Lithos最新文献

{"title":"Diamond resorption in non-igneous settings evidenced by AFM of fine surface textures coincident with radiation stains","authors":"Roy Bassoo ,&nbsp;Taryn Linzmeyer ,&nbsp;Mike Breeding ,&nbsp;Bernd Zechmann ,&nbsp;Sally Eaton-Magaña","doi":"10.1016/j.lithos.2025.108315","DOIUrl":"10.1016/j.lithos.2025.108315","url":null,"abstract":"<div><div>Rarely documented fine negative surface topography coincident with “radiation stains” on 16 diamonds are investigated by atomic force microscopy (AFM) to assess surface feature morphology and infer formation conditions. These features are inferred to derive from post-irradiation resorption by oxidizing pore fluids at relatively low temperatures when residing in sedimentary rocks. We document the presence of circular, rounded, acicular, bladed, cubic, prismatic, and tabular surface features exclusively coincident with radiation stains. Surface areas are ≤300 μm² and 17 ± 43 μm² on average. Acicular features have the highest mean length-width ratio of 8 ± 4. Bladed, prismatic, and circular to rounded features have mean length-width ratios of 3 ± 1, 2 ± 2, and ∼ 1 respectively. These features penetrate into the diamond with depths of 4 to &lt;240 nm and most have solely flat-bottomed morphologies. Circular features have the highest mean depths of 115 ± 71 nm. Bladed, acicular, prismatic, cubic, rounded features have mean depths of 54 ± 36 nm, 32 ± 21 nm, 33 ± 22 nm, 23 ± 5 nm, and 22 ± 15 nm respectively. Raman transects across radiation stains hosting these features have higher 1332 cm⁻¹ full width at half maximum (FWHM) values than in colorless zones on the same diamond indicating the presence of tetragonal to tetrahedral amorphous carbon. During residence in ancient conglomerates, diamonds could be subjected to irradiation by nearby radioactive minerals which transforms irradiated sites to amorphous carbon. We suggest when amorphous carbon is exposed to oxidizing pore fluids it preferentially dissolves and leaves behind a resorption pit coincident with radiation stains. Our study suggests diamonds can be resorbed in non-igneous settings and likely during residence in ancient sedimentary rocks.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"518 ","pages":"Article 108315"},"PeriodicalIF":2.5,"publicationDate":"2025-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474871","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":"Cenozoic granulite-facies metamorphism and crustal anatexis in a deep-seated shear zone: Implications for initiation of shearing and leucogranitic genesis","authors":"Haobo Wang ,&nbsp;Shuyun Cao ,&nbsp;Xuemei Cheng ,&nbsp;Lirong Tao ,&nbsp;Yixuan Zhao ,&nbsp;Yanlong Dong ,&nbsp;Jianhua Liu ,&nbsp;Yujuan Qin ,&nbsp;Dingkui Zhou ,&nbsp;Jianwei Fan","doi":"10.1016/j.lithos.2025.108311","DOIUrl":"10.1016/j.lithos.2025.108311","url":null,"abstract":"<div><div>The exhumation of a continental-scale, deep-seated shear zone presents a unique opportunity to trace the interrelated processes of crustal anatexis, metamorphism, and deformation. Migmatites and leucogranites are extensively exposed in the Ailao Shan–Red River shear zone (ASRR-SZ) in Southeast Asia, suggesting a potential genetic linkage between these two rock types. Detailed petrographic analysis of migmatites from the ASRR-SZ reveals that the high-grade metamorphic rocks experienced granulite-facies metamorphism. Pseudosection modelling indicates the peak metamorphic conditions of approximately 830 °C and 8.5 kbar, following a clockwise P–T path, with up to 22 mol% melt generated primarily through heating relative to the protolith. The leucogranites exhibit low Sr and Ba contents alongside high Rb, and a linear negative correlation between the Rb/Sr ratio and Ba and Sr concentrations, indicating that their genesis is linked to mica dehydration melting. Zircon ε_Hf(t) values suggest that the magmas forming the Ailao Shan leucogranites were primarily derived from juvenile crustal sources. U<img>Pb dating of monazites and zircons documents metamorphic and partial melting events that occurred between 34 Ma and 26 Ma within the ASRR-SZ. We propose that the ASRR-SZ not only facilitated lower-crustal anatexis but also served as an effective conduit for the ascent of leucogranitic magmas. These findings suggest that the ASRR-SZ functioned not merely as a lateral strike-slip zone accommodating the eastward extrusion of Eurasian continental blocks but also played a significant role in orogenic processes involving crustal thickening and high-grade metamorphism.