Chemical Geology最新文献

{"title":"Radiation-enhanced fluid diffusion and alteration around uraniferous inclusions in Cenomanian resinite from North Bohemia","authors":"Vladimír Strunga ,&nbsp;Vladimír Havránek ,&nbsp;Jan Lorinčík ,&nbsp;Kristína Sihelská ,&nbsp;Pavel Krist ,&nbsp;Martina Havelcová ,&nbsp;Bohuslava Čejková ,&nbsp;Jiří Mizera","doi":"10.1016/j.chemgeo.2024.122554","DOIUrl":"10.1016/j.chemgeo.2024.122554","url":null,"abstract":"<div><div>Advanced analytical methods including SEM/EDX and μ-PIXE/RBS microanalyses were used to investigate chemical alterations around uraniferous inclusions in a Cenomanian fossil resin (resinite). Studied alterations related to several types of discontinuities in resinite matrix are a model example of the phase interface between solid polymeric hydrocarbon and aqueous fluids exposed to long-term irradiation by heavy energetic ions resulting mostly from the natural decay of uranium. Computational models of ion ranges correspond well with the observed range of alterations about 35 μm from uraniferous inclusions. The major alteration is found within a 20 μm inner zone. It is characterized by distinct sulfur enrichment and an increase in the O/C ratio. No sulfur enrichment in the resinite matrix occurs apart from the uraniferous phases. Proton beam-induced alterations of the resinite were investigated and compared with the natural ones. The differences indicate the importance of aqueous fluids in the natural radiation-induced alteration process. It is concluded that radiation-enhanced mass transfer and reactions occur at solid-fluid interfaces during the long-term energy deposition by alphas, alpha recoils, and fission fragments combined. The role of thermal effects and and formation of radical species by radiolysis of aqueous fluids on a microscale is discussed.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"673 ","pages":"Article 122554"},"PeriodicalIF":3.6,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142858009","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":"Non-conservative behaviour of molybdenum in the Ganga (Hooghly) River estuary, India: Role of solute-particle interaction and sediment diagenesis","authors":"Rakesh K. Tiwari ,&nbsp;Tarun K. Dalai ,&nbsp;Rupak Samadder ,&nbsp;Waliur Rahaman ,&nbsp;Sunil K. Singh","doi":"10.1016/j.chemgeo.2024.122526","DOIUrl":"10.1016/j.chemgeo.2024.122526","url":null,"abstract":"<div><div>This study is focussed on understanding of molybdenum (Mo) cycling in the mesotidal to macrotidal estuary of the Ganga (Hooghly) River in India. Our investigation encompasses the composition of water and suspended particulate matter (SPM) samples collected in three separate periods (pre-monsoon: PrM, monsoon: M and post-monsoon: PoM) over two consecutive years, surface sediments, exchangeable phases of surface and suspended sediments, one sediment core, urban and industrial effluent waters and ground waters. The observed dissolved Mo concentrations in the estuary are in excess of those expected from conservative mixing of seawater and river water. The “excess” Mo values, observed in the mid-to-high salinity regions (4–27 ‰) for four out of the six study periods, are the highest in the monsoon samples. The bulk and exchangeable phase compositions are supportive of release of Mo from the Fe-Mn oxyhydroxide phases of the SPM and surface sediments in the estuary. Mass balance calculations indicate that Mo release from the SPM and surface sediments can account for up to 40 % of the median value of the “excess” Mo in the estuary. The compositions of the sediment core provide evidence for the mobilization of Mo and its release to porewater due to reductive dissolution of Fe-Mn oxyhydroxides. The tidally induced sediment resuspension likely facilitates the transport of porewater Mo to the overlying water. Mass balance calculations indicate that Mo loss from the sediment column can account for the bulk of the “excess” Mo in the estuary waters. This study further demonstrates that industrial effluents, urban waste waters and groundwaters do not constitute significant sources of dissolved Mo in the estuary.</div><div>The average annual Mo flux from the estuary is (∼2–3) × 10⁶ mol, of which ∼30–50 % of Mo is due to estuarine addition. More significantly, Mo contribution from the Hooghly River estuary, accounting for ∼0.7–1.0 % of the global riverine Mo flux, is ∼3–4 folds higher than its water contribution (∼0.25 %) to the global river water flux. Our study highlights the role of interactions between oxyhydroxide phases and estuarine water, diagenetic mobilization of elements in the sediment column and porewater transport in the cycling of Mo in a monsoon-dominated tropical estuary with high sediment loads. We also demonstrate that the mobilization of Mo through chemical weathering is driven by physical weathering in the catchments of the South Asian Rivers.