• Journal of the Korean earth science society
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• v.23 no.7
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• pp.565-574
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• 2002

Based on previous investigations of aerial photographs and topographical surveys, this study focuses on the sedimentologic features of the Daebudo area including sedimentation processes, sedimentary facies and hydrologic conditions of the erosional coast. A total of 137 surface sediments and one core (by hand auger) sediment were obtained to interpret the depositional environment of the erosional coast in the macro-tidal coast. Surface sediments are distributed from sandy gravel (sG) to silt (Z). Textural parameters are characterized not only by coarse, poorly sorted, positive skewed and multi-modal distribution in the supra-tidal flat, but also finer, relatively well-sorted, symmetric distribution in the intertidal flat. According to the C/M diagram, sediment transport modes of study area are characterized by the mixed mode of suspension and bedload in the upper-, middle-tidal flat and by uniform suspension in the lower-tidal flat due to tidal effect. Vertical sediment distribution of the core, collected near shoreline, shows coarsening-upward, poorly sorted pattern by the input of detritus resulting from coastal erosion. Considering the sedimentological features of the study area, it appears to be composed of a coastal zone changed by not only artificial reclamation, but also by natural processes such as strong wave action due to typhoons and storms during high water level and long/short-term sea level rising. As a result, tide-dominated erosional coasts show that the shore is affected by local, temporal and hydrological conditions near high tide level and that the intertidal flat is represented by a general tide-dominated sedimentary environment.

• Journal of the Korean earth science society
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• v.22 no.5
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• pp.377-387
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• 2001

In order to elucidate sedimentation processes and depositional environments in transitional area between continental shelf and coastal zone, sedimentologic study has been done with 84 surface sediments sampled in nearshore/offshore off the mid-western coast of the Korean Peninsula for 3 years (1996${\sim}$1999). The surface sediment can be classified into 4 facies (gravelly sand, sand, silty sand and sandy silt). Mean grain size, sorting, skewenss and kurtosis varies -0.39${\sim}7.82{\Phi}$, 0.36${\sim}4.68{\Phi}$, -0.38${\sim}$0.86, -1.56${\sim}$3.43, respectively. The textural parameters show a finer-grained and poorly-sorted trend shoreward, northward and southward from the central part of the study area. The positively-skewed distribution and relationship of each textural parameters indicate a tide-dominated depositional environment. According to C/M diagram, there are 3 different domains (mode A, B, C) of sediment transport mode. The northern part is characterized by bedload transport (mode A) and represents co-influence of wave and tide, whereas domain C in the southern part is controlled by uniform suspension transport (mode C), correlating with sandy-silt area. In the broad middle area, transport processes are complex (the mixture of bedload, graded suspension and uniform suspension; mode B). Hence, the subdivision depositional environments of this study area may be classified by 3 depositional environments dependent on the interplay of sediment supplies from river, relict sediments and hydrologic conditions. In results, the nearshore and offshore areas are thus characterized as a mixing zone between coastal terrigenous sediments and relict sediments in the continental shelf by complex processes (tide, wave and river flow). These sedimentation processes play an important role in producing distinct sedimentologic features in the transitional zone linking coastal and shelfal areas.

• The Journal of the Petrological Society of Korea
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• v.13 no.1
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• pp.34-45
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• 2004

This paper describes the textural relations of mantle xenoliths and fluid inclusions in mantle-derived rocks found in alkaline basalts from Jeju Island which contain abundant ultramafic, felsic, and cumulate xenoliths. Most of the ultramafic xenoliths are spinel-lherzolites, composed of olivine, orthopyroxene, clinopyroxene and spinel. The felsic xenoliths considered as partially molten buchites consist of quartz and plagioclase with black veinlets, which are the product of ultrahigh-temperature metamorphism of lower crustal materials. The cumulate xenoliths, clinopyroxene-rich or clinopyroxene megacrysts, are also present. Textural examination of these xenoliths reveals that the xenoliths are typically coarse grained with metamorphic characteristics, testifying to a complex history of evolution of the lower crust/upper mantle source region. The ultramafic xenoliths contain protogranular, porphyroclastic and equigranular textures with annealing features, indicating the presence of shear regime in upper mantle of the Island. The preferential associations of spinel and olivine with large orthopyroxenes suggest a previous high temperature equilibrium in the high-Al field and the original rock-type was a Al-rich orthopyroxene-bearing peridotite without garnet. Three types of fluid inclusions trapped in mantle-derived xenoliths include CO$_2$-rich fluid (Type I), multiphase silicate melt (glass ${\pm}$ devitrified crystals ${\pm}$ one or more daughter crystals ＋ one or more vapor bubbles) (Type II), and sulfide (melt) inclusions (Type III). C$_2$-rich inclusions are the most abundant volatile species in mantle xenoliths, supporting the presence of a separate CO$_2$-rich phase. These CO$_2$-rich inclusions are spatially associated with silicate and sulfide melts, suggesting immiscibility between them. Most multiphase silicate melt inclusions contain considerable amount of silicic glass. reflecting the formation of silicic melts in the lower crust/upper mantle. Combining fluid and melt inclusion data with conventional petrological and geochemical information will help to constrain the fluid regime, fluid-melt-mineral interaction processes in the mantle of the Korean Peninsula and pressure-temperature history of the host xenoliths in future studies.

