Search Results (48)

The Wunuer deposit is an important hydrothermal Zn-Pb-Ag-Mo polymetallic deposit in the central Great Xing’an Range, NE China. The zinc–lead polymetal mineralization is closely hosted by the volcanic rocks of the Manketouebo formation (rhyolite and lithic crystal tuff) and related to the Mesozoic granite porphyry. Field evidence and petrographic observations have identified three mineralization stages within this deposit from deep to shallow: (1) late magmatic stage with vein-type Mo mineralization characteristics and mainly related to the deep granite porphyry; (2) magmatic–hydrothermal transition stage characterized by breccia-type Zn mineralization, which occurred within a steep cryptoexplosive breccia; and (3) hydrothermal stage featured by vein-type Zn-Pb-Ag mineralization hosted by the ore-bearing fractured zone. In this contribution, we present the mineralogy, zircon U-Pb age, sphalerite Rb-Sr dating, whole-rock geochemistry, and Hf-S-Pb isotopes of the Wunuer deposit. LA-ICP-MS zircon U-Pb dating of the ore-related granite porphyry, rhyolite, and lithic crystal tuff suggests that the Mo mineralization from the late magmatic stage occurred between 144.8 Ma and 145.8 Ma. The Rb-Sr isochron dating of sphalerite indicates that the hydrothermal stage Zn mineralization age is 121 ± 2.3 Ma, which is related to the volcanism of Baiyin’gaolao Formation in the Wunuer area. The concentrated and positive δ³⁴S_V-CDT values (0.17‰~5.40‰) of sulfides, as well as uniform Pb isotope compositions of granite porphyry intrusion and galena, jointly imply a magmatic source of metallogenic materials for Pb-Zn mineralization. Whole-rock geochemistry and Hf-Pb isotopes reveal that the granite porphyry and rhyolite both originated from a mantle-derived juvenile component and assimilated by minor ancient crustal material in an extensional setting. Our study demonstrates the prospect of further exploration for two mineralization events in the hydrothermal polymetallic deposits of the central Great Xing’an Range. Full article

Large-scale Mesozoic granites are widespread in the offshore area of eastern Shandong Province, China. This study aims to refine the granite classification and explore the degree of granite differentiation and ore-bearing potential in the study area. We conducted field investigations in Dazhushan, Xiaozhushan, and Laoshan plutons. The analytical methods included petrography, whole-rock geochemistry, Sr–Nd–Pb–Li isotopes, zircon U–Pb dating, in situ Hf isotopes, and microanalysis (LA-ICP-MS) of plagioclase. The results reveal high-silica (SiO₂ > 70%), highly differentiated (DI > 90) granites emplaced during the Early Cretaceous (113.12–121.78 Ma). Sr–Nd–Pb isotopes indicate magma derived from a crustal source (I_Sr = 0.7032–0.7242; εNd(t) = −12.45~−20.46). Critically, the spodumene-bearing Dazhushan granites exhibit high Li content with limited isotopic fractionation (δ⁷Li = 1.00–4.62‰; Li = 8.64–93 ppm), signaling high ore potential. In contrast, the Xiaozhushan granites are barren (δ⁷Li = 3.31–4.92‰; Li = 0.66–4.01 ppm). This study identified I-type (Laoshan) and I-S type (Dazhushan and Xiaozhushan) highly differentiated granites formed by plagioclase fractionation, with Dazhushan being the most promising for mineralization. Full article

