The Shuangjianzishan silver polymetallic deposit is located in the copper–tin–lead–zinc–silver polymetallic metallogenic belt in the Southern Great Xing’an Range, with silver resources of more than 18,000 t, which is the largest silver polymetallic deposit in Asia. Early studies concluded that the Shuangjianzishan deposit is typically an epithermal Ag-Pb-Zn deposit that lacks a high-temperature mineralization stage. In recent years, with the deepening of research, a large amount of Cu-Sn mineralization has been found in the deep part of the Shuangjianzishan deposit, but it is less studied. The laser-ablation inductively coupled mass spectroscopy (LA-ICP-MS) technique is used to investigate the distribution and substitution of trace elements in chalcopyrite and cassiterite. In this paper, the trace element study of chalcopyrite and cassiterite from the Shuangjianzishan deposit reveals that Sn, In, As, Se, Sb, and Tl mainly exist in chalcopyrite in isomorphic form, while Pb, Bi, and Ni mainly exist in chalcopyrite in the form of mineral inclusions. The enrichment of the high-temperature elements Sn and Se in chalcopyrite, and the deficit of the middle- and low-temperature elements Ga, Sb, etc., reflect that the chalcopyrite in the Shuangjianzishan deposit was formed in a middle- and high-temperature environment, and it also indicates that the early ore-forming hydrothermal solution may be rich in Sn. Fe, In, Co, and Ni mainly exist in cassiterite in isomorphic form, and the content of W in cassiterite is high. There are two main forms, one is isomorphic and the other is wolframite inclusion. Cassiterite has Fe-rich and W-U-poor characteristics, indicating that cassiterite from the Shuangjianzishan deposit was formed under relatively oxidized conditions, and the relative enrichment of elements such as Fe, W, Zr, and Hf indicates that the temperature of cassiterite formation was high. The elemental content and inter-ionic coupling relationships suggest that the cassiterite from the Shuangjianzishan deposit may have an elemental replacement mechanism of W⁶⁺ + Fe²⁺ ↔ 2Sn⁴⁺ or Fe³⁺ + OH⁻ ↔ Sn⁴⁺ + O²⁻. The trace elements in cassiterite of the Shuangjianzishan deposit are rich in Fe and Mn and depleted in Nb and Ta, according to the Fe-W diagram, and the tin mineralization of the Shuangjianzishan deposit belongs to cassiterite–sulfide-type tin mineralization. Chalcopyrite Co/Ni ratios >1 are consistent with the characteristics of chalcopyrite genesis in hydrothermal deposits.

The formation of columbite-group mineral phases in peraluminous granite has not been demonstrated to date. Here, a nanoscale study of the columbite-tantalite mineral in the Zhaojinggou Nb-Ta deposit in North China Craton elucidated its formation mechanism and the role of fluids in Nb-Ta mineralization. Transmission electron microscopy (TEM) analysis of a focused ion beam cut of the columbite-tantalite mineral revealed a comparatively well-ordered mineral structure. Energy-dispersive X-ray spectroscopy (EDS) revealed the presence of Nb, Ta, Mn, W, Fe, Sn, and Pb in the columbite-tantalite mineral. Furthermore, detailed TEM images depicted the nanoscale hydrothermal fluid occurring within the columbite-group mineral grain as well as between columbite-tantalite mineral and quartz grains. K, Al, Si, and O were found to be enriched in the hydrothermal fluid that was present between the quartz grains and the columbite-tantalite mineral. It did not react with the mineral grains of the columbite group. The ultrastructure of the columbite-tantalite mineral suggested the columbite-group mineral in the Zhaojinggou Nb-Ta deposit formed during magmatic crystallization rather than from hydrothermal fluids. Furthermore, HR-TEM images provided the first nanoscale observations of the fluid-mediated mineral dissolution and amorphous phase formation. This study also revealed that the mineral dissolution, element transport, and reprecipitation were significantly influenced by the fluid amorphous phase in the Nb-Ta deposits.

To reveal the evolution of the North China Craton (NCC) and the breakup process of the Columbia supercontinent, this study conducted zircon geochronology and garnet mineralogical analyses on kimberlites from the Bayan Obo area, on the northern margin of the NCC. Zircon U-Pb dating yielded four groups of concordant ages: 2505 ± 46 Ma, 2210 ± 57 Ma, 1928 ± 58 Ma, and 1455 ± 88 Ma. Among these, 1455 ± 88 Ma represents the formation age of the kimberlite, corresponding to a regional extensional tectonic setting. The other three groups are xenocrystic zircon ages, recording the formation of the Archean basement of the NCC, extensional magmatic activity in the middle Paleoproterozoic, and collisional metamorphic events in the late Paleoproterozoic, respectively. The major element characteristics of the garnets indicate they are granulite-facies crust-derived garnets (G4 type), formed under temperature and pressure conditions of 791 ± 50–876 ± 50 °C and 14 ± 3.0 kbar. This corresponds to a mantle heat flow value of approximately 60 ± 5 mW/m², suggesting an unstable state of the lithosphere in the study area. Combined with the regional geological background, the depositional age of the Bilute Formation in Bayan Obo is determined to be between 1455 and 1524 Ma. The emplacement of kimberlite is related to extensional rifting driven by the breakup of the Columbia supercontinent, and garnets hosted in kimberlite record the crustal extension and mantle magma underplating during the rift-spreading stage of this period. This study provides key petrological and chronological evidence for the tectonic evolution of the northern margin of the NCC and the breakup of the Columbia supercontinent.

