Fukutoku-oka-no-ba Volcano: A new perspective on the Alkalic Volcano Province in the Izu–Bonin – Mariana arc |
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| Authors: | CHIH-HSIEN SUN ROBERT J STERN TAKEYOSHI YOSHIDA & JUN-ICHI KIMURA |
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| Institution: | Center for Lithospheric Studies, University of Texas at Dallas, Box 830688, Richardson, Texas 75083–0688, USA,;Institute of Mineralogy, Petrology &Economic Geology, Graduate School of Science, Tohoku University, Kawauchi, Aoba-Ku, Sendai, 980–77, Japan,;Regional Sciences Laboratory, Faculty of Education, Fukushima University, Asakawa Sugumichi 2, Fukushima City, 960–12, Japan |
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| Abstract: | Pumice samples from Fukutoku-oka-no-ba in the Izu–Bonin – Mariana (IBM) arc were analysed for 40 trace elements and Sr, Nd, and Pb isotopic compositions. These samples are shoshonites (59.4–61.8 wt% SiO2), characterized by high contents of K2O (3.74–4.64 wt%), Ba (1274–1540 p.p.m.), Rb (91–105 p.p.m.), and light rare earth elements. The characteristics of alkali-element enrichment are similar to those of other parts of the Alkalic Volcano Province (AVP) in the northern Mariana and southernmost Volcano arcs. Sr (87Sr/86Sr = 0.7036–0.7038) and Pb isotopic compositions (206Pb/204Pb = 19.08–19.11, 207Pb/204Pb = 15.62–15.63, 208Pb/204Pb = 38.85–38.91) of Fukutoku-oka-no-ba pumice are relatively radiogenic, whereas Nd is unradiogenic (143Nd/144Nd = 0.51283–0.51286). Fukutoku-oka-no-ba is isotopically distinct from Iwo Jima and is similar to the Hiyoshi Volcanic Complex, suggesting that Fukutoku-oka-no-ba might have a magma source similar to that of the Hiyoshi volcanic complex. Plots of Pb and Nd isotopes for AVP lavas trend toward the fields of ocean island basalt (OIB) source and pelagic sediments, which are possible sources of AVP enrichments. |
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| Keywords: | Fukutoku-oka-no-ba igneous rocks island arc Izu–Bonin – Mariana arc shoshonites |
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