• 한국해양학회지
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• v.25 no.2
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• pp.74-83
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• 1990

The similarity in Mesozoic geology between the Antarctic Peninsula and South America indicates the possibility that they had situated along the same tectonics line before the separation of southwestern Gondwanaland. The igneous activity around the Antarctic Peninsula, including the South Shetland islands, can be correlated with the South American Cordillera Orogeny due to the subduction of Farallon/Phoenix plate until late Mesozoic. However igneous activity in Tertiary correlates with the tectonics movement accompanying the formations of Drake passage and Scotian sea. The south Shetland islands form a Jurassic-Quaternary miasmatic island arc on the sialic basement of schist and deformed sedimentary rocks. Forming of the South Shetland Islands arc began during the latest Jurassic or earliest Cretaceous from the southwestern part of the archipelago. The igneous activity migrated northeasterly and continued in most areas until late Tertiary. The entire arc-forming period, between late Jurassic and late tertiary times, was characterized by emplacement and eruption of magmas of intermediate between island-arc tholeiite and calc-alkaline types. However, Quaternary volcanic rocks show strong alkaline affinities which corresponds to the switch from compressional to intra: plate tensional tectonics. The rocks of late Cretaceous to Tertiary, mainly found in King George Island, consist of lava of basalt to andesite and intercalated pyroclastic rocks. Some of the volcanic rocks, which ofter called quartz-pyrite lodes'are severely altered and include much content of calcite,silica and pyrite.The stratographic succession of King George Island can be divided into two formation:Fields formation and Hennequin formation.The Fildes formation crops out at the west side of Admiralty Bay n King George Island,while the Hennequin formation at the east side of the bay.These two formtions are thought to be formed contempiranceously.The Fildes formation consists of altered olivine-basalt and basaltic andestie, whereas the Hennequin formation consists of fine-grained hypersthene-augite-andesite.Both formations interclate pyroclastic rocks.

• Journal of the Mineralogical Society of Korea
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• v.16 no.3
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• pp.255-263
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• 2003

Margarite, occurring in an Unkyori Formation of Miwon area, Chungcheongbukdo, South Korea, was investigated using a high-resolution transmission electron microscope (HRTEM) to reveal the microstructural intergrowth textures of margarite. HRTEM images of margarite, which was previously confirmed to have intergrowth textures by petrographic microscope and back-scattered electron images, show that chlorite occurs as thin packets of layers interlayered within margarite crystals, and intercalated chlorite layers are intergrown irregularly in areas as a few hundred angstroms thick slabs or isolated chlorite unit layers. Margarite crystals observed by HRTEM consist of a well-ordered 2M polytype, and electron diffraction pattern shows no prominent streaking along the 001 (or $c^{*}$) direction, indicating that there is no significant stacking disorder in margarite. Intercalated extra brucite-like layers, which are approximately 5 $\AA$ thick, are observed locally within margarite crystals. Insertion of such extra brucite-like layer at the interlayer of margarite would result in a chlorite-like structure unit. (001) margarite layers are parallel to (001) of chlorite, and margarite layers are not extended from (001) of chlorite, indicating that margarite was apparently produced through a dissolution-precipitation mechanism.m.

• The Journal of Engineering Geology
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• v.21 no.3
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• pp.221-230
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• 2011

The movement of rock cut slopes may result in upheaval of an adjacent road. Because most cut slopes consist of rock, road upheaval due to the movement of a cut slope is a rare phenomenon in Korea. We found that the movement of rock slopes which are heavily weathered and with strongly developed weak zones is governed by circular failure of the overall rock formation rather than by failure along discontinuities. The results of a numerical analysis revealed that the application of a ubiquitous joint model in a continuum analysis is appropriate for anisotropic rocks (e.g., schist) and for slopes for which the stability is influenced by a particular discontinuity. The results of a field investigation and numerical analyses suggest that retaining walls and anchors should be used to stabilize rock slopes and that real-time monitoring equipment should be installed to assess the reinforcing effect of the remedial measures.

