Abstract:The Central Asian Orogenic Belt (CAOB) is the largest Phanerozoic accretionary orogenic belt on Earth, and central Inner Mongolia is widely regarded as the key segment marking the final closure of the Paleo-Asian Ocean within the CAOB. As a critical region for constraining the tectonic transition that followed the closure of the Paleo-Asian Ocean, central Inner Mongolia has long attracted considerable attention owing to its complex tectono-magmatic evolution. In this study, the monzogranite exposed in the Wulantaolegai area was investigated through petrography, whole-rock major- and trace-element geochemistry, LA-ICP-MS zircon U-Pb geochronology, and zircon Hf isotopic analyses to constrain its emplacement age, magma source, and tectonic setting. The results show that the monzogranite yields a zircon U-Pb age of 259.2±3.8 Ma (MSWD=1.2), indicating emplacement in the Late Permian. Whole-rock geochemical data indicate that the pluton is characterized by high silica (SiO₂=73.43%~75.15%), elevated Al₂O₃ (13.32%~14.24%), high total alkalis (Na₂O+K₂O=8.18%~8.61%), and low Fe-Mg contents, with aluminum saturation indices (A/CNK) of 1.05~1.11. It is enriched in light rare earth elements and large-ion lithophile elements such as Rb, Th, and K, but depleted in heavy rare earth elements and in Nb, Sr, P, and Ti, and is dominated by negative Eu anomalies, thus belonging to weakly peraluminous Ⅰ-type granite. Zircon Hf isotopic compositions yield εHf(t) values of -16.44 to -2.04 and two-stage Hf model ages (t_DM2) of 2 322~1 413 Ma, suggesting that the magma was derived predominantly from partial melting of ancient crustal materials, with the possible involvement of a very minor depleted component. In combination with the regional tectono-magmatic evolutionary framework, we propose that the Late Permian monzogranite in the Wulantaolegai area was generated by crustal remelting under a post-closure lithospheric thinning or extensional regime following the closure of the Paleo-Asian Ocean, indicating that central Inner Mongolia had entered a post-collisional to post-orogenic extensional tectonic regime by the Late Permian.

Abstract:The Gaochun Cu polymetallic deposit, located in the northern part of the Xuancheng ore concentration district within the Middle-Lower Yangtze River Metallogenic Belt, is a newly discovered mineralization area. This study focuses on diorite porphyry and quartz diorite porphyry exposed by drilling in the Gaochun mining area. Through zircon LA-ICP-MS U-Pb dating, whole-rock major and trace element analysis, zircon in-situ Hf isotopes, and whole-rock Sr-Nd isotope measurements, the formation age, magma source, and petrogenesis of the intrusive rocks are systematically investigated. The results show that the zircon U-Pb ages of diorite porphyry and quartz diorite porphyry are 134.1±2.0 Ma and 133.9±2.2 Ma, respectively, indicating they were products of Early Cretaceous magmatic activity. Geochemically, the rocks are characterized by high-K calc-alkaline and metaluminous affinity, enrichment in large ion lithophile elements (e.g., Rb, Ba, Th), depletion in high field strength elements (e.g., Nb, Ta, and Ti), significant fractionation of light and heavy rare earth elements, and weak Eu anomalies. Sr-Nd-Hf isotopic compositions suggest that the magmas were derived from mixing of an enriched mantle source and ancient crustal materials (Archean-Paleoproterozoic basement), accompanied by varying degrees of fractional crystallization and assimilation. Comparisons with intrusive rocks from the adjacent Chating ore district and the Tongling ore cluster indicate that the Gaochun intrusions are genetically linked to the first stage of crust-mantle interaction in the Middle-Lower Yangtze River Metallogenic Belt, formed in an intracontinental extensional setting following the subduction of the Paleo-Pacific Plate, involving magmatic underplating and mixing. This study provides new petrogeochemical evidence for understanding the deep magmatic-mineralization mechanisms in the Xuancheng ore cluster.