The Baijianshan deposit is the sole skarn Zn-Cu polymetallic deposit in the Xiaoshitouquan ore field, Xinjiang, China. Its ore genesis remains controversial, which hinders understanding of the relationship between skarn-type Zn-Cu and adjacent epithermal Ag-Cu-Pb-Zn mineralization and consequently impedes further regional exploration. LA-ICP-MS U-Pb dating on zircons from the granite and granite porphyry from the mining area yielded ages of 311 ± 1.7 Ma and 312 ± 1.6 Ma, respectively. The corresponding zircon ε_Hf(t) values and T_DM ages are 8.7–9.9 and 624–555 Ma for the granite, and 7.2–9.9 and 673–552 Ma for the granite porphyry. These granites are metaluminous, high-K calc-alkaline I-type granites, with high LREE/HREE ratios (4.92–9.03) and pronounced negative Eu anomalies. They are enriched in K, Th, U, Zr, and Hf, with significant depletions in Sr, P, and Ti. Combined geological and geochemical evidence indicate that these Late Carboniferous granites were derived from the juvenile crustal and formed in subduction-related back basin. Two-phase aqueous inclusions in the ore-bearing quartz and calcite have homogenization temperatures ranging from 117 to 207 °C and 112 to 160 °C, respectively, with the salinities in the ranges of 0.18~7.17 and 0.53~5.26 wt% NaCl eq. The S and Pb isotopic compositions of sulfides in the ores indicate that the ore-forming metals were sourced from the medium-acidic magmatite. The δ¹⁸O_H2O and δD_H2O values of hydrothermal fluids range from −6.97% to −5.84% and −106.8% to −99.6%, respectively, suggesting that the ore-forming fluids originated from the mixing of magmatic and meteoric water. Fluid mixing and corresponding conductive cooling were identified as the principal mechanism triggering the metallic mineral precipitation. The Baijianshan skarn Zn-Cu polymetallic deposit shares contemporaneous magmatic-mineralization ages and analogous material sources with the epithermal polymetallic deposits in the Xiaoshitouquan ore field, collectively constituting a unified skarn-epithermal metallogenic system. This hypothesis indicates that the deep parts of the epithermal deposits within the Yamansu volcanic rocks possess potential for exploring the porphyry-skarn-type deposits. Full article

The Chaluo granite is situated in the middle section of the Yidun magmatic arc in western Sichuan Province, China. It holds great significance for the study of the geological evolution of the Paleo-Neotethys tectonic belts. The Chaluo granite mainly consists of alkaline feldspar, quartz, and biotite, with a small amount of apatite. LA-ICP-MS zircon U-Pb dating yielded crystallization ages of (87 ± 3) Ma for the Chaluo granite, indicating its formation in the Late Cretaceous. Elemental geochemical testing results showed that the Chaluo granite exhibits I-type granite characteristics. It has undergone significant fractional crystallization processes, with high SiO₂ contents (72.83–76.63 wt%), K (K₂O/Na₂O = 1.33–1.53), Al₂O₃ (Al₂O₃ = 12.24–13.56 wt%, A/CNK = 0.91–1.08), and a high differentiation index (DI = 88.91–92.49). Notably, the MgO contents were low (0.10–0.26 wt%), and there were significant depletions of Nb, Sr, Ti, and Eu, while Rb, Pb, Th, U, Zr, and Hf were significantly enriched. The total rare earth element (REE) contents were relatively low (211–383 ppm), showing significant light REE (LREE) enrichment (LREE/HREE = 4.46–5.57) and a pronounced negative Eu anomaly (δEu = 0.09–0.17). In situ zircon Hf analyses, combined with ²⁰⁶Pb/²³⁸U ages, gave ε_Hf(t) values ranging from −3.8 to 1.72 and two-stage Hf ages (t_DM2) of 875–1160 Ma. Together with the S and Pb isotope compositions of the Chaluo granite, its magma likely originated from the partial melting of Middle–Neoproterozoic sedimentary rocks enriched in biogenic S. The tectonic-setting analysis indicates that the Chaluo granite formed in a post-orogenic intracontinental extensional environment. This environment was triggered by the northward subduction-collision of the Lhasa block, followed by slab break-off and the upwelling of the asthenosphere in the Neo-Tethys orogenic belt. We propose that the Paleo-Tethys tectonic belt was influenced by the Neo-Tethys tectonic activity, at least in the Yidun magmatic arc region during the Late Cretaceous. Full article

