Abstract: Based on the comprehensive research on field geology, petrography, geochronology and geochemistry of the Early Cretaceous intermediate-acidic magmatic rocks of Xiaoxinancha copper (gold) deposit in Yanbian, Jilin Province, the isotopic ages are determined to be(101.69±0.61) Ma (quartz diorite), (101.14±0.58) Ma (tonalite), (100.82±0.62) Ma (granodiorite) and (100.20±1.10) Ma (diorite porphyrite). The magmatism occurred at the end of the Early Cretaceous (102-100 Ma), which is the product of the same tectonic evolution process. The diorite porphyrite has the geochemical characteristics of typical adakitic rocks, with w(SiO₂)=61.419%-62.153%， w(Al₂O₃)=16.872%-17.329%,w(MgO)=2.339%-2.643%,w(Na₂O)=5.749%-6.623%, w(K₂O))=1.483%-1.786%, w(Sr)=(691-888)×10^-6,w(Yb)=(0.71-0.83)×10^-6,Sr/Y=87.4-120.0.The enrichment of LREE is formed by the in-situ intrusion of adakitic magma generated by partial melting of the subducted oceanic slab. The adakitic magma mixed with the acidic magma produced by the remelting of the lower crust during the upwelling process to form the enriched mantle source magma which was upwardly emplaced, and formed the calc-alkaline granitic complexes such as quartz diorite, tonalite and granodiorite. The magmatic hydrothermal fluid is mixed with atmospheric precipitation during the ascent along the regional faults, extracted the metallogenic materials in the surrounding rocks, and formed the metallogenic hydrothermal fluid rich in copper (gold) components, and unloaded and precipitated at a suitable location to form vein-type copper (gold) mineralization. Yanbian area was located in the continental margin environment where the paleo Pacific plate subducted to the Eurasian plate in the Late Mesozoic. The subduction of the paleo-Pacific plate was the direct driving force for the formation of Early Cretaceous quartz diorite, tonalite, granodiorite, diorite porphyrite (dikes)and hydrothermal vein-type copper (gold) mineralization in Xiaoxinancha deposit.

Key words:  Xiaoxinancha copper (gold) deposit in Yanbian area, Jilin Province, Early Cretaceous, intermediate-acidic magmatic rocks; geochronology, geochemistry, tectonic evolution