• Economic and Environmental Geology
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• v.16 no.3
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• pp.163-221
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• 1983

Main aspects of this study are to clarify geochronology and petrogenetic processes of the so-called Hongjesa granite, which is a member of various intrusive rocks exposed in the northeastern part of the Ryongnam Massif, one of the Precambrian basements of South Korea. In this study, the Hongjesa grainte is divided into four rock units based on the geologic age, mineralogical and chemical constituents, and texture: the Precambrian Hongjesa granite gneiss (Hongjesa granite Proper) and leucogranite gneiss, the Paleozoic gnessic two mica granite, and the Jurassic muscovite granite. The Hongjesa granite gneiss is identified by its grayish color, slight foliation, and porphyroblastic texture. The leucogranite gneiss is distinct by its light gray color, sand medium to coarse grained texture. The gneissic two mica granite is distinguished from others by its strong foliation, containing gray-colored feldspar phenocrysts with biotite and muscovite in varying amounts. The muscovite granite occurs as a small stock containing feldspar phenocrysts along margin of the stock. These granitic rocks vary widely in composition, reflecting the facts that they partly include highly metamorphosed xenolith and schlierens as relics of magmatic and anatectic processes. In particular, grayish porphyroblasts of microcline perthite is characteristic of the Hongjesa granite gneiss, whereas epidote and garnet occur in both the Hongjesa granite gneiss and leucogranite gneiss. These minerals are considered to be formed by potassic metasomatism and contamination of highly metamorphosed rocks deeply buried under the level of the Hongjesa granite emplacement. The individual synchronous granitic rocks plotted on Harker diagram show mostly similar trends to the Daly's values. The plots of the Hongjesa granite gneiss and gneissic two mica granite concentrate near the end part of the calc-alkalic rock series on the AMF diagrams, whereas those of the leucogranite gneiss and muscovite granite indicate the trend of the Skaergaard pluton. These granitic rocks plotted on a Q-Ab-Or diagram (petrogeny's residua system) fall well outside the trough of the system. This can be attributed to the potassic matasomatism of these rocks. On the ACF diagram, these rocks appear to be dominantly I-type prevailing over S-type. The K-Ar ages, obtained from a total of 7 samples of the leucogranite gneiss, gneissic two mica granite, muscovite granite, porphyritic alkali granite, and rhyolitic rock, in addition to the Rb/Sr ages of the Hongjesa granite gneiss by previous workers, permit the rock units to be arranged in the following chronological order: The middle Proterozoic Hongjesa granite gneiss (1714-1825 m.y.), the upper proterozoic leucogranite gneiss (875-880 m. y.), the middle Paleozoic gneissic two mica granite (384 m. y.) the upper Jurassic muscovite granite (147 m. y.), the Eocene alkali granite (52 m. y.), and the Eocene rhyolitic rock (45 m. y.). From the facts and data mentioned above, it is concluded that the so-called Hongjesa granite is not a single granitic mass but is further subdivided into the four rock units. The Hongjesa granite gneis, leucogranite gneiss, and gneissic two mica granite are postulated to be either magmatic or parautochtonous, intrusive, and the later muscovite granite is to be magmatic in origion.

• Economic and Environmental Geology
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• v.21 no.1
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• pp.69-83
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• 1988

Orthogneiss of the study area is meta-igneous complex that composed of granite gneiss, porphyroblastic gneiss and migmatitic gneiss. Migmatitic gneiss produced from granite gneiss and porphyroblastic gneiss by strong ductile shearing. These rocks show mostly gneissic and partly mortar textures by strong regional metamorphism and ductile shearing during several orogenies. $^{40}Ar-^{39}Ar$ incremental-release ages of these rocks have been determined for 1 hornblende. 1 biotite and 3 muscovite concentrates separated from orthogneisses in this area. Ages of regional metamorphism and ductile shearing of these rocks are more than 5 stages(1500 Ma, 260 Ma, 190 Ma, 180-170 Ma and 160 Ma) under $300^{\circ}C$ to $500^{\circ}C$. These rocks had not been nearly effected by Daebo orogeny, because this area is far from Daebo granite bodies. The general trend of major chemical composition and mineral composition of these orthogneisses suggest that these rocks are some series of differentiated products from magma.