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"673 ","pages":"Article 122526"},"PeriodicalIF":3.6,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142815873","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 ,&nbsp;Minfang Yang ,&nbsp;Jing Lu ,&nbsp;Zhongfeng Jiang ,&nbsp;Lei Wang ,&nbsp;Yuanyuan Zhu ,&nbsp;Wenjing Guo ,&nbsp;Zejing Li ,&nbsp;Zhibiao Shi ,&nbsp;Pan Wang ,&nbsp;Kai Zhou ,&nbsp;Xiaotao Xu ,&nbsp;Longyi Shao ,&nbsp;Jason Hilton","doi":"10.1016/j.chemgeo.2024.122555","DOIUrl":"10.1016/j.chemgeo.2024.122555","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"673 ","pages":"Article 122555"},"PeriodicalIF":3.6,"publicationDate":"2025-02-05","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":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Scandium mineralization during ultramafic-mafic magmatism in the subduction zone","authors":"Xin Chen ,&nbsp;Hans-Peter Schertl ,&nbsp;Junaid Khan ,&nbsp;Pengjie Cai ,&nbsp;Dongyang Lian ,&nbsp;Jinshou Wang ,&nbsp;Chengtao Yu ,&nbsp;Hao Lin ,&nbsp;Xiaojia Jiang","doi":"10.1016/j.chemgeo.2024.122556","DOIUrl":"10.1016/j.chemgeo.2024.122556","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Sandium (Sc) has gained strategic importance due to its diverse applications. Magmatic ultramafic-hosted deposits are emerging as significant Sc reservoirs, not only for their direct reserves but also as precursors for laterite-hosted Sc deposits. However, the processes controlling Sc enrichment in magmatic systems remain poorly understood. This study reveals the discovery of a potentially significant Sc mineralization within an ultramafic complex of the Shangzhuang P–REE deposit, situated in the Lajishan region of western China. The ultramafic complex comprises fluorapatite-rich biotite clinopyroxenite and calcite-amphibole-K-feldspar-rich clinopyroxenite hosted in biotite clinopyroxenite. Whole-rock concentrations of Sc range from 35.9 to 134 ppm in these three rocks mentioned, while clinopyroxenes in the complex exhibit Sc concentrations ranging from 56 to 203 ppm. Zircon U&lt;img&gt;Pb dating on three ultramafic clinopyroxenites yield consistent crystallization ages of 465 ± 2 Ma, indicating an Ordovician magmatic and Sc mineralization event coinciding with the subduction stage of the Proto-Tethys Ocean beneath the central Qilian block. Field observations, consistent ages, narrow range of Hf and Sr isotope data (zircon ε&lt;sub&gt;Hf&lt;/sub&gt;(t): +3.2 − +13.5; clinopyroxene &lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr: 0.704534–0.705715), and decreasing Mg&lt;sup&gt;#&lt;/sup&gt; trend observed in both clinopyroxene-bearing whole-rock and clinopyroxene single-grain samples from the three ultramafic rocks suggest a common magmatic origin with varying degrees of fractional crystallization and crystal accumulation within an evolved magmatic system. The parent magma likely originated from a potassium-Sc-REE-rich basaltic composition. This magma was primarily sourced from carbonated phlogopite-garnet lherzolite lithospheric mantle, but had been modified by carbonate-rich fluids derived from subducted oceanic sediments during the subduction of the Proto-Tethys Ocean. The comprehension of multistage growth processes in clinopyroxene effectively signifies the extent of magmatic differentiation and points to the involvement of magma sources in the formation of Sc deposits. Significant fluctuations of Sc concentration within clinopyroxene can be attributed to variable magma compositions. Enrichment of phosphate and fluorine effectively promotes Sc migration during magma evolution, while partition coefficient of Sc into clinopyroxene may be significantly higher in a P-F-rich magma, which causes Sc to concentrate in the apatite-rich biotite clinopyroxenite. The relatively high amount of Sc in the parent magma may be related to its initial enrichment in the carbonated fertile mantle. These compositions likely result from different amounts of phosphate and fluorine in the subduction-related fluid percolating through ultramafic mantle rocks. This study significantly advances our understanding of intricate processes involved in developing Sc mineralization in an ultramafic