Abstract:In recent years, a new breakthrough in mineral exploration has been achieved in the Choushuigou area of Beishan, Gansu Province, where medium-sized and above VMS-type copper polymetallic deposits have been discovered. However, there is still controversy over their diagenesis and mineralization age, and a lack of precise dating basis has constrained the summary of mineralization laws and analysis of mineralization processes. Based on field geological surveys, the LA-ICP-MS zircon U-Pb dating was employed to conduct high-precision isotopic chronology on the ore-hosting phyllitic basaltic tuff. The U-Pb age of the zircon is 277.4±0.72 Ma, which is from the late Early Permian period. Therefore, it is classified as the Permian Jinta Formation rather than the previously classified Carboniferous Hongliuyuan Formation, indicating that the late Early Permian was also an important period for submarine volcanic-hydrothermal mineralization in the area. Comprehensive analysis demonstrates that the diagenesis and mineralization in the Choushuigou area occurred within an extensional rift setting during the Early Permian. The deposit exhibits definitive characteristics of the VMS-type copper polymetallic deposit, and the phyllitic basaltic tuff of the Permian Jinta Formation and VMS-type copper polymetallic deposits are key directions for breakthroughs in regional mineral exploration.

Abstract:The Qingchengzi ore concentration area in eastern Liaoning Province is located within the Jiao-Liao-Ji tectonic belt. Since the gold and polymetallic ore deposits are strictly controlled by the "silicon-calcium interface" within transitional zone between the Paleoproterozoic Dashiqiao and Gaixian formations of the Liaohe Group, precise correlations of ore-hosting strata are crucial for regional and deep metallogenic prediction and exploration. This study focuses on 170 marble core samples from the Dashiqiao Formation and 2 granite porphyry core samples intruding into the marble, collected from one 1 000 m deep drillhole (ZK12-11) and two 2 000 m deep drillholes (ZK11-8, ZK12-20) recently conducted in the Qingchengzi ore concentration area. Carbon-oxygen isotopic and zircon U-Pb geochronological analyses were conducted on the marble and granite porphyry samples, respectively. Carbon-oxygen isotopic results show that the δ¹³C_V-PDB values of the marbles from the three drillholes have no positive anomaly. This suggests that the protoliths of marbles were deposited after the Lomagundi-Jatuli Event (2.33~2.06 Ga or 2.22~2.1 Ga) and stratigraphically correspond to the upper, thin- to medium-bedded, ore-bearing marble member of the Dashiqiao Formation. Therefore, the bottoms of the 1 000~2 000 m drillholes have not yet reached the lower-middle, non-ore-bearing, thick-bedded marble member of the Dashiqiao Formation that are characterized by positive carbon isotope anomaly. This finding indicates significant potential for deep metallogenic prediction and exploration beneath the currently explored horizons in the Qingchengzi ore concentration area. Zircon U-Pb dating of two granite porphyry samples intruding into the marbles in drillhole ZK11-8 from Taoyuan area yielded crystallization ages of 221±3 Ma and 222±1 Ma, respectively. These results confirm that the emplacement of granite porphyry dykes and the main mineralization epoch in the Qingchengzi area occurred during the Late Triassic at around 220 Ma. In addition, the carbon-oxygen isotopic results demonstrate that the intrusion of dykes and subsequent hydrothermal alteration significantly impacted the isotopic compositions of the carbonate rocks, leading to decreases in their δ¹³C_V-PDB and δ¹⁸O_V-SMOWvalues. In contrast, regional metamorphism had no significant or inhomogeneous effect on the carbon-oxygen isotopes of the carbonate rocks. Even within high-grade metamorphosed orogenic belts, some marbles may largely retain the primary carbon-oxygen isotopic signatures of their sedimentary protoliths, and can therefore provide critical evidence for paleoenvironmental studies and regional stratigraphic correlation. It is recommended that future deep metallogenic explorations in the Qingchengzi ore concentration area should focus on the upper member of the Dashiqiao Formation near regional faults such as the Jianshanzi and Erdaogou faults showing no positive carbon isotope anomaly, especially the strata with strong hydrothermal alteration and low carbon-oxygen isotopic compositions within this formation, as well as the peripheral zones of Late Triassic granitic porphyry dykes within this sequence.