The Southern Beishan Orogenic Belt (SBOB), an integral part of the Southern Central Asian Orogenic Belt (CAOB), is characterized by extensive Late Paleozoic magmatism. These igneous rocks are the key to studying the tectonic evolution process and the ocean–continent tectonic transformation in the southern margin of the CAOB and Paleo-Asian Ocean. We present zircon U-Pb chronology, in situ Lu-Hf isotopes, and whole-rock geochemistry data for Early–Middle Devonian volcanic rocks in the Sangejing Formation and granites from the Shuangyingshan-Huaniushan (SH) unit in the SBOB. The Wudaomingshiu volcanic rocks (Ca. 411.5 Ma) are calc-alkaline basalt-basaltic andesites with low SiO₂ (47.35~55.59 wt.%) and high TiO₂ (1.46~4.16 wt.%) contents, and are enriched in LREEs and LILEs (e.g., Rb, Ba, and Th), depleted in HREEs and HFSEs (Nb, Ta, and Ti), and weakly enriched in Zr-Hf. These mafic rocks are derived from the partial melting of the depleted lithosphere metasomatized by subduction fluid and contaminated by the lower crust. Wudaomingshui’s high-K calc-alkaline I-type granite has a crystallization age of 383.6 ± 2.2 Ma (MSWD = 0.11, n = 13), high Na₂O (3.46~3.96 wt.%) and MgO (1.25~1.68 wt.%) contents, and a high DI differentiation index (70.69~80.45); it is enriched in LREEs and LILEs (e.g., Rb, Ba, and Th) and depleted in HREEs and HFSEs (e.g., Nb, Ta, and Ti). Granites have variable zircon ε_Hf(t) values (−2.5~3.3) with Mesoproterozoic T_DM2 ages (1310~1013 Ma) and originated from lower crustal melting with mantle inputs and minor upper crustal assimilation. An integrated analysis of magmatic suites in the SBOB, including rock assemblages, geochemical signatures, and zircon ε_Hf(t) values (−2.5 to +3.3), revealed a tectonic transition from advancing to retreating subduction during the Early–Middle Devonian. Full article

A diverse range of granitoids in the North Qilian Orogenic Belt (NQOB) offers valuable insights into the region’s tectonomagmatic evolution. In this study, we undertook a geochronological, mineralogical, geochemical, and zircon Hf isotopic analysis of granodiorites from the Yaogou area of the NQOB. Zircon U-Pb dating reveals that the Yaogou granodiorites formed during the Early–Middle Ordovician (473–460 Ma). The Yaogou granodiorites have high SiO₂ (63.3–71.1 wt.%), high Al₂O₃ (13.9–15.8 wt.%) contents, and low Zr (96–244 ppm), Nb (2.9–18 ppm), as well as low Ga/Al ratios (10,000 × Ga/Al ratios of 1.7–2.9) and FeO^T/MgO ratios (1.9–3.2), and are characterized by elevated concentrations of light rare earth elements and large-ion lithophile elements such as Rb, Th, and U, coupled with significant depletion in heavy rare earth elements and high-field-strength elements including Nb, Ta, and Ti. Additionally, the presence of negative europium anomalies further reflects geochemical signatures typical of I-type granitic rocks. The zircon grains from these rocks display negative ε_Hf(t) values (−14.6 to −10.7), with two-stage Hf model ages (T_DM2) from 2129 to 1907 Ma. These characteristics suggest that the magmatic source of the Yaogou granodiorites likely originated from the partial melting of Paleoproterozoic basement-derived crustal materials within a tectonic environment associated with subduction in the North Qilian Ocean. Integrating regional geological data, we suggest that during the Early Paleozoic, the North Qilian Oceanic slab underwent double subduction: initially southward, followed by a northward shift. Due to the deep northward subduction of the Qaidam continental crust and oceanic crust along the southern margin of the Qilian Orogenic Belt, the southward subduction of the North Qilian ocean was obstructed, triggering a reversal in subduction polarity. This reversal likely decelerated the southward subduction and initiated northward subduction, ultimately leading to the formation of the Yaogou granodiorites. These findings enhance our understanding of the complex tectonic processes that shaped the North Qilian Orogenic Belt during the Early Paleozoic, emphasizing the role of subduction dynamics and continental interactions in the region’s geological evolution. Full article

