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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 1, Issue 2 - Dec 1992
Volume 1, Issue 1 - Sep 1992
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Metamorphism of the Gyeonggi Massif in the Gapyeong-Cheongpyeong area
Lee Kwang Jin ; Cho Moonsup ;
The Journal of the Petrological Society of Korea, volume 1, issue 1, 1992, Pages 1~24
Precambrian metamorphic rocks of the Gapyeong-Cheongpyeong area consist of banded gneiss, augen gneiss, leucocratic gneiss, quartz schist and quartzite, together with minor intercalations of serpentinite, amphibolite and marble. Mineral assemblages of meta-sedimentary rocks are classified into three types: sillimanite-free; sillimanite-bearing; and sillimanite+K-feldspar-bearing assemblages. Compositions of metamorphic phases depend on the type of mineral assemblages. In particular, the Ca contents of plagioclase and garnet are high in sillimanite-free assemblges. Kyanite occurs in three samples, and coexists with sillimanite in one sample. The presence of kyanite indicates that metamorphic rocks of the study area have experienced the Barrovian type metamorphism. Peak metamorphic conditions estimated from various geothermobarometers and phase equilibria are 618-674
2.0 kbar for sillimanite-free assemblages, and 701-740
0.8 kbar for sillimanite-bearing assemblages, respectively. Furthermore, a clockwise P-T-time path is deduced for the study area, based on the following observations: (1) the polymorphic transition of kyanite to sillimanite, (2) the occurrence of sillimanite and K-feldspar belonging to the upper amphibolite facies, and finally (3) the retrograde metamorphism characterized by muscovite-, chlorite-, and actinolite-bearing assemblages.
A study on the metamorphism in the southwestern part of Gyeonggi Massif
Na Ki Chang ;
The Journal of the Petrological Society of Korea, volume 1, issue 1, 1992, Pages 25~33
The southwestern part of Gyeonggi Massif consists mainly of Archean Seosan and Daesan Groups, and Paleoproterozic Bucheon Group with Bucheon and Seosan gneiss complexes which are members of Gyeonggi gneiss complex. In the eastern part of Dangjin fault, Mesoproterozoic Anyang Group and Anyang granite gneiss occur, and in the western part of the fault Taean Group uncomformably overlies Archean and Paleoproterozoic Groups. Metamorphic facies of Archean Groups is mainly upper amphibolite facies which was overprinted by the second amphibolite facies metamorphism and the third greenschist facies metamorphism. Bucheon and Anyang Groups belong to amphibolite and greenschist facies and are partly overprinted by greenschist facies metamorphism which is characteristic for Taean and Daedong Groups.
Petrological and geochemical study of the Precambrian granitic gneiss in the Danyang- Yecheon area
Yun Hyon Soo ;
The Journal of the Petrological Society of Korea, volume 1, issue 1, 1992, Pages 34~41
The Precambrian granitic gneisses are widely distributed in the Danyang-Yecheon area, eastern part of Korea, where the Ryeongnam massif borders the Ogcheon fold belt. They are composed of migmatitic, biotite granitic, garnet-bearing and granoblastic granitic gneisses. The common joint sets of the granitic gneiss are NE and NS directions, which are probably related to the effects of Daebo orogeny and Bulgugsa disturbance, respectively. Mineral assemblages of the banded gneiss xenolith in the garnet-bearing granitic gneiss are quartz-plagioc1ase-biotite-mus-covite-orthoclase and quartz-plagioc1ase-biotite-garnet, belonging to the amphibolite facies. The granoblastic granitic gneiss is felsic, metaluminous, and granitic, and shows subalkaline trend. The garnet-biotite geothermometry of garnet-bearing granitic gneiss yields 640
at pressure of 4 kb.
Synthesis and stability relations of zoisite
(OH) at 2-4 kbar
Kim Hyung Shik ; Park Chan Soo ;
The Journal of the Petrological Society of Korea, volume 1, issue 1, 1992, Pages 42~48
The equilibrium pressure-temperature curve of the reaction: 6 Ca
O zoisite anorthite grossularite corundum was experimentally determined using both externally and internally heated pressure vessels in the pressure range of 2-4 kbar. Synthetic zoisite, anorthite, grossularite and corundum were used as starting materials. Starting materials were synthesized at 13-16 kbar using the piston-cylinder apparatus. The dehydration temperature of zoisite at 2 kbar is 550
and at 4 kbar is 575
. Low thermal stability of synthetic zoisite relative to natural zoisite at 4 kbar is attributed to the structural disorder of synthetic anorthite.
