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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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The Journal of the Petrological Society of Korea
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Journal DOI :
Petrological Society of Korea
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Volume & Issues
Volume 11, Issue 3_4 - Dec 2002
Volume 11, Issue 2 - Sep 2002
Volume 11, Issue 1 - Mar 2002
Volume 11, Issue 3 - 00 2002
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Metamorphic Evolution of Metabasites and Country Gneiss in Baekdong Area and Its Tectonic Implication
The Journal of the Petrological Society of Korea, volume 11, issue 3_4, 2002, Pages 103~120
In the Baekdong-Hongseong area, the southwestern part of the Gyeonggi Massif in Korea, ultramafic rocks occur as lenses within Precambrian granitic gneiss. At Baekdong area, ultramafic lens contains metabasite boudin which had undergone at least three stages of metamorphisms. The mineral assemblage on the first stage, Garnet+Sodic Augite+Hornblende+Plagioclase+Titanite, is recognized from the inclusions in garnet. The second stage is represented by the assemblage in matrix, Garnet+ Augite+Hornblende+Plagioclase, while the third stage is identified by the Hornblende+Plagjoclase
Garnet assemblage in the symplectite formed around garnet. The P-T conditions of the first and the third stages are
, 11.8-15.9 kb and
, 4.0-6.3 kb, respectively. These data indicate that metabasite in Baekdong area had experienced a retrouade P-T path from the eclogite(EG) - high-pressure granulite (HG)-amphibolite (AM) transitional facies to the AM through HG-AM transitional facies. The core and rim of garnet in country granitic gneiss give
, 10.7-16.0 kb and
, 5.4-7.0 kb, respectively, indicating that the retrograde P-T path of granitic gneiss is similar to that of metabasite. Trace element data reveals that the tectonic setting of metabasite is island uc. The general geology, the metamorphic evolution, the mineral chemistry and the tectonic setting of Baekdong area indicate that the Baekdong-Hongseong area in Korea is a possible extension of the Sulu collision Belt in China. On the other hand, the Sm-Nd whole rock-garnet isochron ages of metabasites are 268.7-297.9 Ma which are older than the ages of UHP metamorphism (208-245 Ma) in the Dabie-Sulu Collision Belt. The older metamorphic ages suggest that collision between Sino-Korea and Yangtz plates may have occurred earlier in Korean Peninsula than China.
Metamorphic Evolution of the Ogcheon Metamorphic Belt: Review of Recent Studies and Remaining Problems
The Journal of the Petrological Society of Korea, volume 11, issue 3_4, 2002, Pages 121~137
Metamorphic evolution of the Ogcheon metamorphic belt has been studied by many investigators for the past few decades. P-T conditions of the Ogcheon metamorphic belt were estimated as 4.2-9.4 kbar and
, corresponding to the medium-pressure type. In addition, the clockwise P-T-t path suggests a crustal-thickening event in association with the formation of thrust nappes. However, some details on deformation and orogeny of the Ogcheon metamorphic belt have been ambiguous yet. Although the metamorphic age has been also equivocal, recent isotopic studies strongly suggest that the peak metamorphism in the Ogcheon metamorphic belt has occurred at ca. 300-280 Ma between Late Carboniferous and Early Permian. It is thus inferred that the Ogcheon metamorphic belt and the Taebaegsan basin have evolved as separate terranes and that both were sutured at ca. 250-220 Ma. These results are partly in contrast with those of previous workers and require a revised framework for tectonic evolution of the Ogcheon belt. In addition, it is likely that the Ogcheon belt is correlative with the Hida marginal belt and the Hida metamorphic belt.
Petrogenesis and Metamorphism of Charnockite of Eastern Jirisan Area
The Journal of the Petrological Society of Korea, volume 11, issue 3_4, 2002, Pages 138~156
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
(0.12~0.08) and increasing
(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
and 2.5~7.5 kbar respectively. The results of P-T estimates indicate an anticlockwise P-T evolution path.
