase transformation and influencing the transformation pathway of Fh. Considering the widespread occurrence of natural semiconductors and organic chemicals, we propose that photoelectron-induced transformation of Fh is an important yet overlooked process in Earth's near-surface environments.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"690 ","pages":"Article 122887"},"PeriodicalIF":3.6,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144189827","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":"Crustal reworking and Eo-Paleoarchean metamorphism of the northern Pikwitonei domain, Superior Province: U-Pb-Hf-TE analysis of 3.9–3.2 Ga detrital zircon","authors":"J.W.D. Strong ,&nbsp;C.G. Couëslan ,&nbsp;C.R.M. McFarlane ,&nbsp;K. Ross ,&nbsp;J. Marsh ,&nbsp;J. Simmons ,&nbsp;P. Thurston","doi":"10.1016/j.chemgeo.2025.122886","DOIUrl":"10.1016/j.chemgeo.2025.122886","url":null,"abstract":"<div><div>U-Pb-Lu-Hf-trace element analysis of detrital zircon from two metasedimentary rocks of the Armstrong assemblage in the northern Pikwitonei granulite domain of the NW Superior Province (Manitoba, Canada) are used to explore the Eo-Paleoarchean crustal formation history and zircon petrogenetic processes of the proto-Superior craton. The zircon age spectrum from each sample spans a billion-year period from 3.85 to 2.65 Ga, with a predominant 3.85–3.40 Ga detrital zircon age population. The ca. 3.85 Ga detrital zircon grains from each sample have subchondritic εHf(t) values between −3.9 and − 1.0, consistent with initial crystallization from a suite of late-Hadean to early-Eoarchean protoliths. Semi-continuous Eo-Paleoarchean crustal reworking is subsequently inferred based on the single uniform Hf isotope evolution trend for 3.85–3.20 Ga detrital zircon grains, which is comparable to igneous zircon populations from the Nuvvuagittuq greenstone belt on the eastern shore of Hudson Bay in Quebec. Trace element analysis of detrital zircon grains from both metasedimentary samples indicate the limited presence of detrital metamorphic zircon at 3.67 Ga, 3.5 Ga and 3.4 Ga, which reveal potential metamorphic events within the Eo-Paleoarchean Superior Province. In addition, the detrital igneous zircon grains have trace element compositions consistent with either partial melting of hydrous source rocks or magmatic reworking/assimilation of felsic rocks. The trace element compositions are broadly similar to ca. 3.9–3.2 Ga igneous zircon populations from Acasta and Saglek regions, while demonstrating the importance of calculating initial U concentrations for Hadean – Archean zircon.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"690 ","pages":"Article 122886"},"PeriodicalIF":3.6,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144167137","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 influence of primary depositional conditions on Hg behaviour during early thermal maturation","authors":"Asri O. Indraswari ,&nbsp;Joost Frieling ,&nbsp;Erdem Idiz ,&nbsp;Tamsin A. Mather ,&nbsp;Alexander J. Dickson ,&nbsp;Hugh C. Jenkyns ,&nbsp;Stuart A. Robinson ,&nbsp;Isabel M. Fendley ,&nbsp;Oliver Neilson","doi":"10.1016/j.chemgeo.2025.122884","DOIUrl":"10.1016/j.chemgeo.2025.122884","url":null,"abstract":"<div><div>Mercury (Hg) behaviour in sedimentary rocks is important to understand both in terms of its potential volatilization during magmatic intrusions (e.g., those associated with large igneous province activity) and its redistribution during thermal maturation associated with burial and, in some cases, hydrocarbon generation. Mercury behaviour varies significantly across different lithologies, likely influenced by the amount and type of organic matter present and sulfur chemistry. This study investigates the effects of lithology on Hg dynamics during thermal maturation through pyrolysis experiments at isothermal conditions of 325 °C for various durations (24, 336, 500, and 840 h). To study Hg behaviour in different lithologies, representing different depositional environments and OM-types (organic-rich vs organic-lean), we analysed a relatively Hg-rich sample from the Lower Jurassic (Pliensbachian) Belemnite Marls, a marine carbonate-rich sequence exposed in southern England, and a coal sample from the Eocene Tanjung Formation, Indonesia composed of terrestrial organic matter. Before and after pyrolysis, we generated data on Hg concentrations, total organic carbon (TOC), hydrogen index (HI), and oxygen index (OI) and compared our results with existing data from the Posidonienschiefer, a marine, highly organic-rich, black shale of Toarcian age from Germany. Results indicate substantial Hg loss, with the coal and Belemnite Marls samples losing over 80 % of their Hg in the first 24 h, compared to a 50 % loss in the Posidonienschiefer. Thermal desorption profiles (TDPs) allow us to align the Hg losses in the isothermal heating experiments with the initial Hg speciation in the sedimentary rocks. Both the Belemnite Marls sample and Tanjung Formation coal are dominated by lower temperature Hg species, potentially bound to or associated with organic matter. These findings enhance our understanding of the interplay between lithology, thermal maturation, and Hg behaviour, which is critical for interpreting historical Hg cycling and the environmental impacts associated with the formation of large igneous provinces (LIPs).</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"690 ","pages":"Article 122884"},"PeriodicalIF":3.6,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144177847","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}