Abstract:Neoproterozoic mafic dyke swarms are key indicators for reconstructing the timing and dynamic processes of the Rodinia supercontinent breakup. Based on systematic analyses of zircon chronology, whole-rock geochemistry, and zircon Lu-Hf isotopes, this study investigates the petrogenesis and geodynamic setting of a newly discovered diabase dyke swarm in the Mianning area on the western Yangtze Block, South China. LA-ICP-MS zircon U-Pb dating reveals that the Mianning diabase crystallized at 835.8±4 Ma, indicating its formation during the Neoproterozoic. The diabase exhibits variable SiO₂ content (45.2% to 48.0%) and MgO (6.82% to 8.15%) contents, as well as Mg^# values (46~57), along with high Al₂O₃ (14.00%~15.75%) content. The studied rocks display relatively flat rare earth element (REE) distribution patterns, with enrichment in Rb, Ba, and K, and depletion in Nb, Ta, Sr, and P. The studied rocks exhibit enriched zircon Lu-Hf isotopes [εHf(t) = -2.2~1.6]. Petrogenetic analysis indicates that the Mianning diabase originated from low-degree partial melting of an enriched mantle wedge, with the mantle source having been modified by fluids derived from altered oceanic crust. The Neoproterozoic Mianning diabase on the western Yangtze Block formed in an extensional continental arc setting, implying that the western margin of the Yangtze Block may have been located at the periphery of the Rodinia supercontinent during the Neoproterozoic era.

Abstract:Late Neoarchean granitoid gneisses are widely distributed in the Early Precambrian metamorphic basement of the Liaonan Block, the North China Craton (NCC), and record important information on the formation and evolution of the continental crust in the Early Precambrian. In this study, we present zircon LA-ICP-MS U-Pb ages, trace element compositions, and Lu-Hf isotopic data from four granitoid gneiss samples collected from the Liaonan Block. Most zircons exhibit oscillatory zoning and high Th/U ratios (0.18～2.21), along with REE patterns characterized by depleted LREEs and enriched HREEs, consistent with a magmatic origin. The ²⁰⁷Pb/²⁰⁶Pb weighted mean ages of the four granitoid samples are 2 529±10 Ma (MSWD=0.12, n=14), 2 475±27 Ma (MSWD=3.1, n=13), 2 502±15 Ma (MSWD=2.7, n=14), and 2 478±8 Ma (MSWD=0.81, n=25), respectively, recording the magmatic events related to crustal differentiation during the late Neoarchean. Zircon Hf isotopic compositions show positive εHf(t) values (+0.11 to +5.29), with two-stage model ages (t_DM2) ranging from 2.9 to 2.7 Ga, suggesting the granitoids were derived mainly from partial melting of juvenile crust formed during this period. A few zircons yield negative εHf(t) values (-3.2 to -0.8) and older t_DM2 ages of 3.12～2.90 Ga, reflecting the involvement of ancient reworked continental crustal components older than 2.9 Ga. Combining the new results with published zircon Hf isotope data, it has been demonstrated that the Liaonan Block experienced major crustal growth during 2.9～2.7 Ga and crustal reworking at 2.5 Ga and 2.47 Ga, which were driven by upwelling mantle. The resulting widespread potassic granitic rocks signify the stabilization and cratonization of the block.