• 한국해양학회지
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• v.24 no.3
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• pp.132-147
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• 1989

A total of 83 surface sediments and 55 sea water samples, collected from the southwestern sea of Cheju Island, were analyzed in order to understand their textural characteristics, geochemical composition and the clay mineralogical features. The sediments were subdivided into ten textural classes, namely clayey sand, slightly gravelly muddy sand, sandy clay, clay and mud. The coarse and fine-grained mixed sediments are distributed in the northern part and around the Island, whereas the fine-grained deposits are mainly distributed in the central and southern parts of the study area; small scale mud patches are distributed in the southwestern and northern parts of Cheju Island. The high concentration of total suspended matter in study area gradually increase toward the southwestern and northwestern offshore area. The concentration of geochemical elements is as follow: the content of Mn, Al, Zn, Cr, Cu and Sn increase toward the southern part which is covered mainly with fine-grained deoposits, whereas the content of Ca, Mg and Ag is higher in the northern area; the elements such as Ni, Na, Fe and Pb are more concentrated relatively in muddy deposits rather than in sandy sediments. The light minerals such as Na-Ca feldspars show a high content around the Socotra Rock, toward the Soheugsan and Cheju Islands, but the K-feldspars are relatively high around the Cheju Island. It was noticed that the provenance of these sediments is partly influenced by the geological characteristics near the island. X-ray diffractogram for clay minerals from the southeastern mud patch and around the Soheugsan Island shows the diagnostic calcite peak indicating that the greater part of these clay fraction may have been derived from present and ancient Hwangho River. The high concentration of smectite in the northern part near the Cheju and around the Soheugsan Islands, eastern side of Socotra Rock probably result from supplies smectite altered from volcanic materials distributed in the Cheju Island and Socotra Rock, whereas the samples near the Chuja and northern parts of the Cheju Island contain weak calcite peak and high concentration of kaolinite and chlorite which is closely related to the geolgical characteristics on the adjacenting land area.

• Journal of the Korean earth science society
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• v.38 no.1
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• pp.64-79
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• 2017

We have reported the petrographic properties on the soda straw primarily based on the field measurements and discussed the causes of their traits. 156 soda straws in district B of the Baeg-nyong Cave nominated with the natural monument No. 260 have been investigated to estimate physical, sedimentological and textural characteristics. The soda straws have an average length of 3.05 cm with a standard deviation of 1.7 cm and a mean diameter of 6.0 mm. This result shows that the average diameter of the soda straws measured in this study is thicker than previous reports by 20%. Although the drip rates of cave water from 85.3% of all the soda straws are exceedingly lower than 1 drop per 10 minutes, almost all soda straws have a dripping water. We firstly report growth lamina in the Korean soda straw from 85.3% of all samples, and this textural dominance indicates that the growth lamina are one of the common features of the soda straws at least in the study area. Secondary precipitations inside the soda straw were identified from 68.6%. Notably, the strong inverse correlation between growth lamina and secondary precipitates was represented from 70.5% of all samples. This finding might be explained by the seasonality of cave drip water supplied into the soda straws or the increased opacity caused by secondary precipitates. Based on petrograhic characteristics, the soda straws in the study area can be classified into normal and erratic types. Hopefully our results on the soda straws in Baeg-nyong Cave would provide a basis for the descriptions of soda straws from other caves and paleoclimatic applications.

