Search Results (321)

The Lower Cretaceous volcanic–sedimentary succession in the Dehui Graben of the southern Songliao Basin preserves critical records of syn-rift volcanism and basin filling in NE China. This study presents an integrated dataset of zircon cathodoluminescence (CL) imaging, LA-ICP-MS U-Pb geochronology, trace-element geochemistry, and LA-MC-ICP-MS Lu-Hf isotopic analyses for four representative Yingcheng Formation samples collected from three boreholes (D102, D21, and D83) in the Dehui Graben. Zircon grains from samples S1 (gray crystal-vitric tuff, Well D102, 3050.5 m) and S3 (gray tuff, Well D21, 2287 m) are predominantly euhedral to subhedral with well-developed oscillatory zoning, elevated Th/U ratios (>0.4), and chondrite-normalized REE patterns characterized by depletion in light REEs, enrichment in heavy REEs, and pronounced negative Eu anomalies, all of which are diagnostic of a magmatic origin. The 37 zircon analyses from S1 yield ²⁰⁶Pb/²³⁸U ages ranging from 109 to 122 Ma, with a KDE peak at ~116 Ma and two inherited grains at 158 Ma and 262 Ma, whereas the 43 analyses from S3 define a narrow age population between 110 and 123 Ma with a KDE peak at ~114 Ma and a single inherited grain at 145 Ma. Together, these ages constrain Yingcheng Formation felsic volcanism in the Dehui Graben to the Aptian stage of the Early Cretaceous. In marked contrast, the 54 zircon analyses from S2 (dark gray crystal-rich tuff, Well D21, 2288 m) exhibit a polymodal distribution dominated by an Early Jurassic population (KDE peak ~181 Ma), with subordinate Permian–Triassic (~251 Ma) and Carboniferous (~325 Ma) components and a complete absence of Cretaceous-aged zircons. We interpret this population entirely as inherited (xenocrystic) zircons entrained from conduit wall rocks during the incipient phase of volcanic eruption. Notably, S2 and S3 were collected from the same well at depths separated by only 1 m, yet they display fundamentally contrasting zircon age spectra. This abrupt vertical discontinuity is consistent with a two-phase eruptive model in which an early xenocryst-rich volcaniclastic unit (S2), possibly related to conduit-wall entrainment during the initial eruptive stage, was rapidly followed by a juvenile magma-derived tuff (S3). Sample S4 (gray coarse sandstone, Well D83, 3273 m) contains 84 detrital zircon grains spanning 112 to 440 Ma, with a dominant Early Jurassic peak (~179 Ma) that correlates with widespread granitoids in the Zhangguangcai Range and a youngest single-grain age of 110.5 Ma that constrains the maximum depositional age of the Yingcheng Formation. All 86 zircon Lu-Hf analyses yield positive εHf(t) values (+0.8 to +9.2), with two-stage Hf model ages (TDM2) clustering between 536 and 1100 Ma and peaking at ~700–800 Ma (Neoproterozoic). These data indicate that the parental magmas were predominantly derived from partial melting of Neoproterozoic juvenile crust extracted from a depleted mantle source. Among the four samples, S3 records the highest mean εHf(t) (+7.1) and the youngest mean TDM2 (~672 Ma), which may indicate a relatively stronger depleted-mantle affinity during the extensional stage at ca. 114 Ma. The positive εHf(t) values of the ~181 Ma S2 xenocrysts further imply that the Early Jurassic magmatic event in this region also sampled juvenile Neoproterozoic crust, which thus served as the common source basement for both episodes of magmatism. A regional compilation reveals a systematic north-to-south younging trend of syn-rift volcanism across the Songliao Basin (Yingtai ~119 Ma, Dehui ~115 Ma, Wangfu ~110 Ma), with the Dehui Graben occupying a critical intermediate position that is consistent with the southeastward migration of back-arc extension possibly related to Paleo-Pacific slab rollback. Full article

