Lithos最新文献

{"title":"Petrogenesis of early Paleozoic mafic rocks in the North Qaidam, NW China: Evidence for lithosphere–asthenosphere interaction in continental arc–back-arc settings","authors":"Lei Wang ,&nbsp;Manlan Niu ,&nbsp;Xiucai Li ,&nbsp;Chen Li ,&nbsp;Zhen Yan ,&nbsp;Hang Liu ,&nbsp;Zhe Heng ,&nbsp;Taichang Zhu","doi":"10.1016/j.lithos.2025.108359","DOIUrl":"10.1016/j.lithos.2025.108359","url":null,"abstract":"<div><div>The North Qaidam tectonic belt preserves a series of Early Paleozoic <em>syn</em>-subduction continental arc mafic rocks that provide key insights into the compositional evolution of mantle sources within the overlying mantle wedge. Herein, we present an integrated petrographic, geochronological, and geochemical study of gabbro within the North Wulan metamorphic complex to investigate crust–mantle interaction processes and elucidate the geodynamic mechanisms operating in the North Qaidam tectonic belt during the tectonic transition from the subduction of the Proto-Tethyan oceanic slab to slab rollback. Zircon U<img>Pb isotopic dating constrains the emplacement time of the mafic rocks at ∼499–479 Ma. These intrusions exhibit enriched mid-ocean ridge basalt (<em>E</em>-MORB)-like trace element patterns, coupled with slightly enriched Nd<img>Hf isotopic compositions (εNd(t) of −5.3 to −1.1; εHf(t) of −2.8 to −2.6). These geochemical signatures were likely derived from an enriched mantle source metasomatized by subduction-related materials from the dehydration melting of the oceanic slab outside the rutile stability field. Geochemical simulations further indicate that the magmas were generated by ∼12–20 % partial melting of a pyroxenite-dominated mantle source at the lithosphere–asthenosphere boundary (LAB). We attribute this magmatism to lithospheric partial melting induced by asthenospheric upwelling in response to the rollback of the Proto-Tethyan oceanic slab. By synthesizing the records in arc-like and ocean-island basalt (OIB)-like mafic rocks, we can establish an arc–MORB–OIB geochemical progression to illuminate the spatiotemporal evolution of the mantle underlying an Early Paleozoic continental arc–back-arc setting in the North Qaidam.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"522 ","pages":"Article 108359"},"PeriodicalIF":2.5,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145692680","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":"Titanium isotope fractionation during granitic magma evolution: A case study of the Fangshan pluton, North China craton","authors":"Chunxia Yi ,&nbsp;Xinmiao Zhao ,&nbsp;Tao Shi ,&nbsp;Jin Li ,&nbsp;Bing Liu ,&nbsp;Junjie Luo ,&nbsp;Jian Zhao ,&nbsp;Xiaojun Wang ,&nbsp;Fang Liu ,&nbsp;Xiangkun Zhu ,&nbsp;Hongfu Zhang","doi":"10.1016/j.lithos.2025.108357","DOIUrl":"10.1016/j.lithos.2025.108357","url":null,"abstract":"<div><div>To elucidate the geochemical behavior and fractionation mechanisms of titanium (Ti) isotopes during granitic magma evolution, we conducted a systematic Ti isotopic analysis of I-type granodiorites, quartz diorites, and their associated mafic microgranular enclaves (MMEs), along with major Ti-bearing minerals biotite, hornblende, and titanite from the Early Cretaceous Fangshan pluton, North China Craton (NCC). The granodiorites and quartz diorites exhibit a narrow range of δ^49/47Ti values (+0.14 ‰ to +0.25 ‰; average + 0.18 ± 0.07 ‰, 2SD, <em>n</em> = 15), comparable to that of the upper continental crust (UCC, δ^49/47Ti = +0.18 ± 0.07 ‰; 2SD). These values show no discernible correlation with conventional magmatic differentiation indices (e.g., SiO₂, TiO₂, MgO), suggesting limited Ti isotope fractionation during I-type granite differentiation. Thermodynamic modeling and mass balance calculations indicates that the isotopically enriched Ti signatures of the Fangshan granodiorites and quartz diorites result from partial melting (5–20 %) of rutile-bearing eclogitic sources in a thickened lower crust. In contrast, the MMEs display a wider range of δ^49/47Ti values (+0.04 ‰ to +0.33 ‰) that correlates with SiO_2, TiO₂, and MgO contents, consistent with mixing between mantle-derived mafic and crustal-derived felsic magma, coupled with fractional crystallization. Mineral separates reveal clear intra-mineral Ti fractionation: titanite is consistently enriched in lighter Ti isotopes (δ^49/47Ti = −0.09 ‰ to +0.09 ‰) relative to coexisting biotite (+0.22 ‰ to +0.44 ‰) and hornblende (+0.16 ‰ to +0.35 ‰), consistent with differences in the Ti coordination environments between the melt and crystallizing mineral. Taken together with previous studies, our results demonstrate that although Ti isotopes alone offer limited discrimination between I- and S-type granites, they act as a reliable tracer of A-type granites, where extensive fractional crystallization produces pronounced Ti isotope fractionation. Overall, these findings advance our understanding of Ti isotope behavior in granitic systems and highlight their potential as a tracer for granite petrogenesis and crustal evolution.