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"518 ","pages":"Article 108311"},"PeriodicalIF":2.5,"publicationDate":"2025-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145525995","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Crustal growth of Assam Meghalaya Gneissic complex related to Kuunga Orogeny: Insights from A2-type granitoids of the West Mikir Hills (Assam), Northeast India","authors":"Ashima Saikia ,&nbsp;Priyanka Negi ,&nbsp;Eyozele Kiso ,&nbsp;Ivan Belousov ,&nbsp;Leonid V. Danyushevsky","doi":"10.1016/j.lithos.2025.108312","DOIUrl":"10.1016/j.lithos.2025.108312","url":null,"abstract":"<div><div>The Assam Meghalaya Gneissic Complex (AMGC) is a northeastern extension of the Indian Shield encompassing the Shillong plateau and Mikir Hills. It is considered a significant crustal domain of East Gondwana and was likely juxtaposed against the Western Australia and East Antarctica during the East Gondwana assembly. Owing to the abundance of Neoproterozoic lithologies, the AMGC holds key insights into the magmatic and metamorphic evolution of Pan-African orogens.</div><div>This study presents new zircon U<img>Pb geochronology, trace-element geochemistry, whole-rock major and trace element compositions, and mineral chemistry of A₂-type granitoids from the Mikir Hills, West Karbi Anglong (Assam), India, aimed at constraining their petrogenesis and tectonic significance. The granitoids are coarse- to medium-grained, porphyritic, compositionally range from monzonite to granite, and show an overall alkali-enrichment trend. Mineralogically, they are composed mainly of K-feldspar, plagioclase, quartz and biotite, with accessory titanite, zircon and magnetite.</div><div>Primitive mantle-normalized trace element patterns reveal enrichment in Y, Zr, Pb, and Th, and depletion in Ti and P. Chondrite-normalized REE patterns show LREE enrichment with weak to moderate negative Eu anomalies. Zircon crystallization temperatures range from 816 to 926 °C. Magmatic oxygen fugacity estimates suggest oxidizing conditions during zircon crystallization. The granitoid melt temperatures are estimated to range from 919 to 1091 °C and emplacement depths of 8–17 km (209–450 MPa).</div><div>Zircon U<img>Pb LA-ICP-MS dating yields emplacement ages of 502 ± 5.0–509 ± 2.4 Ma, indicating post-collisional, extension-related magmatism associated with the Kuunga Orogeny, and the terminal assembly of East Gondwana.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"518 ","pages":"Article 108312"},"PeriodicalIF":2.5,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474962","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":"Petrogenesis of Triassic intermediate-felsic intrusions from three skarn tungsten deposits in the East Kunlun Orogenic Belt, NW China: Evidence from zircon UPb geochronology, petrochemistry, and Hf isotopic characteristics","authors":"Yan Tan ,&nbsp;Jin-Xiang Li ,&nbsp;Fang Xu ,&nbsp;Yan-Qian Yang ,&nbsp;De-Xin Zhang ,&nbsp;Hua-Liang Lai ,&nbsp;Sheng-Qiang Ma ,&nbsp;Shun-Long Yang ,&nbsp;Yi-Jun Yang ,&nbsp;Chen Wu ,&nbsp;Ya-Hui Yue ,&nbsp;Chao Wang ,&nbsp;Lin Ding","doi":"10.1016/j.lithos.2025.108310","DOIUrl":"10.1016/j.lithos.2025.108310","url":null,"abstract":"<div><div>The Sanchakou, Keteli, and Tielemu skarn tungsten (W) deposits have recently been discovered in the East Kunlun Orogenic Belt, northwestern China. However, the formation ages and petrogenesis of the W-fertile intermediate-felsic intrusions remain poorly constrained. In this study, zircon U<img>Pb dating results show that the intrusions formed in two epochs, Middle Triassic (∼250–238 Ma) and Late Triassic (∼230 Ma). The first epoch of intermediate-felsic intrusions (the ∼242 Ma Sanchakou and Tielemu monzogranites and the ∼238 Ma Keteli granodiorite) is closely associated with skarn W mineralization, except for the slightly older (∼247 Ma) and barren garnet-bearing monzogranite at Keteli. The ∼250–238 