Pub Date : 2025-12-01Epub Date: 2025-11-19DOI: 10.1016/j.chemer.2025.126353
Larbi Rddad , Abdessamad Jinari , Benjamin F. Walter , Mohsin Raza , Rachid Benaouda , El Mostafa Mouguina
This study investigates the genesis of hydrothermal mineralization at the Amensif ZnCu (Pb-Ag-Au) ore deposit, hosted within Cambrian carbonates. Three stages of mineralization are identified, beginning with a pre-ore phase characterized by early pyrite precipitation from high-temperature (395–426 °C), highly saline (53.0–59.3 wt% NaCl + CaCl2) magmatic-hydrothermal fluids under reducing conditions, consistent with a negative Eu anomaly in the Rare Earth Elements and Yttrium (REY) data. Stage I is marked by homogenization temperatures (340–395 °C) and moderate salinities (23.3–24.4 wt% NaCl + CaCl2), indicating mixing of magmatic and cooler meteoric fluids. Stage II involves cooler (225–260 °C), less saline (17.6–20.4 wt% NaCl + CaCl2) fluids, indicating dilution with meteoric waters. Principal Component Analysis (PCA) of crush-leach data indicates the involvement of both brine and vapor phases in metal transport and mineralization.
Lead isotopic and REY data point to a common metal source derived from both mantle and crustal reservoirs, with isotopic uniformity indicating thorough Pb mixing. This aligns with a conceptual metallogenic model in which deep-seated ENE-WSW faults enable magma ascent during post-collision collapse, whereas reactivated NE-SW and NW-SE faults provide pathways for metal-rich magmatic-hydrothermal fluids exsolved from a Permian granitic magma. Fluid mixing and fluid-rock interaction processes facilitated ore deposition in the Cambrian carbonates. These findings provide new insights into the structural and geochemical factors controlling ore genesis at the Amensif deposit and similar magmatic-hydrothermal skarn systems associated with the Hercynian/Variscan orogeny.
{"title":"Fluid evolution and ore genesis of the Amensif ZnCu (Pb-Ag-Au) distal skarn deposit (western High Atlas, Morocco): Constraints from fluid inclusions, crush-leach analysis, REY geochemistry, and Pb isotopes","authors":"Larbi Rddad , Abdessamad Jinari , Benjamin F. Walter , Mohsin Raza , Rachid Benaouda , El Mostafa Mouguina","doi":"10.1016/j.chemer.2025.126353","DOIUrl":"10.1016/j.chemer.2025.126353","url":null,"abstract":"<div><div>This study investigates the genesis of hydrothermal mineralization at the Amensif Zn<img>Cu (Pb-Ag-Au) ore deposit, hosted within Cambrian carbonates. Three stages of mineralization are identified, beginning with a pre-ore phase characterized by early pyrite precipitation from high-temperature (395–426 °C), highly saline (53.0–59.3 wt% NaCl + CaCl<sub>2</sub>) magmatic-hydrothermal fluids under reducing conditions, consistent with a negative Eu anomaly in the Rare Earth Elements and Yttrium (REY) data. Stage I is marked by homogenization temperatures (340–395 °C) and moderate salinities (23.3–24.4 wt% NaCl + CaCl<sub>2</sub>), indicating mixing of magmatic and cooler meteoric fluids. Stage II involves cooler (225–260 °C), less saline (17.6–20.4 wt% NaCl + CaCl<sub>2</sub>) fluids, indicating dilution with meteoric waters. Principal Component Analysis (PCA) of crush-leach data indicates the involvement of both brine and vapor phases in metal transport and mineralization.</div><div>Lead isotopic and REY data point to a common metal source derived from both mantle and crustal reservoirs, with isotopic uniformity indicating thorough Pb mixing. This aligns with a conceptual metallogenic model in which deep-seated ENE-WSW faults enable magma ascent during post-collision collapse, whereas reactivated NE-SW and NW-SE faults provide pathways for metal-rich magmatic-hydrothermal fluids exsolved from a Permian granitic magma. Fluid mixing and fluid-rock interaction processes facilitated ore deposition in the Cambrian carbonates. These findings provide new insights into the structural and geochemical factors controlling ore genesis at the Amensif deposit and similar magmatic-hydrothermal skarn systems associated with the Hercynian/Variscan orogeny.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 4","pages":"Article 126353"},"PeriodicalIF":2.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145617954","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}
Pub Date : 2025-12-01Epub Date: 2025-10-22DOI: 10.1016/j.chemer.2025.126343
Makoto Kimura , Michael K. Weisberg , Richard C. Greenwood , Akira Yamaguchi
In this paper, we examine the diverse features of CM (Mighei-type) and related carbonaceous chondrites, including their petrologic classification, secondary heating, brecciation, and we explore anomalous CM-like chondrites. CM chondrites experienced varying degrees of aqueous alteration, resulting in a range of petrologic subtypes from 3.0 to 2.0. The most abundant subtypes are 2.3–2.0, which may reflect melting of significant amounts of ice, resulting in the formation of the heavily altered CM chondrites in the inner regions of the parent body. Additionally, some CM and related chondrites have undergone secondary heating after aqueous alteration. The source of heat for these chondrites is still uncertain, but impacts are the most likely the cause due to the evidence for a short duration of heating. CM chondrites are mainly genomict breccias and contain clasts of various petrologic grade and degree of heating, though some CMs contain xenolithic clasts. Highly recrystallized clasts are particularly important, as they might have formed