Chemie Der Erde-Geochemistry最新文献

{"title":"Enhanced analysis of hydrothermal alteration and mineral prospecting through integration of ASTER and aeroradiometric data: A case study from the Ouarzazate region, Morocco","authors":"Ilham El Hakimi,&nbsp;Lahsen Achkouch,&nbsp;Younesse El Cheikh,&nbsp;Mohammad Taadid,&nbsp;Houda Bourouda,&nbsp;Ahmed Rachid,&nbsp;Ahmed Attou","doi":"10.1016/j.chemer.2025.126296","DOIUrl":"10.1016/j.chemer.2025.126296","url":null,"abstract":"<div><div>The study area, situated in the western segment of the Saghro Massif within the Anti-Atlas belt, is characterized by mineralized deposits, intricate lithological formations, and distinctive tectonic features. This research integrates ASTER imagery analysis with gamma-ray spectrometry data to map alteration zones and examine the geochemical and mineralogical processes that influence radioactive element distribution. Specific analytical techniques are applied to investigate relationships among argillic, phyllic, propylitic alterations, iron oxides, and regions with elevated concentrations of radiometric elements. Gamma-ray spectrometry data, including mono-elemental maps of radiometric components (potassium in %, equivalent uranium in ppm, and equivalent thorium in ppm), are analyzed alongside interpreted ASTER images to identify potential mineralization zones. Ratios of K/eU and K/eTh, along with the F parameter, are processed within a fuzzy model framework, which combines these datasets into a comprehensive mineral prospectivity map that serves as a tool for guiding exploration. This analysis identifies four hydrothermal alteration zones as highly promising for mineral exploration, suggesting a likely association between magmatic processes and spatially correlated hydrothermal alteration, thereby supporting further detailed exploration initiatives.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126296"},"PeriodicalIF":2.6,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143883029","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemistry, zircon UPb ages and Hf isotopes of Tra Bong granitoid from Kontum massif, central Vietnam, and its petrogenetic significance","authors":"Nguyen Huu Trong ,&nbsp;Pham Trung Hieu ,&nbsp;Pham Minh ,&nbsp;Bui Kim Ngoc ,&nbsp;Nguyen Dinh Luyen ,&nbsp;To Xuan Ban","doi":"10.1016/j.chemer.2025.126295","DOIUrl":"10.1016/j.chemer.2025.126295","url":null,"abstract":"<div><div>Tra Bong granitoid, distributed in the northern area of Kontum, primarily consists of diorite and granodiorite. The main rock-forming minerals contain plagioclase (26–60 %), K-feldspar (8–22 %), quartz (15–33 %), biotite (3–7 %), and hornblende (9–20 %). The accessory minerals are sphene, apatite, zircon, and magnetite. Tra Bong granitoids are characterized by SiO₂ (58.83–65.8 %), total alkali (6.68–8.03 %), and A/CNK (0.80–0.90). They show high-K and relative enrichment of large-ion lithophile elements (Sc, Rb, and K), and the relative depletion of Nb, Ta, and Ti elements. The P₂O₅ content decreases with increasing SiO₂, and Th increases with Rb, a trend typical of I-type granites. All observed petrographic and geochemical characteristics suggested that the Tra Bong granitoid is typical of the I-type granite, formed in a subduction zone. The U<img>Pb crystallization age ranges from 254.5 to 255.0 Ma, coinciding with the Late Permian-Early Triassic magmatic activity, which was previously reported in the Truong Son belt. The ε_Hf(t) value together with the Hf zircon model ages (T_DM2) ranges from 1011 to 1159 Ma. The Tra Bong granitoid is a result of partial melting Mesoproterozoic mafic-intermediate magmatic rocks, with a minor amount of metasedimentary crust remelting. In conjunction with other Permian-Triassic magmatic rocks along Truong Son belt and the Song Ma suture, the Tra Bong granitoid represents magmatic activity related to subduction-collision of the Indochina and South China blocks and closure of Paleo-Tethys Ocean in the Late Permian-Early Triassic, along the Song Ma suture.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126295"},"PeriodicalIF":2.6,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143895853","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Identifying geochemical element distribution patterns through multiple-point geostatistical simulation and singularity analysis: A case study of the Wulonggou-Balong Area, Qinghai, China","authors":"Mengyu Zhao ,&nbsp;Qinglin Xia ,&nbsp;Wenjun Li","doi":"10.1016/j.chemer.2025.126294","DOIUrl":"10.1016/j.chemer.2025.126294","url":null,"abstract":"<div><div>The identification of geochemical element distribution patterns, the extraction of anomalies from geochemical exploration data, and the analysis of deep-level mineralization information are essential to guiding mineral prospectivity mapping. The spatial distribution of geochemical