Chinese Journal of Polar Research (极地研究) 2013/25:4 PP.425-435
Thermal ionization mass spectrometry (TIMS) is one of the most important isotopic measurement techniques. TIMS technology has a broad prospect of application in cosmochemistry because of its high accuracy and sensitivity. TRITON TIMS can measure high-precision isotopic compositions of the Re-Os, Cr, Sr, Nd and Pb systematics of meteorites. Small loads (10 pg to 100 ng Sr) of international standard NBS 987 were analyzed for 87Sr/86Sr isotope ratios with a precision of 5% to 5 ppm by TIMS. The ratio of 143Nd/144Nd of LaJolla-Nd is 0.511 842±0.000 005 (2 SE, n=28) in our lab, and the best precision is better than 2 ppm. Using the 207Pb204Pb double spike, the reproducibilities of 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios can be better than ±0.003 4, ±0.004 6 and ±0.010 0 (n=28, 2SD) for samples with a content of 5 to 20 ng Pb, respectively. 187Os/188Os isotopic ratios are determined under a negative thermal ion mode with a precision of better than 0.2% for approximately tens of pg, and 20 ppm for ~1 ng. In addition, Cr isotopes can also be measured by the TIMS technique in the static multicollection mode. The precisions of 50Cr/52Cr, 53Cr/52Cr, and 54Cr/52Cr ratios are 1, 2 and 2 ppm, respectively. These methods include a range of isotope systematics related to lithophile and siderophile elements, long-lived radionuclides, and short-lived extinct radionuclides. Additionally, they provide support for the further study of Antarctic meteorites.