Caledonian hydrothermal vein-type Mo deposits are largely restricted to eastern Guangxi, South China, yet the magmatic controls on molybdenum (Mo) mineralization remain poorly constrained. The adjacent Guiling (Mo–mineralized) and Daning (Mo–barren) plutons in this region represent a natural pair for deciphering these issues. Zircon U–Pb dating, whole-rock geochemistry, and mineralogical characteristics indicate that the Daning pluton (~440 Ma) is an I-type granite, whereas the younger Guiling pluton (~425 Ma) is a more evolved I-type granite, with higher SiO₂ contents (avg. 71.17 wt.% vs. 65.88 wt.%), stronger negative Eu anomalies (avg. 0.53 vs. 0.63), lower Nb/Ta ratios (avg. 6.5 vs. 9.9), and Zr/Hf ratios (avg. 30.6 vs. 33.4), as well as higher Rb/Sr ratios (avg. 3.6 vs. 1.1). Sr–Nd–Hf isotopes are consistent with a Paleoproterozoic crustal source for both plutons, whereas coeval mafic microgranular enclaves in the Guiling pluton exhibit positive ε_Nd(t) values (+3.43 to +3.58), providing evidence for mantle input. Biotite geochemistry shows that the Guiling pluton is enriched in F and Cl, as reflected by lower log(ƒ_H2O/ƒ_HF)^fluid values and higher log(ƒ_H2O/ƒ_HCl)^fluid values. Our integrated study suggests that the Daning and Guiling plutons were emplaced in an intracontinental orogenic setting during the transition from compression to extension, but the more pronounced extension facilitated a greater input of mantle-derived heat and volatiles into the Guiling pluton, favoring Mo enrichment. However, the similar biotite crystallization temperatures and moderate oxygen fugacities of both plutons suggest that these factors were not the decisive factors. Collectively, we propose that the contrasting Mo fertility between the two plutons reflects the interplay of magmatic and structural factors. Magmatically, crust–mantle source mixing, high degrees of fractionation, and volatile enrichment promoted Mo concentration, whereas ductile shear zones likely served as fluid conduits that facilitated mineralization. Accordingly, the southwestern segment of the Yingyangguan (YYG) ductile shear zone between the Daning and Guiling plutons could be a prospective target for Mo prospecting in eastern Guangxi. Full article

The No. VI ore block of the Galinge skarn system in the Qimantagh metallogenic belt, East Kunlun, contains proximal Fe-oxide mineralization and distal Pb–Zn sulfide mineralization that are spatially zoned and locally overprinted along faults and interlayer fracture zones. To constrain the controls on Fe–Pb–Zn zonation and overprinting within this ore block, we integrated LA–ICP–MS zircon U–Pb dating, zircon Lu–Hf isotopes, whole-rock major and trace elements, and in situ trace elements of magnetite, pyrite, chalcopyrite, pyrrhotite, and arsenopyrite. Zircon U–Pb ages indicate two Indosinian intrusive pulses: an early granodiorite at 235.1 ± 0.51 Ma and a younger granodiorite–quartz diorite at 229.52 ± 0.46 Ma. Excluding the hydrothermally altered sample ZK26804-805, the intrusive rocks are metaluminous, medium- to high-K calc-alkaline I-type granitoids mainly derived from remelting of ancient crustal material, with a greater juvenile crustal or mantle contribution in the younger phase. Magnetite is generally Zn-rich and Pb-poor, whereas late pyrite and chalcopyrite are enriched in Pb, Ag, Cd, and Bi; local Sb–As anomalies in magnetite and arsenopyrite indicate late hydrothermal overprinting. The Fe and Pb–Zn mineralization is best interpreted as staged products of one multipulse magmatic–hydrothermal system controlled not only by intrusive pulses but also by inherited structural pathways, host-rock reactivity, and evolving redox-sulfidation conditions. The interpretation of Sb–As enrichment in magnetite is therefore used cautiously because these elements may occur as lattice substitutions and/or micro- to nano-inclusions introduced or modified during retrograde alteration. Full article

