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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 6, Issue 3 - Dec 1997
Volume 6, Issue 2 - Oct 1997
Volume 6, Issue 1 - Jun 1997
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Petrology of the Volcanic Rocks in Geoje Island, South Korea
The Journal of the Petrological Society of Korea, volume 6, issue 1, 1997, Pages 1~18
Andesitic pyroclastics and lava flows are deposited as a part of composite volcanoes by Cretaceous volcanic activity in Geojae Island, off the coast of Korea. The andesitic pyroclastics are composed of tuff breccia and lapilli tuff minor intercalated tuff. Lava flows are divided into dense and porphyritic andesite containing phenocrysts of plagioclase, pyroxene, and/or hornblende. The andesitic rocks represent charactersitcs of carc-alkaline BAR association with basalt, basaltic andesite, andesite, and dacite to rhyolite. Major element variations of the volcanic rocks show that
, total FeO, CaO, MgO and
decrease with increasing
and total alkalis increase, and represent differntiation trend of calc-alkaline rock series. In spider diagram, contents of Sr, K, Rb, Ba, and Th are relatively high, but contents of Nb, P, Ti and Cr are low. These petrochemcial characteristics are similar to those of rocks from island arc or continental margein related to plate subduction. Chondrite-normalized REE patterns of volcanic rocks are paralle to subparallel, with LREE enriched than HREE, and show gradual increase of negative Eu anomaly from basalt to dacite and rhyolite, suggesting comagmatic fractional crystallization with minor effects of assimilation and magma mixing. Andesitic rocks are assumed medium-K orogenic andesites that formed in the tectomagmatic environment of subduction zone under normal continental margin arc.
Petrochemical Study on the Cretaceous Volcanic Rocks in Kageo island, Korea
The Journal of the Petrological Society of Korea, volume 6, issue 1, 1997, Pages 19~33
This study reports the results about the petrography and geochemical characteristics of 10 representative volacanic rocks. The Cretaceous volcanic rocks distributed in the vicinity of the Kageo island composed of andesitic rocks, dacitic welded tuff, and rhyolitic rocks in ascending order. Sedimentary rock is the basement in the study area covered with volcanic rocks. Andesitic rocks composed of pyroclastic volcanic breccia, lithic lapilli tuff and cryptocrystallin lava-flow. Most dacitic rocks are lapilli ash-flow welded tuff. Rhyolitic rocks consists of rhyolite tuff and rhyolite lava flow. Rhyolite tuff are lithic crystal ash-flow tuff and crystal vitric ash-flow tuff with somewhat accidental fragments of andesitic rocks, but dacitic rocks. The variation of major and trace element of the volcanic rocks show that contents of
, FeO, CaO, MgO,
decrease with increasing of
. On the basis of Variation diagrams such as
vs. CaO, Th/Yb vs. Ta/Yb, and
, these rocks represent mainly differentiation trend of calc-alkaline rock series. On the discriminant diagrams such as Ba/La and La/Th ratio, Rb vs. Y + Nb, the volcanic rocks in study area belongs to high-K Orogenic suites, with abundances of trace element and ternary diagram of K, Na, Ca. According to the tectonic discriminant diagram by Wood, these rocks falls into the diestructructive continental margin. K-Ar ages of whole rocks are from andesite to rhyolite
Ma, repectively. Volcanic rocks in study area show well correlation to the Yucheon Group in terms of rock age dating and geochemcial data, and derived from andesitic calc-alkaline magma that undergone low pressure fractional crystallization dominated plagioclase at <30km.
Petrological characteristics on stone resources of granites in the Pocheon-Euijeongbu area
The Journal of the Petrological Society of Korea, volume 6, issue 1, 1997, Pages 34~44
The Jurassic granites, commercially called Yangu stone in the Pocheon-Euijeongbu area, have generally compact and coarse-grained textures, which could be classified into two types; grey granite(Gg) and light pink granite(Gp). Specific gravity, absorption ratio and prosity of Gg and Gp in physical property are 2.64 and 2.61, 0.32 % and 0.44 %, 0.86% and 1.13 %, respectively. These higher values of two latters of Gp than those of Gg are due to the more abundant microcracks in Gp. Compressive strength og Gg than those of Gg are due to more abundant microcracks in Gp. Compressive strength og Gg and Gp are 1,726 kg/cm2 and 1,717 kg/cm, respectively and bestrength has a positive proportion with Qz+Af+Pl(quartz+alkali feldspar+plagioclase) modes without trending with Bt+Ac(biotite+accessories). Tensile strength has the positive proportions with Qz+Af+Pl and Bt+Ac. While Bt+Ac has a negative trend with abrasive hardness, Qz+A+Pl shows a positive one. These may suggest Qz+Af+Pl mainly affects on strenghts potentional dimension stone than Gp.
The Feature of Indosinian Movement and its comparison with Yanshanian Movement in the Yanshanian area, China
The Journal of the Petrological Society of Korea, volume 6, issue 1, 1997, Pages 45~51
Tectonic movements in the Mesozoic were significant events to structural evolution in East China, so far as to West Pacific area. Typical Mesozoic structures were formed and outcropped in Yanshanian mountain area in which Yanshanian movement was named. It is generally considered that the most of outcropping structures in this area were formed in Yanshanian movement. But general studies indicated recently that more than half of the folds were formed in Yanshanian movement. But general studies indicated recently that more than half of the folds were formed and most of fault were in great reverse activity during Indosinian movement in Late-Triassic epoch. The tectonic dynamics setting of Indosinian move ment is a N-S compressive stress system originated by northward movement of Sino-Korean massif and its collison with Xingan-Mongolia fold zone. A series of closed folds (nearly E-W axial trace)and some overturned folds were formed in Indosinian movement and incoaxially superposed by Yanshanian deformation, Faulting characteristcs in the area were thrust faulting caused by compressive stress in Indosinian movement, some of which appear to be positive structural inversion, and oblique-thrust caused by compressive-shear in Yanshanian movement.
Regional-scale metasomatism of Al, K, and Na during stauroliteandalusite- grade contact metamorphism, in the southwestern Nova Scotia, Canada
Sang-Gi Hwang ;
The Journal of the Petrological Society of Korea, volume 6, issue 1, 1997, Pages 52~64
Pelitic rocks of southwestern Nova Scotia have been affected by widespread contact metamorphism due to the intrusion of the Shellburne Pluton, with aureole up to 15 km wide. Well-preserved pseudomorphic textures indicate that common staurolite and andalusite metacrysts formed at the expense only of plagioclase, muscovite and biotite. Excess components (K, Na and Ca) from such replacement reactions imply extensive metasomatism throughout the contact aureole. Modal analysis of a typical andalusite-bearing rock indicates a one-to-one volume ratio of product to reactant. However the products of the replacement reactions contain approximately three times more aluminum than the reactants, indicating that the regional metasomatism also involved aluminum.