Search Results (460)

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

The lamprophyre dikes and multi-generational pyrite and arsenopyrite developed in the Jinshan gold deposit in the West Qinling metallogenic belt provide critical evidence for understanding the role of mantle-derived magmatism in gold mineralization processes. In this study, we conducted zircon U-Pb dating of lamprophyre to constrain the timing of magmatic activity and the mineralization age, and performed EMPA and LA-ICP-MS analyses on sulfides from the main metallogenic stage (Py II–III, Apy II–III) and lamprophyre-hosted pyrite (Py L) to constrain the formation conditions and metal sources of the Jinshan deposit. The results show that the mantle-derived magmatism represented by lamprophyre yields an age of 206 ± 2 Ma, which provides a lower-limit constraint on the timing of gold mineralization, corresponding to the subduction-to-extension transition period in the region. Stage II mineralization occurred at 270–320 °C with logƒS₂ of −9 to −5, dominantly as Au-HS complexes, indicating medium-temperature hydrothermal conditions with low sulfur fugacity, consistent with microscopic mineral assemblages and thermodynamic simulations. Systematic δ³⁴S variations reveal: stage II values (9.24–5‰) indicate granitic/Devonian sedimentary sources; Py L values (2.19–3.6‰) reflect mantle contributions; stage III signatures (−2.3–1.93‰) record late meteoric water mixing. Complementary δ⁵⁶Fe data show that Py II (0.2–0.3‰) and Py L (0.58–0.68‰) preserve magmatic fingerprints, while negative values of Py III (−2.29 to −0.71‰) document increasing sedimentary Fe incorporation. Combined with geochronology, S-Fe isotopes, and physicochemical constraints, we propose that the Jinshan gold deposit formed in a tectonic setting transitioning from compression to extension during the Late Indosinian (ca. 237–201 Ma). Mineralization was initiated by the partial melting of the metasomatized mantle, where hydrous magmas efficiently extracted Au and volatiles. These components ascended through transcrustal faults, with Au partitioning into exsolved fluids that precipitated gold through immiscibility and boiling in secondary structures. Full article

Early Cretaceous volcanic rocks are widely developed in the Longzi area, southern Tibet. Their petrogenesis and tectonic setting are important for understanding the initial breakup of eastern Gondwana and its deep geodynamic mechanisms. This study integrates field observations, petrography, zircon U-Pb geochronology and trace elements, whole-rock major and trace element geochemistry, and Sr-Nd-Pb isotopes to investigate the origin and tectonic significance of these rocks. The analyzed suite comprises diabase and rhyolite, with no intermediate compositions in the studied samples, thus defining a mafic–felsic volcanic association. Zircon U-Pb ages indicate Early Cretaceous magmatism at 132–138 Ma for the diabase and 132–134 Ma for the rhyolite. Geochemically, the mafic rocks are enriched in LREEs and HFSEs and display OIB-like trace-element characteristics, with ε_Nd(t) values ranging from −0.2 to +4.4, indicating derivation from low-degree partial melting of a spinel–garnet lherzolite source modified by limited interaction with the lithospheric mantle. The felsic rocks show pronounced negative Eu anomalies, A-type granite affinities, and ε_Nd(t) values ranging from −12.2 to −11.9, indicating derivation mainly from partial melting of upper-crustal materials. The marked geochemical and isotopic contrast between the mafic and felsic rocks argues against simple fractional crystallization from a common parental magma. Combined with regional geological data, these results indicate that the Longzi mafic–felsic volcanic association formed in an intraplate extensional setting related to Kerguelen-plume thermal input during the initial breakup of eastern Gondwana. 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