The Huomaxie granite in Ningdu, southern Jiangxi Province, is located in the central part of the Cathaysia Block. Previous studies assigned this pluton to the Huitong batholith as S-type granite, but lacked precise geochronological and petrogenetic constraints. This paper presents systematic petrography, whole-rock geochemistry, zircon U–Pb dating, in situ Hf isotopic analysis, and electron microprobe analysis (EPMA) of muscovite from the muscovite monzogranite of the pluton. The weighted mean ²⁰⁶Pb/²³⁸U age is 420.1 ± 3.1 Ma. The rocks are silicic, high-K calc-alkaline, and peraluminous S-type granites. Zircon ε_Hf(t) values range from −15.0 to −11.8, with two-stage Hf model ages (T_DM2) of 2360–2150 Ma. Geochemical characteristics and muscovite composition data indicate that the magma was derived from high-temperature partial melting of psammitic sedimentary rocks. Tectonic discrimination diagrams suggest that the pluton formed in a post-orogenic extensional setting. It was generated by lower crustal melting induced by asthenospheric upwelling. Full article

The South Tianshan Orogenic Belt, as the southernmost part of the Central Asian Orogenic Belt (CAOB), records the final closure of the Paleo-Asian Ocean and the subsequent collision between the Tarim Craton and the Central Tianshan–Yili Block. However, the timing of this collision and the subduction polarity of the South Tianshan Ocean remain controversial. In this study, we present integrated detrital zircon U-Pb geochronology, Lu-Hf isotopes, and rare earth element (REE) geochemistry for Carboniferous to Permian sedimentary rocks from the northern Tarim Craton and the South Tianshan Orogenic Belt. Our results show that the detrital zircon age spectra are dominated by peaks at ~290 Ma, ~420 Ma, ~640–620 Ma, ~840–830 Ma, and ~1900–1800 Ma, with a notable scarcity of 380–310 Ma zircons. The ε_Hf(t) values of Paleozoic zircons are predominantly negative, consistent with the magmatic records of the Tarim Craton but distinct from those of the Central Tianshan–Yili Block. These provenance signatures indicate that most of the Carboniferous–Permian sedimentary rocks were derived from the Tarim Craton, with only a minor mixed-source component (e.g., the Balikelike Formation silty limestone) involving the Central Tianshan–Yili Block. The absence of significant 380–310 Ma detrital zircons in the foreland strata, together with the passive margin affinity of the northern Tarim, supports northward subduction of the South Tianshan Ocean. A sharp decrease in detrital zircon r_Dz values and crystallization temperatures at ~310 Ma signals a tectonic transition from convergence to collision, constraining the final closure to the Late Carboniferous (~310 Ma). Furthermore, crustal thickness estimates based on zircon Eu anomalies remain stable at ~60 km across the subduction and collision stages, suggesting limited tectonic shortening and thus a soft collision. Full article

The southern region of the South China Block hosts a super-large metallogenic province. However, the Mesozoic differential metallogeny between the southern Cathaysia Block (W-Sn) and the southern Yangtze Block (Au-Sb) remains enigmatic. To characterize the crustal architecture beneath different metallogeny belts, we integrate 3239 published ε_Hf(t) values of synmagmatic zircons from Mesozoic igneous rocks and corresponding whole-rock ε_Nd(t) datasets to generate coupled Hf–Nd isotopic mappings. The results show that ε_Hf(t) values range from −19.3 to +11.6 (T_DM2: 464–2419 Ma) and ε_Nd(t) values are from −12.2 to +5.0 (T_DM2: 580–2008 Ma) in the southern part of South China Block. High ε_Hf(t) (−4~+11.6) and ε_Nd(t) (−4~+5.0) zones are concentrated along the Honghe Fault and Chenzhou–Linwu Fault systems, while low-value Hf–Nd isotopic (ε_Hf(t) = −10.6 to −4; ε_Nd (t) = −12.2 to −4) zones are mainly distributed in the interior of the southern Yangtze Block. The W-Sn deposits in the southern Cathaysia Block are genetically linked to the heterogeneous ε_Hf(t)-ε_Nd(t) isotopic domains. The ore-forming materials of these high-temperature W-Sn polymetallic deposits may primarily derive from crust hybrid magmas that have undergone multistage crustal reworking. In contrast, low-temperature Au-Sb deposits in the northern Youjiang basin are distributed in areas characterized by elevated ε_Hf(t)-ε_Nd(t) isotopic signatures, which are primarily derived from reworked crust with significant mantle contributions. Most magmatic rock-associated Au deposits tend to cluster at the boundaries of Hf-Nd isotopic anomalies, which indicates the contribution of crust-mantle interaction to Au mineralization. Our Hf-Nd isotopic mappings reveal that mantle-crust deep-seated process controls the Mesozoic differential metallogeny between the southern Cathaysia Block (W-Sn) and the southern Yangtze Block (Au-Sb). Full article