This study presents a comprehensive case analysis of pyrite-hosted solid inclusions and their metallogenic significance in the Bainaimiao porphyry Cu deposit in NE China, which is genetically linked to the early Silurian granodiorite intrusion and porphyry dykes. Solid inclusions in pyrite from the deposit’s southern ore belt were analyzed across distinct mineralization stages. Using Electron Probe Micro-Analysis (EPMA) and in situ sulfur isotope analysis (MC-ICP-MS), inclusion assemblages in pyrite were identified, including pyrrhotite-chalcopyrite solid solutions, biotite, and dolomite. The results demonstrate that these inclusions primarily formed through coprecipitation with pyrite during crystal growth. Early-stage mineralizing fluids exhibited extreme temperatures exceeding 700 °C, coupled with low oxygen fugacity (fO₂) and low sulfur fugacity (fS₂). Sulfur isotope compositions (δ³⁴S: −5.85 to −4.97‰) indicate a dominant mantle-derived magmatic sulfur source, with contributions from reduced sulfur in sedimentary rocks. Combined with regional geological evolution, the Bainaimiao deposit is classified as a porphyry-type deposit. Its ore-forming materials were partially derived from Mesoproterozoic submarine volcanic exhalative sedimentary source beds, which were later modified and enriched by granodiorite porphyry magmatism.

The Erentaolegai silver deposit is located within the Derbugan metallogenic belt in the eastern segment of the Central Asia–Mongolia giant orogenic belt. The ore bodies are primarily hosted in the volcanic rocks of the Middle Jurassic Tamulangou Formation of the Mesozoic. The mineralization process of the deposit is divided into three stages: Stage I: Pyrite–Quartz Stage; Stage II: Sulfide–Quartz Stage; Stage III: Quartz–Manganese Carbonate Stage. This paper discusses the ore-forming fluids, ore-forming materials, and deposit genesis of the Erentaolegai silver deposits using fluid inclusions microthermometry, laser Raman spectroscopy, and H-O-S isotope analyses. Fluid inclusion microthermometry and laser Raman spectroscopy analyses indicate that the Erentaolegai silver deposit contains exclusively fluid-rich two-phase fluid inclusions, all of which belong to the H₂O-NaCl system. Homogenization temperatures of fluid inclusions in the three stages (from early to late) ranged from 257 to 311 °C, 228 to 280 °C, and 194 to 238 °C, corresponding to salinities of 1.91 to 7.86 wt%, 2.07 to 5.41 wt%, and 0.70–3.55 wt% NaCl equivalent, densities of 0.75 to 0.83 g/cm⁻³, 0.80 to 0.86 g/cm⁻³ and 0.85 to 0.89 g/cm⁻³. The mineralization pressure ranged from 12.2 to 29.5 MPa, and the mineralization depth was 0.41 to 0.98 km, indicating low-pressure and shallow-depth mineralization conditions. H-O isotope results indicate that the ore-forming fluid is a mixture of magmatic fluids and meteoric water, with meteoric contribution dominating in the late stage. The δ³⁴S values of metallic sulfides ranged from −1.8 to +4.0‰, indicating that the metallogenic material of the Erentaolegai silver deposit was dominated by a deep magmatic source. This study concludes that meteoric water mixing and subsequent fluid cooling served as the primary mechanism for silver mineral precipitation. The Erentaolegai silver deposit is classified as a low-sulfidation epithermal silver deposit.

Accurately determining the pore structure and heterogeneity characteristics of marine-continental transitional shale in the Taiyuan Formation is crucial for evaluating the shale gas resources in the northern Ordos Basin. However, the studies on pore characteristics and heterogeneity of marine-continental transitional shales and isolated kerogen are limited. This study collected Taiyuan Formation shale in the northern Ordos Basin, and corresponding kerogen isolated from shale and used N₂ and CO₂ adsorption experiment and Frenkel–Halsey–Hill and Volume-Specific Surface Area model to investigate the pore structure and heterogeneity of both. The results show that the isolated kerogen is dominated by micropores, and the micropore’s specific surface area and volume are 4.7 and 3.5 times the corresponding shale, respectively. In addition, the microporous heterogeneity of the isolated kerogen is stronger than that of shale, while the mesoporous heterogeneity is exactly the opposite. Meanwhile, the micropores fractal dimension D_m is positively correlated with organic matter (OM) content, while mesopores fractal dimension D₁ and D₂ are negatively linearly correlated with TOC content and have no significant relationship with clay mineral and quartz content (but show a significant positive correlation with illite and illite/smectite mixed layer). Isolated kerogen plays an important role in the pore (especially micropores) heterogeneity of shale, while other minerals (such as clay minerals) have a controlling effect on the mesopores heterogeneity of shale. Compared with marine shale, the marine-continental transitional shale of the Taiyuan Formation has a lower fractal dimension and better connectivity, which is conducive to shale gas seepage and migration. The final result can provide a significant basis for the reserve evaluation and the optimization of desert areas in the marine-continental transitional shale gas in the northern Ordos Basin.