elements mainly arises from complex geological processes, making it challenging for standard deterministic interpolation techniques to capture its complex structure. In singularity analysis of element distribution, the size and geometric configuration of the sliding window significantly impact the geochemical anomaly distribution. Accordingly, this study incorporated the complex patterns extracted from multi-scale exploration geochemical data into a multiple-point geostatistical simulation framework to characterize geochemical element distributions at a fine scale. Fractal topography and singularity analysis were integrated as key analytical tools to identify and extract anisotropic geochemical anomalies. Stream sediment geochemical data from the Wulonggou–Balong area, Qinghai, China, were used as a case study to delineate gold-related geochemical spatial distribution patterns. The proposed multiple-point geostatistical (MPS) method enhanced anomaly intensity in local regions while achieving higher fidelity in reproducing spatial distribution patterns that align with regional geological trends. The spatial distribution patterns of geochemical anomalies, analyzed through diverse fractal topological relationships, highlight anisotropic characteristics in geochemical element distributions governed by ore-controlling factors. Practical application demonstrated that the methods effectively identify undetected weak anomalies associated with mineralization-favorable zones within gold geochemical distribution patterns and minimize uncertainty in anomaly interpretation.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126294"},"PeriodicalIF":2.6,"publicationDate":"2025-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143864650","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochronology and petrogenesis of magmatic and high-grade metamorphic rocks in the Eocene Chapedony core complex: New insights into the basement geology of Iran","authors":"Zeynab Gharamohammadi ,&nbsp;Peter A. Cawood ,&nbsp;Ali Kananian ,&nbsp;Reza Nozaem ,&nbsp;Yona Jacobsen ,&nbsp;David Lentz ,&nbsp;Jafar Omrani","doi":"10.1016/j.chemer.2025.126290","DOIUrl":"10.1016/j.chemer.2025.126290","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The Arabia-Eurasia convergence zone provides an evolving record from oblique subduction to continental collision resulting in multiple transient tectonothermal events. Although the subduction of the Neotethys below the Iranian terranes and its relation to the arc and back-arc magmatism throughout the late Mesozoic and Cenozoic in Iran has been documented, the detailed geochemical and isotopic transition from subduction to back-arc extension was not constrained. This study reports the first evidence into the petrogenesis of magmatic diversity of Chapedony core complex (CCC) and the coexistence of Nb-enriched rocks and adakite-like rocks as a result of old crustal recycling. Integrated study of petrography, whole-rock major- and trace-element geochemical data supported with Sr and Nd isotope compositions, zircon U&lt;img&gt;Pb and traces, and zircon Hf isotope analyses reveal a protracted and pulsed evolution of the CCC. The complex consists of leucosome-bearing gabbro-diorite-granodiorite, quartz diorite, and biotite granite that formed between 50 and 40 Ma, but contains amphibolite (metabasite) bodies with zircon cores yielding U&lt;img&gt;Pb ages of 518 Ma and 189 Ma with MORB- and OIB-like characteristics, respectively. Biotite granites are divisible into two types; Type 1 have zircons with a wide range ages, while Type 2 are biotite granites with Eocene ages and lack inherited zircons. Biotite granites Type 1 yield a range of zircon ages (45–3200 Ma) with the youngest magmatic ages late Neoproterozoic-Early Cambrian, Triassic (240 Ma), and Eocene (48 Ma). εHf (t) values for zircon grains range from −23.95 to 13.13 for biotite granites (Type 1), −4.76 to 6.78 for amphibolites, and − 6.25 to 6.96 for Eocene mafic-felsic rock units. Biotite granites (Type 1) have I&lt;sub&gt;Sr&lt;/sub&gt; and εNd values ranging from 0.7177 to 0.7308 and − 14.8 to −7.4, respectively, whereas these values for the amphibolites are 0.7056 to 0.7090 and − 4.4 to 11.3, respectively. The mid-Eocene rock units of the CCC have I&lt;sub&gt;Sr&lt;/sub&gt; of 0.7050 to 0.7136 and εNd values of −3.9 to 8.9 gabbro-diorite-granodiorite, 3.3 to 16.3 for quartz diorite, and − 5.3 to −0.9 biotite granite (Type 2). The recorded zircon Hf isotopes along with I&lt;sub&gt;Sr&lt;/sub&gt; and εNd values indicate that a hybrid and old mantle (MORB+OIB) previously metasomatised by subduction of old enriched components (biotite granite Type 1) into the mantle, predating Eocene appinite-like mafic magma generation. Subsequent partial melts of such a source generate Eocene appinite magmas, as transitional rocks, which