• Journal of Korean Tunnelling and Underground Space Association
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• v.3 no.1
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• pp.27-35
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• 2001

Four road tunnels, which consists of biotite gneiss and granite gneiss and shows a similar geological conditions, were selected in this study. Laboratory and field tests, the rock mass rating for the four tunnels were conducted. A regression analysis was performed to find out the correlations of test results. It was proposed an equation of reduction factor which can assess the deformation modulus for biotite gneiss and granite gneiss. It was also found that there was a close correlation between Q and RQD in four tunnels according to the analysis between RMR and Q, RMR and RQD, Q and RQD and laboratory and field tests.

• The Journal of the Petrological Society of Korea
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• v.16 no.1 s.47
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• pp.27-37
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• 2007

Here we discuss a geochemical characterisitc of rare earth element (REE) pattern of a Precambrain leucogranitic gneiss at Imweon, Gangwon Province, Korea. The outcrop includes biotite gneiss xenolith. The leucocratic granite gneiss contacting with biotite gneiss is pegmatitic. However, there is no evidence of contact metamorphism between biotite gneiss and leucocratic-pegmatitic granite gneiss. The leucocratic granite gneiss shows a specific phenomenon of M-type (convex curved) tetrad effect in chondrite-normalized REE patterns with large negative Eu anomaly. The degree of REE tetrad effect in the leucocratic-pegmatitic granitec gneiss is weak and shows partly W-type (concave curved) tetrad effect. The Eu anomaly of leucocratic granite gneiss has close relationship with the degree of tetrad effect as well as Ca/Sr ratio. Our results suggest that the REE tetrad effect from the leucocratic granite gneiss should be formed during differentiation process of granitic magma. We also confirmed that the weathering might affect Eu or Ce anomaly rather than the formation of REE tetrad effect in granitic rock.

• The Journal of the Petrological Society of Korea
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• v.1 no.1
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• pp.34-41
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• 1992

The Precambrian granitic gneisses are widely distributed in the Danyang-Yecheon area, eastern part of Korea, where the Ryeongnam massif borders the Ogcheon fold belt. They are composed of migmatitic, biotite granitic, garnet-bearing and granoblastic granitic gneisses. The common joint sets of the granitic gneiss are NE and NS directions, which are probably related to the effects of Daebo orogeny and Bulgugsa disturbance, respectively. Mineral assemblages of the banded gneiss xenolith in the garnet-bearing granitic gneiss are quartz-plagioc1ase-biotite-mus-covite-orthoclase and quartz-plagioc1ase-biotite-garnet, belonging to the amphibolite facies. The granoblastic granitic gneiss is felsic, metaluminous, and granitic, and shows subalkaline trend. The garnet-biotite geothermometry of garnet-bearing granitic gneiss yields 640$^{\circ}$-708$^{\circ}C$ at pressure of 4 kb.

• Tunnel and Underground Space
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• v.6 no.3
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• pp.223-233
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• 1996

Geotechnical Information System (GTIS) for efficient management of three dimensional borehole data has been developed. Geotechnical maps in the vicinity of Bulkwangdong, Seoul station, Itaewon, Han river near Yuido, and Jungrangchon were constructed by Kriging method. In Bulkwangdong and Jungrangchon area where boundary between granite and gneiss is present, gneiss has been more weathered than granite, but in Seoul station and Itaewon area where the boundary is also present, granite has been more weathered than gneiss. It has been inferred that when Seoul granite intruded, the strength of gneiss in Bulkwangdong and Jungrangchon area was lowered by the attitude of foliation plane than in Seoul station and Itaewon area, so the gneiss has been easily fractured and weathered in Bulkwangdong and Jungrangchon area. Geotechnical map in the vicinity of Yuido showed that there is an NW-SE trend weakness zone that might be affected by major faults under Han river and it is expected that the fault zone may be present in construction area of Kyoungbu Highspeed Railway that lies below the Han river like the Subway Line No.5.

• Economic and Environmental Geology
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• v.33 no.3
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• pp.173-180
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• 2000

Main aims of this study are to clarify petrochemistry of the granitic gneiss in the Durye-Suncheon area. The origin of the metamorphic rock is evaluated from the abundance of $Na_2O$, the $TiO_2$/$Al_2O_3$ratios, the Harker variation diagram and $Al_2O_3$($Na_2O$ +$K_2O$ + CaO) ratios of the major elements. and the frequency distribution and average abundance of the trace elements . The trace elements of the granitic gneiss in the studied area are compared with those of the granitic rocks with shales in the other areas. The abundance of $Na_2O$ is lower than 3.27% and the $TiO_2$/$Al_2O_3$ ratio is 0.04. Also the Harker's variation diagram indicate this granitic gneiss correspond to sedimentary origin or S-type granite. The average abundance for trace elements of the granitic gneiss is similar to that of the shale, and the frequency distribution shows extensive distribution and irregularly . But xenolith are observed in the field survey, it is evidence of igneous origin , and then origin of the granitic gneiss in studied area is S-type granite.

