• The Journal of the Petrological Society of Korea
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• v.26 no.1
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• pp.13-43
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• 2017

In the Hapcheon area, hypersthene-bearing monzonite (mangerite) and syenite are recognized. The main minerals of syenite are alkali feldspar, plagioclase, amphibole, biotite, and quartz. Anhedral hornblende and biotite are interstitial between feldspar and quartz, indicating that the hydrous minerals were crystallized later on. Based on petrochemical studies of major elements, syenite is alkaline series, metaluminous, and I-type. The variation patterns in the trace and rare earth elements of mangerite and syenite show the features of subduction-related igneous rock such as depletion of HFSE, relative enrichment in LILE to LREE, and negative Nb-P-Ti anomalies. Based on the experimental data and petrographic characteristics of the syenite, Hapcheon syenitic magma is considered to be formed by partial melting in a dry system. SHRIMP U-Pb zircon data yield the Triassic age as $227.4{\pm}1.4Ma$ in mangerite, $215.3{\pm}1.2Ma$ in syenite, and $217.9{\pm}2.6Ma$ in coarse-grained syenite, respectively. The mangerite age is similar to those of post-collisional plutonic rocks in Hongseong (226~233 Ma), Yangpyeong (227~231 Ma), and Odaesan (231~234 Ma) areas in the Gyeonggi Massif. Syenites were intruded after about 10 Ma. The features seen in the mangereite and syenite rocks can be explained by models such as the continental collision and slab break-off and the lithosphere thinning and asthenosphere upwelling model.

• The Journal of the Petrological Society of Korea
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• v.19 no.2
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• pp.123-139
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• 2010

The properties of fracture system in Precambrian Jangbong schist and Mesozoic granites from Seokmo-do, Ganghwa-gun were investigated and analyzed. Most of the fractures measured at outcrops are nearly vertical or steeply dipping. Orientations of fracture sets in terms of frequency order are as follows: Set $1:N2^{\circ}E/77^{\circ}SE$, Set $2:N17^{\circ}E/84^{\circ}NW$, Set $3:N26^{\circ}E/64^{\circ}SE$, Set $4:N86^{\circ}W/82^{\circ}SW$, Set $5:N80^{\circ}W/77^{\circ}NE$, Set $6:N60^{\circ}W/85^{\circ}SW$, Set $7:N73^{\circ}E/87^{\circ}NW$, Set $8:N82^{\circ}W/53^{\circ}NE$, Set $9:N23^{\circ}W/86^{\circ}SW$, Set 10: $N39^{\circ}W/61^{\circ}NE$. Especially, the rose diagram of fracture strikes(N:240) indicates that there are two dorminant directions of N-S~NNE and WNW. These distribution pattern of fractures from Seokmo-do correponds with those of major lineaments from South Korea suggested in previous study. Meanwhile, the scaling properties on the length distribution of fracture populations have been investigated. First, fracture sets from Precambrian Jangbong schist and Mesozoic granites(north and south rock body) has been classified into five groups(group I~V) based on strike and frequency. Then, the distribution chart generalized the individual length-cumulative frequency diagram for above five groups were made. From the related chart, five subpopulations(group I~V) that closely follow a power-law length distribution show a wide range in exponents(-0.79~-1.53). These relative differences in exponent among five groups emphasizes the importance of orientation effect. From the related chart, the diagram of group III occupies an upper region among five groups. Finally, the distribution chart showing the chracteristics of the length frequency distribution for each rock body were made. From the related chart, the diagram of each rock body shows an order of porphyritic biotite granite < hornblende granodiorite < medium-grained biotite granite(south rock body) < medium-grained biotite granite(north rock body) < Precambrian Jangbong schist. From the related chart, the diagram of more older rock body in the formation age tends to occupy an upper region. Especially, the diagram of Precambrian Jangbong schist occupies an upper region compared with the diagrams of Mesozoic granites. These distributional chracteristics suggests that coexistence of new fracture initiation and growing of existing fractures corresponding with stress field acted since the formation of rock body.