• Journal of the Korean earth science society
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• v.28 no.7
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• pp.914-924
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• 2007

This study is to compare differences in the depositional environments of natural beaches with those of beaches developed with artificial structures in the East Coast of Korea. Naksan-Osan beaches were selected for the examination of natural beaches and Anmok-Yumjun beaches for that of developed beaches. The study was performed on the foreshores and backshores of the selected beaches, and was based on the field research during the flood period of year 2004 and the dry period of year 2005. In Naksan-Osan beaches, pain size is fuel and sorting is better from northern coast to southern coast. Furthermore, sediment undergoes changes regularly and seasonal variations are small. But in Anmok-Yumjun beaches, grain size is coarser and sorting is worse than in Naksan-Osan beaches, showing irregular tendencies. The characteristic features of the two beaches would be effected by longshore currents which change along the type of coast line and have an effect on sediment. Especially, long shore currents interrupted by artificial structures in Anmok-Yumjun beaches may cause sedimental environment changes. In Anmok-Yumjun beaches, harbor expansions will be continued, and thus more changes are expected to occur in the beaches.

• Economic and Environmental Geology
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• v.30 no.5
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• pp.395-406
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• 1997

Some RE (Zr, Nb, REE) ore deposits are located in the middle part of the Korean peninsula. Geotectonically, the RE ore deposits situated on the Kyemyeongsan Formation of northern margin of the Okcheon geosynclinal belt and in the transitional zone between Kyeonggi massif and Okcheon belt. The rare metal deposits distributed in Kyemyeongsan Formation which consists of schist and alkaline granite. The alkali granite has suffered extensive post-magmatic metasomatism and hydrothermal processes. The ore contains mainly Ce-La, Ta-Nb, Y, Y-Nb, Ti-Nb-(U), Nd-Th group minerals. Fergusonite, one of Nb-Y rich REE minerals belonging to the A-B oxides, is most common mineral in the rare metal deposits. The fergusonite bearing rocks may be devided into four types by occurrence features and mineral association, that is, zircon type, allanite vein, feldspar type, and fluorite type. Fergusonites show wide variations in optical properties, due to part of differences in their chemical composition (depending on the types), but also the degree of crystalinity of the individual specimens. Fergusonite metamicts enclosed in biotite are generally surrounded by well developed pleochroic haloes. Usually, fergusonite is accompanied with zircon and other REE-bearing minerals. Petrographical and chemical data are presented for fergusonites which collected different types. $Nb_2O_3$ and $Y_2O_3$ contents range from 48.51 to 53.01 wt.% and 29.18 to 42.02 wt.% respectively. Also, $ThO_2$, (1.83~6.93), $UO_2$, (0.17~2.84), ${\sum}RE_2O_3$ (except to Y) (1.11~8.73), and $TiO_2$, (0.19~1.19 wt.%) contents show variational compositions according to fergusonite types. The ${\sum}RE_2O_3$ of fergusonites are positive relation with $Y_2O_3$ and negative relaton with $ThO_2$ and $({\sum}{RE_2O_3}-{Y_2O_3})$. The $Nb_2O_3$ is sightly negative relation with $Ta_2O_3$. Back-scattered electron microscope images (BEI) of fergusonite show the mineral composition and textural feature is very complicated. The variation of Nb, Th and REE content of fergusonite and the modes of occurrence of mineral, suggests that REE may have been mobilized during the circulation of hydrothermal fluids related to contact metamorphism (metasomatism). The chemical variation of the fergusonites with occurrences and mineral association can be related to metasomatism of alkaline fluid was probably the dominant ore-forming process in Chungju district.

• The Journal of Engineering Geology
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• v.27 no.4
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• pp.489-500
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• 2017