• The Journal of the Petrological Society of Korea
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• v.8 no.1
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• pp.14-23
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• 1999

The northeastern part of the Gyeongsang Basin is widely covered by the Cretaceous Hayang Group (Aptian to Albian). The Hayang Group consists of the IIjig. Hupyeongdong, Jeomgog, and Sagog formations. Heavy mineral analysis was carried out to define the possible source rocks of the Haynag Group snadstones. Heavy minerals separated from IIjig, Hupyeongdong, and Jeomgog sandstones are hematite, ilmenite, leucoxene, magnetite, pyrite, actinolite, andalusite, apatite, biotite, chlorite, epidote, garnet, hornblende, kyanite, monazite, muscovite, rutile, sphene, spinel, staurolite, tourmaline, and zircon. Based on their close association and sensitiveness, the heavy mineral assemblages can be classified into 6 syutes: 1)apatite-green tourmaline-sphene-colorless/yellowish zircon; 2) colorless garnet-epidote-rutile-brown tourmaline; 3) rounded purple zircon-rounded tourmaline-rounded rutile; 4) augite-hornblende-color- less zircon; 5) epidote-garnet-sphene; and 6) blue tourmaline. The possible source rocks corresponding to each assemblage are 1) granitic rocks; 2) metamorphic rocks (schist and gneiss) ; 3) older sedimentary rocks; 4) andesitic rocks; 5) metamorphosed impure limestone; and 6) pegmatite, respectively. Previous paleocurrent data suggest that the sediments of the study area were mainly derived from the northeastern to southeastern directions. Thus, the most possible source areas would be the east extension part of the sobaegsan metamorphic complex to the northeast and the Cheongsong Ridge to the southeast.

• The Journal of the Petrological Society of Korea
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• v.13 no.3
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• pp.142-151
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• 2004

The metamorphic rocks of Yongin-Anseong area in Gyeonggi massif are composed of high-grade gneisses and schists which are considered as Precambrian basement, and Jurassic granite which intruded the metamorphic rocks. In this paper, we discuss the geochemical characteristics of metamorphic rocks and granites in this area based on REE and Nd isotope geochemistry. And we also discuss the petrogenetic relationship between metamorphic rocks and granites in this area. Most of Nd model ages (T$\_$DM/$\^$Nd/) from the metamorphic rocks range ca. 2.6Ga～2.9Ga which are correspond to the main crustal formation stage in Gyeonggi massif by Lee et. al. (2003). And Nd model ages show that the source material of quartzofeldspathic gneiss is slightly older than that of biotite banded gneiss. In chondrite-normalized rare earth element pattern, the range of (La/Yb)$\_$N/ value from biotite banded gneiss is 37～136, which shows sharp gradient and suggests that biotite banded gneiss was originated from a strongly fractionated source material. However, that of amphibolite is 4.65～6.64, which shows nearly flattened pattern. Particularly, the chondrite normalized REE patterns from the high-grade metamorphic rocks show the REE geochemisoy of original source material before metamorphism. In addition, the values of (La/Yb)$\_$N/ and Nd model ages of granite are 32～40 and 1.69Ga～2.08Ga, respectively, which suggest that the source material of granite is different from that of Precambrian basement such as biotite banded gneiss and quartzofeldspthic gneiss in the area.

• The Journal of the Petrological Society of Korea
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• v.3 no.2
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• pp.156-170
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• 1994

The talc ore deposits can be divided into chloritic and dolomitic ores according to mineral assemblages. The former is mainly composed of chlorite and talc accompanied with dolomite, muscovite and opaque mineral, and the latter of dolomite and talc with serpentine, calcite and magnesite in places. Talc was originated from chlorite and serpentine. Carbonate minerals were formed either directly from the introduced hydrothermal solution or secondarily as a by-product of steatitization of chlorite and serpentine. The process of talc formation may be governed by the chemical composition of the host rocks and the amount and/or chemical composition of the hydrothermal solution which may be different in places. However, the representative reactions producing talc from chlorite and serpentine are as follows : (1) chlorite+$Mg^{++}+Si^{4+}+H_2O$=talc, (2) chlorite+$Mg^{++}+Si^{4+}+Ca^{++}+CO_2+O_2+H_2O$=talc+ dolomite+ magnesite, and (3) serpentine +$Mg^{++}+Fe^{++}+Si^{4+}+Ca^{++}+CO_2+H_2O$=talc+dolomite. The reactions indicate that the carbonate minerals can be formed when the hydrothermal solution have high $fO_2$ and $fCO_2$. The steatitization might be proceeded by the hydrothermally metasomatic reaction between chlorite schist or chlorite gneiss intercalated in the granitic gneiss and hydrothermal solution accompanied to the wet granitization.