Ma intrusions are mainly metaluminous and belong to the calc-alkaline to high-K calc-alkaline series. They show LREE-rich patterns with weak negative to positive Eu anomalies (La_N/Yb_N = 3.66–41.9 and Eu/Eu* = 0.52–1.10), enrichments in LILEs (e.g., Rb, K, Th, and U), and depletions in HFSEs (e.g., Nb, Ta, Ti, and P). In comparison, the ∼230 Ma syenogranite exhibits similar geochemical characteristics, except for more pronounced negative Eu anomalies (Eu/Eu* = 0.20–0.28). All studied intrusions reveal a negative correlation between SiO₂ and P₂O₅, indicating an evolutionary trend of I-type granitic melts. The two epochs of intrusions have relatively consistent zircon Hf isotopic compositions (ε_Hf(t) = −7.7 to 3.2 and − 4.5 to −0.8, respectively), suggesting that they may have been derived from the partial melting of Meso-Proterozoic basement rocks with a minor addition of mantle-derived material. Moreover, the W-fertile intrusions show hydrous and weakly oxidized features, evidenced by relatively low zircon saturation temperatures (738–789 °C), Zr/Sr (0.11–0.70), and <em>f</em>O₂ values (∆FMQ = 0.07–0.55). Based on new geochemical data and regional geological investigations, we propose that the Middle Triassic intrusions (∼250–238 Ma) formed during the late-stage of northward subduction of the Paleo-Tethys oceanic plate. In contrast, the Late Triassic (∼230 Ma) syenogranite was generated in a local extensional setting related to oceanic slab rollback following the collision between the East Kunlun and the Hoh-Xil-Songpan-Ganzi terranes.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"518 ","pages":"Article 108310"},"PeriodicalIF":2.5,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474835","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":"Tourmaline and muscovite chemistry as a proxy for the origin and evolution of Paleoproterozoic lithium pegmatites in Kaustinen, western Finland","authors":"Artur V. Tvauri,&nbsp;Henrik Kalliomäki,&nbsp;O. Tapani Rämö,&nbsp;Kathleen A. Law,&nbsp;Eemu Ranta,&nbsp;Christoph Beier","doi":"10.1016/j.lithos.2025.108306","DOIUrl":"10.1016/j.lithos.2025.108306","url":null,"abstract":"<div><div>The Paleoproterozoic Kaustinen lithium province in western Finland hosts numerous Li deposits in Li-Cs-Ta (LCT) pegmatites of the albite-spodumene type. As for many rare-element pegmatite populations, the source of the pegmatite-forming melts in Kaustinen is not fully understood. In this study, we use major and trace element chemistry of tourmaline and muscovite to test whether a genetic link exists between the Kaustinen albite-spodumene pegmatites and the nearby Kaustinen pegmatite granite, and to explore the internal evolution of albite-spodumene pegmatites. The compositional variation in tourmaline and muscovite from crystal to regional scales reveal differences in the internal evolution and probable melt sources of individual albite-spodumene pegmatites. We interpret differences in intra- and inter-sample variation between individual pegmatites to reflect differences in solidification vectors. Contamination from wall rocks during the solidification of pegmatites is shown to affect mineral chemistry even in the inner zones of some of the pegmatites, evidenced by the elevated concentrations of Mg, Ca, Ti and Sr in the rims of the sharply zoned tourmaline crystals. Large-Ion Lithophile Element (LILE) concentrations and ratios in tourmaline and muscovite vary between pegmatites and do not agree with fractional crystallization trends calculated for the Kaustinen pegmatite granite. The major differences in LILEs between individual pegmatites suggest multiple melt sources for the albite-spodumene pegmatites of Kaustinen, with the variations likely reflecting the mineral proportions involved in the melting reactions and subsequent fractionation of the nascent melts.