in the interior, hotter regions of the CM parent body. Subsequently, these clasts may have been mixed with other typical CM lithologies due to impact events. CM chondrite fragments are commonly found in other meteorites, such as HED meteorites and ordinary chondrites. This indicates a widespread distribution of CM chondrite fragments in the main asteroid belt, with incorporation into other meteorites taking place significantly later than chondrule formation. There have been numerous descriptions of anomalous CM or related chondrites. We tentatively classify these anomalous CMs into four categories: highly 16O-rich, medium 16O-rich, an unusual mineral group, and others. However, the processes involved in the formation of these anomalous chondrites and their relationships to the more typical CMs remain unclear, as detailed documentation of most of the anomalous CMs is currently lacking. CM chondrites primarily consist of chondrules, refractory inclusions, opaque minerals, and a matrix material, similar to other C chondrites. The petrographic and bulk chemical features of CMs are most similar to CO chondrites. However, CM and CO chondrites did not originate from a single parent body. CM chondrites provide valuable information about the conditions and processes that operated in the outer region of the early solar system.
{"title":"The diversity, classification, and formation of the CM chondrite group: A review","authors":"Makoto Kimura , Michael K. Weisberg , Richard C. Greenwood , Akira Yamaguchi","doi":"10.1016/j.chemer.2025.126343","DOIUrl":"10.1016/j.chemer.2025.126343","url":null,"abstract":"<div><div>In this paper, we examine the diverse features of CM (Mighei-type) and related carbonaceous chondrites, including their petrologic classification, secondary heating, brecciation, and we explore anomalous CM-like chondrites. CM chondrites experienced varying degrees of aqueous alteration, resulting in a range of petrologic subtypes from 3.0 to 2.0. The most abundant subtypes are 2.3–2.0, which may reflect melting of significant amounts of ice, resulting in the formation of the heavily altered CM chondrites in the inner regions of the parent body. Additionally, some CM and related chondrites have undergone secondary heating after aqueous alteration. The source of heat for these chondrites is still uncertain, but impacts are the most likely the cause due to the evidence for a short duration of heating. CM chondrites are mainly genomict breccias and contain clasts of various petrologic grade and degree of heating, though some CMs contain xenolithic clasts. Highly recrystallized clasts are particularly important, as they might have formed in the interior, hotter regions of the CM parent body. Subsequently, these clasts may have been mixed with other typical CM lithologies due to impact events. CM chondrite fragments are commonly found in other meteorites, such as HED meteorites and ordinary chondrites. This indicates a widespread distribution of CM chondrite fragments in the main asteroid belt, with incorporation into other meteorites taking place significantly later than chondrule formation. There have been numerous descriptions of anomalous CM or related chondrites. We tentatively classify these anomalous CMs into four categories: highly <sup>16</sup>O-rich, medium <sup>16</sup>O-rich, an unusual mineral group, and others. However, the processes involved in the formation of these anomalous chondrites and their relationships to the more typical CMs remain unclear, as detailed documentation of most of the anomalous CMs is currently lacking. CM chondrites primarily consist of chondrules, refractory inclusions, opaque minerals, and a matrix material, similar to other C chondrites. The petrographic and bulk chemical features of CMs are most similar to CO chondrites. However, CM and CO chondrites did not originate from a single parent body. CM chondrites provide valuable information about the conditions and processes that operated in the outer region of the early solar system.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 4","pages":"Article 126343"},"PeriodicalIF":2.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145417462","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}
Pub Date : 2025-12-01Epub Date: 2025-11-07DOI: 10.1016/j.chemer.2025.126350
Hang Yang , Peng Wu , Anlin Liu , Zhigang Kong , Xinfu Wang , Shoukui Li , Yu Jiang , Jianjun Liu , Jiaan Qu
In collisional zones, potassic-ultrapotassic intrusions with high K2O contents and K2O/Na2O ratios commonly provide insights into magmatic evolution following collision and regional Au polymetallic mineralization. Here, we report a systematic dataset for the petrology, geochronology, and geochemistry of the Oligocene Yao'an complex (YAC), which is genetically related to the Indo-Asia collision within the western Yangtze Craton (WYC). The YAC includes shoshonitic syenite porphyries, shoshonitic mafic microgranular enclaves (MMEs), and potassic-ultrapotassic lamprophyres. Zircon UPb dating yields crystallization ages of ca. 33 Ma for MME and host syenite porphyries, which coincide with those of potassic-ultrapotassic mafic rocks (PUPMR) in this complex. The YAC samples have high K2O and elevated K2O/Na2O ratios, and show enriched SrNd isotopic signatures [(87Sr/86Sr)i = 0.7087–0.7107, εNd(t) = −12.1 to −8.2] as well as variable zircon εHf(t) values (−19.0 to −6.1). The lamprophyres are enriched in large ion lithophile elements (LILEs) and depleted in high field strength elements (HFSEs), as well as characterized by high Rb/Sr, and low Ba/Rb and Nb/U ratios, most likely originating from partial melting of an enriched lithospheric mantle with abundant metasomatic phlogopite, formed by subduction-related fluids. The syenite porphyries have high SiO2 (65.24–69.70 wt%) contents without adakite-like affinities. They define linear trends on Harker diagrams, and display similar SrNd isotope compositions, REE and trace-element patterns compared to the published data of coeval PUPMR, which can be attributed to fractional crystallization processes. MMEs hosted in the syenite porphyries exhibit disequilibrium textures, implying origin from magma mingling between potassic-ultrapotassic mafic and primitive shoshonitic felsic end-members in varying proportions. Thus, we conclude that fractional crystallization of K-rich, mantle-derived mafic melts, together with the injection of ultrapotassic mafic melts (UPMM) leads to the enrichment of K2O in the shoshonitic felsic intrusions, and may promote the enrichment of Au. Besides, the presence of sulfides in the least altered MME indicates that the mafic melts probably supplied part of metal to the Yao'an porphyry Au system. Our data reinforce previously proposed models and help elucidate the origin, evolution, potassium enrichment mechanism, and associated Au polymetallic mineralization of potassic magmas in post-collisional settings.
{"title":"Genesis of potassic-ultrapotassic intrusions and associated Au polymetallic mineralization in collision zones: An example from the Oligocene Yao'an complex in western Yangtze Craton, SW China","authors":"Hang Yang , Peng Wu , Anlin Liu , Zhigang Kong , Xinfu Wang , Shoukui Li , Yu Jiang , Jianjun Liu , Jiaan Qu","doi":"10.1016/j.chemer.2025.126350","DOIUrl":"10.1016/j.chemer.2025.126350","url":null,"abstract":"<div><div>In collisional zones, potassic-ultrapotassic intrusions with high K<sub>2</sub>O contents and K<sub>2</sub>O/Na<sub>2</sub>O ratios commonly provide insights into magmatic evolution following collision and regional Au polymetallic mineralization. Here, we report a systematic dataset for the petrology, geochronology, and geochemistry of the Oligocene Yao'an complex (YAC), which is genetically related to the Indo-Asia collision within the western Yangtze Craton (WYC). The YAC includes shoshonitic syenite porphyries, shoshonitic mafic microgranular enclaves (MMEs), and potassic-ultrapotassic lamprophyres. Zircon U<img>Pb dating yields crystallization ages of ca. 33 Ma for MME and host syenite porphyries, which coincide with those of potassic-ultrapotassic mafic rocks (PUPMR) in this complex. The YAC samples have high K<sub>2</sub>O and elevated K<sub>2</sub>O/Na<sub>2</sub>O ratios, and show enriched Sr<img>Nd isotopic signatures [(<sup>87</sup>Sr/<sup>86</sup>Sr)<sub><em>i</em></sub> = 0.7087–0.7107, <em>ε</em><sub>Nd</sub>(t) = −12.1 to −8.2] as well as variable zircon <em>ε</em><sub>Hf</sub>(t) values (−19.0 to −6.1). The lamprophyres are enriched in large ion lithophile elements (LILEs) and depleted in high field strength elements (HFSEs), as well as characterized by high Rb/Sr, and low Ba/Rb and Nb/U ratios, most likely originating from partial melting of an enriched lithospheric mantle with abundant metasomatic phlogopite, formed by subduction-related fluids. The syenite porphyries have high SiO<sub>2</sub> (65.24–69.70 wt%) contents without adakite-like affinities. They define linear trends on Harker diagrams, and display similar Sr<img>Nd isotope compositions, REE and trace-element patterns compared to the published data of coeval PUPMR, which can be attributed to fractional crystallization processes. MMEs hosted in the syenite porphyries exhibit disequilibrium textures, implying origin from magma mingling between potassic-ultrapotassic mafic and primitive shoshonitic felsic end-members in varying proportions. Thus, we conclude that fractional crystallization of K-rich, mantle-derived mafic melts, together with the injection of ultrapotassic mafic melts (UPMM) leads to the enrichment of K<sub>2</sub>O in the shoshonitic felsic intrusions, and may promote the enrichment of Au. Besides, the presence of sulfides in the least altered MME indicates that the mafic melts probably supplied part of metal to the Yao'an porphyry Au system. Our data reinforce previously proposed models and help elucidate the origin, evolution, potassium enrichment mechanism, and associated Au polymetallic mineralization of potassic magmas in post-collisional settings.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 4","pages":"Article 126350"},"PeriodicalIF":2.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145519726","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}
Pub Date : 2025-12-01Epub Date: 2025-11-21DOI: 10.1016/j.chemer.2025.126361
Yufei Xuan , Jin Liu , Zhenghong Liu , Wang Ding , Liqiang Liu
The evolution and differentiation of early continental crust remain a fundamental research frontier, with potassic granitoids providing critical insights into these processes. This study investigates the petrogenesis and tectonic setting of Late Mesoarchean (3.0–2.9 Ga) potassic granitoids in the Anshan area of the North China Craton (NCC) through comprehensive geochronological, geochemical, and zircon Hf-O isotopic analyses. Zircon U-Pb dating reveals the studied Late Mesoarchean potassic granitoids include ca. 2.95 Ga Tiejiashan biotite monzogranitic-quartz monzonitic gneisses and ca. 3.0 Ga Donganshan monzogranitic gneisses.
