Highly fractionated granites are widespread in the middle part of the northern margin of the North China Craton (MNNCC), and several are accompanied by rare metal mineralization. The Dongjin rare metal mineralized intrusion, which is representative of this region, is composed of fine-grained alkali-feldspar granite (FAG) and kali-feldspar granite (KG). The FAG and KG evolve continuously, exemplifying the relationship between magmatic evolution and rare metal mineralization. In this contribution, we present integrated columbite U-Pb geochronology, mineralogy, and whole-rock geochemistry analyses of the Dongjin intrusion to determine the timing of the mineralization, petrogenesis, and geodynamic setting, from which the following results are obtained: (1) LA-ICP-MS U-Pb dating for columbite of the FAG and KG yielded the lower intercept ages between 248.9 ± 1.9 Ma and 250.1 ± 1.1 Ma on the Tera–Wasserburg concordia diagram; (2) Geochemically, the Dongjin intrusion is characterized by an enrichment in Si, Al, Rb, Th, U, Nb, and Zr and a strong depletion in Ba, Sr, P, and Ti, with extremely negative Eu anomalies, high LREE and HREE values, and a noticeable tetrad effect of rare earth elements; as a result, it belongs to high-K calc-alkaline rocks; (3) The Dongjin intrusion belongs to a highly differentiated I-type or A-type granite; (4) The fractional crystallization of plagioclase, K-feldspar, and biotite occurred during magmatic evolution; (5) The Dongjin intrusion was formed in a post-collisional extensional environment. In conclusion, the FAG and KG have a homologous evolution, and the FAG has a higher degree of fractional crystallization. The enrichment and mineralization of Nb-Ta are related to the highly fractionated crystallization of granitic magma and fluid–melt interactions in the final stages of magmatic evolution, and there is a rare metal mineralization related to highly fractionated granite in the MNNCC in the Early Triassic, which deserves full attention in future research and prospecting.

Sn-polymetallic deposits in the Southern Great Xing’an Range (SGXR) are typically marked by the coexistence of Sn, Cu, Pb, Zn, and Ag, yet the mechanisms controlling their paragenesis and separation remain poorly constrained. The Hujiadian deposit hosts Sn, Cu, Pb, Zn, and Ag mineralization that occurs both as intergrown assemblages within individual orebodies and as distinct but spatially associated orebodies, making it an ideal natural laboratory to investigate element coexistence and fractionation. Three hydrothermal stages are identified: pyrite + cassiterite ± chalcopyrite + quartz + chlorite (Stage I); chalcopyrite + sphalerite ± galena + quartz + fluorite + chlorite ± amphibole ± epidote (Stage II); and sphalerite + galena + pyrite + quartz + chlorite + calcite (Stage III). The rhyolite porphyry yields a zircon U–Pb age of 132.3 ± 2.4 Ma, whereas the Sn ores yield cassiterite U–Pb ages of 129.9 ± 1.3 to 131.4 ± 0.8 Ma. These overlapping ages, within analytical uncertainties, constrain the Sn mineralization to the Early Cretaceous. The rhyolite porphyry is geochemically characterized by a peraluminous, high-K calc-alkaline affinity, coupled with elevated SiO₂ and alkali contents, strong negative Eu anomalies, and low fO₂ (ΔFMQ = −4.9 to 1.1). Collectively, these features are consistent with extensive fractionation under reducing conditions, which would have facilitated Sn accumulation in the residual melt. Pervasive chlorite in the deposit records the physicochemical evolution of the hydrothermal system; four chlorite generations document a shift from early acidic conditions during Sn mineralization to near-neutral or weakly alkaline conditions during late Pb–Zn precipitation. We propose that increasing pH played an important role in promoting cassiterite precipitation during Stage I, whereas cooling was the dominant control on Cu precipitation during Stage II. During Stage III, further cooling and increasing pH promoted Pb–Zn precipitation. The observed carbonatization and mineral assemblages are consistent with possible involvement of external fluids, including meteoric water. These changes may have been associated with fluid–rock interaction and possible mixing with meteoric water.

The Southern Great Xing’an Range (SGXR), an important W–Sn polymetallic metallogenic belt in northern China, hosts multiphase magmatism and has witnessed recent discoveries of multiple tungsten–tin polymetallic deposits. The W–Sn mineralization in this area is intimately associated with Early Cretaceous highly fractionated granites. The Chamuhan deposit, a small-sized W–Mo polymetallic deposit in SGXR, is genetically linked to a concealed fine-grained porphyritic alkali feldspar granite intrusion. In this study, we present the LA-ICP-MS zircon U-Pb ages, whole-rock geochemical, and electron probe microanalysis (EPMA) mineral chemistry to constrain the petrogenesis and metallogenic implications of this granite. Zircon U–Pb dating yields a crystallization age of 141.3 ± 1.2 Ma, consistent with molybdenite Re–Os ages. The granite is characterized by elevated SiO₂ (76.9–79.1 wt%) and total alkalis (7.3–8.5 wt%), and exhibits peraluminous high-K calc-alkaline affinity (A/CNK = 1.37–1.57). Geochemical signatures reveal enrichment in large ion lithophile elements (LILEs, e.g., Rb, Th, U) coupled with depletion in high-field strength elements (HFSEs, e.g., Ba, Sr, P, Eu, Ti, Nb, Ta), and are accompanied by right-sloping REE patterns with LREE enrichment and HREE depletion. EPMA data indicate that the mica in the intrusion is primarily zinnwaldite and Li-rich phengite, whereas the plagioclase occurs as albite. The feldspar thermobarometry yields crystallization temperatures of 689–778 °C and 313 MPa–454 MPa, while the melt H₂O content and oxygen fugacity are 8.61–11.1 wt% and −22.58–−14.48, respectively. These geochemical signatures indicate that the granites are highly fractionated I-type granites with extensive fractional crystallization of various minerals like plagioclase, K-feldspar, and apatite, etc. From the Late Jurassic to the Early Cretaceous, the subduction and rollback of the Paleo-Pacific Ocean plate resulted in extensional tectonic environments in eastern China. Asthenospheric upwelling and lower crustal melting generated parental magmas, wherein progressive fractional crystallization during ascent concentrated ore-forming elements and volatiles within residual melts. This process played a key role in the formation of the Chamuhan deposit, exemplifying the metallogenic potential of highly evolved granitic systems in the SGXR.