Detailed investigations on how to choose the optimal double-spike and theoptimal mixture ratios of the two single spikes in the double-spike,as well as on how to determinate the optimal sample/spike ratio range during measurement of calcium isotopic compositions by thermal ionization mass spectrometer(TIMS),were carefully carried out in both theory and practices.Compared to the 42Ca-48 Ca and 43Ca-48 Ca doublespikes,which are used widely,42Ca-43 Ca double-spike has its distinctive advantages.Firstly,althoug...