The Tiejiashan potassic granitoids exhibit high SiO₂ (68.47–75.28 wt%), K₂O (4.32–4.93 wt%) contents, K₂O/Na₂O (1.19–1.53) ratios, low Mg# (23–25) values and strongly negative Eu anomalies (δEu = 0.19–0.31), with metaluminous and ferroan affinities, classifying them as A-type granites. Magmatic zircons yield δ18O values of+4.66 ‰–+6.10 ‰ and εHf(t) values of −10.61 to −6.34, with TDM2 ages of 4.43–3.99 Ga. The geochemical and Hf-O isotope characteristics suggest that Tiejiashan potassic granitoids originated from partial melting of Eo-Paleoarchean TTGs (3.8–3.3 Ga) under shallow crustal conditions. In contrast, the Donganshan monzogranitic gneisses display higher SiO₂ (75.69–76.14 wt%) and peraluminous signatures, with pronounced LREE-HREE fractionation, moderately negative Eu anomalies (δEu = 0.69–0.80) and unradiogenic Hf isotopes (i.e., εHf(t) values = −0.85–+1.87, TDM2 age = 3.63–3.39 Ga), indicating Donganshan monzogranitic gneisses originated from partial melting of short-residence TTGs with garnet and amphibole residues. The emplacement of these potassic granitoids records a crustal recycling process, while primary magmatic fabrics (i.e. L ≫ S, L = S) in the ca. 2.95 Ga Tiejiashan pluton suggest high-temperature plastic flow linked to magma underplating. These findings highlight a Late Mesoarchean crustal reworking/recycling process of NCC, driven by the remelting of ancient crust due to magma underplating associated with mantle upwelling in an extensional setting.
{"title":"Late Mesoarchean crustal reworking/recycling and magma underplating process: Insights from the petrogenesis of 3.0–2.9 Ga potassic granitoids in the Anshan area, North China Craton","authors":"Yufei Xuan , Jin Liu , Zhenghong Liu , Wang Ding , Liqiang Liu","doi":"10.1016/j.chemer.2025.126361","DOIUrl":"10.1016/j.chemer.2025.126361","url":null,"abstract":"<div><div>The evolution and differentiation of early continental crust remain a fundamental research frontier, with potassic granitoids providing critical insights into these processes. This study investigates the petrogenesis and tectonic setting of Late Mesoarchean (3.0–2.9 Ga) potassic granitoids in the Anshan area of the North China Craton (NCC) through comprehensive geochronological, geochemical, and zircon Hf-O isotopic analyses. Zircon U-Pb dating reveals the studied Late Mesoarchean potassic granitoids include <em>ca.</em> 2.95 Ga Tiejiashan biotite monzogranitic-quartz monzonitic gneisses and <em>ca.</em> 3.0 Ga Donganshan monzogranitic gneisses.</div><div>The Tiejiashan potassic granitoids exhibit high SiO₂ (68.47–75.28 wt%), K₂O (4.32–4.93 wt%) contents, K₂O/Na₂O (1.19–1.53) ratios, low Mg# (23–25) values and strongly negative Eu anomalies (δEu = 0.19–0.31), with metaluminous and ferroan affinities, classifying them as A-type granites. Magmatic zircons yield δ<sup>18</sup>O values of+4.66 ‰–+6.10 ‰ and ε<sub>Hf</sub>(<em>t</em>) values of −10.61 to −6.34, with T<sub>DM</sub><sup>2</sup> ages of 4.43–3.99 Ga. The geochemical and Hf-O isotope characteristics suggest that Tiejiashan potassic granitoids originated from partial melting of Eo-Paleoarchean TTGs (3.8–3.3 Ga) under shallow crustal conditions. In contrast, the Donganshan monzogranitic gneisses display higher SiO₂ (75.69–76.14 wt%) and peraluminous signatures, with pronounced LREE-HREE fractionation, moderately negative Eu anomalies (δEu = 0.69–0.80) and unradiogenic Hf isotopes (<em>i.e.</em>, ε<sub>Hf</sub>(<em>t</em>) values = −0.85–+1.87, T<sub>DM</sub><sup>2</sup> age = 3.63–3.39 Ga), indicating Donganshan monzogranitic gneisses originated from partial melting of short-residence TTGs with garnet and amphibole residues. The emplacement of these potassic granitoids records a crustal recycling process, while primary magmatic fabrics (<em>i.e.</em> L ≫ S, L = S) in the <em>ca.</em> 2.95 Ga Tiejiashan pluton suggest high-temperature plastic flow linked to magma underplating. These findings highlight a Late Mesoarchean crustal reworking/recycling process of NCC, driven by the remelting of ancient crust due to magma underplating associated with mantle upwelling in an extensional setting.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 4","pages":"Article 126361"},"PeriodicalIF":2.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145617853","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}
Pub Date : 2025-12-01Epub Date: 2025-11-24DOI: 10.1016/j.chemer.2025.126358
Narantuya Purevjav , Barry Roser
{"title":"Corrigendum to “Geochemistry of Silurian–Carboniferous sedimentary rocks of the Ulaanbaatar terrane, Hangay–Hentey belt, central Mongolia: Provenance, paleoweathering, tectonic setting, and relationship with the neighbouring Tsetserleg terrane” [Geochemistry (volume 73, issue 4) 481–493]","authors":"Narantuya Purevjav , Barry Roser","doi":"10.1016/j.chemer.2025.126358","DOIUrl":"10.1016/j.chemer.2025.126358","url":null,"abstract":"","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 4","pages":"Article 126358"},"PeriodicalIF":2.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145617952","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}