Zircon chemical age of the Precambrian gneisses from Gimcheon area in the central Yeongnam massif, Korea
The Journal of the Petrological Society of Korea, volume 11, issue 3_4, 2002, Pages 157~168
In Gimcheon area of the central Yeongnam massif granite gneiss occurrs with intercalated biotite gneiss at xenolith or restite. In order to understand the evolution of the central Yeongnam massif, it is essential to have absolute age information, but not many age data are available yet. Furthermore the previous age determinations from the study area are not compatible with the outcrop relationship. In this study we determined chemical ages from the zircon grains. We obtained ages of
)Ma from the granite gneiss,
)Ma from the outer rim of a rounded zircon and 1973
)Ma from a longish zircon, both from the biotite gneiss. These ages seem to indicate the timing of granitic magma intrusion and subsequent metamorphism. Ages of
)Ma, and 2219
)Ma obtained from zoned core of the rounded zircon grain from the biotite gneiss suggest various geological events before such metamorphism of the biotite gneiss. Ages in the range of 1450~1670 Ma observed in zircons of both gniesses suggest later metamorphism that the granite gneiss and the biotite gneiss experienced together. The chemical age determination by electron probe micro-analyzer of this study utilized 1
beam diameter and it seems to be a very useful age determination from the zircons with complex growth history because of superior spatial resolution.
Tertiary Dyke Swarms and their Tectonic Importance in the Southeastern Part of the Korean Peninsula
The Journal of the Petrological Society of Korea, volume 11, issue 3_4, 2002, Pages 169~181
Basic~intermediate dike swarms are pervasively developed in the east of the Ulsan Fault, SE Korea. Most of them intruded initially along the NS-trending extensional fractures which developed under EW extension during the East Sea opening in the Early Miocene (before about 17 Ma). The mean-strikes of the basic dikes intruding into the granites are more clockwise rotated in farther eastern side, i. e.
E in the western side, in the just vicinities, and in the eastern side of the YBonil Tectonic Line (YTL), respectively. And the mean-strike of the basic dikes nearby shoreline is also most clockwise rotated (
E in the Guryongpo Peninsula). The spatial variance indicates that the dikes, located only in the east of the YTL, experienced horizontal-clockwise rotation, and that the dikes in farther east from the YTL experienced more clockwise rotation. It is, thus, supported that the NNW dextral shear stress, generated by the spreading of the East Sea, was propagated toward inland from eastern continental margin of the Korean Peninsula, and that the YTL is an westernmost limit of the clockwise crustal rotations which are pervasively observed in the vicinities of the Miocene basins, SE Korea.
Geochemical Study of Dyke Swarms, SE Korea
The Journal of the Petrological Society of Korea, volume 11, issue 3_4, 2002, Pages 182~199
We attempted to show the evolution of the magma and the geochemical characteristics of dikes and dike swarms by using the petrographic and geochemical data from 287 dikes, SE Korea. The dikes can be divided into mafic, intermediate, and felsic dikes in the field. And each of them is subdivided into three groups, two groups, and two groups, respectively. The group (I) among the mafic dikes most pervasively occurs and are distributed in both sides of the Yeonil Tectonic Line (YIL), which petrographic and geochemical characteristics are the same. These facts thus, strongly support the results of the previous studies which showed that they were intruded contemporaneously and that YTL was a main tectonic line which restricted the crustal clockwise rotation during the Early Miocene. The geochemical characteristics are discriminated according to the seven groups divided petrographically. The mafic, intermediate and felsic dikes belong to basalt and basaltic andesite, andesite and facile, and rhyolite, respectively, and the magmas mostly belong to calc-alkaline series. The geochemical data indicate that there were the fractional crystallizations of olivine, clinopyroxene, and plagioclase in the mafic dikes. And the content of characteristic elements and tectonic discrimination diagrams show that the dikes were formed from the magma related to the subduction of plate and that the tectonic setting was related to orogenic volcanic arc.