The Ailinwudui gold deposit is located in central Jilin Province and represents a newly discovered typical vein-type gold deposit hosted in a Paleozoic metamorphic rock series in recent years. At present, the metallogenic epoch and regional metallogenic tectonic setting of the deposit remain poorly constrained, which seriously restricts the understanding of gold metallogenic regularities and subsequent mineral exploration deployment in central Jilin. Previous studies indicate that the Ailinwudui gold deposit is a structurally controlled vein-type gold deposit. In this study, zircon U-Pb and muscovite ⁴⁰Ar/³⁹Ar geo-chronology were employed to precisely constrain the metallogenic timing of the gold mineralization. Zircon U-Pb dating yields an emplacement age of 174.7 ± 0.85 Ma for the granodiorite and a formation age of 209.5 ± 1.40 Ma for the rhyolite porphyry. Muscovite ⁴⁰Ar/³⁹Ar dating yields a plateau age of 180.39 ± 1.83 Ma, which confines the gold mineralization to the Early–Middle Jurassic. Whole-rock geochemical results reveal that the granitoids in the study area are enriched in large-ion lithophile elements (LILEs) and light rare earth elements (LREEs) and depleted in high-field-strength elements (HFSEs), showing typical arc-related magmatic affinities. The formation of this gold deposit is related to the subduction of the Paleo-Pacific Plate during the Early–Middle Jurassic. The research results can provide important geochronological and geochemical evidence for the study of gold metallogenic mechanisms and mineral exploration in central Jilin Province. Full article

The Oligocene–Miocene magmatic rocks extensively developed in the Gangdese magmatic belt are key records of the post-collisional tectono-magmatic evolution of the Tibetan Plateau. In this study, petrological, zircon U-Pb geochronological, zircon Hf isotopic and whole-rock geochemical investigations were carried out on two granitic porphyry stocks exposed in the Chunzhe area of the middle Gangdese belt. LA-ICPMS zircon U-Pb dating, cathodoluminescence (CL) images and trace element characteristics indicate that the granitic porphyries were emplaced at 11.8 ± 0.2 Ma (MSWD = 1.1) and 11.5 ± 0.1 Ma (MSWD = 1.2), with a small number of zircon grains yielding ²⁰⁶Pb/²³⁸U ages of 51.1~59.5 Ma, 29.8 Ma and 19.4~12.2 Ma, which are interpreted as inherited or captured zircon components. The analyzed samples are monzogranite porphyries composed mainly of quartz, plagioclase and alkali feldspar, with variable secondary white mica/sericite. In whole-rock composition, they display high-K calc-alkaline and weakly peraluminous characteristics. These rocks are enriched in large-ion lithophile elements (LILEs) such as Ba, Sr and Rb, and relatively depleted in Nb-Ta-Ti as well as Cr and Ni. They show light rare earth element (LREE) enrichment and heavy rare earth element (HREE) depletion, with distinctly high chondrite-normalized La/Yb ratios (31.05~71.25) and Sr/Y ratios (35.90~49.07), and a positive correlation between the LREE/HREE ratio and La content, indicating robust adakite-like trace element characteristics. Zircon εHf(t) values of the Miocene magmatic rocks range from −4.44 to 2.41, corresponding to two-stage Hf model ages of 1380~944 Ma, suggesting that the magmas were mainly derived from juvenile continental crust materials with the addition of a small amount of ancient continental crust materials. Combined with the regional geological setting, the Chunzhe Miocene granitic porphyries were most likely generated by partial melting of the thickened lower crust in the Gangdese belt during the late stage of Oligocene–Miocene post-collisional magmatism; local lower-crustal delamination may also have contributed, although this is not uniquely constrained by the present dataset. Full article

The late Paleogene White River Group is a post-Laramide sedimentary succession that occurs within Laramide intermontane basins and atop some basement-cored uplifts. Detrital zircon U-Pb dates of tuffaceous sandstones from the uppermost White River Group in eastern Wyoming and western Nebraska yield a maximum depositional age of 23.07 ± 0.46 Ma, which overlaps the emplacement of the Markagunt Gravity Slide in Utah’s Marysvale Volcanic Field at 23.05 + 0.22/− 0.20 Ma. The Marysvale Volcanic Field (~31–18 Ma) lies at the east margin of the Nevadaplano, a longstanding highland in the Sevier Hinterland later dismembered by basin and range extension. Strata both proximal and distal to the Marysvale Volcanic Field show an increase in Marysvale provenance up to the emplacement of the Markagunt Gravity Slide. After emplacement, distal sediment sourcing of Miocene strata in the Great Plains shifted back to older Paleogene volcanic fields farther west in Nevada. This temporal relationship suggests that the collapse of the Marysvale Volcanic Field associated with the emplacement of the Markagunt Gravity Slide forced drainage reorganization and sediment sourcing during the transition from White River to Arikaree Group sedimentation. Full article