The Arkansas Alkaline Province (AAP) is made up of intrusive bodies throughout central Arkansas, one of which is a nepheline syenite body called Granite Mountain. The crystallization age and origin of nepheline syenites from Granite Mountain are still uncertain, in part due to the rarity of zircon grains in silica-undersaturated rocks, such as nepheline syenite. This study reports new zircon U-Pb ages and trace element contents from three nepheline syenite samples from Granite Mountain. The zircon U-Pb ages of these samples are 90.4 ± 0.6 Ma, reflecting the crystallization age for nepheline syenite from Granite Mountain. Zircon rare-earth element patterns display remarkable positive Eu anomalies, indicative of their mantle affinity. Whole-rock geochemical characteristics include depleted Nd–Hf isotopic compositions, high ²⁰⁶Pb/²⁰⁴Pb ratios (19.5), and positive Nb-Ta anomalies. Their Sr-Nd-Pb-Hf isotopic compositions and trace element ratios display characteristics of ocean island basalts (OIBs). The probable magmatic source of these samples is a mixture of enriched mantle 2 (EM2) and high ²³⁸U/²⁰⁴Pb (HIMU). Taken together, the geochemical data, in particular, the HIMU signature, suggest that the Granite Mountain nepheline syenites formed within a mantle plume (likely Bermuda) tectonic setting at 90.4 Ma, although a rifting origin cannot be ruled out. Full article

The Mesozoic dykes in the Xingcheng area of western Liaoning Province in China were investigated through an integrated study involving zircon U–Pb geochronology, whole-rock geochemistry, and zircon Hf isotopic compositions to elucidate their emplacement phases, petrogenesis, and tectonic setting. The dykes are classified into two groups: felsic (granite porphyry, granite aplite) and mafic (diabase, lamprophyre). Emplacement occurred in four discrete phases: Late Triassic (229–212 Ma), Early Jurassic (ca. 179 Ma), Late Jurassic (162–152 Ma), and Early Cretaceous (133–102 Ma). The felsic dykes are characterized by high SiO₂ and alkali contents, low TFeO and MgO abundances, and belong to the high-K calc-alkaline I-type granite series. The mafic dykes exhibit low SiO₂, elevated MgO, and high Na₂O contents, displaying both alkaline and calc-alkaline affinities. Both dyke suites are consistently enriched in light rare earth elements (LREEs) and large-ion lithophile elements (LILEs), and depleted in heavy rare earth elements (HREEs) and high field-strength elements (HFSEs). Zircon ε_Hf(t) values for the felsic dykes range from −22.3 to −7.4, corresponding to two-stage model ages (T_DM2) of 2613–1729 Ma, indicating derivation from partial melting of Neoarchean to Paleoproterozoic crustal material. Late Jurassic mafic dykes yield ε_Hf(t) values between −27.8 and −20.2, consistent with an origin from partial melting of enriched lithospheric mantle. In contrast, Early Cretaceous mafic dykes display a bimodal ε_Hf(t) distribution (−12.9 to −9.5 and +4.3 to +8.4), suggesting a predominant enriched mantle source with variable inputs from depleted mantle components. Integrated with regional tectonic reconstructions, the data indicate that the Xingcheng area evolved within a post-collisional extensional regime following the amalgamation of the North China Craton and the Central Asian Orogenic Belt during the Late Triassic. The Jurassic magmatic pulses are attributed to an active continental margin setting associated with subduction of the Paleo-Pacific Plate, whereas the Early Cretaceous phase reflects regional extension triggered by rollback of the subducting Paleo-Pacific slab. Full article

