关键词: 标准岩石粉末, GSR-1花岗岩, GSR-2安山岩, GSR-3玄武岩, Sr-Nd-Pb同位素

Abstract: In this study, Sr-Nd-Pb isotopic compositions of three Chinese national igneous rock standard materials, GSR-1 granite, GSR-2 andesite, and GSR-3 basalt, were measured by means of the techniques of the isotopic dilution and the thermal ionization mass spectrometry, to investigate the homogeneity of their isotopic compositions and the suitability for the usage as rock standard materials. Three international rock standard materials, BCR-2 basalt, BHVO-2 basalt, and AGV-2 andesite, produced by the US Geological Survey, were simultaneously analyzed as reference materials to check the reliability of the analytical procedures. The analytical results show that three national standard materials of igneous rocks have homogeneous Sr and Nd isotopic compositions. Compared to the GSR-1 granite, the GSR-2 andesite and GSR-3 basalt yield homogeneous Pb isotopic compositions. Relatively large variation in Pb isotopic composition of the GSR-1 granite might be caused by the addition of radiogenic Pb isotopes from those minerals having high U and Th contents. On the basis of the analytical results reported in this study, it is suggested that the three national standard materials of igneous rock powders are suitable as the reference materials for the Sr and Nd isotopic measurements and, the GSR-2 andesite and GSR-3 basalt are also the ideal candidates as reference materials f or the Pb isotopic analysis.

Key words: standard rock powder, GSR-1 granite, GSR-2 andesite, GSR-3 basalt, Sr-Nd-Pb isotopes