• The Journal of the Petrological Society of Korea
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• v.14 no.2 s.40
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• pp.116-126
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• 2005

The Precambrian quartzite and calc-schist layers experienced multi-1310ing events are distributed along the two kinds of U-shaped 1310 (Fold I and II) with $N10^{\circ}E-directed$ fo1d axis in Wollong-myeon, Gwangtan-myeon, Jori-myeon of Paju city, the northeastern part of Gyeonggido. Occurrence of 10 layers of quartzite and 4 layers of calc-schist is not clear whether quartzite and schist layers were deposited sequentially each other or one to two layers of quartzite and schist were distributed repeatedly by isoclinal folding and thrusting, because of lack of sedimentary structures. In this paper, we tried to clarify the correlative relationship among the quartzite beds which are distributed along the U-shaped folds using geochemical tools such as rare earth element (REE) patterns and Nd isotope ratio. Quartzites have characteristics of LREE-flattened, HREE- slightly depleted patterns. They also show Ce negative anomaly whereas there are no Eu anomalies. As a result, quartzite beds occurred along the bilateral sides of fold axis show very similar REE patterns from outer side to inner side of 1314. The Nd model age of quartzite layers shows a trend that the inner part of fold is younger than the outer part of it. Such geochemical characteristics suggest that bilateral quartzite beds occurred along the fold axis were derived from the cogenetic source materials. The REE patterns and trace element geochemistry of mica schist intercalated within quartzite indicate that the quartzite and mica schist may be derived from different source materials. Our results suggest that REE and Nd isotope geochemistries may be very useful in clarifying the relationship of sedimentary deposits which do not show stratigraphical and structural connections in the field.

• The Journal of the Petrological Society of Korea
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• v.19 no.3
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• pp.209-225
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• 2010

The Shinri area near the Yedang Lake, the eastern part of the Hongseong area in SW Gyeonggi Massif, consists of the Neoproterozoic Duckjeongri granodiorite-tonalite, mylonitized amphibole-bearing orthogneiss and impure marble with lens-shaped garnet-bearing metabasites. In this paper, we report mineralogical and geochemical data of Neoproterozoic lens-shaped garnet-bearing metabasites within marble of the Shinri area. The $SiO_2$ contents of garnet-bearing metabasites in marble vary between ~46.98 and 51.17 wt%, and the $Na_2O$ + $K_2O$ contents fall between ~1.95 and 2.85 wt%, similar to the tholeiitic sub-alkaline basaltic rocks. In the Zr/Y vs. Zr diagram, garnet-bearing metabasites also plot in the subalkaline basaltic rocks. The chondrite-normalized REE patterns for Shinri garnet-bearing metabasites show relatively flat patterns to that of chondrite. They show slight LREE-enriched and depleted patterns. The major and trace element data from lens-shaped garnet-bearing metabasites in marble of the Shinri area suggest that these rocks were formed in within plate. In contrast, previous major and trace element data of high pressure type garnet-bearing metabasites from the mafic-ultramafic complex in the Baekdong and Bibong areas suggest that these rocks were formed in a nascent arc to backarc spreading center within subduction zone setting. Based on mineral assemblage and mineral chemistry, P-T estimates for Shinri garnet-bearing metabasites are 9.6-12.7 kb, $695-840^{\circ}C$ for inclusions in the core, and 9.6-13.6 kb, $630-755^{\circ}C$ for those in the rim. These P-T estimates are distinct from those of the Baekdong and Bibong garnet-bearing metabasites with isothermal decompressional retrograde P-T path. In addition to Triassic tectonic activity previously reported in the Shinri area of Hongseong, the details of metamorphic history such as protolith age and Neo-Proterozoic metamorphic episode need to be solved.

• Economic and Environmental Geology
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• v.18 no.4
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• pp.399-410
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• 1985

Bentonites from the Janggi Group of the Lower Miocene age from the Geumgwangdong area, Korea, have been studied for mineralogical and genetic characterization. The Janggi Group is subdivided, in ascending order, into the Janggi Conglomerate, the Nuldaeri Tuff, the Geumgwangdong Shale, the Lower Coal-bearing Formation, the Basaltic Tuff, and the Upper Coalbearing Formation. Bentonites occur as thin or thick beds in all sedimentary units of the Janggi Group, except for the Janggi Conglomerate. Significant bentonite deposits are found in the Nuldaeri Tuff, the Lower Coal-bearing Formation and the Basaltic Tuff. Bentonites consist mainly of smectite (mainly montmorillonite), with minor quartz, cristobalite, opal-CT and feldspar. Occasionally, kaolinite, clinoptilolite or gypsum is associated with bentonites. Bentonites were studied by the methods of petrographic microscopy, X-ray diffraction, thermal analysis (DT A and TG), infrared absorption spectroscopic analysis, SEM, intercalation reaction, and chemical analysis. Smectites commonly occur as irregular boxwork-like masses with characteristic curled thin edges, but occasionally as smoothly curved to nearly flat thin flakes. Most of smectites have layer charge of 0.25-0.42, indicating typical montmorillonite. Crystal-chemical relations suggest that Fe is the dominant substituent for Al in the octahedral layer and there are generally no significant substituents for Si in the tetrahedral layer. Ca is the dominant interlayer cation in montmorillonite. Therefore, montmorillonite from the study area is dioctahedral Ca-montmorillonite. Occurrence and fabrics of bentonites suggest that smectites as well as cristobalite, opal-CT and zeolites have been formed diagenetically from tuffaceous materials. The precursor of smectites is trachytic or basaltic tuff. Smectites derived from the former contain relatively more $Al_2O$ a and less $Fe_2O_3$ than those from the latter.