evolved to Eocene intermediate-felsic rocks through magma-crust interaction and accumulation/fractionation after the initial melts formed in the lower crust. The timing of the CCC formation (50–40 Ma) corresponds to an amphibolite metamorphism involving temperatures of 600–800 °C, associated with partial melting during the regional back-arc extension. The formation of new crust, through the reactivation and recycl","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126290"},"PeriodicalIF":2.6,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143877471","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spectroscopic signatures for expeditious monitoring of contamination risks at abandoned coal mine sites","authors":"Jelena Milinovic ,&nbsp;Patrícia Santos ,&nbsp;Jorge Espinha Marques ,&nbsp;Deolinda Flores ,&nbsp;Aurora Futuro ,&nbsp;Carlos M. Pereira ,&nbsp;Manuel Azenha","doi":"10.1016/j.chemer.2025.126292","DOIUrl":"10.1016/j.chemer.2025.126292","url":null,"abstract":"<div><div>Soil acts as a natural ‘filter’, playing a crucial role in the transfer of geogenic and anthropogenic pollutants from abandoned coal mine sites to surrounding water bodies. Key indicators of soil contamination, such as pH, electrical conductivity (EC), and organic matter (OM), expressed as loss-on-ignition (LOI), can signal contamination risks when they deviate from optimal ranges. To enable sustainable risk assessment through monitoring of pH, EC, and LOI, streamlined spectroscopic techniques Fourier transform infrared (FTIR), near-infrared (NIR), Raman, and X-ray fluorescence (XRF) were applied in combination with multivariate analysis (MVA), to soil samples from two abandoned coal mines in NW Portugal. Partial least squares (PLS) regression models demonstrated that XRF spectroscopic data provided the most accurate assessment of soil pH, EC, and LOI at the local scale (R² = 0.92–0.99). The most significant spectroscopic signatures, identified through weighted regression coefficients (B_w), enabled robust predictions of these key soil parameters. These findings highlight that these geochemical variables outperform molecular spectroscopy techniques for efficient and environmentally relevant risk monitoring of contamination in abandoned coal mine sites.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126292"},"PeriodicalIF":2.6,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143828522","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Melting experiments of an L6 ordinary chondrite: Implications for the formation of alkali-rich achondrites","authors":"S. Iannini Lelarge ,&nbsp;M. Masotta ,&nbsp;L. Folco ,&nbsp;T. Ubide ,&nbsp;M.D. Suttle ,&nbsp;L. Pittarello","doi":"10.1016/j.chemer.2025.126293","DOIUrl":"10.1016/j.chemer.2025.126293","url":null,"abstract":"<div><div>We conducted high-pressure (1 GPa) melting experiments (1100–1400 °C) on the equilibrated ordinary chondrite DAV 01001 (L6) to investigate partial melting scenarios of planetary embryo in the early solar system. At 1100 °C, no melting of the silicate phase is observed, and the initial chondritic texture is preserved, but the metallic-sulphidic phases formed two immiscible Fe–Ni and S-rich liquids. Melting of silicate minerals began at 1200 °C, progressing from plagioclase to high-Ca and low-Ca pyroxene and olivine. As melting advanced, the formation of new olivine and low-Ca pyroxene resulted in the production of trachy-andesitic melt at 1200 °C, basaltic trachy-andesitic melt at 1300 °C, and andesitic melt at 1400 °C. These silicate melts have chemical similarities with some anomalous achondrites (e.g., GRA 60128/9). At the same time, minerals of new formation resemble those of primitive achondrites (e.g., brachinites, ureilites, IAB silicate inclusions, acapulcoites and lodranites). The rapid mineral-liquid re-equilibration suggests that basaltic liquids can form only above 1400 °C and that relatively high degrees of melting (&gt;20 %) and crystallisation are necessary to explain the observed diversity of achondritic lithologies. These findings suggest that partial melting and recrystallization processes within planetary embryos could have played a critical role in the early solar system, contributing to the early differentiation of planetary bodies and the diversity of achondritic lithologies, including (but not limited to) alkali-rich achondrites.