摘要:
对南措铜金矿区与成矿相关的黑云母花岗闪长岩体进行了岩相学、锆石U-Pb年代学、岩石地球化学等方面的研究.结果表明:该岩体年龄为153.40 ±0.67 Ma,属晚侏罗世.岩石为准铝质-过铝质岩石,属钙碱性系列. LaN/YbN=9.31~12.65,轻重稀土元素分馏明显, δEu=1.21~1.66, Eu表现为正异常;样品微量元素表现为相对富集大离子亲石元素(LILE) K、与高场强元素(HFSE) Sr、Zr,而亏损高场强元素(HFSE) U、 Nb、 Ce、 Nd、 P的特征.岩体具有I型花岗岩特征.样品Zr/Hf值为42.23~45.82,平均值为44.2; Rb/Sr比值为0.07~0.19,平均值为0.13; Nd/Th值为1.65~2.18,平均为1.99,具壳源岩浆的特征,并有地幔物质混入.样品的Mg#值为49.80~57.22, Sr值为443.3~874.9, Yb值为0.80~1.39, Y值为8.96~16.60, Na2O/K2O>2 (2.18~2.97),为洋壳型埃达克岩,并在上升过程中可能有少量地幔楔物质混入.结合前人研究成果认为,该花岗闪长岩形成于晚侏罗世班公湖—怒江洋盆向北俯冲的火山弧环境.%Petrography, LA-ICP-MS zircon U-Pb dating and geochemical data of biotite granodiorite in Nan-cuo Cu-Au mining area related to mineralization have been studied.The results show that the diagenetic age of the biotite granodiorite is 153.40 ±0.67 Ma, belonging to Late Jurassic.And the biotite granodiorites are calc-alka-lineseries and quasi aluminum to peraluminous rocks.There is significant fractionation between LREE and HREE, with LaN/YbN=9.31 ~12.65, and there is positive anomaly for Eu, with δEu =1.21 ~1.66.For trace ele-ments, the biotite granodiorite is enriched in LILE for K and HFSE for Sr, Zr.But depleted in HFSE for U, Nb, Ce, Nd and P.Characteristics of I type granite are presented in the rock mass.The Zr/Hf value of the sample is 42.23~45.82, with an average of 44.2, the ratio of Rb/Sr is 0.07~0.19, with an average value of 0.13, and the value of Nd/Th is 1.65~2.18, with an average of 1.99, indicating crust derived magma with mantle materi- als mixed.The Mg# value of the sample is 49.80~57.22, the Sr value is 443.3~874.9, the Yb value is 0.80~1.39, the Y value is 8.96~16.60, and Na2O/K2O>2 (2.18~2.97), indicating oceanic crust adakites, with a small amount of mantle wedge material mixed during the rising process.Combined with previous research, it is suggested that the granodiorite formed in volcanic arc environment during northward subduction of Bangonghu-Nu-jiang oceanic basin, in Late Jurassic.