• 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.

• Economic and Environmental Geology
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• v.45 no.5
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• pp.477-486
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• 2012

High-resolution bathymetry and physico-chemical properties of manganese nodules were explored to identify the relationship between morphological features and nodule occurrences in the KR1, one of the Korean contract nodule fields located in the NE Pacific. The high-resolution seabed mapping showed that the southwestern sector of the KR1 (KR1-1) was relatively deeper than the northeastern sector (KR1-2) which is occupied by small-scale seamounts. In terms of nodule occurrence, manganese nodules in the KR1-1 were comparatively larger (2-4 cm) with rough surface (t-type) and discoidal shapes (D-type), while those in the KR1-2 were generally small (<2 cm) with smooth surface (s-type) and irregular shapes (I-type). In addition, the nodules in the KR1-1 had higher contents of Cu, Mn and Ni. Such connections of water depths to nodule appearances and metal contents are commonly observed in the Pacific nodule fields. On the other hand, the nodules in the KR1-2 tend to be controled by morphological features. The seamounts in the KR1-2 might continuously provide rock fragments as new nuclei of manganese nodules. As a result, the nodules could not grow over than 2 cm and showed the shapes of a newbie (i.e., smooth surface and irregular shapes). As a result, our observations indicate that occurrence features of manganese nodules could be subjected to water depths and seabed morphology simultaneously.

• Economic and Environmental Geology
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• v.45 no.5
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• pp.535-549
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• 2012

Main aspect of this study are to clarify mineral compositions on granites in Youngkwang-Naju area. These granites are is divided into four rock facies based on the geologic ages, mineralogical composition and chemical constituents, and texture : hornblende-biotite granodiorite, biotite granite, porphyritic granite and two mica granite. These granites constitude an igneous complex formed by a series of differentiation from cogenetic magma. In compressive stress field between the Ogcheon folded belt and the Youngnam massif, the foliated and undeformed granites had formed owing to heterogeneous distribution of stress. The geochemical data of study area indicate magma of these rocks would had been generated by melting in lower and middle crust. The major minerals of granitic rocks in study area are plagioclase, biotite, muscovite and hornblende. Plagioclase range in composition from oligoclase ($An_{19.3-27.7}$) to andesine ($An_{28.4-31}$), and shows normal zoning patterns, This uniformed composition indicated slow crystallization, and it is obvious that the growth of these crystal occurred before final consolidation of the magma. The Mg content of biotite are increases with increasing of $f_{O2}$ and grade of differentiation, changing from phlogopite to siderophyllite. Its $Al^{iv}$/$Al^{total}$ ratios are propertional to bulk rock alumina content. Muscovite is primary in origin with high content of $TiO_2$, and Its composition correspond to celadonitic muscovite. Hornblende indicated calc amphibole group ($(Ca+Na)_{M4}{\geq}1.43$, $Na_{M4}<0.67$). and consolidation pressure of granitic body by geobarometer of Hammerstrume and Zen show 11.3~17.2 Km.

• 한국해양학회지
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• v.26 no.1
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• pp.59-66
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• 1991

Laboratory studies were carried out to measure the sound velocity (V/SUB p/) and quality factor (Q/SUB p/, inverse attenuation) in the horizontal (H) and vertical (V) direction on the core sampled sediment of deep-sea basin (1,850 meter water depth), East Sea of Korea (Sea of Japan). Sampled core was about 250 cm long and 500 kHz ultrasonic p-wave transducer was used for a sound soured. V/SUB p/ varies from 1,480 m/sec to 1,500 m/sec, it is not clear which direction is faster, V/SUB PH/ or V/SUB pv/, within${\pm}$ 1.0% anisotropy (A/SUB p/). It is thought because the core sediment facies is highly (or slightly) bioturbated homogeneous mud with very high porosity (more than 80%). The general trend of Q/SUB p/ is decreasing 10 to 5 with the buried depth, it is strongly affected by the variation of sediment texture (increasing silt, decreasing clay) with increasing of CaCO$_3$ and organic matter content, But Q/SUB PH/ is jumping up to 14.9 near the bottom of core sediment as including volcanic ash richly. The relationship between V/SUB PH/ and Q/SUB PH/ shows the mirror image nearly, it is interpreted that not only the geotechnical properties and texture but also sea-water characteristics (high Q/SUB p/, low V/SUB p/) according to rich water content affect strongly in the upper part of the unconsolidated deep-sea basin sediment.