This study investigates the provenance of the Permian Shihezi Formation (Fm) siliciclastic sediments in the Luonan area, southern margin of the North China Block, which constrain the sediment sources and tectonic evolution of the basin. Our research investigates the heavy mineral characteristics, geochemical features, detrital zircon U-Pb geochronology, and Lu-Hf isotope tracing the provenance characteristics of the Shihezi Fm in this region. Zircon yielded three distinct U-Pb age groups as follows: 320–300 Ma, 1950–1850 Ma, and 2550–2450 Ma. The ε_Hf(t) values of zircons ranged from −41 to 50, and the two–stage Hf model’s ages (T_DM2) values are concentrated between 3940 Ma and 409 Ma, suggesting that magmatic sources likely derive from Early Archaean–Devonian crustal materials. The heavy mineral assemblages are primarily composed of zircon, leucoxene, and magnetite. Further geochemical analyses of the rocks indicate a diverse provenance area and a complex tectonic evolution. Taken together, these results suggest that the provenance of the Shihezi Fm is from the North China Block, with secondary contributions from the Qinling Orogenic Belt and the North Qilian Orogenic Belt. The provenance of Luonan shares similarities with the southern Ordos Basin. Investigating the provenance of the Luonan area along the southern margin of the North China Craton provides critical supplementary constraints for shedding light on the Late Paleozoic tectonothermal events in the Qinling Orogenic Belt. Full article

Ion-adsorption rare earth deposits are mainly formed by the weathering and leaching of granite ore-forming parent rocks, and heavy rare earth elements (HREEs) are predominantly hosted in this type of deposit. In this study, we focused on the Late Jurassic REE mineralization parent rock, specifically the Shuitou pluton. We employed chronology, petrogeochemistry, and isotope geochemistry to elucidate the REE enrichment process in the granite. The results show that the zircon U–Pb age of the Shuitou pluton is ~150 Ma, and the monazite U–Pb age is ~145 Ma, suggesting that the pluton was formed in the Yanshan Stage. The rocks have high SiO₂ (72.85–75.55 wt%), Al₂O₃ (12.85–14.63 wt%), and K₂O (4.46–5.27 wt%) content, with A/CNK values of 1.05–1.19, differentiation index (DI) values of 87.48–95.59, zircon saturation temperature values of 689–746 °C, Nb/Ta ratios of 2.72–9.54, and Zr/Hf ratios of 7.12–26.11. In addition, the rocks also contain peraluminous minerals such as muscovite and garnet. These characteristics indicate that these rocks belong to highly fractionated S-type granite. The ε_Hf(t) values of zircon and monazite range from −10.04 to −6.78 and from −9.3 to −8.2, respectively, indicating that the magma was primarily derived from Proterozoic metamorphosed sedimentary rocks of crustal origin. In the extensional tectonic setting of South China, a high temperature promotes the melting of REE-enriched accessory minerals, and a higher content of F increases the solubility of REEs in the molten mass. The presence of heavy rare earth minerals, such as garnet, in these rocks contributes to a high content of heavy rare earth elements (HREEs). Additionally, REE-enriched minerals like titanite, bastnaesite, and allanite create the necessary material conditions for the formation of ion-adsorption REE deposits. Full article

Late Mesozoic magmatism in Southeast China extensively reworked the Cathaysia Block’s crust, linked to the Paleo-Pacific Plate subduction beneath East Asia. The northeastern Cathaysia Block, largely covered by Cretaceous volcanic-sedimentary basins, has limited Jurassic exposure to Early Cretaceous intrusions, which provides critical insights into deep crust-mantle processes. In this study, we present zircon U-Pb geochronology and Hf isotope, whole-rock geochemistry, and Sr-Nd isotopes of the Middle Jurassic syenite-granite suites and Early Cretaceous granites with enclaves in the Qingyuan area (SW Zhejiang Province) to constrain their petrogenesis and tectonic significance. Middle Jurassic syenites and alkali-feldspar granites (169–167 Ma) exhibit calc-alkaline to shoshonitic affinities and weakly peraluminous compositions. Early Cretaceous granites (134 Ma) and their enclaves (136 Ma) are high-K calc-alkaline and weakly peraluminous to metaluminous. All samples show LILE and LREE enrichment, HFSE depletion, and negative Eu and Sr anomalies, with only syenites displaying negative Ce anomalies. We suggest that the Middle Jurassic syenites originated from the partial melting of an enriched lithospheric mantle influenced by subduction-related metasomatism. Alkali-feldspar granites derived from partial melting of the basement of the Cathaysia Block. Early Cretaceous granites formed by partial melting of lower crustal mafic rocks, with enclaves representing earlier crystallization products, which were then mechanically mixed with granites. We propose the NE Cathaysia Block underwent significant reworking from the Middle Jurassic to the Early Cretaceous. Middle Jurassic syenites formed in a compressional setting linked to Paleo-Pacific Plate subduction, while Early Cretaceous magmatism reflects lithospheric extension and crust-mantle interaction triggered by slab rollback. Full article