Investigation of deposystems, sediment routing, and basin architecture during Gondwana breakup refines understanding of Permian–Cretaceous landscape evolution in the central Andes. New chronostratigraphic and provenance constraints from the Eastern Cordillera and Subandean Zone of Bolivia (19–22°S) are based on U-Pb geochronology of detrital and volcanic zircons and ⁴⁰Ar/³⁹Ar dating of interbedded basalts. A discontinuous <2 km-thick Permian–Cretaceous succession records deposition in fluvial, lacustrine, alluvial fan, eolian, and shallow marine environments. Stratigraphic correlations indicate alternations between isolated half-graben subbasins and regional, non-compartmentalized basins. Detrital zircon age spectra from 18 sandstones document sediment recycling from western orogenic and magmatic arc sources and eastern cratonic basement. Synextensional successions of Early Triassic, Early Jurassic, and mid-Cretaceous age were sourced mainly from the west, including Carboniferous and Devonian rocks, while post-extensional fluvial and eolian systems were derived chiefly from the eastern craton. Variations in thickness, facies, and mafic magmatism reflect alternating extensional and neutral tectonic regimes, with localized synextensional subsidence potentially linked to extensional collapse, mantle plume activity, and South Atlantic opening. Comparison with Andean regions in Peru and Argentina indicates that episodic extension and post-extensional thermal subsidence accompanied subduction along the western margin of South America during Gondwana-Pangea breakup. Full article

The reliability of bulk geochemical proxies for provenance analysis in heterogeneous clastic systems remains a critical yet underexplored issue. This study investigates the Lower Permian Shanxi Formation in the Southern North China Basin (SNCB) using an integrated approach combining major and trace element geochemistry, rare earth elements (REEs), and detrital zircon U–Pb geochronology. The results show that major element compositions have been significantly modified by diagenetic processes in tidal flat environments, limiting their applicability in tectonic discrimination. In contrast, immobile trace elements and REE patterns provide more robust constraints on source rock composition, suggesting predominantly felsic upper continental crustal sources. Detrital zircon age spectra reveal two dominant populations at 290–440 Ma and 1800–2500 Ma, indicating mixed provenance from the North Qinling Region (NQR) and the North China Craton (NCC). However, the application of classical discrimination diagrams is challenged by lithological heterogeneity, as the mixed presence of sandstone, sandy mudstone, and mudstone introduces compositional bias. Spatial variations among wells suggest differential contributions from continental island arc and active continental margin, likely controlled by paleogeographic configuration and sediment transport pathways. This study emphasizes the necessity of multi-proxy integration for reliable provenance reconstruction in complex sedimentary systems. Full article

The Zhongdian Arc is an important copper polymetallic ore cluster in China’s Sanjiang Tethyan Metallogenic Domain, and the Langdu deposit is a representative porphyry–skarn Cu deposit in this region. This study aims to constrain the timing of magmatic activity at the Langdu deposit. It also seeks to reveal the magma’s physical–chemical properties and evolution, and to identify the factors controlling mineralization. To achieve these objectives, this study used LA-ICP-MS zircon U-Pb dating and elemental analysis, combined with halogen and trace element data from apatite. Zircon U–Pb dating shows that the Langdu intrusions were emplaced at ca. 216 Ma in a continental arc setting associated with the westward subduction of the Garzê–Litang oceanic crust during the Late Triassic. Geochemical and mineralogical features indicate that the Langdu intrusions are I-type granite. They originated from partial melting of the mantle wedge metasomatized by subduction fluids. During their ascent, these magmas experienced fractional crystallization dominated by amphibole, titanite, rutile, and monazite. Geochemical records from zircon and apatite further reveal that the ore-forming magma of the Langdu intrusions exhibited high oxygen fugacity (ΔFMQ = +1.53), elevated H₂O content (avg. 7.63 wt.%), and enrichment in S (avg. 560 ppm) and Cl (avg. 2141 ppm). This Cl-rich magma experienced fluid exsolution during its early evolutionary stage. This provided the necessary conditions for metal extraction and transport. In summary, the key factors controlling the formation of the Langdu porphyry–skarn Cu deposit are high-oxygen-fugacity magma enriched in water and volatiles (S and Cl), coupled with efficient fluid exsolution. This understanding is important for better understanding regional metallogeny and for guiding mineral exploration. Full article