Thermal history of the Jecheon granite pluton in the Ogcheon Fold Belt, South Korea
Jin Myung-Shik ; Kim Seong-Jae ; Shin Seong-Cheon ; Choo Seung-Hwan ; Chi Se-Jung ;
The Journal of the Petrological Society of Korea, volume 1, issue 1, 1992, Pages 49~57
Whole rock and mineral ages for the Jecheon Granite distributed in the Ogcheon Fold Belt were dated by three radiometric methods, and its thermal history was elucidated as follows, on the basis of isotopic age data. Rb and Sr isotopic compositions of three whole rock and seven mineral concentrates made an isochron of 202.7
1.9 Ma with a strontium initial ratio of 0.7140. Different age data of twelve mineral concentrates agree closely with the retention temperature of each mineral in K-Ar and Fission Track methods. The Jecheon granitic magma was generated by partial melting of crustal materials (S-type), or by mixins between mantle and crustal materials, intruded into the katazone or mesozone (7∼9 km) of the Ogcheon Fold Belt, at least in the Early Jurassic (about 203 Ma), and then crystallized and cooled down rapidly from about 600
(more than 20
/Ma), owing to thermal differences between the magma and the wall-rock. During the Middle to Late Jurassic (190∼140 Ma), the cooling of the granite was likely to stop and keep thermal equilibrium with the wall-rock. The severe tectonism associated with igneous activities and active weathering on the surface in Early to Late Cretaceous time (140∼70 Ma) might have accelerated the granite pluton to uplift rapidly (40∼60 m/Ma in average) up to 3∼4 km and cooled down from 300
/Ma). The granite pluton was likely to keep different uplifting and cooling rate of about 120 m/Ma and 5
/Ma in average from the Late Cretaceous to Early Tertiary (70∼50 Ma), and about 60 m/Ma and 2
/Ma in average from about 50 Ma up to the present, respectively.
K-Ar ages of the hydrothermal clay deposits and the surrounding igneous rocks in southwest Korea
Kim In Joon ; Nagao Keisuke ;
The Journal of the Petrological Society of Korea, volume 1, issue 1, 1992, Pages 58~70
From the K-Ar age determinations for the clay deposits and their surrounded rocks in southwest Korea, the ages of the ore formation in all clay deposits fall in very narrow range from 78.1 to 81.4 Ma. K-Ar ages of clay deposits are slightly younger than those of the Cretaceous volcanic rocks (Hwangsan Formation, 81.4 to 86.4 Ma) and are slightly older than those of the Cretaceous granitic rocks (77.1 to 81.5 Ma). These results indicate that clay deposits were formed with genetical relation to late Cretaceous felsic magmatism. Weolgagsan granite, which has been previously considered to be Cretaceous, is proved to be formed its age in Jurassic (140.9 and 144.8 Ma). The close relationships of K-Ar ages between the clay deposits and Cretaceous granitic rocks suggest that the clay deposits were formed during the hydrothermal alterations caused by the thermal effects (hydrothermal circulation) of the granitic intrusions rather than by the hydrothermal activities associated with volcanic activities.
Petrography and Mineral Chemistry of Some Deep Sea Basaltic Rocks from the Western Caroline Ridge and Yap Trench-Arc System
Park Jun-Beom ; Kwon Sung-Tack ; Ahn Jung-Ho ; Kang Jung-Keuk ;
The Journal of the Petrological Society of Korea, volume 1, issue 1, 1992, Pages 71~84
This paper reports the results about the petrography and mineral chemistry of 13 representative dredged basaltic rocks from the western Caroline Ridge (WCR) and Yap Trench-Arc system, and provides the chemical and tectonic informations based on the compositions of clinopyroxene phenocrysts. Compositions of olivine phenocrysts in some analyzed samples are Fo
. Plagioclase phenocrysts have variable compositions ranging from An
. The compositions of clinopyroxene phenocrysts vary according to geological environments; titansalite in atoll and guyot of WCR, diopside-augite in trough and bank of WCR, and endiopside in Yap Trench-Arc system. Application of the discrimination schemes proposed by Leterrier et al. (1982) suggests: (1) the samples from atoll-guyot belong to within plate alkali basalt, implying that western CR could be the continuation of eastern CR formed by hot spot magmatism, (2) the samples from the Yap Trench-Arc system with no present-day magmatism clearly indicate the occurrence of orogenic tholeiites presumably related to early island arc magmatisms in this area, however, (3) the samples from the bank and trough do not provide definitive informations, which might indicate the complexity of their origins.