• Geophysics and Geophysical Exploration
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• v.13 no.4
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• pp.357-363
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• 2010

In this study, we investigated the geologic structure of the basement and overlying sediments of the construction site of the dinosaur egg fossil museum in Hwasung, Gyeonggi Province through refraction seismology, drilling, and downward seismic velocity measurements in the drill holes. The construction site ($350{\times}750\;m^2$) is located in the reclaimed area south of Sihwa Lake, Gojeong-ri. About 6,950 m of seismic refraction data consisting of 11 lines were acquired using a sledge hammer source. Drilling to the basement was performed at five sites. Sediment samples from drilling were analysed for grain-size distribution and age dating. At two drill holes, seismic velocity was measured with depth using a hammer as a seismic source. The geological structure of the study area consists of, from top to bottom, a tidal flat layer (5 ~ 12 m thick), a weathered soil layer (2 ~ 8 m thick), and the basement. The basement is interpreted as Cretaceous sedimentary rocks that tend to be shallow eastward. The volume of the tidal flat sediments and weathered soil in the study area is estimated as $1.4{\times}10^6\;m^3$, weighing $3.5{\times}10^6$ tons. The rate of sea level rise since 8,000 yrs BP is estimated to be 0.1 ~ 0.15 cm/yr.

• The Journal of the Petrological Society of Korea
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• v.28 no.3
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• pp.157-169
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• 2019

Pseudotachylytes, produced by frictional heating during seismic slip, provide information that is critical to understanding the physics of earthquakes. We report the results of occurrence, structural characteristics, scanning electron microscopic observation and geochemical analysis of pseudotachylytes, which is presumed to have formed after the Late Cretaceous in outcrops of the Paleoproterozoic granitic gneiss on the Bulil waterfall of the Jirisan area, Yeongnam massif, Korea. Fault rocks, which are the products of brittle deformation under the same shear stress regime in the study area, are classified as pseudotachylyte and foliated cataclasite. The occurrences of pseudotachylyte identified on the basis of thickness and morphology are fault vein-type and injection vein-type pseudotachylyte. A number of fault vein-type pseudotachylytes occur as thin (as thick as 2 cm) layers generated on the fault plane, and are cutting general foliation and sheared foliation developed in granitic gneiss. Smaller injection vein-type pseudotachylytes are found along the fault vein-type pseudotachylytes, and appear in a variety of shapes based on field occurrence and vein geometry. At a first glance fault vein-type seudotachylyte looks like a mafic vein, but it has a chemical composition almost identical to the wall rock of granitic gneiss. Also, it has many subrounded clasts which consist predominantly of quartz, feldspar, biotite and secondary minerals including clay minerals, calcite and glassy materials. Embayed clasts, phenocryst with reaction rim, oxide droplets, amygdules, and flow structures are also observed. All of these evidences indicate the pseudotachylyte formed due to frictional melting of the wall rock minerals during fault slip related to strong seismic faulting events in the shallow depth of low temperature-low pressure. Further studies will be conducted to determine the age and mechanical aspect of the pseudotachylyte formation.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.8 no.12
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• pp.425-435
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• 2018

