Rare-earth and trace elements in the Quaternary volcanic rocks of Hokkaido,Japan |
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| Authors: | Yasuyuki Masuda Susumu Nishimura Takashi Ikeda Yoshio Katsui |
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| Institution: | 1. Department of Earth Science, University of Osaka Prefecture, Sakai-city, Osaka Japan;2. Institute of Earth Science, Kyoto University, Kyoto Japan;3. Department of Geology and Mineralogy, Faculty of Science, Hokkaido University, Sapporo Japan |
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| Abstract: | Seven rare-earth elements (La, Ce, Sm, Eu, Tb, Yb, Lu) and Co, Cr, Sc, Ba, Hf and Th have been determined by non-destructive neutron activation analysis on the Quaternary volcanic rocks in Hokkaido, Japan. The trace-element abundances are discussed in terms of the petrological problems, particularly the origin of calc-alkali magma. On the basis of the La/Sm ratio and the contents of K, Ba, Th and La, lateral variations in the contents of trace elements exist across the Kurile and the northern Honshū arcs. The calc-alkali rocks can be classified into three types which correspond to Kuno's three basalt-magma types. There is no essential difference in the rare-earth patterns between the basaltic rocks and the associated calc-alkali rocks in each petrographic province. This suggests that the calcalkali rocks may be derived from the basaltic magmas by fractional crystallization under certain conditions. |
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