• The Journal of the Petrological Society of Korea
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• v.4 no.2
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• pp.186-200
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• 1995

구상구조를 보이는무주 구상편마암은 전북 무주군 왕정리일대에 분포하는 정편마암인 함전기석 복운모 화강편마암내에 배태되어 있다. 구상구조는 구상편마암의 기원암인 화강암내에 포획된 이질암이 변성분화작용을 받아 생성된 것으로 사료된다. 구상편마암은 각의 발달이 없는 초생암구로 구성된 TypeI의 암구와 각의 발딜이 있는 TypeII로 구분이 가능하다. TypeII는 단각암구와 다각암구 그리고 핵의 구조에 따라 다양한 형태로 나눌수 이TEk. 구성암은 내핵, 외학, 각, 그리고 기질부로 구성된다. 핵의 장경은 보통 5cm 내지 8cm이며 구형 또는 타원형의 행태로 암구으 중심부를 이루고 있다. 핵의 화학성분은 $Al_2O_3$, total $Fe_2O_3$, MgO, $K_2O$ LREE가 풍부하고 반대로 $Na_2O$, CaO, HREE가 결정된 것이 특징이며, 핵을 주로 구성하는 변성광물은 근청석-규선석-흑운모-올리고클레이스이다. 각은 운모류의 우혹질 각과 장석류의 우백질 각으로 구분되며 수mm내지 수cm의 두께를 이루며 단일각 내지 다각구조를 이루고 있다. 이들은 핵에 비하여 $Na_2O$, CaO가 상대적으로 부화되고 있으며 기질부를 이루는 화강편마암의 조성과 유사하다. 기지루는 반상변정질로 되어 있고 장석 반상변정의 크기는 대략 2내지 3 mm의 크기로 구성되어 있으며 부수적으로 운모류와 소량의 전기석과 규선석이 존재한다. 또한 후기에 유입된 많은 유체들에 의한 후퇴변성작용의 영향으로 장석은 견운모화내지 전기석화되고, 근청석은 피나이트화 되었다.

• Economic and Environmental Geology
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• v.29 no.4
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• pp.529-541
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• 1996

The granitic rocks, so called Masanite, characterized by the micrographic, mylmekitic and perthitic textures, and zonal structure of the plagioclase in the Masan, Changwon and Jinhae areas belong to normal granite and granodiorite based on the modal analysis. These petrographic features strongly suggest the shallow emplacement of the plutons which are defined a typical calc-alkaline suite and I-type granitoids. The pressures of emplacement of the granitic plutons using the amphibole geobarometer were calculated to be 1.2kbar in the Masan area and 1.4kbar in the Changwon area. Their amphibole-plagioclase equilibrium temperatures were obtained to be $638^{\circ}C$ for the former ones and $724^{\circ}C$ for the latter. Homogenization temperatures and salinities for the type HI and IV fluid inclusions in quartz range from 298 to $541^{\circ}C$ (av. $425^{\circ}C$), and 10.5 to 34.6 wt.% NaCl (av. 28.2 wt.% NaCl), respectively. Gas compositions of the granitic rocks with fairly high $CO_2$ concentration relative to CH, correspond to the magnetite series granite of the mantle source. The terminology of the Masanite is not recommended usage. Because it is hard to discriminate in terms of petrological and petrogenetical characteristics between the Masanite and the Bulguksa granites in the Kyeongsang basin.

• Economic and Environmental Geology
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• v.27 no.2
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• pp.181-190
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• 1994

Petrochemical study on the micrographic granite distributed in the Wando area, the southernmost part of the Yeongdong-Kwangju depression is performed to investigate the petrogenesis and differentiation processes of the granitic magma. Polarized light microscopy for modal analyses, electron probe microanalyses of feldspars and biotite, inductively coupled plasma analyses for major and trace element contents were adopted in the study. The lithology of the study area consists of Precambrian metasediments, Mesozoic volcanic and sedimentary rocks, and micrographic granite which intrude into the former. The micrographic granite in the Wando area are distributed in the shape of a cauldron. Modal and nonnative mineral analyses of the micrographic granite fall in the area of granite and granodiorite. The chemical composition indicates that the micrographic granite is I-type and magnetite series. The micrographic granite is characterized by more than 90% of micrographic texture in volume percent. Feldspars in the micrographic granite is alkali feldspars (Or, 45~93) and plagioclases (albite to oligoclase). The biotite has a intermediate composition between phlogopite and annite solid solution. The results of the petrochemical studies indicate that the granitic magma of calc-alkaline source materials reactivated in a compressional environment at the continental margin, and then was differentiated by fractional crystallization. The micrographic granite intruded into a shallow level of the crust (5~7 km) in the late Cretaceous.