Petrogenesis of Plutonic Rocks in the Andong Batholith
The Journal of the Petrological Society of Korea, volume 11, issue 3_4, 2002, Pages 200~213
The Andong granitoid batholith represents five temporally distinct episodes (phases) of igneous activity. The batholith represents a plutonic complex of five pulsatively emplaced distinct intrusive multiphases. The petrochemical data show that the plutons fall into calc-alkaline series except for the Yean pluton, and plot within the diaenostic range for I-type origin and continental arc orogenic tectonic setting. Each pluton reveals systematic compositional variations of major and trace elements with
or MgO, but different variation trends for some elements and considerably different REE patterns. Thus discontinuous, inconsistent variations in the elements indicate that the five plutons can not be explained by simple fractional crystallization from the same primary magma, but were intruded and solidified from the independent magmas of chemically heterogeneous origin. In the Andong, Dosan and Pungsan plutons, high values of molar CaO/(MgO+
) combined with low
O ratios suggest a magma originated by dehydration melting of a metabasaltic to metatonalitic protolith. Whereas the Imha pluton show similar values of CaO/(MgO+
), but significantly higher ratios of
O implying to a metagreywacke protolith.
Petrochemistry on igneous rocks in the Mt. Mudeung area
The Journal of the Petrological Society of Korea, volume 11, issue 3_4, 2002, Pages 214~233
Igneous rocks of Mt. Mudeung area are composed of Pre-Cambrian granite gneiss, Triassic hornblende-biotite granodiorite, Jurassic quartz diorite and Cretaceous igneous rocks. The Cretaceous igneous rocks consist of volcanic rocks (Hwasun andesite, Mudeung-san dacite and Dogok rhyolite) and granitic rocks (micrograpic granite and quartz porphyry). Major elements of the Cretaceous igneous rocks represent calc-alkaline rock series and correspond to a series of differentiated products from cogenetic magma. Igneous activity of Mt. Mudeung area started from volcanic activity, and continued to intrusive activity at end of the Cretaceous. In chondrite normalized REE pattern, most of igneous rocks of Mt. Mudeung area show similar pattern of Eu (-) anomaly. This is a characteristic feature of granite in continental margin by tectonic movement. Variation diagrams of total REE vs. La/Yb V vs. SiO
indicate differentiation and magnetite fractionation sequential trend of Hwasun andesite longrightarrowMudeungsan dacitelongrightarrowquartz porphyry. In mineral composition of these igneous rocks in mt. Mudeung area, composition of plagioclase and biotite coincidence with variation of whole rock composition, and emplacement and consolidation of magma is about 15 km (about 4.9 Kbar) in Jurassic quartz diorite and 2.0~3.2 km (0.6~1.0 Kbar) in Triassic hornblende-biotite granodiorite used by amphibolite geobarometer. Parental magma type of these granitic rocks of nt. Mudeung area corresponds to VAG field in Pearce diagram, and I-type in ACF diagram.
Geological Structure of Okcheon Metamorphic Zone in the Miwon-Boeun area, Korea
The Journal of the Petrological Society of Korea, volume 11, issue 3_4, 2002, Pages 234~249
The Miwon-Boeun area in the central and northern part of Okcheon metamorphic zone, Korea, is composed of Okcheon Supergroup and Mesozoic Cheongju and Boeun granitoids which intruded it. The Okcheon Supergroup consists mainly of quartzite (Midongsan Formation), meta-calcareous rocks (Daehyangsan Formation, Hwajeonri Formation), meta-psammitic rocks (Unkyori Formation), meta-politic rocks (Munjuri Formation), meta-conglomeratic rocks (Hwanggangni Formation) in the study area, showing a zonal distribution of NE trend. Its' general trend is locally changed into NS to EW trend in and around high-angle fault of NS or NW trend. This study focused on deformation history of the Okcheon Supergroup, suggesting that the geological structure was formed at least by four phases of deformation. (1) The first phase of deformation occurred under ductile shear deformation of top-to-the southeast movement, forming sheath fold or A-type fold, asymmetric isoclinal fold, NW-SE trending stretching lineation. (2) The second phase of deformation took place under compression of NW-SE direction, forming subhorizontal, tight upright fold of M trend in the earlier phase, and formed semi-brittle thrust fault (Guryongsan Thrust Fault) of top-to-the southeast movement and associated snake-head fold in the later phase. (3) The third phase of deformation formed subhorizontal, open recumbent fold through gravitational or extensional collapses which might be generated from crustal thickening and gravitational instability. (4) The fourth phase of deformation formed moderately plunging, steeply inclined kink fold related to high-angle faulting, being closely connected with the local change of NE-trending regional foliation into NS to EW direction of strike in the vicinity of the high-angle fault.