The southern margin of the Beishan orogen is a key region hosting mafic–ultramafic intrusions and Cu-Ni sulfide deposits, yet previous studies have focused mainly on the Xinjiang segment, leaving the eastern extension in Gansu Beishan poorly constrained. To constrain the emplacement age, tectonic setting and assimilation–contamination of the mafic–ultramafic intrusions in the Chengxuan area, and to address the research gaps regarding Cu-Ni sulfide mineralization and magmatic evolution, this study conducted systematic petrographic, geochronological, and whole-rock geochemical and isotopic analyses of the Chengxuanbei intrusions. The intrusions are dominated by olivine gabbro and gabbro facies, with the sulfides predominantly hosted in the olivine gabbro and gabbro; zircon U-Pb dating yields a weighted mean age of 283.5 ± 0.85 Ma, corresponding to the Early Permian. The rocks exhibit pronounced negative Nb-Ta and moderate negative Zr-Hf anomalies, indicating magma derivation from partial melting of the mantle wedge metasomatized by subduction fluids, and high-field-strength element diagrams reveal an island arc calc-alkaline basalt affinity, reflecting a subduction-related extensional setting (e.g., back-arc extension) during the Early Permian. The Sr-Nd-Hf isotopes suggest crustal contamination during magma ascent, while the δ³⁴S values indicate input of crust-derived sulfur; the olivine Fo values (79.8–81.0) and Ni contents (573–1320 ppm) indicate sulfide saturation and Ni extraction processes. A regional correlation confirms that the Chengxuanbei intrusion has favorable magmatic Cu-Ni metallogenic conditions and great exploration potential, providing pivotal theoretical support for Early Permian Cu-Ni prospecting in the southern Beishan belt. Full article

The giant Dulong Sn-Zn polymetallic deposit, located in the eastern part of the southeastern Yunnan metallogenic belt, is a world-class ore system. Despite extensive research on the source of tin and its mineralization processes, the specific ore-related intrusion and the source of copper remain highly debated. Recent deep exploration has revealed a deep-seated granite porphyry, yet its geochronological and geochemical characteristics, along with its genetic link to mineralization, are poorly constrained. This study presents new zircon U-Pb age, whole-rock geochemistry, and Sr-Nd-Hf isotopic compositions of this granite porphyry, integrated with a regional comparison to multi-phase Laojunshan granites. LA-ICP-MS zircon U-Pb dating yields a Late Cretaceous age of 85.1 ± 1.2 Ma. The Dulong granite porphyry is strongly peraluminous and high-K calc-alkaline to shoshonitic, exhibiting typical S-type granite affinities with enrichment in Rb, U, and Ta, as well as depletions in Ba, Sr, Nb, and Eu. Isotopic signatures (ε_Nd(t) = −12.5 to −12.0, t_DM2(Nd) = 1.87 to 1.91 Ga; zircon ε_Hf(t) = −10.24 to −1.44, t_DM2(Hf) = 1.24 to 1.79 Ga) suggest that the parental magma was derived from the partial melting of ancient crust, with possible minor input of mantle-derived components in an extensional tectonic setting. The Dulong granite porphyry represents a moderate-to-high temperature, reduced, and highly evolved magmatic system. Notably, its high concentrations of Sn, W, Zn, and Cu indicate that the parental melt was metal-rich, possessing potential for Sn and Cu mineralization. Accordingly, future exploration should prioritize areas characterized by well-developed granite porphyry dykes, skarn–wallrock contact zones, and deep-seated structural intersections. Full article

