吉林延边小西南岔铜(金)矿床早白垩世中—酸性岩浆岩年代学、地球化学及其成因探讨

小西南岔铜(金)矿床位于吉林省延边地区东部，通过对小西南岔铜(金)矿床早白垩世中—酸性岩浆岩进行野外地质、岩相学、年代学和地球化学等方面的研究，进一步探讨延边乃至东北地区中生代大地构造演化。年代学研究结果表明：其同位素年龄分别为(101.69±0.61) Ma(石英闪长岩)、(101.14±0.58) Ma(英云闪长岩)、(100.82±0.62) Ma(花岗闪长岩)和(100.20±1.10) Ma(闪长玢岩),岩浆作用发生在早白垩世末期(102～100 Ma),是同一构造演化过程的产物。岩石地球化学研究表明，闪长玢岩具有典型埃达克质岩石的地球化学特征，其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)×...

Geochronology,Geochemistry and Genesis of Early Cretaceous Intermediate-Acidic Magmatic Rocksin Xiaoxinancha Copper (Gold) Deposit,Yanbian Area,Jilin Province

Based on the comprehensive research on field geology,petrography, geochronology and geochemistry of the Early Cretaceousintermediate-acidic magmatic rocks of Xiaoxinancha copper (gold) deposit inYanbian, 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 occurredat the end of the Early Cretaceous (102-100 Ma), which is the product of thesame tectonic evolution process. The diorite porphyrite has the geochemicalcharacteristics 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 LREEis formed by the in-situ intrusion of adakitic magma generated by partialmelting of the subducted oceanic slab. The adakitic magma mixed with the acidicmagma produced by the remelting of the lower crust during the upwelling processto form the enriched mantle source magma which was upwardly emplaced, andformed the calc-alkaline granitic complexes such as quartz diorite, tonaliteand granodiorite. The magmatic hydrothermal fluid is mixed with atmosphericprecipitation during the ascent along the regional faults, extracted themetallogenic materials in the surrounding rocks, and formed the metallogenichydrothermal fluid rich in copper (gold) components, and unloaded andprecipitated at a suitable location to form vein-type copper (gold)mineralization. Yanbian area was located in the continental margin environmentwhere the paleo Pacific plate subducted to the Eurasian plate in the LateMesozoic. The subduction of the paleo-Pacific plate was the direct drivingforce for the formation of Early Cretaceous quartz diorite, tonalite, granodiorite,diorite porphyrite (dikes)and hydrothermal vein-type copper (gold)mineralization in Xiaoxinancha deposit.