Tholeiitic and calc-alkaline magma series at Adatara volcano, northeast Japan: 1. Geochemical constraints on their origin

Trace elements and Nd-Sr isotopes of island arc tholeiites from frontal arc of Northeast Japan.

“…g; gravimetry, c; colorimetry, a; atomic absorption method, p; photon activation analysis (Electron Linac of Nuclear Science, Tohoku Univ., Yoshida et al, 1986), i; isotope dilution method using mass spectrometer, I; inductively coupled plasma-op tical emission spectrometry (by N. Onuma), n; neutron activation analysis, x; X-ray fluorescence, y; y-ray spectrometry (with assumption of radiometrical equilibrium, K. Sato and J. Sato, unpublished data Fujinawa (1989) for major and trace elements and from Kurasawa et al (1986) for Sr isotope ratios. Sample description: 2-1; Olivine-augite bearing hypersthene andesite, Maegatake-nishi lava, the second stage.…”

Lateral variation of major and trace elements in the late Miocene volcanic rocks from central part of Northeast Japan.

“…7). Shuto et al (1988), this study, Quaternary volcanic rocks: Togashi (1977), Sasaki et al (1985), Taniguchi (1972), Ishikawa et al (1984Ishikawa et al ( , 1985, , Yoshida et al (1987), Sakayari et al (1984), Shimotori et al (1983), Fujinawa (1988, Ban et al (1987), , Maruyama et al (1988), Aoki and Fujimaki (1982), Hayashi et al (1984), Koizumi et al (1984). Dashed lines are the same as those of Fig.…”

Operation of subduction factory and production of andesite

“…It is generally accepted that the TH differentiation trend can be reproduced by separation of phenocryst phases such as olivine, plagioclase and pyroxene from a parental basaltic magma (e.g. Sakuyama, 1981;Grove and Baker, 1984;Fujinawa, 1988), which is also suggested by MELTS modeling (Ghiorso and Sack, 1995) for a basaltic magma in the presence of 0.5 wt% H 2 O at 0.5 GPa under a QFM buffer (Fig. 4).…”

“…If we accept magma mixing as the mechanism responsible for the petrographic and chemical characteristics of CA andesites, then an ensuing question involves the origin of end member components in magmas, one basaltic and higher T, the other a more differentiated and lower T. A key observation in this problem is the systematic difference in isotopic composition between CA and TH series rocks, e.g., as documented in Quaternary volcanoes in the NE Japan arc (Fujinawa 1988;Tatsumi and Kogiso, 2003). If this observation may be generalized to other arcs, then the two end member magmas would be derived from different sources.…”