The Beishan Orogenic Belt, situated along the southern margin of the Central Asian Orogenic Belt, represents a critical tectonic domain that archives the prolonged subduction–accretion processes and Paleo-Asian Ocean closure from the Early Paleozoic to the Mesozoic. Early Permian magmatism, exhibiting the most extensive spatial-temporal distribution in this belt, remains controversial in its geodynamic context: whether it formed in a persistent subduction regime or was associated with mantle plume activity or post-collisional extension within a rift setting. This study presents an integrated analysis of petrology, zircon U-Pb geochronology, in situ Hf isotopes, and whole-rock geochemistry of Early Permian granites from the Tiancang area in the southern Beishan Orogenic Belt, complemented by regional comparative studies. Tiancang granites comprise biotite monzogranite, monzogranite, and syenogranite. Zircon U-Pb dating of four samples yields crystallization ages of 279.3–274.1 Ma. These granites are classified as high-K calc-alkaline to calc-alkaline, metaluminous to weakly peraluminous I-type granites. Geochemical signatures reveal the following: (1) low total rare earth element (REE) concentrations with light REE enrichment ((La/Yb)_N = 3.26–11.39); (2) pronounced negative Eu anomalies (Eu/Eu* = 0.47–0.71) and subordinate Ce anomalies; (3) enrichment in large-ion lithophile elements (LILEs: Rb, Th, U, K) coupled with depletion in high-field-strength elements (HFSEs: Nb, Ta, P, Zr, Ti); (4) zircon ε_Hf(t) values ranging from −10.5 to −0.1, corresponding to Hf crustal model ages (T_DMC) of 1.96–1.30 Ga. These features collectively indicate that the Tiancang granites originated predominantly from partial melting of Paleoproterozoic–Mesoproterozoic crustal sources with variable mantle contributions, followed by extensive fractional crystallization. Regional correlations demonstrate near-synchronous magmatic activity across the southern/northern Beishan and eastern Tianshan Orogenic belts. The widespread Permian granitoids, combined with post-collisional magmatic suites and rift-related stratigraphic sequences, provide compelling evidence for a continental rift setting in the southern Beishan during the Early Permian. This tectonic regime transition likely began with lithospheric delamination after the Late Carboniferous–Early Permian collisional orogeny, which triggered asthenospheric upwelling and crustal thinning. These processes ultimately led to the terminal closure of the Paleo-Asian Ocean’s southern branch, followed by intracontinental evolution. Full article