The Late Jurassic–Early Cretaceous Oloy complex was formed in the setting of convergence between the Chukotka microcontinent and the Kolyma–Omolon margin. Its evolution reflects the closure of the South Anyui Ocean, with controversial timing estimates. This study emphasizes the integration of lithological data with magmatic and metallogenic information to reconstruct geodynamic processes. The article presents the results of detailed petrographic and geochemical studies, Sm-Nd isotope analyses, and U-Pb dating of detrital zircons from Kimmeridgian–Lower Hauterivian volcaniclastic and epiclastic sandstones. Petrographic studies and U-Pb dating of detrital zircons identified the main sources at different stages and the amount of synchronous pyroclastic material. Isotope-geochemical investigations suggest a young undifferentiated arc provenance for Kimmeridgian deposits, whereas Tithonian–Valanginian sediments accumulated due to the erosion of more differentiated igneous rocks and input of clastic material from the continent. New data on changes in sedimentation environments and provenance enabled the tracing of the evolution of the Oloy arc. In the Kimmeridgian, the Oloy island arc existed on a heterogeneous basement, with south-dipping subduction towards the Kolyma–Omolon margin. During the Late Tithonian, the arc accreted and magmatic activity continued in the active margin setting. Collision initiated in the latter half of the Berriasian, reaching its active phase in the Valanginian time. Full article

The subduction polarity of the Mongol–Okhotsk Ocean (MOO) during the Mesozoic remains contentious, with competing models advocating for southward, northward, or bidirectional subduction. The Xifengshan area in the northern Great Xing’an Range, located south of the Mongol–Okhotsk suture, preserves Early–Middle Jurassic calc-alkaline intrusions, which provides important constraints on this debate. We present zircon U–Pb ages, whole-rock geochemistry, and Lu–Hf isotopes for diorite, granodiorite, and monzogranite from this area. Zircon U–Pb dating yields ages of 178–173 Ma, defining a short-lived magmatic pulse. The suite is calc-alkaline, enriched in LILE and depleted in Nb–Ta–Ti, typical of arc magmas. The diorite represents the most mantle-proximal preserved end-member of the system and records substantial mantle input from a slab-modified mantle wedge. Geochemical trends (increasing Rb/Th, decreasing Sr with differentiation) reflect plagioclase-dominated fractional crystallization with minor AFC. Local adakitic-like signatures are better interpreted as differentiation-related effects than as direct evidence for slab melting. Zircon εHf(t) values (+1.62 to +11.55) and T_DM1 ages (363–772 Ma) are greater than the crystallization ages, indicating substantial juvenile input together with the variable involvement of previously accreted crustal components. We suggest that mantle wedge-derived magmas modified by slab-related components triggered the partial melting of the arc crust, whereas subsequent intracrustal differentiation produced the observed intrusive sequence. The continental arc system provides robust evidence for the southeastward subduction of the MOO during the Early–Middle Jurassic, resolving the long-standing polarity controversy. Full article