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"522 ","pages":"Article 108357"},"PeriodicalIF":2.5,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145692681","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":"Sediment Metasomatism in the early Mesozoic Mafic–Ultramafic Intrusions of the Zhangguangcai Range (NE China): Constraints on the subduction of the Mudanjiang Ocean","authors":"Guang-Ying Feng ,&nbsp;Fei Liu ,&nbsp;Yildirim Dilek ,&nbsp;Dong-Yang Lian ,&nbsp;Xiao-Lu Niu ,&nbsp;Jing-Sui Yang","doi":"10.1016/j.lithos.2025.108356","DOIUrl":"10.1016/j.lithos.2025.108356","url":null,"abstract":"<div><div>The involvement of crustal components in subduction systems (e.g., altered oceanic crust, pelagic and terrigenous sediments) plays a key role in generating mantle heterogeneity. However, identification of these components during subduction processes remains insufficiently studied. This study presents a systematic analysis of mineral chemistry, whole-rock major and trace elements, and Sr–Nd–O isotopic compositions of four subduction-related Late Triassic–Early Jurassic (209–202 Ma) mafic–ultramafic intrusions exposed in the eastern margin of the Zhangguangcai Range in NE China, in order to constrain primarily the mode and nature of the modification of their mantle sources by crustal materials and also to provide new constraints on the tectonomagmatic evolution of the study area. Amphibole compositions indicate that the primary magmas had high water contents of 4.0–8.4 %. Together with their trace element characteristics, the data suggest that these rocks represent typical arc magmatic rocks whose mantle source was significantly modified by fluids/melts derived from subducted sediments, while their elevated δ¹⁸O values further indicate contribution from terrigenous sediments. The relatively enriched Sr<img>Nd isotopic features of these intrusions clearly distinguish them from other Mesozoic mafic–ultramafic rocks in the Zhangguangcai Range that exhibit depleted geochemical signatures. Furthermore, some of the analyzed rocks show evidence for crustal contamination, with mixing trends pointing to the Mashan Complex—the crystalline basement of the Jiamusi Block. These observations collectively suggest that the eastern Zhangguangcai Range shares similar characteristics with the Jiamusi Block and should be considered part of the Paleo-Jiamusi Block. The data further imply that the opening of the Mudanjiang Ocean occurred within the western margin of the Paleo-Jiamusi block, and the westward subduction of the Mudanjiang oceanic plate commenced around 209 Ma.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"522 ","pages":"Article 108356"},"PeriodicalIF":2.5,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145749368","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":"Mid-Neoproterozoic extensional tectonics in the Larsemann Hills, East Antarctica: Implications for Indo-Antarctic correlation in Rodinia","authors":"Sandro Chatterjee ,&nbsp;J. Amal Dev ,&nbsp;Aishi Debnath ,&nbsp;Anuj Ghosh ,&nbsp;Soham Dey ,&nbsp;Anik Mukherjee ,&nbsp;Devsamridhi Arora ,&nbsp;J.K. Tomson ,&nbsp;Fernanda Guimarães ,&nbsp;Naresh Chandra Pant ,&nbsp;Saibal Gupta","doi":"10.1016/j.lithos.2025.108358","DOIUrl":"10.1016/j.lithos.2025.108358","url":null,"abstract":"<div><div>The supercontinents Rodinia and Gondwana are believed to have assembled through orogenic events at ∼1000 Ma and ∼550 Ma, respectively. The Larsemann Hills, part of the extended Rayner Complex of East Antarctica, is a Neoproterozoic granulite terrane that was a part of both supercontinents. The tectonic evolution of the terrane in the Rodinia to Gondwana interval remains uncertain. This study integrates new field, microstructural, metamorphic and geochronological information to unveil a previously undocumented mid-Neoproterozoic thermo-tectonic event in the Larsemann Hills. Granulite