• The Journal of the Petrological Society of Korea
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• v.9 no.2
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• pp.70-83
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• 2000

The purpose of this study is to identify the petrographic and geochemical characteristics of four granitic masses and clanfy for the origin and relationship among the masses. These granitic rocks are distributed in the eastern part of Yangsan fault in the Kyongsang basin, southeastern part of Korea. Based on the mineralogy and texture, the granitic rocks are divided into three facies; granodiorite, porphyritic fine-grained granite, and equigranular granite. According to the result of modal analysis, northern part and most of the southern part of Daebon granitic rocks are plotted in granodiorite field and the rest part of the xocks are plotted in granite field. These granitic rocks belong to the sub-alkaline series, and are subdivided into calc-alkaline series. The rare earth elements normalized bv chondrite show LREE is more enriched than HREE and the lowest values in O-w m- i t e and Daebon equigranular granite. The crystallization pressures and temperatures of minimum melt compositions of granitic rocks estimated from the study area are about 0.5-1 kbar and $700~820^{\circ}C$, respectively. Referring to the petrographic characteristics, geochemical data and radiogenic age data, Oyu granite was emplaced in the Paleocene, but Daebon granodiorite, Sanseo porphyritic granite, and Hoam equigranular granite are co-magmatic differentiation products, were emplaced in the Eocene.

• Korean Journal of Environmental Biology
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• v.22
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• pp.93-102
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• 2004

A total of 110 surface sediment were analyzed in order to understand the geochemical eharacteristics of the surface sediments and to evaluate the benthic environmental condition of Gwangyang Bay. The surface sedimentary distribution can be classified by five facies; mud (M), sandy mud (sM), sand (S), muddy sand (mS) and gravely sand mud ((g)sM). However, mud face is the predominant sedimentary feature of the Gwangyang Bay. The benthic environment based on total organic carbon/total nitrogen (C/N) and total organic carbon/total sulfur (C/S) ratios of organic matter showed that anoxic environment is prevailed in some parts of the study area because the C/S ratio of organic matter was higher than 2.8. The hydrogen sulfide (H$_2$S) content showed extreme variability from site to site. It varies from 307 ppm to 1 ppm (average, 92 ppm). The inter-relationship of redox-sensitive elements (Mn, V, Mo and Cr) showed a relatively strong positive relationship with high accumulation in the sediment at the inner sites of the Bay (left of Myo Island). High content of TOC and hydrogen sulfide, and a high accumulation rate of redox- sensitive element were predominant characteristics in the sediments at the inner sites of the Bay (left of Myo Island), suggesting that this area is in an oxygen deficient, and potentially polluted condition.

• The Journal of the Petrological Society of Korea
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• v.11 no.3_4
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• pp.138-156
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• 2002

Precambrian metamorphic rocks of southwest Sobaeksan massif consist of mainly granitic gneiss, porphyroblastic gneiss and quartzofeldspathic gneiss. The orthopyroxene-bearing rocks(charnockites) are found in the west of Hadong-Sancheong anorthosite complex. The charnockites are 3km wide, 12km long and divided into massive and foliated types based on their texture. The compositions of charnockites are comparable to granodiorite to adamellite and subalkaline. Variations in major and trace elemental abundances show typical magmatic differentiation trends. The geochemical data plotted on tectonic discrimination diagrams reveal that these charnockites were formed in the active tectonic environment. The massive and folidated charnockites are mainly composed of plagioclase, orthopyroxene, microcline, quartz and disseminated garnet. Camels generally show characteristic zonal textures with decreasing $X_{alm}$(0.74~0.83), $X_{Py}$ (0.07~0.12) and $X_{Mg}$ (0.12~0.08) and increasing $X_{grs}$(0.03~0.15) from core to rim. Metamorphic temperature and pressure of the charnockites estimated from orthopyroxene-garnet-plagioclase-quartz assemblages show wide range of variation of $600~900^{\circ}C$ and 2.5~7.5 kbar respectively. The results of P-T estimates indicate an anticlockwise P-T evolution path.