• Journal of Conservation Science
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• v.17 s.17
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• pp.5-18
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• 2005

Rock materials of the Stone Lantern in the Gwanchoksa temple was composed of dark grey granodiorite. This Stone Lantern is partly structural distortion as S-shape, especially, rocks of the upper supports and under the roof materials were highly deterioration due to the surface exfoliation, and strong secondary contaminations owing to the discoloration by oxidation of inserted iron plates between the rock properties, and white grey to dark black contaminants along the rain path way. Rock surface of the Stone Lantern occurred as partly green patches because of coated by algae, lichen and moss. This biological problems are need for cleaning and treatments. The Stone Lantern have to be considered to conservation method that can reduce weathering factors with long-term monitoring about environmental change for structural stability, surface degradation and mechanical weathering. Materials of the Stone Lantern and basement rocks of the area are consisted of same petrogenetic granodiotite based on occurrences, petrological and geochemical characteristics.

• Ocean and Polar Research
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• v.24 no.4
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• pp.465-482
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• 2002

Petrological, geochemical, and geochronological studies of Dokdo volcanic rocks, East Sea, have been carried out to understand their petrogenesis. Dokdo volcanic activity is divided into three stages according to occurrences and eruption ages of rocks. The second-stage activity is accompanied by large volume of pyroclastics and lavas of intermediate composition, and occupies most of the East and West islets. K-Ar biotite and whole-rock ages indicate that Dokdo volcanic activity occurred during late Pliocene and became systematically younger toward later stages: namely, 2.7-2.4 Ma for the first-stage trachyte, 2.4-2.3Ma for the second-stage trachyandesite and 2.2-2.1 Ma for the last-stage trachyte and dikes. Dokdo volcanic rocks are of intermediate to felsic compostions, and have OIB-like alkaline nature. The geochemical similarities between Dokdo and Ulleungdo volcanic rocks suggest that they were formed from the same mantle plume. However, considering the difference of eruption ages between Dokdo (2.7-2.1 Ma) and Ulleungdo (1.4-0.01 Ma) volcanic rocks, the former seems to have been formed by earlier hot spot activity.

• Proceedings of the Mineralogical Society of Korea Conference
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• 2000.05a
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• pp.24-24
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• 2000

We studied about petrological characteristics of the Bangeujin granite belongs to porphyritic biotite granite, petrogenesis of the enclaves in the granite and contact metamorphism of the sedimentary rock around the granite. The enclaves in the granite are concentrated in the eastern part of the Mipo fault but in the western part, these are rare. The enclaves can be divided into three types according to the petrographical characteristics. These three types are: (1) enclaves having few phenocrysts and fine grained igneous texture and ellipsoid is predominant; (2) enclaves similar In petrographical characteristics and having many phenocrysts considered as being originated from the granitic host rock; and (3) enclaves corresponding to granite in mode composition, having large phenocrysts and of which the matrix is corresponding to fine granular. First two types are correspond to mafic micro granular enclaves and the third is corresponds to felsic microgranular enclaves. In addition, the felsic microgranular enclaves capture the mafic microgranular enclaves. The fact that the compositions of biotite and plagioclase in the enclaves are nearly identical with those of biotite and plagioclase in the granitic host rock is considered as the results of supporting magma mingling. The major elements show well the linear variations as the SiOz$.$ content increases. The rare earth elements content decrease with increasing SiOz content, interpreted as the results of magma mingling. Therefore, we can conclude that the Bangeujin granite captured the felsic microgranular enclaves formed by collapse of early chilled margin during the crystallization and there was magma mingling by the injection of the mafic magma after that time. In addition, these aspects are predominant in the eastern part of the Mipo fault is considered as related to the fault movement.vement.

• Economic and Environmental Geology
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• v.19 no.1
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• pp.35-55
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• 1986