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"518 ","pages":"Article 108306"},"PeriodicalIF":2.5,"publicationDate":"2025-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474869","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":"Paleoproterozoic geodynamics of the western margin of Sarmatia, East European Craton","authors":"R.A. Terentiev ,&nbsp;K.A. Savko ,&nbsp;E.H. Korish ,&nbsp;M. Santosh","doi":"10.1016/j.lithos.2025.108305","DOIUrl":"10.1016/j.lithos.2025.108305","url":null,"abstract":"<div><div>The Precambrian Ingul-Bryansk granulite belt forms part of the western margin of the Sarmatian segment of the East European Craton where the dominant rock types belonging to the Bryansk (khondalite) Series are aluminous gneisses and granulites, porphyroblastic biotite-garnet schists and gneisses (kinzigites) and moderately aluminous biotite gneisses, amphibolites. Here we present zircon U<img>Pb geochronological data obtained using SIMS that indicate that the sedimentary protoliths of the Bryansk Series rocks mainly come from Meso-Neoarchean (3.24–2.50 Ga) and Paleoproterozoic (2.2–2.1 Ga) provenances. Minimum ages of detrital zircons and ages of early metamorphic zircons constrain the sedimentation time of the protoliths of the Bryansk Group rocks to be 2.1–2.04 Ga. The Bryansk domain rocks underwent two metamorphic events at 2036 Ma and before 1983 Ma. Petrographic observations and major and trace element geochemical data suggest that the protoliths of this Paleoproterozoic metavolcanic-sedimentary series are composed partly of a sandy-clay suite (kinzigite) that was probably derived entirely from the Mesoarchean Sarmatia province, mafic volcanic rocks (amphibolites) that were erupted subsynchronously with the metasedimentary rocks, and members of moderate- to high-alumina clay-graywacke metasedimentary rocks (gneisses, granulites) from a mixed Archean-Paleoproterozoic province. Geochemical data for the mafic metavolcanic rocks indicate an intraplate tectonic setting. The metasedimentary units are thought to have been deposited in a variable landscape (from subaqueous to subaerial) under tropical climate conditions, which provided low to high sediment maturity and premetamorphic chemical weathering of the protolith. The dominant provenance composition corresponded to felsic rocks with varying proportions of mafic material admixture. We propose that the Ingul-Bryansk belt developed independently on the western margin of Sarmatia as a passive margin before the Columbia supercontinent formation. Juvenile materials of about 2.2–2.1 Ga were added to the source area of <!--> <!-->the Bryansk metasedimentary units, which may indicate an important activity associated with the formation of an unknown ocean and an active margin on the opposite side of the Sarmatia. The collision of these active margins with the passive margin of Sarmatia occurred at approximately 2.04 to after 1.98 Ga ago, which marked the peak of orogeny and led to two-stage metamorphism - first granulite and then associated with exhumation of the region, respectively.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"518 ","pages":"Article 108305"},"PeriodicalIF":2.5,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474836","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":"Magma recharge and hybridization in an alkaline magmatic system: Evidence from clinopyroxene and olivine from the Pariquera-Açu Suite, SE Brazil","authors":"Lina Cetina ,&nbsp;Rogério G. Azzone ,&nbsp;Teresa Ubide ,&nbsp;Vinicius Gonsalves Dias","doi":"10.1016/j.lithos.2025.108304","DOIUrl":"10.1016/j.lithos.2025.108304","url":null,"abstract":"<div><div>Crystal populations in igneous rocks record complex open-system processes within magmatic plumbing systems. These processes remain poorly explored in alkaline plutonic environments. This study investigates zoned clinopyroxene and olivine from the Pariquera-Açu Suite (SE Brazil) to characterize magma evolution in alkaline systems. This fossilized intrusion, with zoned facies from cumulate shonkinites at the margin to inequigranular malignites in the center, provides a natural laboratory for studying open-system processes. We analyzed textures and major and trace element compositions of clinopyroxene and olivine, including LA-ICP-MS trace element mapping, and applied a range of thermobarometric approaches. We identify four clinopyroxene and olivine populations that reflect four main stages in the system's evolution: (1) Crystallization of antecrystic Mg-rich beige clinopyroxene and primitive olivine cores in a deep reservoir (∼580 MPa, ∼1132 °C), with compositional variations