Pub Date : 2025-12-01Epub Date: 2025-09-13DOI: 10.1016/j.chemer.2025.126337
Maryam Shirjang , Abbas Maghsoudi , Reza Ghezelbash
The cruciality of geochemical exploration in discovering new mineral deposits demands the use of high-performance computational techniques to recognize geochemical anomaly patterns associated with mineralization. High dimensionality and complexity of geochemical datasets lead to use of brand-new methods including machine learning tools to get more efficient and accurate outcome. In this regard, advanced clustering methods have gained significant popularity over the years in the field of mineral exploration. This study presents an integrated mineral exploration approach using multiple clustering algorithms to identify Cu mineralization potential in the Kariz-Now district, Razavi Khorasan, northeastern Iran. The methodology uses faults within the study area to weight the catchment basins and brings grade characteristics of role-playing elements along with fault weights to highlight the potential areas. Three clustering techniques including K-Means (KM), Fuzzy C-Means (FCM), and DBSCAN were applied to the variables attached to their corresponding sample catchment basins to predict potential areas. The results were validated by success rate curves of the selected methods and the area under curve was calculated. The results reveal that DBSCAN has higher area under curve (AUC) than KM and FCM. Furthermore, there is a strong correlation between predicted anomalies and Paleogene volcanic and sedimentary rocks, particularly in areas with high fault density.
{"title":"Analysis of clustering methods for geochemical anomaly identification through weighted sample catchment basins","authors":"Maryam Shirjang , Abbas Maghsoudi , Reza Ghezelbash","doi":"10.1016/j.chemer.2025.126337","DOIUrl":"10.1016/j.chemer.2025.126337","url":null,"abstract":"<div><div>The cruciality of geochemical exploration in discovering new mineral deposits demands the use of high-performance computational techniques to recognize geochemical anomaly patterns associated with mineralization. High dimensionality and complexity of geochemical datasets lead to use of brand-new methods including machine learning tools to get more efficient and accurate outcome. In this regard, advanced clustering methods have gained significant popularity over the years in the field of mineral exploration. This study presents an integrated mineral exploration approach using multiple clustering algorithms to identify Cu mineralization potential in the Kariz-Now district, Razavi Khorasan, northeastern Iran. The methodology uses faults within the study area to weight the catchment basins and brings grade characteristics of role-playing elements along with fault weights to highlight the potential areas. Three clustering techniques including K-Means (KM), Fuzzy C-Means (FCM), and DBSCAN were applied to the variables attached to their corresponding sample catchment basins to predict potential areas. The results were validated by success rate curves of the selected methods and the area under curve was calculated. The results reveal that DBSCAN has higher area under curve (AUC) than KM and FCM. Furthermore, there is a strong correlation between predicted anomalies and Paleogene volcanic and sedimentary rocks, particularly in areas with high fault density.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 4","pages":"Article 126337"},"PeriodicalIF":2.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145269664","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}
Pub Date : 2025-12-01Epub Date: 2025-10-01DOI: 10.1016/j.chemer.2025.126338
Rui-Yang Liu
The Qinling orogenic belt experienced magmatic remelting and intrusion, forming Mo mineralization belt associated with Late Yanshanian magmatism, highlighting the role of Yanshan period in Mo enrichment. Ore-bearing granitic rocks (monzogranite and granite porphyry) from northern Qinling were analyzed using petrography, SEM, TIMA, whole-rock geochemistry, Sr-Nd-Pb isotopes, zircon and titanite UPb dating, zircon LuHf isotopes, and EMPA of key minerals (zircon, titanite, pyrite, plagioclase, quartz, biotite). These data constrain the petrogenesis and metallogenic mechanisms of Mo mineralization in the region. The Mangling granites (SiO2 = 64.78–73.36 wt%, Mg# = 34.02–40.65, A/CNK = 1.24–1.67) originated from the lower crust, as indicated by isotopic data (Isr = 0.7064–0.7087, εNd(t) = −7.05 to ∼ −13.97). Magmatic-hydrothermal processes, including ascent (155.7 Ma), emplacement (152.1 Ma), and mixing, formed highly differentiated Mo-bearing granite porphyry (TE1,3 = 1.03–1.45). Partial melting and cooling produced monzogranite as the parental rock at 135.6 Ma. Under favorable conditions, crystallization and differentiation enriched Mo in the residual melt, leading to the formation of ore-bearing granite porphyry during the Early Cretaceous (133.8 Ma). These processes highlight the magmatic controls on Mo enrichment in Mangling area.