Late Jurassic–Early Cretaceous silicic volcanism is widespread along the Southeast China continental margin, yet the timing, magma plumbing, and geodynamic drivers of individual volcanic centers remain debated. Here, we integrate whole-rock geochemistry with zircon U–Pb geochronology, zircon trace elements, and in situ zircon Lu–Hf isotopes for high-silica rhyolites from the Bijiashan volcanic complex, eastern Guangdong, to constrain magmatic evolution and its link to Paleo-Pacific subduction dynamics. LA–ICP–MS zircon U–Pb analyses were used to define two dominant crystallization populations: 145.4 ± 1.2 Ma (n = 14; MSWD = 1.7) for sample BJS-18 and 141.4 ± 1.3 Ma (n = 14; MSWD = 1.6) for sample BJS-27, yielding dominant zircon U–Pb age populations of 141.1–145.4 Ma, thereby constraining the timing of the main silicic volcanism (magma crystallization immediately preceding eruption) to the Jurassic–Cretaceous boundary. Minor older peaks at 157.0 ± 1.6 Ma (BJS-18) and 153.1 ± 1.5 Ma (BJS-27) suggest antecrystic or inherited components from a long-lived trans-crustal magmatic system. Whole-rock data indicate subalkaline, high-K calc-alkaline rhyolitic affinities, with apparent peraluminous signatures affected by post-magmatic alkali mobility. The rhyolites are characterized by pronounced negative Eu anomalies (Eu/Eu* = 0.085–0.395), low Sr contents (5.9–29.0 ppm), and arc-like trace-element signatures with Nb–Ta–Ti depletions. Zircon trace elements indicate crystallization temperatures of 608–842 °C and redox states from ΔFMQ = −3.90 to +1.71, with syneruptive grains clustering near FMQ ± 1 and xenocrystic grains systematically more reduced and hotter, implying vertically and temporally zoned magma storage. Zircon εHf(t) values (−7.4 to −0.9) and Mesoproterozoic TDM2 ages (1.18–1.66 Ga) indicate substantial reworking of ancient Cathaysian crust. In contrast, the relatively radiogenic upper εHf(t) values and the occurrence of mafic lithic fragments suggest limited juvenile or mantle-derived input into the crust-dominated magmatic system. Together with tectonic discrimination diagrams indicating a continental arc affinity, these results support Early Cretaceous arc-related silicic magmatism during a regional transition from compression to extension, plausibly linked to Paleo-Pacific slab rollback beneath Southeast China. Full article

The Cretaceous represents a key period in the geodynamic evolution of the Tibetan Plateau and the initial development of its paleotopography. While widespread orogenesis and magmatism associated with the Lhasa–Qiangtang collision are well documented in southern Tibet, coeval magmatic records in northern Tibet are extremely limited, hindering constraints on the deep processes responsible for surface uplift. Zircon U–Pb ages, whole-rock geochemistry, and Sr–Nd–Hf isotopes are presented for two mafic dyke swarms from the East Kunlun Orogen, northern Tibet. The two dyke swarms were emplaced at 91.8 ± 2.0 Ma and 84.8 ± 0.6 Ma, indicating a previously underrecognized episode of Late Cretaceous mafic magmatism in northern Tibet. They are subalkaline tholeiites enriched in LILEs and LREEs, depleted in HFSEs, and characterized by negative Nb–Ta anomalies. Their decoupled Nd-Hf isotopes (εNd(t) = −4.96 to +0.94; εHf(t) = +3.75 to +5.76) indicate derivation from an enriched lithospheric mantle metasomatized by slab-related fluids during Permian-Triassic Paleo-Tethyan subduction. Partial melting modeling indicates that the magmas were generated by low-degree (1–5%) decompression melting of lherzolite within the spinel–garnet transition zone. We propose that these mafic dyke swarms formed in an intraplate extensional setting triggered by far-field stresses associated with the Lhasa–Qiangtang collision, which reactivated lithosphere-scale faults and induced localized mantle melting. These results provide new petrological constraints on Late Cretaceous intracontinental extension in northern Tibet and highlight mafic dyke swarms as key probes for linking lithospheric reactivation to early surface uplift of the Tibetan Plateau. Full article

