华南南岭地区中生代花岗岩体年代学及氧逸度特征

摘要

华南南岭地区中生代花岗岩钨锡成矿活动十分剧烈。采集了南岭地区清湖岩体、姑婆山岩体（锡矿）、雪花顶岩体、骑田岭岩体（锡钨矿）和九峰岩体5处出露花岗岩锆石样品，并进行锆石 U-Pb年代学和微量元素分析。结果表明：花岗岩年龄主要集中在146～166 Ma之间，与前人所测年龄在误差范围内一致；其锆石Ce4＋/Ce3＋值总体偏低（低于200），EuN/Eu*N值均小于0．4，无论是与锡（钨）矿有关的花岗岩还是普通花岗岩，都显示较低的氧逸度特征，明显低于年龄较老的大宝山铜钼矿、德兴斑岩铜矿的锆石Ce、Eu异常。因此，南岭地区中生代时可能离古太平洋板块俯冲带较远，受到俯冲流体影响较弱，可能形成于古太平洋板块 SW向俯冲背景下。%W-Sn mineralization of Mesozoic granites in Nanling area of South China is very strong. Five granite zircon samples from Qinghu,Guposhan (Sn deposit),Xuehuading,Qitianling (Sn-W deposit)and Jiufeng plutons in Nanling area were conducted and measured by zircon U-Pb geochronology and trace element analysis.The results show that granite ages are mainly formed at 146-166 Ma,consistent with previous measured ages within errors;all the calculated zircon Ce4+/Ce3+ values are lower than 200,the EuN/Eu*N values are less than 0.4,and granites related with W (Sn)deposit or barren granites have lower oxygen fuga city than that of the older Dabaoshan Mo-Cu-W deposit and Dexing porphyry Cu deposit.Therefore, Nanling area is possible far from subduction zone of Paleo-Pacific Plate in Mesozoic,is weakly influenced by subduction fluids,and is affected by SW-trending subduction of Paleo-Pacific Plate.