recording fractional crystallization. (2) Shallow reservoir (∼170 MPa, ∼1110 °C) crystallization fed by an alkali mafic melt carrying antecrysts, forming Ti-Al-rich brown clinopyroxene mantles (overgrowing beige cores) and intermediate olivine cores or rims. (3) Mafic recharge events leading to reverse zoning in clinopyroxene (beige bands) and Ni-rich intermediate olivine cores. (4) Felsic melt input producing green-reddish reaction rims on clinopyroxene and evolved olivine rims. The evolution of this shallow magma chamber is controlled by fractional crystallization, coupled with recharge events that drive mixing and hybridization processes, and trigger a dynamic environment with compaction and mush disintegration and remobilization, imprinting textural features represented by cumulate and inequigranular facies. This study highlights the role of mineral-scale textures and compositions in revealing magmatic processes.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"518 ","pages":"Article 108304"},"PeriodicalIF":2.5,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474960","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":"Evidence of hydrous magmatism and magma mixing in Sittampundi Anorthosite Complex, Southern Granulite Terrain, India: Inferences from petrography and mineral chemistry","authors":"Amandeep Kaur ,&nbsp;Nachiketa Rai ,&nbsp;Rajagopal Krishnamurthi","doi":"10.1016/j.lithos.2025.108309","DOIUrl":"10.1016/j.lithos.2025.108309","url":null,"abstract":"<div><div>The Sittampundi Anorthosite Complex (SAC) is a globally significant Archean layered igneous body dominated by high‑calcium plagioclase (∼An₉₈), with lithological similarities to the Fiskenaesset Complex (Greenland) and the Messina Complex (South Africa). Although previous work suggested its emplacement in a supra-subduction setting, the nature of its parental magma and mineral paragenesis has remained poorly constrained. This study presents new petrographic and mineral chemistry data that reveal disequilibrium textures—such as sieve-textured plagioclase and coexisting pyroxene–amphibole assemblages—indicative of magma mixing between compositionally and thermally contrasting melts. Textural and mineralogical evidence confirms that amphibole, despite later recrystallization, was part of the primary magmatic assemblage. The rare occurrence of gedrite is interpreted as a product of plagioclase recrystallization and homogenization, which took place by utilizing the Ca and Al released from calcic amphibole breakdown and thereby stabilizing the gedrite amphibole. Highly calcic plagioclase (An₉₁), primary magmatic amphibole, and Fe–Al-rich chromite compositions collectively indicate a hydrous (3–5 wt% H₂O), arc-derived parental magma. Additionally, trace-element data from chromite suggest that their formation was derived from picritic parental magmas. These findings provide the first clear evidence that magma mixing played a critical role in forming SAC chromitites and anorthosite units and refine our understanding of crustal evolution in Archean subduction-related settings, despite subsequent granulite-facies overprinting.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"518 ","pages":"Article 108309"},"PeriodicalIF":2.5,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474961","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":"Two-stage leucocratic dyke generation in the Inner Tauride Ocean from Eastern Mediterranean Region in Central Türkiye","authors":"Rahmi Melih Çörtük ,&nbsp;Ömer Faruk Çelik ,&nbsp;Mutlu Özkan ,&nbsp;Joshua H.F.L. Davies ,&nbsp;Andrea Marzoli","doi":"10.1016/j.lithos.2025.108307","DOIUrl":"10.1016/j.lithos.2025.108307","url":null,"abstract":"<div><div>Leucocratic dykes, including plagiogranites occur in small volumes within ophiolitic sequences and they provide highly valuable insights into the formation processes and timing of ancient oceanic domains. The Tauride Belt Ophiolites, located along southern Türkiye in the eastern Mediterranean region, include the Tuzla Ophiolite in the Eastern Taurides, which is unique for preserving plagiogranites formed by distinct petrogenetic processes. The Tuzla Ophiolite consists of mantle rocks and basaltic volcanic rocks representing