Abstract:Currently, scholars at home and abroad have gained profound insights into the genesis mechanisms of porphyry molybdenum deposits developed in arc and rift environments. However, scientific questions regarding the diagenesis, mineral source regions, and other aspects of porphyry molybdenum deposits within the North China Craton remain controversial and warrant further investigation. This paper reports the (rhyolitic porphyry)diagenetic and mineralization ages, along with the Hf isotopic composition of mineralized rhyolitic porphyry from the Dawan porphyry molybdenum deposit within the Laiyuan Complex. The study reveals: the SHRIMP zircon U-Pb age of the rhyolitic porphyry is 137.1±0.6 Ma, the Re-Os isochron age of six molybdenite samples is 140.6±1.9 Ma, and the rhyolitic porphyry has εHf(t) values of -28.2~-22.3, the Re isotopic content of Dawan porphyry molybdenum deposit ranges from 19×10^-6 to 26×10^-6, showing characteristics of a crust-mantle mixed source with a predominant crustal component. The Mujicun porphyry copper deposit and Dawan porphyry molybdenum deposit are spatially associated with relatively consistent diagenetic and mineralization ages. Furthermore, the Hf isotopic compositions of the gabbro-diorite from the Laiyuan complex, the mineralized dioritic porphyry from Mujicun, and the mineralized rhyolitic porphyry from Dawan are similar, suggesting a possible common magmatic source for the gabbro-diorite, dioritic porphyry, and rhyolitic porphyry. Within Late Mesozoic extensional tectonic setting, the ore-bearing rhyolitic porphyry originated from gabbroic parent magma formed by partial melting of enriched lithospheric mantle. During its ascent, the gabbroic magma underwent significant lower crustal mixing. Thermal erosion may be the deep mechanism for the formation of ore-bearing porphyry of Dawan Porphyry Mo deposit in the North China Craton.

Abstract:The Yanshanian granites widely distributed in Southern Jiangxi serve as important metallogenic hosts for granite-type rare metal deposits. Taking the Jiangkengli Nb-Ta deposit in Shicheng as the research object, this study systematically compares the geochemical differences between mineralized and non-mineralized granites through field geological surveys, petrographic analysis, whole-rock geochemical testing, and U-Pb chronology. The results show that the mineralized granites are predominantly sodic calc-alkaline series, which are significantly enriched in Al₂O₃, ^TFe₂O₃, and MnO compared with non-mineralized granites. They are characterized by low total rare earth elements (ΣREE<20×10^-6), low Nb/Ta (<3), low Zr/Hf (<5), and high Rb/Sr (>150), based on which quantitative discrimination indices for mineralized granites are established. Isotopic chronology reveals that the monazite U-Pb age of zinnwaldite-albite granite is 144.9±0.8 Ma. Combined with regional metallogenic age comparisons, it is inferred that 145~140 Ma represents a unique Nb-Ta mineralization period in Southern Jiangxi. The ore-forming mechanism indicates that the deposit formed through the synergistic evolution of highly differentiated magma and F/Li- rich fluid alteration. This study provides key geological references for rare metal prospecting in Southern Jiangxi.

Abstract:The Hangjinqi area in Inner Mongolia is one of the significant uranium-bearing regions in the northern Ordos Basin, with favorable geological conditions and promising exploration prospects for mineralization. This paper conducts sedimentological, petrological and geochemical analyses on the core samples of the Middle Jurassic Zhiluo Formation from the borehole X7-6 in the Hangjinqi area, systematically studying the conditions conducive to uranium enrichment and mineralization. The research results show the lower section of the Zhiluo Formation comprises braided river deposits, mainly composed of the thick-bedded gray sandstone and thin mudstone interbedded with thin coal seams, rich in carbonaceous debris and pyrites, while the upper section is characterized by meandering river and deltaic sedimentation, dominated by purple-red siltstone and mudstone.The geochemical characteristics exhibit a "right-inclined" pattern with enrichment of light rare earth elements and depletion of heavy rare earth elements. The chemical index of alteration (CIA) values rangs from 54 to 77,indicating moderate chemical weathering of the Zhiluo Formation during deposition. The paleoenvironmental and paleoclimatic discrimination indicators Sr/Cu, U/Th, V/Cr, Ni/Co, V/(V+Ni), and Sr/Ba values suggest that the paleowater system during the deposition of the Zhiluo Formation was an oxygen-rich freshwater environment, and the paleoclimate underwent a transition from alternating dry and wet conditions to arid and semi-arid conditions. The tectonic setting of source areas of the Zhiluo Formation are continental arcs, and the provenances are primarily composed of the upper crustal felsic rock. The sedimentary environments, tectonic setting, paleoclimate and provenance characteristics can provide favorable geological conditions for uranium enrichment and mineralization in the Zhiluo Formation of the Hangjinqi area.