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126293"},"PeriodicalIF":2.6,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143873763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deciphering the magmatic evolution of the Hyblean Cretaceous volcanism (SE Sicily, Italy): New geochemical, isotopic and noble gas analyses","authors":"M. Di Bella ,&nbsp;D. Romano ,&nbsp;V. Volpi ,&nbsp;F. Italiano ,&nbsp;A. Correale ,&nbsp;M. Petrelli ,&nbsp;G. De Rosa ,&nbsp;A. Tripodo ,&nbsp;G. Sabatino","doi":"10.1016/j.chemer.2025.126289","DOIUrl":"10.1016/j.chemer.2025.126289","url":null,"abstract":"<div><div>The coupling of helium isotopes in fluid inclusions with conventional geochemical data provided a new perspective on the volcanic processes that took place during the Cretaceous in southern Sicily. Our new investigations reveal that during two distinct volcanic phases in the Late Cretaceous, magmas formed from low degrees of partial melting of a heterogeneous mantle source characterized by spinel lherzolite and varying garnet content. The collected samples, including lava flows, dikes, and sills, exhibit a wide range of rock types, from picritic basalts to hawaiites. Two different magma types were identified: one displaying a bell-shaped pattern akin to ocean island basalts (OIB) and another with an irregular pattern marked by positive spikes in Nb, K, Pb, Sr, Zr, and Ti. Strontium and Neodymium isotope compositions are weakly radiogenic, while the Pb isotope systematics show strong radiogenic values (²⁰⁶Pb/²⁰⁴Pb = 19.64–20.42; ²⁰⁷Pb/²⁰⁴Pb = 15.61–15.70; ²⁰⁸Pb/²⁰⁴ Pb = 39.26–39.98), corresponding to the mantle focal zone (FOZO) component. The observed ³He/⁴He ratios of 3.48 to 6.48 R_c/R_a in pyroxene fluid inclusions reflect the occurrence of pre-eruptive processes such as diffusion-induced fractionation or diffusive exchange taking place during magma residence in the crust. The ³He/⁴He ratios from 7.75 to 9.31 R_c/R_a in olivine crystals are typical of MORB-type basalts, and they likely represent the original signature of the mantle source. The olivine R_c/R_a values may indicate an interaction with recycled (U+Th)-poor lithologies or high ³He/⁴He materials in the upper mantle source. Furthermore, the ³He/⁴He isotope ratios of olivines differ from those determined in the same region for Plio-Pleistocene volcanic products, for which a common origin has been suggested in the majority of previous studies. In light of our findings, the hypothesis that the Hyblean Late Cretaceous and Plio-Pleistocene volcanics are part of a single magmatic suite should be reexamined. Overall, our results indicate that the evolution of those volcanic rocks was influenced by fractional crystallization and accumulation processes providing additional details on the mantle source that may have been overlooked in the past.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126289"},"PeriodicalIF":2.6,"publicationDate":"2025-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143808325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 petrology and geochemistry of the Montagna Grande-Monte Gibele trachytic shield volcano (Pantelleria, Italy)","authors":"John C. White ,&nbsp;Ray Macdonald ,&nbsp;Pierangelo Romano ,&nbsp;Bogusław Bagiński ,&nbsp;Silvio G. Rotolo ,&nbsp;Beata Marciniak-Maliszewska ,&nbsp;Alessandra Cinquegrani","doi":"10.1016/j.chemer.2025.126288","DOIUrl":"10.1016/j.chemer.2025.126288","url":null,"abstract":"<div><div>The 45.7 ± 1.0 ka (2σ) eruption of the compositionally zoned (comenditic trachyte to pantellerite) Green Tuff ignimbrite on the volcanic island of Pantelleria, Italy, was followed by the extrusion of a series of post-caldera metaluminous to mildly peralkaline trachyte lavas between 26.2 ± 2.0 and 22.3 ± 2.9 ka (2σ). This study uses whole-rock major- and trace-element compositions, mineral compositions, geothermobarometry, and petrogenetic models to examine the role of trachytes in the evolution of the Pantelleria magma system. Although previous studies have suggested that all of these units are consanguineous and form a liquid line of descent (LLOD) from metaluminous trachyte to peralkaline trachyte and pantellerite, mineralogical and geochemical evidence, as well as the results of modelling, suggest a much more complex origin. The crystallization of alkali feldspar from metaluminous trachyte liquids (descended from alkali to transitional basaltic magma <em>via</em> fractional crystallization) drives the composition of the residual melt to increasingly peralkaline compositions: pantelleritc trachyte first and then, after &gt;65 % crystallization, to pantellerite. This also results in the formation of a syenitic cumulate. Later intrusion of new mafic melt into the cumulate initiates partial melting, which produces comenditic trachyte melts characterized by low concentrations of incompatible trace elements (Rb, Zr, Nb, Th), high concentrations of Ba and Sr, and strong positive Eu anomalies. Entrainment of trachytic alkali feldspars into these melts as antecrysts further enhances these characteristics in whole-rock compositions. The origin of compositional zoning in the Green Tuff can be attributed to fractional crystallization from metaluminous trachyte within the lower pantelleritic portion and to partial melting of the syenitic cumulate for the upper comenditic trachyte portion.