Chromium in geological standard igneous rocks is precisely determined with a fully automated non-destructive neutron activation analysis. Samples are GSJ standard rocks (JP-1, JB-1, JB-la, JA-3, JGb-1, JB-2, JA-1) and USGS ones (BCR-1 and G-2). Chromium concentration is determined relative to a chemical standard instead of a natural rock standard. Multiple aliquots of a slightly large amount of (200-300mg) sample powder are analyzed to examine the heterogeneity in chromium concentration. The results agree with the consensus values within the errors of consensus values which have large coefficients of variation. The precise analysis and the examination on the distribution of reported values reveal the heterogeneity in chromium concentration of the sample powder. In particular, basaltic samples have heterogeneity in chromium concentration because of a small amount of chromite with extremely high chromium content. A chemical standard is useful to get high accuracy of chromium determination rather than natural standard materials.

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The granitic rocks in the Inje-Hongcheon district grade from hornblende-biotite granodiorite, porphyritic biotite granite, equigranular biotite granite and two-mica granite from the center to the margin. These granitic rocks have gradual boundaries with each other and show a gradual change in mineral compositions. In major element geochemistry, the granitic rocks show a general trend of crystallization differentiation from a granodioritic magma to a granitic magma in the strict sense. From the petrographical and major element geochemical studies, it can be said that the lithological varieties of the granitic rocks are due to the internal differentiation in a single magma chamber.
The hornblende-biotite granodiorite and the porphyritic biotite granite show the characteristics of I-type and magnetite-series granitoids, while the equigranular biotite granite and two-mica granite exhibit those of S-type and ilmenite-series granitoids. The different I-/S-type and magnetite-/ilmenite-series characteristics between the central and marginal parts stem from the different degrees of the reaction of original magma with surroundings and from the consequent differences of redox conditions during solidification of the magma.

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Yufu-Tsurumi volcano group of northeastern Kyushu yields very porphyritic andesite lavas. These lavas show interesting disequilibrium mineral assemblages and contain characteristic dark inclusions. Analyses of phenocryst minerals revealed that basic mineral group have similar compositions of those of dark inclusions.
The volcano group consists of three closely associated volcanoes, which we define as Takahira group, Tsurumi group and Yufu group. Volcanic activity of Takahira group was older than those of Tsurumi and Yufu groups. Volcanic activities of both Tsurumi and Yufu groups continued until some time after 6, 000 y. B. P. Pyroclastic flow deposits dominated older volcanic products, whereas lava flows and lava domes dominated younger products.
Hornblende andesite to dacite are abundant among the volcanic rocks of Yufu-Tsurumi volcano group. Andesites contain phenocrysts of plagioclase (An>80 and An<50), clinopyroxene (Mg/(Mg+Fe)=86-71), orthopyroxene (Mg/(Mg+Fe)<70), amphiboles (pargasite and magnesio-hornblende) and opaque minerals with rare olivine, biotite and quartz. In contrast, dacites contain phenocrysts of Mg-poor orthopyroxene, magnesio-hornblende and An-poor plagioclase. Dark inclusions are nearly equigranular and consist of Mg-rich clinopyroxene, pargasite and An-rich plagioclase, with ± olivine, ± orthopyroxene and ± quartz. Some inclusions have chilled margin at the circumference, which implies that they were incorporated into the host magma as liquid state.
The analyzed samples from Yufu-Tsurumi volcano group have a wide SiO₂ range of 56-65 wt. %, but a nearly constant FeO^*/MgO ratio. Thus they show a typical calc-alkaline character. The SiO₂ content of the dark inclusions ranges from 48 to 55 wt. %. In the variation diagrams, these inclusions and other volcanic rocks form a single trend with the inclusions being the basic end.
Both chemistry and mineralogy of these lavas changes systematically with time. Lavas became more basic toward the younger stage. Modal composition of clinopyroxene increases, and the percentage of dark inclusions becomes progressively greater, as the volcanic products became younger.

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