system, consid","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"673 ","pages":"Article 122556"},"PeriodicalIF":3.6,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142887307","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":"Preservation of biosignatures in Neoproterozoic phosphorites metamorphosed at temperatures >450 °C","authors":"Kenan Cao ,&nbsp;Zhenbing She ,&nbsp;Dominic Papineau ,&nbsp;Jingbo Nan ,&nbsp;Chao Chen ,&nbsp;Reza Deevsalar ,&nbsp;Ayetullah Tunc ,&nbsp;Qunfeng Xiao ,&nbsp;Kang-Jun Huang ,&nbsp;Yuanming Pan","doi":"10.1016/j.chemgeo.2024.122519","DOIUrl":"10.1016/j.chemgeo.2024.122519","url":null,"abstract":"&lt;div&gt;&lt;div&gt;There is still much controversy over whether apatite and graphite can be used as fingerprint mineral assemblages to preserve biosignatures in ancient sedimentary rocks that experienced medium- to high-grade metamorphism. Herein, we present a comprehensive analysis of graphite and associated phases from meta-phosphorites of the Huangmailing Formation in the South Dabie Orogen to assess possible preservation of biosignatures. Stratigraphic correlations and previous geochronological data suggest that the protoliths of Huangmailing Formation was deposited in the Ediacaran, and was metamorphosed during the Triassic Dabie Orogeny as documented by our apatite U&lt;img&gt;Pb dating. Microcrystalline graphite occurs both as inclusions within metamorphic minerals like apatite, and as matrix-hosted disseminations at grain boundaries of other phases. Bulk organic carbon isotopic analyses yield δ&lt;sup&gt;13&lt;/sup&gt;C values between −26.0 ‰ and − 15.2 ‰ and total organic carbon contents from 0.33 to 3.27 wt%. Raman spectra of the two types of graphites yield an average peak metamorphic temperature of 452 °C and 473 °C, consistent with the upper greenschist facies to lower amphibolite facies metamorphic conditions in the area. However, the matrix graphites show a wider range of peak temperature variations, likely containing graphitic carbon with lower crystallinity that was affected by retrograde metamorphic fluids. Notably, two prominent Raman bands at around 325 cm&lt;sup&gt;−1&lt;/sup&gt; and 395 cm&lt;sup&gt;−1&lt;/sup&gt; are observed for the graphite hosted in apatite. This, along with the presence of a peak at 2473 eV in the sulfur &lt;em&gt;K&lt;/em&gt;-edge XANES spectra of some graphite in apatite, and the co-occurrence of &lt;sup&gt;12&lt;/sup&gt;C and &lt;sup&gt;14&lt;/sup&gt;N and local association of &lt;sup&gt;32&lt;/sup&gt;S with &lt;sup&gt;12&lt;/sup&gt;C in graphite inclusions determined by TOF-SIMS, suggest the possible presence of C-S-Fe and N-bearing compounds and functional groups. TEM and EDS analysis reveal that graphite inclusions in apatite are closely associated with amorphous silica, and mainly occur as well crystallized, polygonal grains around 100 to 200 nm across and has an expanded (002) lattice spacing between 3.43 Å and 3.64 Å. This lattice expansion is attributable to the presence of heteroatoms such as S, Fe and Si, and N, in the graphene interlayers. In contrast, matrix graphites exhibit a wider range of structural and compositional variations than their counterpart as inclusion in apatite, which probably arise from interactions with metamorphic fluids or incorporation of fluid-deposited graphitic carbon. Our study documents the ubiquitous preservation of biological carbon as graphite inclusions in apatite from Huangmailing meta-phosphorites, likely as a result of metamorphic recrystallization of organic-bearing Ediacaran phosphorites. This suggests that the organic matter trapped in sedimentary apatite during their co-precipitation or early diagenesis was probably less modified during metamorphic recrystalliz","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"673 ","pages":"Article 122519"},"PeriodicalIF":3.6,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142815783","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 ,&nbsp;Hugo Moreira ,&nbsp;Charles Le Losq ,&nbsp;Max Wilke ,&nbsp;Fleurice Parat","doi":"10.1016/j.chemgeo.2024.122559","DOIUrl":"10.1016/j.chemgeo.2024.122559","url":null,"abstract":"<div><div>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 CO₂-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 Fe³⁺/ΣFe ratio (Fe³⁺/ΣFe = 0.31, indicative of oxidized conditions) and very low S⁶⁺/ΣS ratio (S⁶⁺/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 (<em>f</em>O₂) 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 <em>f</em>O₂ in this chemical system. The Fe³⁺/ΣFe in melt inclusions yields magma redox conditions (<em>f</em>O₂) 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 S⁶⁺/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.