{"title":"Magmatic evolution and molybdenum mineralization potential analysis in the Mangling granite, northern Qinling orogenic belt, China","authors":"Rui-Yang Liu","doi":"10.1016/j.chemer.2025.126338","DOIUrl":"10.1016/j.chemer.2025.126338","url":null,"abstract":"<div><div>The Qinling orogenic belt experienced magmatic remelting and intrusion, forming Mo mineralization belt associated with Late Yanshanian magmatism, highlighting the role of Yanshan period in Mo enrichment. Ore-bearing granitic rocks (monzogranite and granite porphyry) from northern Qinling were analyzed using petrography, SEM, TIMA, whole-rock geochemistry, Sr-Nd-Pb isotopes, zircon and titanite U<img>Pb dating, zircon Lu<img>Hf isotopes, and EMPA of key minerals (zircon, titanite, pyrite, plagioclase, quartz, biotite). These data constrain the petrogenesis and metallogenic mechanisms of Mo mineralization in the region. The Mangling granites (SiO<sub>2</sub> = 64.78–73.36 wt%, Mg# = 34.02–40.65, A/CNK = 1.24–1.67) originated from the lower crust, as indicated by isotopic data (Isr = 0.7064–0.7087, εNd(t) = −7.05 to ∼ −13.97). Magmatic-hydrothermal processes, including ascent (155.7 Ma), emplacement (152.1 Ma), and mixing, formed highly differentiated Mo-bearing granite porphyry (TE<sub>1,3</sub> = 1.03–1.45). Partial melting and cooling produced monzogranite as the parental rock at 135.6 Ma. Under favorable conditions, crystallization and differentiation enriched Mo in the residual melt, leading to the formation of ore-bearing granite porphyry during the Early Cretaceous (133.8 Ma). These processes highlight the magmatic controls on Mo enrichment in Mangling area.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 4","pages":"Article 126338"},"PeriodicalIF":2.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145325618","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}
Pub Date : 2025-12-01Epub Date: 2025-11-05DOI: 10.1016/j.chemer.2025.126347
Yu-hang Liu , Ke-yong Wang , Zhi-gao Wang , Jun-chi Chen , Xue Wang , Fa-Zhen Ma
The Sandaocha gold deposit is located in the Jiapigou mining district and is considered a highly representative deposit. Gold mineralization is hosted in the Neoarchean Jiapigou Group of Sandaogou Formation supracrustal rocks. The orebody is predominantly governed by a series of brittle-ductile structures oriented along a NNE-strike. The geological and petrographic features of the deposit reveal that the mineralization process at Sandaocha can be divided into four stages: (I) Pyrite-milky quartz stage, (II) Quartz-pyrite stage, (III) Quartz-polymetallic sulfide stage and (IV) Quartz‑carbonate stage. Four types of primary fluid inclusions were identified in the quartz vein: liquid-rich two-phase aqueous inclusions (L-type), mixed aqueous‑carbonic inclusions (C-type), rich carbonic inclusions (RC-type) and pure carbonic inclusions (PC-type). C-type, RC-type, PC-type and L-type inclusions are captured in stage I, stage II and stage III quartz sample, while only L-type inclusions are found in stage IV quartz. During the mineralization process, the influx of atmospheric precipitation led to the transformation of the fluid system from the moderate-temperature and moderate-low salinity NaCl-H2O-CO2 system to the low-temperature and low-salinity NaCl-H2O system. The results of C-H-O-He-Ar isotopes collectively indicate that the ore-forming fluid of the Sandaocha gold deposit is magmatic water formed from the differentiation of a mantle-crust mixed magma. LA-ICP-MS data indicates that gold mineralization primarily occurred during the stage II and stage III. Additionally, continuous input of meteoric water led to immiscibility of the fluids. The physical and chemical conditions of the ore-forming fluid changed as significant gas-phase components escaped, leading to the decomposition of AuS complexes and a reduction in gold solubility, which facilitated the deposition of gold and other ore-forming elements.