• The Journal of the Petrological Society of Korea
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• v.11 no.3_4
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• pp.157-168
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• 2002

In Gimcheon area of the central Yeongnam massif granite gneiss occurrs with intercalated biotite gneiss at xenolith or restite. In order to understand the evolution of the central Yeongnam massif, it is essential to have absolute age information, but not many age data are available yet. Furthermore the previous age determinations from the study area are not compatible with the outcrop relationship. In this study we determined chemical ages from the zircon grains. We obtained ages of $1970\pm$ 78(l$\sigma$)Ma from the granite gneiss, $1814\pm$77(l$\sigma$)Ma from the outer rim of a rounded zircon and 1973$\pm$97(l$\sigma$)Ma from a longish zircon, both from the biotite gneiss. These ages seem to indicate the timing of granitic magma intrusion and subsequent metamorphism. Ages of $2954\pm$ 158($l\sigma$)Ma, 2440$\pm$58(l$\sigma$)Ma, and 2219$\pm$36($l\sigma$)Ma obtained from zoned core of the rounded zircon grain from the biotite gneiss suggest various geological events before such metamorphism of the biotite gneiss. Ages in the range of 1450~1670 Ma observed in zircons of both gniesses suggest later metamorphism that the granite gneiss and the biotite gneiss experienced together. The chemical age determination by electron probe micro-analyzer of this study utilized 1$\mu\textrm{m}$ beam diameter and it seems to be a very useful age determination from the zircons with complex growth history because of superior spatial resolution.

• The Journal of the Petrological Society of Korea
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• v.14 no.3 s.41
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• pp.127-140
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• 2005

The Samyuri area of Jeoksang-myeon, Muju-gun at the Middle Yeongnam Massif consists of granitic gneiss, porphyroblastic gneiss and leucocratic gneiss, which correspond to Precambrian Wonnam Series. Here we discuss a geochemical implication of the data based on major element composition, trace element, rare earth element (REE), Sm-Nd and Rb-Sr isotope systematics of the boring cores in the granite gneiss area. The boring cores are granitic gneiss (including biotite gneiss) and amphibolite. The major and trace element compositions of granitic gneiss and amphibolite suggest that the protolith belongs to TTG (Tonalite-Trondhjemite-Granodiorite) and tholeiitic series, respectively. Chondrte-normalized REE patterns vary in LREE, HREE and Eu anomalies. The granitic gneiss and amphibolite have Sm-Nd whole rock age of $2,026{\pm}230(2{\sigma})$ Ma with an initial Nd isotopic ratio of $0.50979{\pm}0.00028(2{\sigma})$ (initial ${\epsilon}_{Nd}=-4.4$), which suggests that the source material was derived from old crustal material. Particularly, this initial ${\epsilon}$ Nd value belongs to the range of the geochemical evolution of Archean basement in North-China Craton, and also corresponds to the initial Nd isotope evolution line by Lee et al. (2005). In addition, chondrite-normalized REE pattern and initial Nd value of amphibolite are very similar to those of juvenile magma in crustal formation process.

• The Journal of the Petrological Society of Korea
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• v.26 no.4
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• pp.353-360
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• 2017

The preservation treatment for the outer rampart of Namhansanseong fortress is needed due to partial collapse and separation of stone materials. In this study, we investigated the petrological features of the stone materials used for the outer rampart and estimated their provenances through the geologic survey. Through the above study, the suitable replacement stone in the maintenance of outer rampart were suggested. The stone materials of the above outer rampart consist of the banded gneiss, augen gneiss, granitic gneiss and porphyroblastic gneiss. Among these four kinds of rocks, granitic gneiss is quantitatively the most abundant. Petrological comparisons between stone materials and rocks distributed around the fortress, lead to the conclusion that the above materials are likely to have been delivered from around the fortress. Judging from the results of the comparison on frequency of use and strength characteristics among the above rocks, the granitic gneiss is considered to be suitable for restoration of the outer rampart of the fortress.