• The Journal of the Petrological Society of Korea
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• v.7 no.3
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• pp.177-189
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• 1998

Proterozoic gneisss complex of the Paju-Gimpo area, Northwestern Gyeonggi Massif, consists of mainly gneiss and schist with locally intercalated quartzite and metamorphic calcareous rocks. Mineral assemblages of the gneiss and schist are classified into two type: sillimanite free (garnet zone) and sillimanite bearing (sillimanite zone) assemblages. In the Goyang area, Kyanite occurs as metastable relict grain in two gneiss samples, in which sillimanite, garnet, biotite, K-feldspar and plagioclase occur. Cordierite bearing mineral assemblages of gneiss are biotite+garnet+sillimanite+cordierite+plagioclase+quartz ($\pm$K-feldspar, muscovite), and represent the upper amphibolite or granulite facies metamorphism. The metamorphic complex has experienced two different regional metamorphism. The prograde metamorphism is a medium-pressure type characteries by kyanite. The peak metamorphic P-T condition of the prograde metamorphism calculated from the kyanite bearing rock is 7.0~9.4 kb and $718~778^{\circ}C$. The retrograde metamorphism, after the prograde metamorphism, is the low-pressure type characteries by occurrence of cordierite. The peak metamorphic P-T condition of later calculated from the cordierite bearing rock is 3.6~5.5 kb and $750~889^{\circ}C$. Together with the occurrence of relict kyanite, garnet+biotite+plagioclase assemblage as relict in the cordierite, and the result of estimated P-T metamorphic conditions indicate a clockwise P-T path.

• The Journal of the Petrological Society of Korea
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• v.3 no.2
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• pp.138-155
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• 1994

Granitic gneiss containing biotite banded gneiss relict around the Daeheung talc deposit are widely distributed which were formed by regional metamorphism of both epidote-amphibolite and iater greenschist facies and granitization. They were derived from same silico-aluminous rocks of sedimentary origin. The mineral assemblages, which are common in the biotite banded gneiss, formed during regional metamorphisms, are survived in the granitic gneiss. The mineral assemblages of the latter greenschist facies may be formed retrogressively from the first epidote-amphibolite facies. The chemical compositions of biotite, muscovite, and chlorite, the important constituents of the gneisses, were controlled by the bulk composition, the chemical composition of the original mineral, and environment of the regional metamorphisms and granitization. The chemical equilibrium between coexisting'minerals, especially biotite and muscovite, is relatively well established, which was controlled mainly by tschermakitic and phengitic substitutions. Cholrite was formed mainly from either biotite or muscovite by retrogressive alteration or granitization, and have nearly similar chemical compositions regardless of the occurrences. The orientation trend of the foliation, joint and quartz vein developed in the gneisses was analyzed by equal area projection which the latter two show nearly identical trend in the strike and dip. This may suggest that the hydrothermal solution was introduced along joint during wet granitization.

• The Journal of the Petrological Society of Korea
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• v.23 no.2
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• pp.31-43
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• 2014

The Yeongdeok granite emplaced in the eastern Yeongyang subbasin is typically a medium- to coarse-grained massive biotite granite. It intruded into Precambrian schist & gneiss complex and is unconformably overlain by Cretaceous sedimentary rocks. In this study, we attempt to investigate the magma type which formed Yeongdeok granite and estimate the emplacement depth using Al-in-hornblende geobarometer to mineral composition. According to the magma fractionation, $TiO_2$, $Al_2O_3$, $Fe_2O_3{^*}$, FeO, $Fe_2O_3$, MnO, MgO, CaO, $Na_2O$ and $P_2O_5$ show positive trend but $K_2O$ indicate negative trend with $SiO_2$ contents. Those are identified as calc-alkaline series in AFM diagram and show the chemical characteristics of the I-type magma through the oxidation tendency of the iron ion and the portion of the alkaline composition. When calculated using the equation of Hollister et al. (1987), the emplacement depths of the Yeongdeok granite range from 8.98 to 17.19 km and average depth was estimated 13.03 km approximately.

• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.355-360
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• 2006

The Alkali-Silica Reaction(ASR) may cause a serious failure in the concrete pavements and structures. Several researches in some nations have conducted the continuous studies to prevent failure of the concrete structures by the ASR distress as well as the studies to manifest the mechanism. The researches on the ASR have not been performed affluently in Korea because the distress due to ASR has seldom been reported literarily. In this study, we tried to set up the systematic scheme practically for verifying the cause of distress due to ASR by using the visual inspections in field, the chemical method, petrographic analysis, and Electron Dispersive X-ray Spectrometer(EDX) method of Scanning Electron Microscopy(SEM) in laboratory. The chemical method, petrographic method using SEM, and X-ray method were used to verify the cause of pattern crack on the surface and internal crack in the plain concrete pavement. It can be concluded that the distress of a specific site in plain concrete pavement was mainly due to ASR. The chemical method, the petrographic method and EDX method using SEM may be the effective tools for verifying the cause of AAR distresses.