facies metamorphism (M₁), synchronous with the deformation, D₁, is interpreted to have occurred in the Larsemann Hills at ∼1000 Ma, followed by a crustal shortening (D₂) event that continued from ∼990–900 Ma, signifying the incorporation of the Rayner crustal unit into Rodinia. Subsequent mid-Neoproterozoic extensional deformation (D₃), characterized by NW-SE trending S₃ shear zones, reoriented pre-existing structural fabrics. The extensional deformation operated under amphibolite facies metamorphic conditions (M₂) and resulted in a post-peak decompressive P-T trajectory. U<img>Pb LA-ICPMS dates on zircons separated from metapelites within high D₃ strain zone yield clusters at ∼700 Ma; zircons immediately adjacent to the shear zone yield ages around ∼990–900 Ma. A thermal overprint at ∼550 Ma is evident but weakly manifested in the western Larsemann Hills, with no unambiguously correlatable structural or metamorphic evidence, suggesting distance from the Gondwana orogenic front. The extensional deformation documented here is contemporaneous with extension in the northern Eastern Ghats Province, India that was contiguous with the Rayner Complex in the Neoproterozoic. This suggests that a major terrane-wide extensional event was associated with the disintegration of Rodinia. In the Neoproterozoic, the EGP-Rayner unit was therefore a tectonic entity distinct from cratonic India, with only the former being an integral component of Rodinia.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"522 ","pages":"Article 108358"},"PeriodicalIF":2.5,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145748389","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":"Asthenosphere-crust interactions in a continental-subduction channel: Records from UHP peridotite-hosted pyroxenites","authors":"Si-Yi Cao ,&nbsp;Qing Xiong ,&nbsp;Jian-Ping Zheng ,&nbsp;Hong-Kun Dai ,&nbsp;Qiang Ma ,&nbsp;Wen Zhang ,&nbsp;Hong-Da Zheng ,&nbsp;Hao-Qin Sun ,&nbsp;William L. Griffin ,&nbsp;Suzanne Y. O'Reilly","doi":"10.1016/j.lithos.2025.108354","DOIUrl":"10.1016/j.lithos.2025.108354","url":null,"abstract":"<div><div>The onset of continental subduction causes major changes in material cycling within the subduction zone. However, the interactions and cycling of materials between the asthenosphere, supracrustal rocks and the deeper crust during continental subduction initiation are poorly documented. Here, we present a systematic petrochemical, isotopic and geochronological study of a pyroxenite vein system crosscutting the Svartberget garnet peridotite in Norway (probably with an origin of ultramafic cumulates within the Baltica's deep crust). The vein includes inner garnet clinopyroxenites (locally as garnetites) and outer MgO-rich websterites. Geochemical features suggest that the inner zone originally crystallized at high pressures from asthenosphere-derived mafic magmas. U<img>Pb ages, trace-element patterns and Hf<img>O isotopic compositions of zircons from the garnet clinopyroxenite show a complex history. A cluster of igneous zircons crystallized from the mafic magmas at ∼438 Ma, and their Hf<img>O isotopic compositions suggest that the asthenospheric magmas assimilated ∼10–30 % supracrustal sediments. Three types of older zircons show that the supracrustal materials including two major crustal sources (∼1.6 &amp; ∼1.1 Ga) and a few Paleoproterozoic components from the Baltica margin were mechanically mixed into the 438 Ma mafic magmas, which then intruded the internally fragmented lower crust of the initially subducted Baltica front (∼50–60 km in depth). The mafic magmas and/or later hydrous fluids reacted with the wall-rock peridotites to form the MgO-rich websterites. These assemblages were further subducted and metamorphosed to ultrahigh-pressure conditions (∼3.2–3.5 GPa) at ∼407 Ma. This study thus reveals previously less-known mass cycling and interactions between asthenosphere, supracrustal sediments and the deep continental crust in the early stages of continental subduction.