The principle, analytical procedures and applications of Rb-Sr dating for minerals and rocks are described. Sr was separated by ion exchange resin 71-616 (1) (made in China) and inorganic ion-exchanger ZrP (prepared i...The principle, analytical procedures and applications of Rb-Sr dating for minerals and rocks are described. Sr was separated by ion exchange resin 71-616 (1) (made in China) and inorganic ion-exchanger ZrP (prepared in our laboratory). All Sr determinations were made by isotope dilution and mass spectrometry. The concentration of Rb was analysed by flame spcetrophotometry. Rb-Sr ages of three micas (one from pegmatite from Inner Mongolia, and the other two are from granites from Kiangsi province) are in agreement with the K-Ar.rages and geological observations, indicating that the retention of radiogenic Sr^87 in micas is excellent. But systematic defferenee between K-Ar and Rb-Sr mica ages has been found in the other granite from Kiangsi province, suggesting possible eontaminations of radiogenic Sr^87 from magraas of different resources. Based on the isochrons formed by six total rocks and one feldspar, two metamorphie episodes of Jolmo Lungma series, Tibet, China (659±20, 17±6 m.y.) have been established. A similar conclusion has been reached by the U-Pb two stage model(modified eoncordia) ages, K-Ar dating as well as field investigations. It is believed that if sufficient geological data and suitable specimens are avilable, Rb-Sr isochron method may be a powerful toot to bring out multi-metamorphism in a given geological system.展开更多
文摘The principle, analytical procedures and applications of Rb-Sr dating for minerals and rocks are described. Sr was separated by ion exchange resin 71-616 (1) (made in China) and inorganic ion-exchanger ZrP (prepared in our laboratory). All Sr determinations were made by isotope dilution and mass spectrometry. The concentration of Rb was analysed by flame spcetrophotometry. Rb-Sr ages of three micas (one from pegmatite from Inner Mongolia, and the other two are from granites from Kiangsi province) are in agreement with the K-Ar.rages and geological observations, indicating that the retention of radiogenic Sr^87 in micas is excellent. But systematic defferenee between K-Ar and Rb-Sr mica ages has been found in the other granite from Kiangsi province, suggesting possible eontaminations of radiogenic Sr^87 from magraas of different resources. Based on the isochrons formed by six total rocks and one feldspar, two metamorphie episodes of Jolmo Lungma series, Tibet, China (659±20, 17±6 m.y.) have been established. A similar conclusion has been reached by the U-Pb two stage model(modified eoncordia) ages, K-Ar dating as well as field investigations. It is believed that if sufficient geological data and suitable specimens are avilable, Rb-Sr isochron method may be a powerful toot to bring out multi-metamorphism in a given geological system.