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"673 ","pages":"Article 122559"},"PeriodicalIF":3.6,"publicationDate":"2025-02-05","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":"Linking the oxygen-17 compositions of water and carbonate reference materials using infrared absorption spectroscopy of carbon dioxide","authors":"Justin Chaillot ,&nbsp;Samir Kassi ,&nbsp;Thibault Clauzel ,&nbsp;Marie Pesnin ,&nbsp;Mathieu Casado ,&nbsp;Amaëlle Landais ,&nbsp;Mathieu Daëron","doi":"10.1016/j.chemgeo.2024.122450","DOIUrl":"10.1016/j.chemgeo.2024.122450","url":null,"abstract":"<div><div>Joint measurements of the ¹⁸O/¹⁶O and ¹⁷O/¹⁶O ratios of carbonate minerals and waters are increasingly used to investigate various geochemical, physical and biological processes. Diverse analytical methods, each of them technically challenging in one way or another, have been developed or refined in recent years to measure oxygen-17 anomalies (Δ’¹⁷O) with instrumental precisions of 10 ppm or better. A critical underpinning of all these methods is how the international carbonate reference materials currently anchoring the VPDB ¹⁸O/¹⁶O scale are linked to the primary VSMOW-SLAP scale in (¹⁸O/¹⁶O, ¹⁷O/¹⁶O) space. For now, however, substantial systematic discrepancies persist between different groups and methods, even after all measurements are nominally standardized to VSMOW-SLAP.</div><div>Here we take advantage of VCOF-CRDS, a novel spectroscopic method combining the ease and simplicity of near-infra-red absorption measurements in pure CO₂ with metrological performance competitive with state-of-the-art IRMS techniques, to precisely characterize, based on previously reported equilibrium fractionation factors between water and CO₂, the relative triple oxygen isotope compositions of international water standards (VSMOW2, SLAP2, GRESP) and CO₂ produced by phosphoric acid reaction of carbonate standards (NBS18, NBS19, IAEA603, IAEA610, IAEA611, IAEA612). The robustness of our results derives from the demonstrated linearity of our measurements (RMSE ≈ 1 ppm), but also from the fact that, when equilibrated with or converted to CO₂, all of these reference materials yield analytes with closely comparable oxygen-18 compositions. In light of these observations, we revisit potential causes of the large inter-laboratory discrepancies reported so far. Collectively reconciling the different types of measurements constraining the relative ¹⁷O/¹⁶O ratios of the two standards most often used to normalize carbonate analyses (NBS18, IAEA603) is a matter of high priority.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"673 ","pages":"Article 122450"},"PeriodicalIF":3.6,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142815784","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":"Unraveling the link between worldwide adakite-like rocks and porphyry Cu deposits","authors":"Chao Wu ,&nbsp;Guoxiong Chen ,&nbsp;Huayong Chen","doi":"10.1016/j.chemgeo.2024.122521","DOIUrl":"10.1016/j.chemgeo.2024.122521","url":null,"abstract":"<div><div>Adakite-like rocks, as an important recorder of magmatic evolution in mantle and crust, are closely associated with major porphyry Cu deposits. However, the underlying mechanism connecting these associations remains insufficiently elucidated. This study compiles ca. 7000 whole-rock geochemical data from Phanerozoic adakite-like rock samples and from ore-forming porphyries in porphyry Cu deposits. Machine learning investigations are performed to characterize the geochemical variations of adakite-like rocks from various orogenic or cratonic systems and investigate any geochemical similarities with rocks associated with porphyry ore systems. Principal component analysis (PCA), along with t-distributed Stochastic Neighbor Embedding (t-SNE), highlights elemental distinctions between adakite-like rocks formed in mature and juvenile crust and the similarities of rocks from porphyry Cu<img>Mo deposits with the former and rocks from porphyry Cu<img>Au deposits with the latter. Extreme Gradient Boosting (XGBoost) and Support Vector Machine (SVM) analyses are applied to the original dataset and the PCA data derived from the dataset to discriminate adakite-like rocks from various geodynamic settings from each other and from rocks associated with porphyry ore deposits. Our models show that XGBoost and SVM can identify the tectonic regions of adakite-like