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"520 ","pages":"Article 108354"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145748350","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":"From spreading to subduction: Timelines of induced subduction zones recorded in the Central Palawan Ophiolite","authors":"Gabriel Theophilus V. Valera ,&nbsp;Betchaida D. Payot ,&nbsp;Tetsuo Kawakami ,&nbsp;Shuhei Sakata ,&nbsp;Sota Niki ,&nbsp;Takafumi Hirata","doi":"10.1016/j.lithos.2025.108346","DOIUrl":"10.1016/j.lithos.2025.108346","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Exposures where the petrological evolution of the nascent island arc and the slab-mantle wedge interface can be investigated provide unique opportunities to understand incipient stages of subduction. In this study, novel petrological information on the layered mafic-ultramafic sequence of the central Palawan ophiolite (CPO) and radiometric age dates for its metamorphic sole are presented. The CPO is a Late Eocene-Early Oligocene fossil oceanic lithosphere which experienced Tethyan-type subduction following an inferred mid-ocean ridge inversion. Mafic-ultramafic sequences of the CPO are exposed in Simpocan (gabbronorites) and Bacungan (olivine websterites, clinopyroxenites, dunites and minor gabbronorite). These rocks represent the lower crust to upper mantle cumulate section of this fossil island arc based on the low olivine forsterite (Fo&lt;sub&gt;86–88&lt;/sub&gt;) and NiO content (= 0.10–0.27 wt%), high spinel Cr# (= 0.55–0.65), and high plagioclase anorthite content (An&lt;sub&gt;89–94&lt;/sub&gt;). The mafic-ultramafic cumulates likely represent magmas that stagnated beneath a juvenile island arc at or near the Moho Transition Zone based on their obtained equilibration conditions (830–940 °C; 5–7 kbars).&lt;/div&gt;&lt;div&gt;In order to constrain the timing of the subduction event, zircons were separated from the metamorphic sole of the CPO referred to as the Dalrymple Amphibolite. Specifically, U&lt;img&gt;Pb ages (lower intercept age = 35.20 ± 0.26 Ma) were obtained for the metamorphic overgrowth rims of the matrix sample B214-2G. These rims have lower Th/U ratios (= 0.04–0.34) than the inherited cores (0.25–3.35). Previous works on the petrogenesis and &lt;em&gt;P-T-D&lt;/em&gt; history of B214-2G have shown that this kyanite-garnet-biotite-hornblende-staurolite schist preserved peak metamorphic conditions (∼700 °C, 13 kbars) and was less affected by later retrograde metamorphic stage. Our results reveal the timing of prograde metamorphism of the subducting slab at moderately low &lt;em&gt;P/T&lt;/em&gt; gradients (∼16 °C/km) linked with incipient subduction. Together with compiled radiometric ages for the CPO by previous works (= 40.01 Ma), these results indicate that subduction begun at ∼35 Ma. Furthermore, adopting the spreading to subduction inversion hypothesis of previous studies would suggest that subduction in the region was initiated within five million years of CPO-related oceanic spreading. The age of metamorphism presented in this work (= 35.20 ± 0.26 Ma) thus possibly indicate a rapid rate of reversal from spreading to subduction in induced subduction zones. The paleogeothermal gradient preserved in the Dalrymple Amphibolite is however significantly cooler than other ophiolites. Our results further document the short timeframe (∼1–2 Ma) needed to cool the slab-mantle interface from the high &lt;em&gt;T/P&lt;/em&gt; gradients during very early stages of subduction initiation (&gt;25 °C / km), to geothermal gradients more comparable to hot subduction zones (∼16 °C/km) which was likely brought","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"522 ","pages":"Article 108346"},"PeriodicalIF":2.5,"publicationDate":"2025-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145692679","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":"Apatite geochemistry as a tool for understanding the petrogenesis of layered mafic-ultramafic rocks in the Bushveld Complex, South Africa","authors":"Peace Zowa ,&nbsp;Ben Hayes ,&nbsp;Grant Bybee ,&nbsp;N. Alex Zirakparvar","doi":"10.1016/j.lithos.2025.108347","DOIUrl":"10.1016/j.lithos.2025.108347","url":null,"abstract":"<div><div>The sources of the magmas that formed the Rustenburg Layered Suite of the Bushveld Complex in South Africa remain debated, despite decades of research. Vertical and lateral variation in bulk rock and mineral separate Sr-Nd isotopic compositions, which generally indicate enriched sources, demonstrate that the layered sequence was formed by the emplacement of multiple batches of magma, crucially resulting in episodes of PGE-Cr-V mineralisation. The Lu-Hf isotope compositions of zircon are, however, at odds with the bulk rock Sr-Nd isotopic heterogeneity as they show near homogeneous compositions throughout the layered sequence (εHf_{(2.06 Ga)} = −8). This lack of variation in Hf isotope