• The Journal of the Petrological Society of Korea
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• v.14 no.3 s.41
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• pp.157-168
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• 2005

Trachytic rocks among the bimodal metavolcanic rocks of the Gyemyeongsan Formation and adjacent areas are investigated. Some rocks reveal very high content of iron and most rocks show very high abundances of rare earth elements and high field strength elements. Most rocks show significant Eu negative anomaly, which can be interpreted as the result of plagioclase fractionation. Lack of noticeable Nb negative anomaly indicates not-involvement of crustal material in their generation, which excludes the arc environment or remelting of continental crust from their genetic process. Metatrachytes of the Gymyeongsan Formation are plotted within the within-plate environment of the tectonic discrimination diagram utilizing immobile high field strength element Nb and Y. They also show typical characteristics of A-type magma, such as high Ga content. Considering their affinity to Al-type of Eby (1992) and their age of 750 Ma (Lee et al., 1998), they seem to have been produced by the differentiation of mantle-derived within-plate magmatism at the rift, related with the separation of Neoproterozoic supercontinent Rodinia. Possible connection of Gyemyeongsan and Munjuri Formations of the Okcheon metamorphic belt, at least part of them, to the Cathaysia block of South China during the Neoproterozoic is strongly suggested.

• The Journal of the Petrological Society of Korea
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• v.5 no.1
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• pp.66-83
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• 1996

We report petrography, mineral chemistry, and major and trace element chemistry for rare tholeiites in Cheju island where alkalic rocks predominate. Available age data indicate that the tholeiitic magmatism was younger than 0.49Ma, possibly younger than 0.17 Ma. The tholeiites are generally fine-grained, porphyritic rock and show intergranular texture with lath-shaped plagioclase ($An_{61-46}$), orthopyroxene (bronzite) and olivine ($Fo_{78-67}$). Characteristically, two kinds of clinopyroxene (pigeonite and augite) occur only in groundmass. The tholeiites have normative quartz and show limited compositional variations ($SiO_2$=51.0-52.5 wt%; Mg＃=54-60). Major and transitional metal element variations of tholeiites are distinct from those of alkaline rocks in MgO diagram, suggestingthat the two rock types cannot be simply related to differentiation process from the same magma. The ratios among $K_2O$, Rb, Ba, Nb and La are similar for both tholeiites and alkali basalts, however the ratios between the elements (P, Y and Yb) having an affinity with garnet and the above elements are higher for tholeiites than for alkali basalts. These trace element ratios suggest that the tholeiites and alkali basalts were produced by different degrees of partial melting from a similar sources material (garnet lherzolite mantle).

• Korean Journal of Plant Taxonomy
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• v.31 no.3
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• pp.283-309
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• 2001

Acer pictum complex (A. pictum Thunb. ex Murray with varieties, A. okamotoanum Nakai, A. truncatum Bunge) in eastern Asia causes frequent difficulty in identification. One hundred twenty five specimens from A. pictum complex of China, Korea and Japan and A. cappadocicum var. sinicum of China were compared to investigate patterns of intra- and interspecific variation and to evaluate a recognition of several species as well as many varieties using 22 characters for morphometric analysis. The first three PCA accounted for 59% of the total variance. No strong discontinuities existed among taxa with respect to fruit and leaf characters. Much overlap among all taxa occurred the central region of the scatter diagram. Many characters appeared to show some clinal variation with changes from east of China to Japan through Korea. This was true not only when all species as considered as a single taxon, but when characters of individual taxa were compared with geography. As one considers a path from the western part of the ranges to areas to the east, the leaves become larger in most respects and become increasingly many lobed (five to seven or nine). In general, there was a tendency toward larger nutlet with smaller wing in the area toward northeast of China (=A. truncatum), while in the east of ranges (Island Ullung-do), plants were larger with respect to characters of fruit and leaves (=A. okamotoanum). The morphological differentiation between A. okamotoanum and Japanese and Korean individuals of A. pictum was not considered sufficient to warrant recognition of either specific or varietal status and should be treated as con specific under A. pictum var. mono. Since the lectotype of Acer pictum had minute hairs uniformly on the under surface of leaves(A. pictum var. pictum), the glabrous type of A. pictum was called A. pictum var. mono as Ohahsi suggested. The univaraite analysis (the mean and maximum/minium of nutlet size and wing/nutlet length ratio) indicated geographical differentiation of northeastern populations, A. truncatum, was distinctive, but Korean individuals of A. truncatum showed an affinity between Chinese individuals of A. truncatum and Korean individuals of A. Pictum var. mono. The current results, together with qualitative character, trunk features, justify subspecific status for this taxon. The previous varieties of A. mono in Korea were indistinguishable from typical form of A. Pictum var. mono on the basis of the wing angle and nutlet size, rejecting continued recognition of these taxa as distinctive varieties. Therefore, it is recommended that only one polymorphic species of A. pictum be recognized in addition to three varieties.