闽北麻源群Sm-Nd、Rb-Sr同位素年龄研究

The Sm-Nd, Rb-Sr Isotopic Age-Dating of Mayuan Group in Northern Fujian

福建北部元古代麻源群地层发育,对其中7个变质岩和2个白云母花岗岩样品进行了Sm-Nd及Rb-Sr同位素年龄研究。7个样品的Sm-Nd同位素全岩等时线年龄为2116±22(2δ)Ma,INd=0.51027±2(2δ),εNd(t)=7.29±0.17。6个样品的Rb-Sr同位素全岩等时线年龄为375±28(2δ)M,(87Sr/86Sr)i=0.707±34(2δ).2116Ma的年龄值代表麻源群原岩的成岩年龄,375Ma年龄值代表麻源群的变质年龄。

The Proterozoic Mayuan group is well developed in Northern Fujian province. 7 samples of epi-meso metamorphic rocks from the Mayuan group and 2 samples of muscovite granites were taken to be measured by Sm-NdandRb-Sr radioactive isotopic method. The Sm-Nd isotopic isochron age of whole rock for 7 samples is 2116±22(2σ)Ma, I_(Nd)=0.51027+2(2σ), ε_(Nd)(t)=7.29+0.17. Rb-Sr isotopic isochron age of whole rock for 6 samples is 375+28(2σ)Ma, ^(87)Sr/^(86)Sr(i)=0.707+3(2σ). The age of 2116Ma, the earliest age of strata in Fujian and Jiangxi provinces, represents a formation age of the Mayuan group and the age of 375Ma ——metamorphic age of the Mayuan group. From the data of ε_(Nd) (t) and^(87)Sr/^(86)Sr (i), it may be postulated that original rocks of the Mayuan group in Northern Fujian province had been mostly formed through volcanism.