composition has been attributed to deep, continental lithospheric mantle-related and/or crustal contamination of plume-derived Bushveld magmas. In this study, we analysed the major, trace element and Sr-Nd isotope geochemistry of apatite in the Rustenburg Layered Suite. Apatite occurs as an intercumulus mineral in the lowermost regions and a cumulus mineral in the uppermost regions of the layered sequence and can therefore be used to test existing models for the isotopic disequilibrium between bulk rock Sr-Nd and zircon Hf isotopic compositions. Apatite is largely chlorapatite in the lowermost regions and fluorapatite in the uppermost regions of the layered sequence. The Merensky Reef is unusual in that it comprises both chlorapatite and fluorapatite. Apatite throughout the layered sequence is generally unzoned and shows no evidence of late-stage alteration. Trace element data show that apatite is enriched in L/HREE, with common negative Eu-Sr anomalies. These trace element signatures are consistent with a magmatic origin for the apatite grains, with prior, or concurrent, plagioclase crystallization from the same melt. Variability in <em>in situ</em> Sr and Nd isotope compositions of apatite is recorded throughout the layered sequence with εNd_{(2.06 Ga)} compositions varying between −2.5 and − 10.2 and initial ⁸⁷Sr/⁸⁶Sr compositions varying between 0.7079 and 0.7103 (for the Marikana dikes only). The variability in Sr-Nd isotope compositions of apatite is consistent with the bulk rock (and mineral separate) variation in Sr-Nd isotope compositions, suggesting apatite preserves primary magmatic compositions in the Rustenburg Layered Suite.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"522 ","pages":"Article 108347"},"PeriodicalIF":2.5,"publicationDate":"2025-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145692722","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The light δ65Cu of the WKOB meimechite: Mantle infiltration of oxidized fluids or partial melting of reduced metal-saturated mantle source","authors":"Xiujin Liu ,&nbsp;Li Zhang ,&nbsp;Wanzhi Yang ,&nbsp;Hangxin Cheng ,&nbsp;Jiangtao Tian","doi":"10.1016/j.lithos.2025.108342","DOIUrl":"10.1016/j.lithos.2025.108342","url":null,"abstract":"<div><div>High MgO ultramafic rocks commonly show similar δ⁶⁵Cu value to primitive mantle source. However, the Triassic meimechite found in the West Kunlun Orogenic Belt (WKOB) exhibit remarkably lighter δ⁶⁵Cu (‐−0.26 ± 0.04 ‰), which may confirm mantle heterogeneity of Cu isotope. The WKOB meimechite is characterized by porphyritic texture, low contents of SiO₂ and alkali, and high contents of MgO and TiO₂. The disorder of depletion degree of Co, Ni, Cu, and PGE, high Cu concentration (1.2–12.5 ppm) in olivine, and magma evolutionary trend of olivine accumulation without sulfide fractionation or segregation revealed by Fo and Ni in olivine suggest that the WKOB meimechite was derived from a sulfide-undersaturated magma. Thus, Cu isotope would not be significantly fractionated by magmatic fractionation, but mainly be controlled by Cu isotopic composition of mantle source or partial melting process. In the WKOB, Cu-hosted minerals in mantle source, redox conditions and degree of partial melting were primary controlling factors on light δ⁶⁵Cu of the meimechite. The light δ⁶⁵Cu of the WKOB meimechite could be explained by mantle infiltration of recycled crustal oxidized fluids when sulfide is the only copper-containing mineral in mantle source, which underwent high degree of partial melting. Moreover, preferential melting of sulfide relative to Fe<img>Ni alloy will be responsible for light δ⁶⁵Cu of the WKOB meimechite, when Cu is mainly hosted by Fe<img>Ni alloy and sulfide.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"522 ","pages":"Article 108342"},"PeriodicalIF":2.5,"publicationDate":"2025-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145840425","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":"Miocene N-MORB-type diabase dike in the Himalayan terrane attests the incomplete tearing of Indian continental slab","authors":"Hongliang Li ,&nbsp;Yong Huang ,&nbsp;Fuguang Yin ,&nbsp;Qiang Zheng ,&nbsp;Pengcheng Zhang ,&nbsp;Fanqing Meng","doi":"10.1016/j.lithos.2025.108345","DOIUrl":"10.1016/j.lithos.2025.108345","url":null,"abstract":"<div><div>Mafic dikes are important indicators of regional extensional tectonics and carry valuable constraints on deep mantle geodynamic processes. This study