the upper crustal section, intruded by plagiogranites and dolerites. Geochemical data obtained for the basaltic volcanics, and isolated dikes indicate a supra-subduction zone (SSZ) affinity, consistent with the geodynamic setting of other Tauride Belt ophiolites. Within this framework, we distinguish two types of plagiogranites based on field observations, geochemical data, and crystallization age. Type-I dykes are sheeted, parallel dykes that intrude massive basalts occurring in the crustal section. They exhibit similar ratios of incompatible elements and continuous chemical trends, in conjunction with coexisting basalts and dolerites, and petrogenetic modelling, suggest that high degree (75 %–80 %) fractional crystallization of MORB-type magmas. Type-II dykes intruded through the mantle section of the Tuzla Ophiolite have distinctive REE patterns and they likely reflect partial melting of subducted oceanic crust. The existence of alkali and Fe-Mg rich amphiboles in Type-II dykes, suggests that they were influenced by sea floor hydrothermal metasomatism. LA-ICP-MS U-Pb zircon dating reveals two distinct magmatic phases: Type-I plagiogranites yield an age of 92.2 ± 0.4 Ma (εHf(t) = +1.3 to +19.7), marking the SSZ spreading stage of the Inner Tauride Oceanic crust, while Type-II plagiogranites yield an age of 82.8 ± 0.3 Ma (εHf(t) = +2 to +12.3), reflecting later-stage magmatic activity derived from sediments and mafic rocks of the subducted slab during ongoing intra-oceanic subduction.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"518 ","pages":"Article 108307"},"PeriodicalIF":2.5,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474959","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Formation of the Da'anhe reduced gold skarn in NE China: Evidence from U-Pb geochronology, and whole-rock and mineral geochemistry","authors":"Litian Zhang ,&nbsp;Qihai Shu ,&nbsp;Kai Xing ,&nbsp;Fan Yu ,&nbsp;Yanjun Wang ,&nbsp;Zhonghai Zhao ,&nbsp;Bing Li ,&nbsp;Qingfei Wang ,&nbsp;Jun Deng","doi":"10.1016/j.lithos.2025.108308","DOIUrl":"10.1016/j.lithos.2025.108308","url":null,"abstract":"<div><div>The Da'anhe skarn Au deposit is located in the Lesser Xing'an-Zhangguangcai Range, northeastern China. The timing of the skarn mineralization and the causative intrusion is still unclear, and the magmatic physicochemical properties responsible for the gold mineralization need further investigation. In this study, U-Pb ages of the magmatic zircon and hydrothermal garnet, as well as whole rock and zircon geochemistry, have been determined to address the issues. The garnet U-Pb ages of two skarn samples from Da'anhe are 181.9 ± 7.1 Ma and 181.0 ± 9.0 Ma, respectively, which are consistent with the zircon U-Pb ages of the two gabbrodiorite samples (184.1 ± 0.6 Ma and 184.3 ± 1.3 Ma, respectively). The results indicate a genetic relationship between the gabbrodiorite and skarn mineralization. The gabbrodiorite in Da'anhe belongs to the high-K calc-alkaline to calc-alkaline series and is similar to typical arc magmas, which is characterized with enrichment of LILEs and depletion of HFSEs. The relatively low whole-rock Fe₂O₃/(FeO + Fe₂O₃) ratios (&lt;0.4) and estimated magmatic oxygen fugacities (ΔFMQ = −1.29 to +1.45 with an average of −0.43) from zircon trace elements, which are significantly lower than those oxidized porphyry Cu/Mo systems in the region, suggest that the ore-forming magmas are highly reduced. Moreover, the absence of whole-rock Eu anomalies and the relatively high zircon <span><math><mn>10000</mn><mo>×</mo><mfenced><mrow><mi>Eu</mi><mo>/</mo><msup><mi>Eu</mi><mo>∗</mo></msup></mrow></mfenced><mo>/</mo><msub><mi>Yb</mi><mi>N</mi></msub></math></span> ratios (3.50–10.03, average 5.53) from the less evolved gabbrodiorite sample indicate a high-water parental magma, a favorable condition for hydrothermal mineralization. The present study suggests that Au-only skarn deposits like Da'anhe could be generated from a reduced, high-H₂O magmatic system.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"518 ","pages":"Article 108308"},"PeriodicalIF":2.5,"publicationDate":"2025-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474958","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}