Granites associated with hydrothermal uranium deposits provide critical insights into the processes governing uranium enrichment and mobilization within the continental crust. The Yangjiaonao deposit, situated in the Lujing ore field within the Nanling Metallogenic Belt (South China), is a typical granite-related hydrothermal vein-type uranium deposit. This study presents integrated zircon U-Pb geochronology, whole-rock geochemistry, whole-rock Nd isotopes and zircon Hf isotopes for the medium-to-coarse-grained porphyritic biotite (MCB) and medium-to-fine-grained two-mica (MFM) granites from the Yangjiaonao (YJN) granitic pluton. Both units yielded Triassic ages (~235–233 Ma), indicating synchronous emplacement during the Early Mesozoic period. However, they exhibit distinct metallogenic fertilities rooted in their petrogenesis. MCB granite, derived from greywacke-dominated sources, shows typical S-type characteristics, whereas uranium remained mineralogically sequestered in refractory accessory phases (e.g., zircon, monazite) during differentiation, evidenced by high and stable Th/U ratios. Conversely, MFM granite represents L-type peraluminous systems originated from felsic, arkose-like protoliths. Advanced fractionation in the MFM system triggered significant Th-U decoupling, driving Th/U ratios down to ~0.5 and promoting uranium enrichment in the residual melt. This differentiation-driven concentration of ‘leachable’ uranium identifies MFM granite as the primary fertile source for the Yangjiaonao hydrothermal mineralization. Full article

The Arco Verde Complex, exposed in the Serra do Inajá region of the Rio Maria Domain (Carajás Province, Amazonian Craton), represents one of the oldest TTG granitoid association of the province (3.00–2.92 Ga). While TTG magmatism is well constrained in the northern domain, its southern sector lacks precise geochronological data. This study integrates petrographic, geochemical, U–Pb zircon geochronology, and Nd–Hf isotopes to constrain the age, source, and crustal significance of these granitoids. Uranium–Pb zircon dating of two granodiorites yielded ages of 2979 ± 8 and 2979 ± 11 Ma, extending the 2.98 Ga TTG magmatic episode to the southern sector of the Rio Maria Domain. Geochemical data indicate dominant tonalites formed by partial melting of a similar mafic source at different crustal depths, whereas subordinate granodioritic and monzogranitic rocks show transitional TTG affinities. These features indicate coeval mafic and felsic crust rapidly reworked after formation. Hf and Nd model ages of 3.0–3.2 Ga, with positive ε_Hf–Nd at 2.98 Ga, reinforce the Early Mesoarchean as the main crustal growth period in the province. In addition, we propose that the differentiation of the depleted mantle (DM) beneath the Carajás Province may have initiated around 3.8 Ga. Full article

Baixintan is a magmatic Ni–Cu sulfide deposit discovered in the central Tuwu–Yandong porphyry Cu belt of the Eastern Tianshan Orogen (ETO) of NW China in 2016. It is in close proximity (~5 km) to the Tuwu Cu deposit, the largest Carboniferous porphyry Cu deposit (~336 Ma) in Xinjiang. The Baixintan Ni–Cu ore is characterized by a high Cu/Ni ratio, but the reason for it remains unclear. To resolve this question, we present petrographic, geochronological, whole-rock geochemical, and S, Pb, Cu, and Lu–Hf isotopic data. Ore-related hornblende olivine websterite (HOW) and hornblende olivine gabbro (HOG) were emplaced at 296.6 ± 1.1 Ma and 289.7 ± 1.2 Ma, respectively, which were formed in an Early Permian post-collisional extensional setting. Whole-rock Pb and zircon Lu–Hf isotopes suggest that the parental magmas were predominantly mantle-derived. The Baixintan HOW and HOG contain abundant hornblende and are enriched in LILEs and LREEs but depleted in HFSEs, suggesting subduction-related metasomatism in their magma source. The sulfide (chalcopyrite, pyrrhotite, and pentlandite) δ³⁴S values cluster around 0‰ (–0.13 to 0.11, n = 11), and the chalcopyrite has uniformly negative but variable δ⁶⁵Cu values (–0.96 to –0.13, n = 6), which suggest that the ore-forming materials were mainly derived from the subduction-metasomatized mantle. Olivine Ni contents are significantly lower than those crystallized under sulfide-unsaturated conditions, implying that olivine fractional crystallization was an important trigger for sulfide melt segregation at Baixintan. Baixintan is the only known magmatic Ni–Cu sulfide deposit in the ETO that shares a Cu-preconcentrated, metasomatized mantle source with a giant porphyry Cu system. Copper pre-enrichment in the magma source may be the main factor for the relatively high Cu/Ni ratio observed in the Baixintan deposit. Full article