presents zircon U<img>Pb geochronology, whole-rock geochemistry, and Sr–Nd–Pb isotopic data of samples from newly identified Miocene Sajia diabase in the central Himalaya. This diabase was emplaced into <em>syn</em>-extensional shear fractures along the margins of the Dingjie–Shenzha Rift (DSR) in southern Tibet. Geochronological results indicate an emplacement age of 22.6 Ma, marking an episode of Early Miocene mafic magmatism in the Himalaya and constraining the onset of DSR. The Sajia diabase is geochemically characterized by slight enrichment in large-ion lithophile elements (LILE, e.g., Ba, Th, U, Sr) and mild depletion in high field strength elements (HFSE, e.g., Nb, Ta, Ti), with no significant Ce or Eu anomalies—consistent with a typical normal mid-ocean ridge basalt (N-MORB) signature. Pb isotopic compositions include (²⁰⁶Pb/²⁰⁴Pb)_<em>t</em> = 18.437–18.634, (²⁰⁷Pb/²⁰⁴Pb)_<em>t</em> = 15.623–15.658, and (²⁰⁸Pb/²⁰⁴Pb)ₜ = 38.537–38.791, with averages of 18.592, 15.647, and 38.731, respectively—values that closely resemble those of the continental lithospheric mantle. The diabase also displays relatively low (⁸⁷Sr/⁸⁶Sr)_t ratios (0.706289–0.712231, average 0.708204), high (¹⁴³Nd/¹⁴⁴Nd)_t ratios (0.512854–0.512933, average 0.512883), and consistently positive ε_Nd(t) values (+4.8 to +6.3, average + 5.4). Integrating geochemical and isotopic evidence, we infer that the Sajia diabase originated from partial melting of the Indian continental lithospheric mantle, with limited (less than 2 %) crustal contamination during ascent. Combined with the previous regional geophysical observations, our results support a model in which the Indian continental slab experienced incomplete tearing along the DSR during the Early Miocene. This incomplete slab tearing triggered mantle-derived mafic magmatism, which subsequently acted as a significant metallogenic source contributing to the widespread Sb–(Au) mineralization within the Tethyan Himalayan Sequence (THS).</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"520 ","pages":"Article 108345"},"PeriodicalIF":2.5,"publicationDate":"2025-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145623268","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 mixing underpins collisional porphyry mineralization","authors":"Jinlong Qian ,&nbsp;Qingfei Wang ,&nbsp;Lin Yang ,&nbsp;Qi Chen ,&nbsp;Lijun Liu","doi":"10.1016/j.lithos.2025.108340","DOIUrl":"10.1016/j.lithos.2025.108340","url":null,"abstract":"<div><div>The magmatic processes responsible for Cenozoic porphyry deposits in Tibetan post-collisional settings remain debatable. By employing integrated whole-rock (major-trace element, Sr<img>Nd isotope, and PGE) and mineral geochemical analyses of lamprophyres, mafic enclaves of distinct origins, and host porphyries from the Machangqing deposit in southeastern Tibet, this study revealed a two-stage magma mixing process underpinning the porphyry mineralization. Gabbroic enclaves within lamprophyres exhibit elevated metals and volatiles, along with mineral assemblages transitional between lamprophyre and juvenile lower-crustal products (e.g., felsic intrusions and xenoliths), denoting a hybrid mafic magma (HMM) generated during Stage I (mixing between ∼64 % lamprophyric magma and 36 % juvenile lower crust at 39–48 km depth). Stage II mixing between HMM and porphyry magma, documented by MMEs at 28–35 km depth, triggered marked enrichment of volatiles and metals in porphyries, as evidenced by elevated Cl (0.08 to 0.25 wt%) and SO₃ (0.27 to 0.49 wt%) in apatite, along with Cu contents (8.52 to 100 ppm) comparable to the HMM. Notably, the decrease in total PGE contents from lowly-mixed to highly-mixed MMEs (1.67–0.57 ppb), coupled with chalcopyrite entrapment in the latter, strongly suggests a sulfide saturation process. Controlled by sulfide saturation levels in these MMEs, ionic Cu diffusion (slight saturation) and sulfide segregation (intense saturation) are revealed to underpin metal transfer from HMM to the porphyry system via Stage II mixing. This multistage magma mixing process enables the transfer of metals and volatiles from juvenile lower crust and mantle sources, laying the foundation for efficient porphyry mineralization.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"522 ","pages":"Article 108340"},"PeriodicalIF":2.5,"publicationDate":"2025-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145645566","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}