It is not rare that pseudotachylite, dark colored rock with glassy texture, is recognizable in deep core samples drilled up to 900 m from the surface. Pseudotachylite with widths varying few to 20 cm is sharply contacted or interlayered with the host rocks composed of Jurassic granite and Precambrian amphibolite gneiss, showing moderately ductile deformation or slight folding. Pseudotachylite occurring at varying depths in the deep drill core are slightly different in texture and thickness. There is evidence of fault gouge at shallower depths, although brittle deformation is pervasive in most drill cores and pseudotachylite is identified at random depth intervals. Under scanning electron microscope (SEM), it is evident that the surface of pseudotachylite is characterized by a smooth, glassy matrix even at micrometer scale and there is little residual fragments in the glass matrix except microcrystals of quartz with embayed shape. Such textural evidence strongly supports the idea that the pseudotachylite was generated through the friction melting related to strong seismic events. Based on X-ray diffraction (XRD) quantitative analysis, it consists of primary minerals such as quartz, feldspars, biotite, amphibole and secondary minerals including clay minerals, calcite and glassy materials. Such mineralogical features of fractured materials including pseudotachylite indicate that the fractured zone might form at low temperatures possibly below $300^{\circ}C$, which implies that the seismic activity related to the formation of pseudotachylite took place at shallow depths, possibly at most 10 km. Identification and characterization of pseudotachylite provide insight into a better understanding of the paleoseismic activity of deep grounds and fundamental information on the stability of candidate disposal sites for high-level radioactive waste.

• Food Science and Preservation
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• v.15 no.5
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• pp.669-674
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• 2008

Mul-kimchi is more watery than traditional kimchi and is prepared using large amounts of salted water, Chinese cabbage, radishes, and carrots. The quality characteristics of Mul-kimchi prepared with Chaenomelis Fructus water extract (1, 3, or 5%, w/v) (CF Mul-kimchi) or water (control) were investigated during fermentation for 21 days at $10^{\circ}C$. The initial pH values were 6.53 (control), 4.14 (1% CF Mul-kimchi), 3.61 (3% CF Mul-kimchi), and 3.54 (5% CF Mul-kimchi). The pH did not change significantly in CF Mul-kimchi but gradually decreased in the control during fermentation. Changes in titratable acidity were reflected in pH movements. Viable lactic acid bacteria in CF Mul-kimchi were at lower levels than in the control. Viable bacterial levels in Mul-kimchi decreased with increasing concentration of CF water extract. Textural features, such as hardness, cohesiveness, chewiness, and springiness, were higher in CF Mul-kimchi than in control. Anti-oxidative activity, measured by DPPH radical scavenging and nitrite scavenging, of CF Mul-kimchi, were higher than in control, and the activities rose with increasing levels of CF water extract. The sensory qualities of 1% CF Mul-kimchi showed the highest values in taste and overall acceptability among the Mul-kimchi preparations tested.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.1
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• pp.53-64
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• 2020

The Samgwang deposit has been one of the largest deposits in Korea. The deposit consists of series of host rocks including Precambrian metasedimentary rocks and Jurassic Baegunsa formation, which unconformably overlies the Precambrian metasedimentary rocks. The deposit consists of eight lens-shaped quartz veins which filled fractures along fault zones in Precambrian metasedimentary rock, which feature suggest that it is an orogenic-type deposit. Laminated quartz veins are common in the deposit which contain minerals including quartz, ankerite, white mica, chlorite, apatite, rutile, arsenopyrite, sphalerite, chalcopyrite and galena. The structural formulars of white micas from laminated quartz vein and wallrock alteration are determined to be (K_1.02-0.82Na_0.02-0.00Ca_0.00)(Al_1.73-1.58Mg_0.26-0.16Fe_0.23-0.10Mn_0.00Ti_0.03-0.01Cr_0.01-0.00)(Si_3.35-3.22Al_0.79-0.65)O₁₀(OH)₂ and (K_0.75-0.67Na_0.01Ca_0.00) (Al_1.78-1.74Mg_0.16-0.15Fe_0.15-0.13Mn_0.00Ti_0.04-0.02Cr_0.01-0.00)(Si_3.33-3.26Al_0.74-0.67)O₁₀(OH)₂, respectively. It suggest that white mica from laminated quartz vein has higher interlayer cation (K+Na+Ca) and Fe+Mg+Mn+Ti content in octahedral site compared to the white mica from the wallrock alteration. Compositional variations in white mica from laminated quartz vein can be caused by phengitic or Tschermark substitution ((Al³⁺)^VI+(Al³⁺)^IV <-> (Fe²⁺ or Mg²⁺)^VI)+(Si⁴⁺)^IV) and (Fe³⁺)^VI <-> (Al³⁺)^VI substitution. Ankerite from laminated quartz vein has compositional variations of FeO and MgO contents along crystal growth direction. The geochemical and textural features suggest that laminated quartz vein from the Samgwang gold-silver deposit was formed during ductile shear stage, which is an important main gold-silver ore-forming event in orogeinc deposit.