• Economic and Environmental Geology
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• v.30 no.5
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• pp.477-491
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• 1997

In the Bibong area of the western part of Chungcheongnam-do, ultramafic masses occur as discontinuous isolated lenticular bodies in the Precambrian Kyeonggi gneiss complex. They extend for about 200 m long to NNE directions which are parallel to fault lines in the gneiss complex. The ultramafic masses contact with the adjacent gneiss complex as steeply dipping faults. They are dunites and harzburgites and many of them are partially or completely serpentinized. The ultramafic rocks dominantly show protogranular, equigranular and equigranular-$m{\grave{o}}saic$ textures. They also show porphyroclastic (megacrystic) or recrystallized textures reflecting several stages of metamorphism. They contain varying amounts of olivine $(Fo_{89-92})$, enstatitic to bronzitic orthopyroxene, diopsidic clinopyroxene, tremolitic to pargasitic hornblende, and spinel with serpentine, talc, chlorite, calcite and magnetite. The ultramafic rocks have high magnesium numbers and transitional element contents, low alkali contents and show deplete REE patterns. Comparing with available data, geochemical and mineralogical characteristics shown in the ultramafic rocks of the Bibong area are similar to those of worldwide mantle xenoliths and orogenic related ultramafic rocks. The field evidences, petrographical, geochemical and mineralogical characteristics shown in the ultramafic rocks of the Bibong area are similar to alpine type ultramafic rocks emplaced into the crust by the faulting as mantle slab types. With the petrographical characteristics, these mineralogical compositions suggest that the ultramafic rocks of the Bibong area have experienced several stages of retrogressive metamorphism in a condition ranging from the upper amphibolite facies to greenschist facies.

• Journal of the Mineralogical Society of Korea
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• v.21 no.1
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• pp.1-15
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• 2008

The Cretaceous Gajok gold-silver deposit within porphyry granite is located nearby the Cretaceous Pungam basin at the northeastern area in Republic of Korea. The Gajok gold-silver deposit is distinctively composed of a multiple-complex hydrothermal veins with comb, crustiform chalcedony quartz and vug textures, implying it was formed relatively shallower depth. The hypogene open-space filling veins could be divided into 5 paragenetic sequences, increasing tendency of Ag-rich electrum and Ag-phases with increasing paragenetic time. Electrum with high gold contents (${\sim}50$ atomic % Au) as well as sphalerite with high FeS contents (${\sim}6$ mole % FeS) are representative ore minerals in the middle stage. The late stage is characterized by silver-phase such like native silver and/or argentite, coexisting with Ag-rich electrum ($10{\sim}30$ atomic % Au) and Fe-poor sphalerite (< 1 mole % FeS). The ore-forming fluids evolution started at relatively high temperature and salinity (${\sim}360^{\circ}C$, ${\sim}7\;wt.%$ eq. NaCl) and were evolved by dilution and mixing mechanisms on the basis of fluid inclusion study. The gold-silver mineralization proceeded from ore-forming fluids containing greater amounts of less-evolved meteoric waters(${\delta}^{18}O$; $-0.6{\sim}-6.7\;%o$). These results imply that gold-silver mineralization of the Cretaceous Gaiok deposit formed at shallow-crustal level and could be categorized into low-sulfidation epithermal type, related to Cretaceous igneous activity.

• 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.

• 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.

• Journal of the Korean earth science society
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• v.22 no.1
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• pp.10-19
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• 2001

There are three scoria cones and their eruptive materials in Sarabong-Byeoldobong-Hwabukbong area Cheju Island. And they made complicated volcanic stratigraphy. In Byeoldobong tuff, basalt and granite xenoliths are present. It is presumed that the granite is a kind of basement of Cheju island. And Biseokgeori hawaiite has many kaersutite phenocrysts. Therefore, this area is very important for the study about history of volcanic activity of Cheju island. The lowest beds are Shinheung basalt and Byeoldobong tuff. Byeoldobong tuff has xenoliths of granite and phenocrystalline basalt. After the formation of these rocks, the Hwabukbong volcanism commenced. First of all this volcanism formed Biseokgeori hawaiite that has lots of kaersutite, a member of amphibole group, characteristically. Over this rock, Hwabukbong scoria cone was formed. The next Sarabong volcanism effused Keonipdong hawaiite that has lots of plagioclase and olivine phenocrysts and then Sarabong scoria cone was made up. Basalt xenolith in Byeoldobong tuff is different from Shinheungri basalt with regard to petrography, therefore this offers suggestion about existence of another basalt between basement and Shinheungri basalt. Granite xenolith derived from the basement of this area has features of the Jurassic granite in the Korea Peninsula, for example a lot of myrmekitic texture, microcline, and absolute age (172.4 Ma) by K-Ar method.

• Economic and Environmental Geology
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• v.49 no.2
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• pp.147-153
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• 2016

SHRIMP U-Pb age determination was carried out for deformed granites in the Aneui quadrangle, SW Yeongnam Massif. Dating of zircons from a highly deformed mylonitic granite with banded structure and a relatively less deformed porphyritic to augenic granites, that were known as Precambrian gneisses, yielded the same age of ca. 195 Ma. On the basis of this result and previous age data, Early to Middle Mesozoic igneous activity around the Aneui area was interpreted as follows; Subduction-related granitic magmatism started with the intrusion of the Hamyang Granite in the middle Triassic (ca. 225-219 Ma) mainly in the west of the area and ended with syenitic intrusion at the end of Triassic period (ca, 220-210 Ma). After a relatively short period of quiescency, granitic magmatism restarted with the intrusion of magma forming deformed granites dated in this study at the Early Jurassic of ca. 195 Ma and continued to ca. 189 Ma and dioritic intrusion was associated around the late stage of granitic magmatism.