Cenozoic plutonic rocks in northeast Saveh, part of the central Urumieh–Dokhtar Magmatic Arc (UDMA) in Iran, comprise monzonite, monzodiorite, gabbro, and gabbrodiorite. Geochemical, zircon U-Pb geochronology, and Hf isotopic data reveal that these plutonic rocks belong to a medium-K calc-alkaline, metaluminous series with arc-related signatures. Zircon U-Pb ages (ca. 60 to 3 Ma) indicate prolonged magmatic evolution from the Middle Paleocene to the Middle Pliocene. Contrary to earlier reports of a 15 Ma period of reduced magmatic activity (ca. 72–57 Ma), our data indicate a shorter interval (ca. 10–12 Ma) during which magmatic activity decreased significantly. Key magmatic pulses occurred during the Late Eocene (ca. 40–47 Ma), Early Miocene (ca. 23–18 Ma), and Late Miocene–Pliocene (ca. 11–5.2 Ma), with geochemical data indicating a subduction-related origin. The most recent magmatic pulses in the central UDMA, potentially extending across the entire UDMA, are dated between 5 and 2.5 Ma, identified in a cluster of zircons from gabbroic rocks, which could correspond to the concluding stages of slab steepening related to continental subduction. Zircon εHf(t) values (−11.43 to 12.5) and geochemical data suggest fractional crystallization, crustal assimilation, and mantle-derived melts. The clinopyroxene crystallization temperatures (1150–1200 °C) and supporting geochemical data imply that magma was produced in a metasomatized spinel–lherzolite mantle at depths <80 km. This generation is associated with asthenospheric upwelling and slab rollback, which, in turn, triggered the partial melting of the lithosphere and fueled the region’s magmatic activity. Full article

The Proto-Tethys Ocean existed between Gondwana and Laurussia during the late Neoproterozoic to Early Paleozoic. As part of the northern margin of East Gondwana, the Lhasa terrane records subduction-related processes of the Proto-Tethys Ocean. This study analyzes mylonitized granites from the Guomang-Co area in the central Lhasa terrane, focusing on their major and trace elements, U-Pb age values, and Sr-Nd-Pb-Hf isotopes. Geochemical and isotopic data consistently indicate S-type affinity derived from Paleoproterozoic metasedimentary sources, and likely formed in a syn-collisional setting. Combined with previous studies, the granites are interpreted as products of the Early Paleozoic Andean-type orogeny along the northern margin of East Gondwana, which indicate southward subduction of the Proto-Tethys Ocean during the Cambrian–Ordovician. Full article

The Xing’an–Mongolia Orogenic Belt (XMOB) is located in the eastern part of the Central Asian Orogenic Belt (CAOB). The region’s notable tectonic complexity and extensive tungsten mineralization offer a unique opportunity to explore metallogeny mechanisms in orogenic areas. This study focuses on the Shamai tungsten deposit as a case study, presenting results from LA–ICP–MS U–Pb dating of fine-grained, medium-grained, and porphyritic biotite monzogranite samples from the deposit, along with in situ zircon Hf isotopic and plagioclase Pb isotopic analyses. The fine-grained, medium-grained, and porphyritic biotite monzogranite were emplaced at 142.5, 141.9, and 140.2 Ma, respectively. These samples contain zircons with εHf(t) values ranging from 3.2 to 7.9 and 4.2 to 7.6, respectively, yielding T_DM2 model ages from 996 to 692 Ma and 923 to 708 Ma. These findings suggest that the magmas in the Shamai deposit were produced by partial melting of juvenile crustal material mixed with mantle-derived components. The tungsten mineralization periods in the Eastern XMOB region can be divided into three stages: Early Paleozoic (ca. 520–475 Ma), Triassic (ca. 250–200 Ma), and Jurassic to Early Cretaceous (ca. 190–130 Ma). The highest concentration of tungsten mineralization in the XMOB occurs within the Xing’an Block during the Jurassic to Early Cretaceous period. Yanshanian magmatism and the most significant tungsten metallogenic events are likely influenced by an extensional setting and oceanic slab rollback, shaped by the tectonic evolution of the Mongol-Okhotsk Ocean and the Paleo-Pacific Ocean. Full article