Quantification of Cheongsan granite deformation using wavy extinction of quartz
The Journal of the Petrological Society of Korea, volume 11, issue 3_4, 2002, Pages 250~258
The wavy extinction of quartz can be used as a standard indicator showing the degree of rock deformation. To determine the degree of rock deformation, the intensity of wavy extinction (IWE) of quartz was measured using petroggraphic microscope, digital camera, and NIH image. In this study, this method was applied to the Cheongsan porphyritic granite, Cheongsan two mica granite, and Baekrok granite to investigate the deformation intensity of Cheongsan area. NIH Image data show a high-grade deformation in the vicinity of the strike-slip fault (between Cheongsan granite and Baekrok granite) and the unconformity (between Cheongsan granite and Youngdong basin). Thus, the main deformation in these areas is most likely to be concentrated on the faults that generate Yeongdong basin and the strike slip faults between Cheongsan granite and Baekrok granite.
Geochemistry of tourmalines in the Ilgwang Cu-W breccia-pipe deposit, Southeastern Gyeongsang Basin
The Journal of the Petrological Society of Korea, volume 11, issue 3_4, 2002, Pages 259~270
A small granodiorite-quartz monzonitic stock containing sericitic and propylitic alteration assemblages hosts a Cu-W breccia-pipe deposit in the southeastern Cyeongsang basin. The mineralized breccia-pipe contains angular to subangular brecciated fragments of granitic rocks showing clast-supported textures. An assemblage of quartz, tourmalines, sulfide minerals (mainly chalcopyrite, arsenopyrite and pyrrhotite) and calcite was precipitated as a hydrothermal cement between the brecciated fragments. A tourmaline aureole surrounds the breccia pipe. Extensive tourmalinization of the granitic rocks near and within the pipe and no tourmalinization in the sedimentary and volcanic rocks. The tourmalines are marked by Fe-rich, black charcoal-like schorl (80 mol% schorl relative) nearer the schorl-dravite solid solution. The chemical changes in the hydrothermal fluid are reflected by variations in compositional Boning from cores to rims. They generally contain cores with low values of Fe/(Fe+Mg) and high values of Na/(Na+ca) relative to rims. This is because of an increase Fe and Ca contents toward rims. The main trend of these variations is a combination of the exchange vectors Ca(Fe, Mg)
It is thought that boiling causes the loss of
into the vapor phase resulting in the oxidation of Fe in the aqueous phase. pH of the melt would be one of important controlling factors for the tourmaline stability. The tourmalines could be precipitated when the system evolved to the acidic hydrothermal regime as most hydrothermal brines and acidic gases exsolved from the magma. The Ilgwang tourmaline crystallization is products of hypogene orthomagmatic hydrothermal processes that were strongly pipe-controlled.
A note on absence of Giseong Series and relation of Precambrian Pyeonghae Series and Wonnam Series of Pyeonghae-Uljin area
The Journal of the Petrological Society of Korea, volume 11, issue 3_4, 2002, Pages 271~277
Pyeonghae Series, Giseong Series. Wonnam Series, Pyeonghae Unite gneiss, Hada leuco-granite gneiss are the Precambrian gneisses distributed in the north-eastern part of the Yeongnam massif. Even though there are no difference in lithologies between Pyeonghae and Wonnam Serieses. they have been regarded as different Serieses because of the presence of Giseong Series which has been considered meta-volcanics. However, field investigations reveal that the Giseong Series represents ductile shear zone having meta-volcanics-like appearances in some outcrops. The fact that both Pyeonghae and Wonnam Serieses experienced high grade metamorphism reaching upper amphibolite facies implies that any volcanics between these two Serieses should also occur as high-grade metamorphic rocks at present. The absence of Giseong Series as a low-grade meta-volcanics indicates the absence of logical base to distinguish Pyeonghae and Wonnam Serieses. Therefore, these two Serieses should be regarded as identical Series.