• The Journal of the Petrological Society of Korea
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• v.8 no.3
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• pp.149-170
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• 1999

The volcanic lavas in the Janggi area are plotted on basalt, basaltic andesite and andesite field (SiO$_2$; 48-61 wt.%) in the TAS diagram and belong to subalkaline series. Nineteen chenmical analyses of lavas show two distinct differentiation trends; tholeiitic and calc-alkaline. Calc-alkaline basaltic andesites composed of plagioclase and two-pyroxenes (cpx, opx) in their phenocrysts. Tholeiitics basaltic lavas can be classified into two sub-types. The one is porphyritic basalts composed of plagioclase, clinopyroxene and olivine phenocryst, and the other is aphyric basalt and more evolved lavas (aphyric basaltic andesite) with the same mineral phases. Incompatible elements and REE patterns show the enrichment of LILE and depletion of HFSE. This characteristics indicate that these lavas are evolved from the magmas related to subduction. Howeverm calc-alkaline basaltic andesite lavas show that slightly higher enrichment of LILE and the depletion of HFSE than those of tholeiitic basaltic lavas. On the tectonic discriminant diagram such as Ba/Th and La/Th ratios, calc-alkaline basaltic andesite lavas belong to orogenic medium to high-K suites, whereas tholeiitic basaltic lavas belong to medium-K suites and MORB. On the other diagram, such as La/Yb vs. Th/Yb, the volcanic lavas in the study area plotted in the field of oceanic arc basalt. Tholeiitic basaltic lavas are located in more prinitive environment than calc-alkaline andesitic lavas.

• Tuberculosis and Respiratory Diseases
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• v.43 no.2
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• pp.228-235
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• 1996

Idiopathic bronchiolitis obliterans with organizing pneumonia(BOOP) is a specific clinicopathologic syndrome characterized by a pneumonia-like illness, with excessive proliferation of granulation tissue within bronchioles, alveolar ducts and alveoli. The changes are most numerous in alveolar ducts. The presence of intraluminal tufts of organizing connective tissue in alveolar ducts and more distal airspaces has been termed organizing pneumonia. The radiologic manifestations are distinctive with bilateral, diffuse alveolar opacities predominantly in the subpleural and lower lung zone. Patchy migratory pneumonic foci or solely nodular infiltrates are rarely present in BOOP. BOOP is a diagnosis of importance because of its dramatic response to steroids.

• The Journal of the Petrological Society of Korea
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• v.13 no.2
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• pp.47-63
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• 2004

This study focuses on the petrography and petrochemical characteristics of the volcanic and plutonic rocks in Gadeog island, Busan, Korea. Based on textural and mineralogical characteristics, intermediate volcanic rocks can be divided into andesitic lava flows (porphyritic and massive andesites) and andesitic pyroclastics. Felsic volcanic rocks are composed of rhyolite, rhyolitic welded tuff, and tuff breccia. Plutonic rocks are intruded rhyolite and andesitic rocks, and composed of hornblende granodiorite which contains lots of mafic magma enclaves. Volcanic rocks are composed of andesite, dacite and rhyolite having a range in SiO$_2$ from 59 to 78wt.%. The volcanic rocks belong to the calc-alkaline rock series. Plutonic rocks have a range in SiO$_2$ from 63 to 69wt.%. This compositional variations correspond to those of Cretaceous volcanic and plutonic rocks in the southeastern Gyeongsang basin. The trace element composition and rare earth element patterns of the volcanics, which are characterized by high LREE/HFSE ratios and enrichment in LREE, suggest that they are typical of calc-alkaline volcanic rocks produced in the subduction environment around continental arc. We concluded that volcanic and plutonic rocks in Gadeog Island were evolved from orogenic andesitic magma which was produced by partial melting of the mantle wedge in the subduction environment.

• The Journal of the Petrological Society of Korea
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• v.25 no.3
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• pp.261-281
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• 2016

Our knowledge of the lithosphere beneath the Korean Peninsula has been improved through petrologic and geochemical studies of upper mantle xenoliths hosted by Quaternary intraplate alkali basalts from Jeju Island. The xenoliths are mostly spinel lherzolites, accompanied by subordinate harzburgite and pyroxenites. The mantle xenoliths represent residual mantle material showing textural and geochemical evidence for at least a three-stage evolution, fractional partial melting, recrystallization, and metasomatism. Their composition primarily controlled by early fractional melt extraction and porphyroclastic and mylonitic fabrics formed in a shear-dominated environment, which was subsequently modified by residual slab-derived fluids (or melts). Modal metasomatic products occur as both anhydrous phase(orthopyroxene) and hydrous phase (phlogopite). Late-stage orthopyroxene is more common than phlogopite. However, chemical equilibrium is evident between the primary and secondary orthopyroxene, implying that the duration of post-metasomatic high temperatures enabled complete resetting/reequilibration of the mineral compositions. The metasomatic enrichment pre-dates the host Jeju Quaternary magmatism, and a genetic relationship with the host magmas is considered unlikely. Following enrichment in the peridotite protolith in the mantle wedge, the upper mantle beneath proto-Jeju Island was transformed from a subarc environment to an intraplate environment. The Jeju peridotites, representing old subarc fragments, were subsequently transported to the surface, incorporated into ascending Quaternary intraplate alkali basalt. The result of this study implies that long term material transfer in the transformation of geotectonic setting from a subarc to intraplate may have played a significant role in the evolution of lithospheric mantle, resulting in the enriched mantle domains, such as EM I or EM II in the lithospheric mantle beneath East Asia.