• The Journal of the Petrological Society of Korea
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• v.18 no.2
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• pp.137-151
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• 2009

Synthetic analyses of field data, including rock facies, contact relationships, petrography, structural elements, and etc., and previous geochemical and absolute age data of the Tertiary Churyeong Breccia and its surrounding volcanics in the Gyeongju city, Korea, have led to the following results. (1) The Tertiary rocks are divided into the dacitic tuffs, Churyeong Breccia, and andesitic rocks in ascending order. The dacitic tuffs are unconformably overlain by the Churyeong Breccia which is intruded by or conformably overlain by the andesitic rocks. (2) The dacitic tuffs are correlated with the Paleocene${\sim}$Eocene Wangsan dacitic volcanics, while the Churyeong Breccia and andesitic rocks are correlated with the early Early Miocene Andongri Formation and Yongdongri Tuffs in the Waeup Basin, respectively. (3) The Churyeong Breccia accumulated rapidly in the NE-trending graben about 1.5 km in width during the crustal extension in the NW-SE direction due to the East Sea opening. (4) Dacitic${\sim}$andesitic volcanism and crustal extension were active during the early Early Miocene times in SE Korean peninsula. During the deposition the Churyeong Breccia, especially, the volcanism ceased for some time, but the active normal faulting led to the formation of grabens in places.

• Journal of the Korean earth science society
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• v.21 no.3
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• pp.323-336
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• 2000

Ultramafic rocks in Choongnam area are mainly serpenitinites which are parent rock of talc and asbestos ore deposits. About 10 $^{\circ}$ NNE-trending parallel serpentinites masses occur as discontineous isolated lenticular intrusive bodies in Precambrian gneiss complex between Hongseong-Kwangcheon line and Onyang-Cheongyang line. The sizes of serpentinites vary from several centimeters to 1 kilometer in width and from several meters to 5 kilometers in length. The serpentinites show high SiO$_2$(39.99wt.% in average), MgO(38.46wt % in average), Cr(>1011ppm), Ni(>1660ppm), and Co(>80ppm). Most serpentinites contain serpentine more than 50%. Some serpentines contain original minerals such as olivine, pyroxene and chromite. Also, serpentinites body may contain a little serpentinized peridotite, and some talc and asbestos ore deposits. The original rocks of the serpentinites interpreted as Alpine type ultramafic rocks, and dunite and/or harzburgite which were originated from slightly depleted upper mantle(30${\sim}$40km deep), and emplaced in the crust through the large fault zones. It seems that main serpentinization from the original rocks was occurred during greenschist and/or amphibolite facies regional metamorphism in Choongnam area.

• Journal of the Korean earth science society
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• v.21 no.3
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• pp.337-348
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• 2000

The Middle Carboniferous Manhang and Geumcheon formations in Taebaek area consist of sandstones, shales, and limestones. The limestones of the formations contain abundant conodonts, fusulinids, crinoids, brachiopods, bryozoans, corals, etc. This study was carried out to investigate the microfacies of limestones and conodont faunas of the formations and to determine their paleoecology in detail. The limestones of the Manhang and Geumcheon formations of the study area consist of wackestone and packstone which are composed of crinoid fragments and other various fossil fragments. Some limestone beds of the Geumcheon Formation consist of only Chaetetes corals which indicate that the limestones deposited in a warm shallow sea. Conodonts found from limestones of the Manhang Formation are Neognathodus bothrops, N. medexultimus, Hindeodus minutus, Diplognathodus coloradoensis, D. edentulus, Idiognathodus delicatus, Streptognathodus elegantulus, and S. sp. And conodonts found from the limestones of the Geumcheon Formation are Neognathodus medexultimus, N. roundyi, N. dilatus, Gondolella bella, Diplognathodus coloradoensis, D. edentulus, Hindeodus minutus, Idiognathodus delicatus, and Streptognathodus elegantulus. Among these conodonts, Diplognathodus coloradoensis, D. edentulus, and Hindeodus minutu, are found generally from limestones which deposited in the shallow seas. According to the limestone facies and conodont faunas of the Manhang and Geumcheon formations of the study area, it can be concluded that the limestones of the formations deposited in the shallow sea.