Submarine volcanic-hosted iron oxide deposits are critical archives for reconstructing the interplay between hydrothermal activities and marine redox conditions, yet the genesis of these deposits remains controversial. Here, we present a comprehensive geochronological and geochemical study on the Shikebutai iron deposit in the Western Tianshan, northwestern China, to constrain the mineralization age, the source of iron, and deposit genesis. The stratiform-to-lenticular orebodies are hosted within the Late Carboniferous marine volcanic–sedimentary sequence of the Yishijilike Formation. The iron ores consist primarily of hematite and quartz, with minor siderite and barite, exhibiting massive to locally banded textures. SHRIMP zircon U-Pb dating of the overlying andesite yields an age of 315.8 ± 1.5 Ma, consistent with the Sm–Nd isochron age of the iron ore samples (319 ± 26 Ma), precisely constraining the mineralization age to the Late Carboniferous (ca. 315–320 Ma). The geochemical compositions of the iron ore samples indicate negligible syn-depositional detrital contamination, as evidenced by low Al₂O₃ (<1.00 wt%) and TiO₂ (<0.20 wt%) contents. Low abundances of trace elements, including Sr (0.33–31.18 ppm), Hf (0.05–1.77 ppm) and Rb (1.49–39.02 ppm), further support the minimal detrital influence. Geochemical signatures, such as pronounced positive Eu anomalies (Eu/Eu = 1.62–7.12, mean 4.14), LREE enrichment ((La/Yb) _(PAAS) = 0.58–4.78), and near-chondritic Y/Ho ratios (mean 28.5), suggest a significant high-temperature (>250 °C) hydrothermal contribution. Moreover, the ε_Nd(t) values of iron ore samples (+1.99 to +2.93) are comparable to those of coeval andesites (+2.75 to +3.44) but exceed those of associated metasiltstones (+0.41 to +0.95), suggesting that ore-forming materials were derived from hydrothermal fluids leaching juvenile crust. The Shikebutai iron deposit exhibits geochemical and mineralogical similarities to modern Red Sea and East Pacific Rise metalliferous sediments, establishing the deposit as a product of active vent-proximal hydrothermal systems rather than marine chemical sediments such as banded iron formations. Full article

The timing of uranium mineralization in the Xiangshan ore field has long been controversial. Although various geochronometers have been applied by previous researchers, including pyrite Rb-Sr, mica Ar-Ar, and fluorite Sm-Nd, the results remain inconsistent and inconclusive. In recent years, the discovery of abundant Pb-Zn veins in the deeper parts of the Xiangshan ore field has further complicated the interpretation of its metallogenic history. In this study, abundant vein-type hydrothermal apatites closely associated with U-Pb-Zn polymetallic mineralization were identified in both uranium and Pb-Zn ore veins. Combined major-element Electron Probe Microprobe Analysis (EPMA), Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) U-Pb dating, and trace-element analysis were conducted on these apatite grains. The results suggest a mineralization age of 130.9 ± 1.1 Ma for the Shannan uranium deposit, which is consistent with the previously reported apatite U-Pb age of 131.3 ± 7.2 Ma from the Zoujiashan uranium deposit and coincides with the main pulse of volcanic-intrusive activity in the Xiangshan ore field (133–137 Ma). The deep Niutoushan Pb-Zn deposit suggests a younger mineralization age of 124.5 ± 1.3 Ma, which is consistent with a thermal event age of 125.6 Ma determined by zircon fission-track dating and the zircon LA-ICP-MS U-Pb age of late-stage granite porphyry (125.4 ± 1.0 Ma). These ages may constrain the timing of U-Pb-Zn polymetallic mineralization in the Xiangshan ore field. Both magmatic and hydrothermal apatites are classified as fluorapatite and exhibit similar chondrite-normalized rare earth element (REE) patterns. Compared with magmatic apatites, hydrothermal apatites are characterized by elevated Th, U, Ca, and Sr contents, depletion in light rare earth elements (LREEs), Mn, and Na, and distinctly lower Th/U ratios. On major-element variation diagrams, magmatic and hydrothermal apatites define coherent trends but display clear compositional differences related to their formation stages. Apatites from uranium ore veins show strongly negative Eu anomalies and weakly positive Ce anomalies, similar to magmatic apatites. In contrast, apatites from Pb-Zn ore veins display positive Eu anomalies and weakly negative Ce anomalies, with lower Mn and Ga contents and higher SO₃ contents relative to both magmatic apatites and hydrothermal apatites from uranium ore veins. These features indicate that the ore-forming fluids during Pb-Zn mineralization were characterized by significantly higher oxygen fugacity than those during uranium mineralization and magmatism. Combined with published Sr isotopic data for the Xiangshan ore field, we propose that both uranium and Pb-Zn mineralization were genetically linked to the prolonged magmatic evolution of the deep volcanic-intrusive complex. The subsequent incursion of meteoric water modified the physicochemical conditions of the ore-forming system, particularly during the formation of the Pb-Zn mineralization. Full article