rocks and rocks from porphyry copper systems with high efficiency and confidence e.g., accuracy = 0.88–0.94 and area under curve (AUC) = 0.69–0.86. The application of SHapley Additive exPlanations (SHAP) values is employed to elucidate the parameters that discriminate the different environments, providing insight into the underlying petrogenetic processes, including diverse levels of formation depth and extent of mantle interaction. Additionally, when examining ore-forming porphyries and adakite-like rocks, the incorporation of heatmaps into taxonomic classification (HTC) provides significant distinguishing factors with substantial geological implications. These findings suggest potential geological processes (e.g., remelting of Cu-sulfide-bearing cumulates or flotation of Cu-sulfide phases attached to vapor bubbles) that may enrich the source magma of ore-forming porphyries beyond the conventional geological processes responsible for adakite-like rock formation, which could serve as an exploration indicator.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"673 ","pages":"Article 122521"},"PeriodicalIF":3.6,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142815835","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 ,&nbsp;Xuewan Wu ,&nbsp;Wei Zhang ,&nbsp;Zhifeng Wan ,&nbsp;Yifei Dong ,&nbsp;Xi Xiao ,&nbsp;Yang Wu ,&nbsp;Xiaoyu Wu ,&nbsp;Junxi Feng ,&nbsp;Qianyong Liang","doi":"10.1016/j.chemgeo.2024.122524","DOIUrl":"10.1016/j.chemgeo.2024.122524","url":null,"abstract":"<div><div>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<img>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 δ¹³C values (from −36.13 ‰ to −32.18 ‰) indicate anaerobic oxidation of methane during carbonate formation. The response of δ¹³C to changes in the methane flux is not obvious. The gradual increase in δ¹⁸O from the outer to the inner portions suggests that the methane flux affected δ¹⁸O. The samples have relatively high enrichment factors (EFs) of molybdenum (Mo) and high molybdenum/uranium (Mo/U) ratios. The U_EF values show an increasing trend from the outer to the inner portions, whereas the changes in Mo_EF, Cd_EF and V_EF are not obvious. However, Mo_EF, Cd_EF, and V_EF 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.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"673 ","pages":"Article 122524"},"PeriodicalIF":3.6,"publicationDate":"2025-02-05","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":"Single quartz δ18O: A new frontier in detrital provenance analysis (Bengal Fan, IODP Expedition 354)","authors":"Mara Limonta ,&nbsp;Christian France-Lanord ,&nbsp;Albert Galy ,&nbsp;Andrey Gurenko ,&nbsp;Nordine Bouden ,&nbsp;Eduardo Garzanti","doi":"10.1016/j.chemgeo.2024.122525","DOIUrl":"10.1016/j.chemgeo.2024.122525","url":null,"abstract":"<div><div>Quartz is the most abundant mineral in sediments and sedimentary rocks but efforts to reliably identify its provenance have been only partially fruitful so far. Even advanced methods such as cathodo-luminescence, Raman spectroscopy, synchrotron X-ray absorption spectroscopy, and laser ablation spectrometry have led to limited success. This article demonstrates how the δ¹⁸O of detrital quartz provides useful additional insight. The oxygen-isotope signature primarily depends on source rocks and their formation conditions, being highly different for different crustal sources and highest for carbonate rocks.</div><div>This study illustrates a new protocol to analyze δ¹⁸O signatures of single quartz grains and shows how provenance from magmatic, metamorphic, or sedimentary domains can be discriminated. In each sand sample from rivers draining exclusively a single Himalayan tectonic domain (e.g., Trans-Himalaya, Greater Himalaya, Lesser Himalaya, and Tethys Himalaya), ∼200 quartz grains were analyzed by ion microprobe LG-SIMS (Large Geometry Secondary Ion Mass Spectrometry) to characterize their oxygen-isotope variability. In each turbidite sample collected from the Bengal Fan during IODP Expedition 354, ∼150 quartz grains were analyzed next to quantify the relative contribution of each Himalayan domain. This allowed us to complement data obtained with other bulk-sediment to single-mineral approaches, thus enhancing provenance resolution and highlight the erosional evolution of the Himalayan-Tibetan orogen through time.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"673 ","pages":"Article 122525"},"PeriodicalIF":3.6,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142858013","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}