The Waxing Mo polymetallic deposit is located in the central part of the Lesser Xing’an–Zhangguangcai Range (LXZR), NE China. The Mo (Cu) mineralization in the deposit is dominantly hosted by quartz veinlets and stockworks and is closely related to silicification and potassic alteration, while the W mineralization is most closely related to greisenization. Zircon samples from granodiorite, biotite monzogranite, granodiorite porphyry, and syenogranite in the Waxing deposit yielded U-Pb ages of 172.3 Ma, 172.8 Ma, 173.0 Ma, and 171.4 Ma, respectively. Six molybdenite samples from porphyry Mo ores yielded a Re-Os isochron age of 172.0 ± 1.1 Ma. The granitoids in the ore district are relatively high in total alkali (Na₂O + K₂O), are metaluminous to weakly peraluminous, and are classified as I-type granitoids. The zircon samples from all granitoids showed a relatively consistent Hf isotopic composition, as shown by positive ε_Hf(t) values (3.1–8.3) and young T_DM2 ages (0.69–1.25 Ga). These results, combined with the whole-rock geochemistry, suggest that the magma source of these rocks most likely derived from partial melting of a juvenile middle-lower continental crust, with a minor contribution from the mantle. These granitoids have compositional characteristics of adakites such as relatively high Sr contents (e.g., >400 ppm) and Sr/Y ratios (e.g., >33), as well as weak Eu anomalies (e.g., Eu/Eu* = 0.8–1.1), indicating extensive fractionation crystallization of a hydrous magma. The apatite geochemistry indicates that the ore-related magma in Waxing is F-rich and has a relatively low content of sulfur. The zircon geochemistry reveals that the granodiorite, biotite monzogranite, and granodiorite porphyry have relatively high oxygen fugacity (i.e., ΔFMQ = +1.1~1.3), whereas the fO₂ values of the granite porphyry and syenogranite are relatively low (i.e., ΔFMQ = +0.1~0.5). The whole-rock and mineral geochemistry suggest that the Mo mineralization in Waxing is probably genetically related to granitoids (i.e., granodiorite, biotite monzogranite, and granodiorite porphyry), with higher oxygen fugacity and a high water content, whereas the magmatic S concentration is not the key factor controlling the mineralization. A comparison of the geochemical compositions of ore-forming and barren stocks for porphyry Mo deposits in the LXZR showed that geochemical ratios, including Eu/Eu* (>0.8), 10,000*(Eu/Eu*)/Y (>600), Sr/Y (>33), and V/Sc (>8), could be effective indicators in discriminating fertile granitoids for porphyry Mo deposits from barren ones in the region. Full article

The Anwangshan gold deposit is located in the northwestern part of the Fengtai Basin, Western Qinling Orogen (WQO). The gold ore is hosted within quartz syenite and its contact zone. The U–Pb weighted mean age of the quartz syenite is 231 ± 1.8 Ma. It is characterized by high potassium (K₂O = 10.13%, K₂O/Na₂O > 1) and high magnesium (Mg^# = 55.31 to 72.78) content, enriched in large ion lithophile elements (Th, U, and Ba) and light rare earth elements (LREE), with a typical “TNT” (Ti, Nb, and Ta) deficiency. The geochemical features and Hf isotope compositions (ε_Hf(t) = −6.68 to +2.25) suggest that the quartz syenite would form from partial melting of an enriched lithospheric mantle under an extensional setting. Three generations of gold mineralization have been identified, including the quartz–sericite–pyrite (Py1) stage I, the quartz–pyrite (Py2)–polymetallic sulfide–early calcite stage II, and the epidote–late calcite stage III. In situ sulfur isotope analysis of pyrite shows that Py1 (δ³⁴S = −1.1 to +3.8‰) possesses mantle sulfur characteristics. However, Py2 has totally different δ³⁴S (+5.1 to +6.7‰), which lies between the typical orogenic gold deposits in the WQO (δ³⁴S = +8 to +12‰) and mantle sulfur. This suggests a mixed source of metamorphosed sediments and magmatic sulfur during stage II gold mineralization. The fluid inclusions in auriferous quartz have three different types, including the liquid-rich phase type, pure (gas or liquid)-phase type, and daughter-minerals-bearing phase type. Multiple-stage fluid inclusions indicate that the ore fluids are medium-temperature (concentrated at 220 to 270 °C), medium-salinity (7.85 to 13.80% NaCleq) CO₂–H₂O–NaCl systems. The salinity is quite different from typical orogenic gold deposits in WQO and worldwide, and this is more likely to be a mixture of magmatic and metamorphic fluids as well. In summary, the quartz syenite should have not only a spatio-temporal but also a genetical relationship with the Anwangshan gold deposit. It could provide most of the gold and ore fluids at the first stage, with metamorphic fluids and/or gold joining in during the later stages. Full article