DETERMINING TECHNIQUES FOR Sm-Nd ISOTOPIC SYSTEMATICS AND THEIR APPLICATION
Mao Cunxiao Zhu Naijuan Zhu Bingquan Shi Zeen Huang Rongsheng(Institute of Geochemistry, Academia Sinica)
In sample preparation four spikes (149Sm, 116Nd, 84Sr, 87Rb) were put into the sample.After dissolution and separation, the solutions of Sm, Nd, Sr and Rb could be obtained, respectively. The isotopic compositions and concentrations were measured in one mass spec-trometric analysis using the computer program edited by us. In order to enhance the sensiti-vity of Nd+ analysis with a single filament, an emission reagent was developed.The measured value for La Jolla Nd standard is 145Nd/144Nd = 0.511845± 0.000006(2a) which is very close to that obtained by Lugmair. NBS987 was measured with 87Sr/86Sr = 0.710221 ±0.000003.The developed Sm-Nd technique has been used to study the origin of granites and the che-mical heterogenity of subcontinental mantle in eastern and southwestern China.Several Sm-Nd isochrons for the Archean restites in tonalites from Shanxi Province and the Precambrian metavolcanics and ultramafic rocks from Yunnan and Shandong provinces were also measured, respectively.