The purpose of this study is to investigate the cultural value as well as business value of Juk-Bang-Ryeum(fishing instrument made by bamboo weir) by the investigation of remains in Gyeongnam Sacheon area and reviewing various historical literatures. The research will contribute to make back data necessary for the registration of World Heritage(UNESCO) and Globally Important Agricultural Heritage Systems(FAO). Fisheries, along with agriculture, have been great significance in human history. In particular, the Fisheries has been considered very important industry due to the geopolitical characteristics of our country surrounded by the sea. We can imagine may types of fishing practices and instruments at the agricultural age. Nonetheless, there are a few fishery heritages such as collecting and hunting tools that remains today. Fortunately, there are many Juk-Bang-Ryeum which is actually operate now from the past 500 years ago at the The Sacheon and Namhae areas. We could found some literature records about it in the historical ancient literatures. We could also infer that Juk-Bang-Ryeum was an important fishery resource of the country for a long time. It was built on the basis of scientific principles to capture fishes using the rapid tide of the natural geological straits, and it prove the wisdom of our ancestors. We also could found some unique cultural heritages that was important to the local community. Naturally, it has been managed as an important asset for the residents. In addition to such historical and humanistic values, it also has business and educational value. It can be useful to understand scientific fishery principles as well as fishery experience field. It has business value as an important tourism resource in the region in connection with historical relics and geological environment resources. In conclusion, it is a valuable asset to be handed down as a valuable cultural heritage.

• Journal of radiological science and technology
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• v.37 no.4
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• pp.287-294
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• 2014

Gallstone is the most common disease of the biliary system. Korean has experienced an increase in the percentage of cholesterol gallstones. The major risk factors associated with cholesterol gallstones are age, gender as well as obesity. This study was designed to determine the prevalence of gallstones in the last three years and evaluate the associated risk factors in the population who underwent health screening. The study population consisted of 2,484 males and 2,212 females who visited the health promotion center in Dalseogu, Daegu in Korea from January 2011 to December 2013. Each participant in the study had their biliary system gallbladder examined using ultrasonography. Classified as underweight, normal weight or overweight using the population of obese according to the body mass index, and classified according to mood diagnosis of diabetes presented by the American Diabetes Association. Fasting blood glucose and number of liver function, the divided the control group by referring to the normal liver function values used herein. The geological map, I was classified as NCEP APT III. A showed of total 148 people were found to have gallstones. The prevalence of sex among 148 patients (3.15%) 84 men (1.79%) and 64 women 1.36%) which shows significantly there is little difference. 1.84% 40 years and below, 3.38% 40's showed age prevalence was 4.66% in 50's and above. In addition, Total-cholesterol was at the most in 52 people, LDL-cholesterol in 398 people, Triglyceride in 36 people, HDL-cholesterol in 19 people. The abnormal group, was created from the total-cholesterol categories from a physical examination of a subject that has been found to be gallstones in the gallbladder. A result of conducting the univariate analysis shows the prevalence of gallstones, a correlation that is meaningful. The logistic regression analysis of multiple ages was chosen to show risk factors age independent cholelithiasis. In spite of the conclusion, gallstones are not displayed in relation to the metabolic syndrome but in order to clarify this, not only the subject of a health examination is needed but, a further study of the general public when possible.

• The Journal of the Petrological Society of Korea
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• v.19 no.2
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• pp.109-121
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• 2010

Mt. Mudeung is located in Gwangju city, Damyang-Gun, Hwasun-Gun and its round form give us the mood of soft and rich. Its location is $126^{\circ}06'-127^{\circ}01'E$ and $35^{\circ}06'-35^{\circ}10'N$ and its highest peak is Cheonwang-bong with the height of 1,187 m. The Gwangju city is located in the West of Mt. Mudeng and the mountain range with a small basin in its East. The pavilion such as the Soswaewon, Songganjeong, Sigyongjeong are distributed along the stream in the north of Mt. Mudeung. The mountain is formed from the volcanic activity, Gwangju cauldron during the Cretaceous. The top part of Mt. Mudeung is composed of dark gray quartz-andesite and its K-Ar whole rock age is $48.1{\pm}1.7Ma$. The composition of the north area, where the Wonhyosa temple is located, is micrographic granite, whereas the composition of south area is rhyolite mainly. The main ridge of Mt. Mudeung runs from North, starting from the Bukbong, to south, passing Cheonwangbong, Jangbuljae and ending Anyangsan. Geologic feature of the mountain includes volcanic landform, mountaineous landform, and stream landform. The Seosukdae, Ipseokdae, Gyubongam, which are main ridges and formed from volcanic activity, are composed of mainly columnar joint. Saeinbong and Majipbong in the south-west are composed of mainly cliff and dome. The typical erosion landform of the mountain has three different types of the weathering-cave, each of which reflect the property of the original rock. Four different area of wide block stream, they makes the geological feature of spring-water, though its scale is small compared to that of water fall.