{"title":"Fluid origin and ore genesis of the Sandaocha gold deposit in Jilin Province, Northeast China: Constraints from C-H-O-He-Ar isotopes and trace element compositions of pyrite and fluid inclusion","authors":"Yu-hang Liu , Ke-yong Wang , Zhi-gao Wang , Jun-chi Chen , Xue Wang , Fa-Zhen Ma","doi":"10.1016/j.chemer.2025.126347","DOIUrl":"10.1016/j.chemer.2025.126347","url":null,"abstract":"<div><div>The Sandaocha gold deposit is located in the Jiapigou mining district and is considered a highly representative deposit. Gold mineralization is hosted in the Neoarchean Jiapigou Group of Sandaogou Formation supracrustal rocks. The orebody is predominantly governed by a series of brittle-ductile structures oriented along a NNE-strike. The geological and petrographic features of the deposit reveal that the mineralization process at Sandaocha can be divided into four stages: (I) Pyrite-milky quartz stage, (II) Quartz-pyrite stage, (III) Quartz-polymetallic sulfide stage and (IV) Quartz‑carbonate stage. Four types of primary fluid inclusions were identified in the quartz vein: liquid-rich two-phase aqueous inclusions (L-type), mixed aqueous‑carbonic inclusions (C-type), rich carbonic inclusions (RC-type) and pure carbonic inclusions (PC-type). C-type, RC-type, PC-type and L-type inclusions are captured in stage I, stage II and stage III quartz sample, while only L-type inclusions are found in stage IV quartz. During the mineralization process, the influx of atmospheric precipitation led to the transformation of the fluid system from the moderate-temperature and moderate-low salinity NaCl-H<sub>2</sub>O-CO<sub>2</sub> system to the low-temperature and low-salinity NaCl-H<sub>2</sub>O system. The results of C-H-O-He-Ar isotopes collectively indicate that the ore-forming fluid of the Sandaocha gold deposit is magmatic water formed from the differentiation of a mantle-crust mixed magma. LA-ICP-MS data indicates that gold mineralization primarily occurred during the stage II and stage III. Additionally, continuous input of meteoric water led to immiscibility of the fluids. The physical and chemical conditions of the ore-forming fluid changed as significant gas-phase components escaped, leading to the decomposition of Au<img>S complexes and a reduction in gold solubility, which facilitated the deposition of gold and other ore-forming elements.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 4","pages":"Article 126347"},"PeriodicalIF":2.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145571632","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}
Pub Date : 2025-09-01Epub Date: 2025-04-11DOI: 10.1016/j.chemer.2025.126290
Zeynab Gharamohammadi , Peter A. Cawood , Ali Kananian , Reza Nozaem , Yona Jacobsen , David Lentz , Jafar Omrani
<div><div>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<img>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<img>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<sub>Sr</sub> 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<sub>Sr</sub> 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<sub>Sr</sub> 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
{"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 , Peter A. Cawood , Ali Kananian , Reza Nozaem , Yona Jacobsen , David Lentz , Jafar Omrani","doi":"10.1016/j.chemer.2025.126290","DOIUrl":"10.1016/j.chemer.2025.126290","url":null,"abstract":"<div><div>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<img>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<img>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<sub>Sr</sub> 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<sub>Sr</sub> 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<sub>Sr</sub> 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":"2025-09-01","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}
Pub Date : 2025-09-01Epub Date: 2025-07-16DOI: 10.1016/j.chemer.2025.126318
M. Trieloff , E.V. Korochantseva , A.I. Buikin , J. Hopp , A.V. Korochantsev
<div><div>We performed high-resolution <sup>40</sup>Ar/<sup>39</sup>Ar dating of a suite of lunar meteorites from hot deserts: Dhofar 025, 309, 730, 733, 1442, Northwest Africa 6888, and Sayh al Uhaymir 449. The identification of terrestrial and lunar trapped argon components via isochrons allowed us to identify in situ radiogenic argon and to obtain proper chronological information. The last total reset ages of all studied samples are in the range of 3.1 to 4.2 Ga, coeval with the intense cratering period on the Moon and mare volcanism. Only Northwest Africa 6888 was totally reset <2.5 Ga ago. The most deeply buried breccia Dhofar 733 has the oldest age of 4.23 ± 0.04 Ga within this series of meteorites. Dhofar 733, 1442, and NWA 6888 were furthermore affected by recent impact events ≤1 Ga. All meteorites were irradiated by galactic cosmic rays on the surface of the Moon for several up to hundreds of Ma. A simple irradiation history is revealed for only one meteorite Dhofar 733 delivered to Earth within ~0.5 Ma. The comparison of exposure ages, solar argon abundances and partial loss of cosmogenic and radiogenic argon of lunar breccias indicates that long surface residence enhances accumulation of solar wind implanted <sup>36</sup>Ar but also diffusive gas loss, most likely by surface thermal effects as solar and/or impact heating.