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126288"},"PeriodicalIF":2.6,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143776468","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Permo-Triassic magmatism in the Damaraland Igneous Province, NW Namibia: The Ondurakorume alkaline‑carbonatite complex","authors":"Andreja Ladisic ,&nbsp;Michael A.W. Marks ,&nbsp;Benjamin F. Walter ,&nbsp;R. Johannes Giebel ,&nbsp;Aratz Beranoaguirre ,&nbsp;Gregor Markl","doi":"10.1016/j.chemer.2025.126287","DOIUrl":"10.1016/j.chemer.2025.126287","url":null,"abstract":"<div><div>The four spatially associated igneous complexes of Kalkfeld, Ondurakorume, Osongombo and Etaneno are situated within the Damaraland Igneous Province (northwestern Namibia), which formed in response to the rifting of the South Atlantic during the early Cretaceous. Spatially-resolved LA-ICP MS U-Pb age dating on zircon and titanite confirms the Cretaceous age for Etaneno (mean of 139.2 ± 6.7 Ma), while Triassic and Permian emplacement ages are indicated for nepheline syenites from Kalkfeld (249.6 ± 3.2 and 249.4 ± 2.9 Ma) and Ondurakorume (272.1 ± 1.5 Ma). Furthermore, apatite ages for nepheline syenites from Etaneno (mean of 122.8 ± 3.8 Ma) and Kalkfeld (217.4 ± 24.5 Ma), and for carbonatites of Ondurakorume (248.1 ± 4.8 Ma) broadly agree with the zircon and titanite ages, while apatite from basement marbles yields a presumably metamorphic age of 479.6 ± 2.6 Ma and 465.1 ± 7.0 Ma.</div><div>Detailed petrographic analysis of syenites, nepheline syenites, carbonatites, silicocarbonatites and fenites from Ondurakorume reveals variable interaction processes between alkaline-silicate rocks and carbonatites. Syenites and nepheline syenites contain interstitial calcite with burbankite or carbocernaite inclusions (as commonly found in calcite carbonatites) and baddeleyite-zircon replacement textures. In some carbonatites and in silicocarbonatites, local contamination with (nepheline) syenites and granitic basement caused elevated Si activity, triggering enhanced formation of clinopyroxene, amphibole and mica.</div><div>Compositional variations in the released fenitizing fluids are indicated by clinopyroxene compositions that vary from nearly end-member aegirine (Aeg_69-91Di_0-10Hed_0-7) in proximal fenites to less sodic aegirine-augite (Aeg_54-96Di_0-17Hed_0-16) in more distal fenite samples, with the latter containing additional sodic amphibole. Compared to clinopyroxene in nepheline syenites and carbonatites, clinopyroxene in fenites shows elevated Ti contents (mostly &gt;0.05 apfu Ti) that are highest in distal fenites (up to 0.22 apfu Ti), suggesting Ti mobility. These changes suggest either a compositional evolution during fluid-rock interaction or two different fluid sources (carbonatites and (nepheline) syenites, respectively).</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126287"},"PeriodicalIF":2.6,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143776469","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"From error ellipse to Bayesian estimation: Strategies for optimizing T-W diagrams in UPb dating","authors":"Yao Mu ,&nbsp;Can Ge ,&nbsp;Fangyue Wang ,&nbsp;Xiuyu Li ,&nbsp;He Sun ,&nbsp;Haiou Gu ,&nbsp;Feng Yuan","doi":"10.1016/j.chemer.2025.126286","DOIUrl":"10.1016/j.chemer.2025.126286","url":null,"abstract":"<div><div>This study examines the application of the T-W diagram (Tera-Wasserburg Concordia Diagram) in uranium‑lead (U<img>Pb) isotope dating technology, especially for samples containing common lead. The core of the research lies in evaluating and optimizing the accuracy, precision, and determination of confidence intervals of T-W diagram dating. We propose a new formula based on the geometric mean method for correcting the calculation of error ellipses to reduce bias from high data noise levels. The study further elaborates on the application of the error-correlated independent weighted least squares method in determining the confidence intervals of linear models and intersection ages. Through simulation analysis, we evaluate the performance of least square methods in terms of dating accuracy and precision with both well-distributed and poorly distributed data. In view of the limitations of least square methods, a Bayesian method based on intercept constraints or the evolution model of terrestrial common lead is proposed, significantly improving the accuracy, precision, and success rate of dating analysis. The new methodology of this study not only provides a more reliable analytical tool for the field of radiometric dating, but is also applicable to single-point age analysis.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126286"},"PeriodicalIF":2.6,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143739074","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}