Calibration of Sm-Nd mixed spike by teflon powder method

Isotopic composition of Sm-Nd mixed spike was calibrated by teflon powder method. Sm and Nd isotopic compositions of the spike were externally calibrated with reference to the nNdβ standard and normal Sm. Sm and Nd concentrations in the mixed spike were determined by isotope dilution protocol. Sm and Nd were separated by teflon powder method from the mixture of the spike with an interlaboratory standard (CIT Sm-Nd standard). We confirmed that precise Sm/Nd ratio (< 0.1 % error) and undisturbed Nd isotopic composition can be measured at the same time on condition that the sample to spike ratio is optimized. Garnet from the shear zone between the Gyeonggi massif and the Imjingang belt (Gyeonggi shear zone) was dated as a practical test of our experimental procedure. The Sm-Nd data of garnet, K-feldspar and whole rock samples from the shear zone define an Early Proterozoic age of 1730±71 Ma, indicating that Sm-Nd system of the garnet was not disturbed during Triassic deformation.