</div><div>The surficial regolith breccias Dhofar 025, 1442, NWA 6888, SaU 449 contain lunar trapped argon with <sup>40</sup>Ar/<sup>36</sup>Ar ratios varying from 6 to 15, while the deep-derived breccia Dhofar 730 contains argon with (<sup>40</sup>Ar/<sup>36</sup>Ar)<sub>trapped</sub> ratio of 81. This could indicate that the composition of trapped argon in lunar meteorites may depend on rock layering depth. We suggest that the final capture of gases happens during sintering and agglutination along grain boundaries caused by thermal processes accompanying shock-induced compaction. Dhofar 1442 contains two distinct lunar trapped argon components with (<sup>40</sup>Ar/<sup>36</sup>Ar)<sub>trapped</sub> ratios of 14.58 ± 0.28 and 5.5 ± 0.7 indicating that lunar meteorites may contain more than one extraterrestrial trapped component incorporated during different thermal events.</div><div>Our new <sup>40</sup>Ar/<sup>39</sup>Ar ages of lunar meteorites significantly increase the number of high- resolution plateau age spectra, providing more compelling evidence of geochronologically meaningful pre 3.9 Ga ages. The different age distribution when compared to Apollo samples that were frequently dominated by Imbrium ejecta may be related to the fact that lunar meteorites provide a more random and thus complete sampling of the lunar surface, encompassing ejecta of older large basins, thereby favoring scenarios of more continuous or episodic pre 3.9 Ga bombardments. A possible scenario leading to episodic small body disturbances and bombardments involves close stellar encounters within the massive stellar cluster in which the
{"title":"Thermal and irradiation history of lunar meteorites by the 40Ar/39Ar technique: Dhofar 025, 309, 730, 733, 1442, Northwest Africa 6888, and Sayh al Uhaymir 449","authors":"M. Trieloff , E.V. Korochantseva , A.I. Buikin , J. Hopp , A.V. Korochantsev","doi":"10.1016/j.chemer.2025.126318","DOIUrl":"10.1016/j.chemer.2025.126318","url":null,"abstract":"<div><div>We performed high-resolution <sup>40</sup>Ar/<sup>39</sup>Ar dating of a suite of lunar meteorites from hot deserts: Dhofar 025, 309, 730, 733, 1442, Northwest Africa 6888, and Sayh al Uhaymir 449. The identification of terrestrial and lunar trapped argon components via isochrons allowed us to identify in situ radiogenic argon and to obtain proper chronological information. The last total reset ages of all studied samples are in the range of 3.1 to 4.2 Ga, coeval with the intense cratering period on the Moon and mare volcanism. Only Northwest Africa 6888 was totally reset <2.5 Ga ago. The most deeply buried breccia Dhofar 733 has the oldest age of 4.23 ± 0.04 Ga within this series of meteorites. Dhofar 733, 1442, and NWA 6888 were furthermore affected by recent impact events ≤1 Ga. All meteorites were irradiated by galactic cosmic rays on the surface of the Moon for several up to hundreds of Ma. A simple irradiation history is revealed for only one meteorite Dhofar 733 delivered to Earth within ~0.5 Ma. The comparison of exposure ages, solar argon abundances and partial loss of cosmogenic and radiogenic argon of lunar breccias indicates that long surface residence enhances accumulation of solar wind implanted <sup>36</sup>Ar but also diffusive gas loss, most likely by surface thermal effects as solar and/or impact heating.</div><div>The surficial regolith breccias Dhofar 025, 1442, NWA 6888, SaU 449 contain lunar trapped argon with <sup>40</sup>Ar/<sup>36</sup>Ar ratios varying from 6 to 15, while the deep-derived breccia Dhofar 730 contains argon with (<sup>40</sup>Ar/<sup>36</sup>Ar)<sub>trapped</sub> ratio of 81. This could indicate that the composition of trapped argon in lunar meteorites may depend on rock layering depth. We suggest that the final capture of gases happens during sintering and agglutination along grain boundaries caused by thermal processes accompanying shock-induced compaction. Dhofar 1442 contains two distinct lunar trapped argon components with (<sup>40</sup>Ar/<sup>36</sup>Ar)<sub>trapped</sub> ratios of 14.58 ± 0.28 and 5.5 ± 0.7 indicating that lunar meteorites may contain more than one extraterrestrial trapped component incorporated during different thermal events.</div><div>Our new <sup>40</sup>Ar/<sup>39</sup>Ar ages of lunar meteorites significantly increase the number of high- resolution plateau age spectra, providing more compelling evidence of geochronologically meaningful pre 3.9 Ga ages. The different age distribution when compared to Apollo samples that were frequently dominated by Imbrium ejecta may be related to the fact that lunar meteorites provide a more random and thus complete sampling of the lunar surface, encompassing ejecta of older large basins, thereby favoring scenarios of more continuous or episodic pre 3.9 Ga bombardments. A possible scenario leading to episodic small body disturbances and bombardments involves close stellar encounters within the massive stellar cluster in which the","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126318"},"PeriodicalIF":2.6,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144685852","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}
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