The area of this study is located in the Sang dong district, Youngwol Gun, Kangwon Do, where the Ogcheon fold belt comes into contact with the Ryongnam massif. The area is covered by the Precambrian metasedimentary rocks of Yulri Group in the south from the line of Ungyosan-Maebongsan-Jansan-Taebaegsan Mountains and by the Cambro-Ordovician sedimentary rocks of Choseon Supergroup in the north. The Choseon Supergroup unconformably overlies the Yulri group. Several granitic intrusives occur in the Precambrian and Cambro-Ordovician terrain. The purpose of this study is to clarify the geochronology, mineralogical composition, geochemical characteristics, petrogenesis and tectonic settings of the Precambrian granitic rocks, and to evaluate the P.T. conditions of granitic intrusions. The K/Ar ages obtained from the muscovite of Nonggeori Granite, Naedeogri granite and pegmatite intruded into the Yulri Group are Early Proterozoic ($1805{\pm}18Ma$ to $1642{\pm}23Ma$), and those from the migmatitic pegmatite are Late Carboniferous ($305{\pm}4Ma$), respectively. The Precambrian granitic rocks are characterized by the presence of muscovite, tourmaline and grey feldspar with faint lineation of mafic minerals. In terms of mineralogical and chemical composition, the granitic rocks are felsic, calc-alkalic, peraluminous and S-type (ilmenite-series). The geochemical characteristics of major and trace elements indicate that the granitic rocks belong to syn-collision setting at the compressional plate margin. They were formed by progressive melting of relatively homogeneous crustal materials under 1~3kb and $670^{\circ}{\sim}720^{\circ}C$ in aqueous fluid conditions, and the Naedeogri granite was more fractionated than the Nonggeori granite. During the Taebaeg disturbance, Nonggeori granite, Naedeogri granite and pegmatite were intruded and emplaced into the Yulri Group. Migmatitic pegmatite occurring in the southwestern area, however, gave much younger muscovite age than the pegmatite intruded into the Yulri Group in rest of the area did, that might be due to the regional metamorphism of the Post-Choseon disturbance. The Geodo granitic mass and the Imog granite were intruded during the Bulgugsa disturbance.

• Economic and Environmental Geology
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• v.29 no.3
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• pp.281-291
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• 1996

Samples of Badwater greenstones from the Crystal Falls terrane in northeastern Wisconsin have been analyzed for major, trace and rare earth elements. Geochemical characteristics of the rocks provide clues to the petrologic character and paleotectonic environment of basaltic magma generation. They have chemical composition typical of continental tholeiites. The low Mg values and abundances of Ni and Cr indicate that the lavas were extensively fractionated prior to extrusion. The variations of incompatible elements suggest that the rocks were affected by interaction with crustal rocks. The samples least affected by contamination have trace element compositions similar to those of T-type mid-ocean ridge basalts. The parent was modified by crustal contamination process and this process shifted the rock compositions to that of continental tholeiites as the rock evolved. Interpretations of the chemical characteristics of the rocks, based on modem analogs, favor their emplacement in an extensional tectonic regime.

• The Journal of the Petrological Society of Korea
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• v.26 no.4
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• pp.361-371
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• 2017

We investigated geochemical characteristics of the Dodong Basaltic Rocks in the lower part of the Ulleung Island. They have lithological range of alkali basalt to trachybasalt, belonging to Na and K subseries of alkaline series. They mostly fall within the field of alkalline within-plate basalts on tectonic discrimination diagrams, and then plot in the field of oceanic island basalt (OIB). Geochemically, extension of lithospheric mantle and asthenospheric upwelling after East Sea under an Cenozoic extensional tectonic setting might be a heat source for partial melting of the enriched lithospheric mantle, which might generate the basaltic magma. But we cannot exclude that mantle plume might also be a heat source for melting of the lithospheric mantle.

• Economic and Environmental Geology
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• v.18 no.2
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• pp.139-150
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• 1985

Skarn at the Dielette formed largely in calc-silicate hornfels at the contact with the Flamanville granite. The skarn consists mainly of garnet and pyroxene, and less frequently vesuvianite. Traversing toward calc-silicate hornfels wall rock from a central zone of the skarn, the general sequence of formation of mineral assemblages is: (1) dark brown garnet (2) pale brown garnet-vesuvianite-pyroxene, and (3) pyroxene-prehnite-scapolite-wollastonite envelopes (designated as transition zone) developed between skarn and calc-silicate hornfels. The central zone of the skarn consists mainly of dark brown garnets (garnet I) that contain little or no pyroxene. The pale brown garnet (garnet II) is associated with pyroxene and vesuvianite. The sequence of these garnets results from the zonal growth outward. There is an abrupt discontinuity in composition between garnet I formed in early stage and garnet II in late stage, while each garnet shows relatively uniform composition. At the zone in contact with the granite, the iron contents of garnets decrease toward the marginal zone of the skarn, from an average value of 36 mole % andradite in garnet I to 18 mole % andradite in garnet II. At the zone distant from the granite, the andradite component decreases from 28 mole % in garnet 1 to 19 mole % in garnet II. The variation of the iron contents of pyroxenes is also similar to that of garnets. The sharp discontinuity in composition of garnets and pyroxenes suggests that the skarn of study area was formed by infiltration metasomatic process. The results of the analyses of mineral assemblages of the transition zone by chemical potential diagrams suggest that the transition zone was made by the diffusion of the elements Ca, K and Fe from the skarn to the calc-silicate hornfels contact zone. The estimated temperatures and $Xco_2$ for the formation of the transition zone show $300^{\circ}C$$440^{\circ}C$ and $0.07{\pm}0.05<Xco_2<0.02{\pm}0.01$ at 1 Kb respectively.