Abstract:The Mesozoic magmatic activity in the Bozhushan area of southeastern Yunnan plays an important role in regional tectonic evolution and mineralization. A large number of aplite bodies are developed around the Bozhushan pluton in this area, yet previous studies on the timing and petrogenesis of such rocks remain limited. This paper focuses on the Dashanjiao aplite in Bozhushan and investigates its genesis and metallogenic implications through LA-ICP-MS zircon U-Pb dating, whole rock major and trace element analysis, and zircon Lu-Hf isotopic testing. Dating results indicate that it formed in the Late Cretaceous (89.1~87.5 Ma), consistent with the age of regional Yanshanian granites. Geochemical characteristics reveal that it is a highly fractionated S type granite, characterized by peraluminous to metaluminous composition, enrichment in silicon and alkali, and depletion in magnesium and iron. Zircon εHf(t) values range from -7.79 to -5.07, with t_DM2 model ages of 1 451~1 300 Ma, suggesting that the magma was derived from partial melting of Mesoproterozoic crust. The pluton formed in a post collisional extensional setting under the background of Pacific Plate subduction. Its geochemical features (e.g., depletion in Ba and Sr, high Rb/Sr ratio) reveal significant magmatic crystallization differentiation. Combined with previous research findings, it is concluded that the aplite and the granites in the region are products derived from the same source region but underwent different degrees of crystallization differentiation, the Late Cretaceous highly fractionated S-type aplite originated from the low-temperature melting of Mesoproterozoic clay-rich crust, and the associated magmatic hydrothermal differentiation process played an important controlling role in regional W-Sn-Ag polymetallic mineralization.

Abstract:The Qijia gold deposit is a recently discovered quartz-vein type gold deposit located in the Chifeng-Chaoyang gold district along the northern margin of the North China Craton, hosted in the Mesozoic porphyroid granite. The gold mineralization can be divided into three mineralization stages: quartz±pyrite, quartz-polymetallic sulfide, and quartz-carbonate±pyrite. The gold mineralization is closely related to the silicification and sericitization. Based on field geological investigations, we systematically studied the occurrence state of gold from the Qijia gold deposit by using optical microscope and scanning electron microscope observations, combined with electron microprobe analysis for gold grains. The results indicate that gold in the Qijia gold deposit primarily occurs in three forms: fissure gold, interstitial gold, and inclusion gold. Gold grains are mainly observed in pyrite, followed by quartz, with occasional occurrences of chalcopyrite and galena. According to the grain size, gold can be subdivided into coarse-grained gold, medium-grained gold, fine-grained gold, and micro-grained gold, with fine-to micro-grained gold dominant. Gold exhibits diverse morphologies, predominantly granular-based, along with needle-like, leaf-like, hook-like, and branch-like forms. The compositions of gold grains are primarily Au and Ag, with gold fineness range between 678 and 883. They are mainly native gold and electrum, containing trace amounts of Te, Fe, and S. Based on comprehensive geological and geochemical characteristics, we proposed that the Qijia gold deposit belongs to the mesothermal magmatic-hydrothermal type gold deposit.