• Proceedings of the Petrological Society of Korea Conference
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• 2009.05a
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• pp.73-73
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• 2009

• The Journal of the Petrological Society of Korea
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• v.21 no.1
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• pp.31-45
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• 2012

We investigated the various lithologies and zircon U-Pb ages of metasedimentary rocks from the Yeongheung-Seonjae-Daebu Islands, western Gyeonggi Massif, whose geologic and geochronologic features are poorly constrained in spite of their significance for tectonic interpretation. Major lithology consists of quartzites or meta-sandstones commonly alternating with semi-pelitic schists, together with lesser amounts of calcareous sandstones with matrix-supported quartzite clasts, calcareous schists, and pelitic schists. Pelitic schists uncommonly contain large porphyroblasts of garnet as well as quartz veins with large crystals of muscovite and andalusite or kyanite. SHRIMP U-Pb ages of detrital zircons from two analyzed metasandstones define four age populations: Neoarchean (~2.5 Ga), Paleoproterozoic (~2.0-1.5 Ga), Neoproterozoic (~1.1-0.7 Ga), and Early Paleozoic (~560-400 Ma). The youngest zircon ages are clustered at ~420 Ma. These results suggest that the deposition of meta-sandstones took place after the Silurian, possibly during the Devonian, and are analogous to those of the Taean Formation reported from the western part of the Gyeonggi Massif. Moreover, The age distribution patterns of detrital zircons and the Barrovian-type metamorphic facies of pelitic schists are similar to those reported from the Imjingang belt, suggesting that the Taean Formation likely corresponds to southwestward extension of the Imjingang Belt.

• The Journal of the Petrological Society of Korea
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• v.28 no.2
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• pp.143-156
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• 2019

We carried out the sensitive high resolution ion microprobe zircon U-Pb age dating and whole rock geochemical analysis of granites in the Gudambong and Sainam geosites, Danyang Geopark. The granites crop out in the western and southern parts of Danyang County, and intruded sedimentary successions of the Yeongweol and Taebaek Groups, respectively. The U-Pb isotopic compositions of zircon from the Gudambong and Sainam granite samples yielded the Cretaceous intrusion ages of $90.4{\pm}0.5Ma(t{\sigma})$ and $90.0{\pm}1.5Ma(t{\sigma})$, respectively. The major and trace elements compositions of the samples showed an affinity of typical A-type granite, indicating their petrogenesis during the late stage of the Bulguksa orogeny or a tectonic dormancy. The geochronologic and geochemical results are identical to those of granites previously reported from the Cretaceous Muamsa and Wolaksan suites.

• The Journal of the Petrological Society of Korea
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• v.12 no.4
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• pp.155-169
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• 2003

In the northwest Okcheon metamorphic belt, the metaigneous rocks in the Gyemyeongsan Formation have wider chemical ranges for major, trace and REE elements compared with metaigneous rocks in the Munjuri Formation and do not represent bimodal igneous activity which is characteristic for a continental rifting. The metaigneous rocks in the Munjuri Formation are regarded as products of single magmatic evolution, whereas those in the Gyemyeongsan Formation may be formed through multiple magmatic episodes. The felsic metavolcanic rocks in the Gyemyeongsan Formation show weaker Eu negative anomalies compared with those in the Munjuri Formation but those in both formations show similar degrees of enrichment from LREE to HREE. The metabasites in the Munjuri Formation do not show Eu anomalies but those in the Gyemyeongsan Formation show both positive and negative Eu anomalies(0.59

• Korean Journal of Mineralogy and Petrology
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• v.36 no.1
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• pp.73-94
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• 2023

We carried out the sensitive high resolution ion microprobe (SHRIMP) zircon U-Pb age dating and whole-rock geochemical analysis of granitoids and felsic porphyries in the Ssangyong Valley, Yongchu Valley, and Mungyeong Saejae geosites in the Mungyeong Geopark. The igneous rocks crop out in the western, northwestern and central parts of the Mungyeong city area, respectively, and intruded (meta)sedimentary successions of the Ogcheon Metamorphic Belt, Cambro-Ordovician Mungyeong Group and Jurrasic Daedong Group. The U-Pb isotopic compositions of zircon from two felsic porphyries and one granite samples in the Ssanyeong Valley yielded the Cretaceous intrusion ages of 93.9±3.3 Ma (tσ), 95.1±4.0 Ma (tσ) and 94.4±2.0 Ma (tσ), respectively. On the other hand, a felsic dike sample and a granite in the Yongchu Valley and a porphyritic granite in the Mungyeong Saejae had intrusion ages of 90.2±2.0 Ma (tσ), 91.0±3.0 Ma (tσ) and 88.6±1.5 Ma (tσ), respectively. Based on the average standard error calculated in combination with results of previous studies in this area (Lee et al., 2010; Yi et al., 2014; Aum et al., 2019), the geochronological results show that spatial variation in intrusion age of ~5 Myr between the Ssangyong (94.5±0.2 Ma) and Yongchu Valleys (89.7±0.4 Ma) is apparent. The geochemical compositions of major and trace elements in the samples showed an affinity of typical post-orogenic granite, indicating their petrogenesis during the late stage of Early Cretaceous magmatic activity possibly in association with subduction events of the Izanagi Plate.

• The Journal of the Petrological Society of Korea
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• v.18 no.1
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• pp.31-47
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• 2009

We performed petrological, geochemical, and geochronological study for the Pyeonghae granite gneiss and the Hada leuco-granite gneiss intruding the Paleoproterozoic meta-sedimentary rocks (pyeonghae formation and Wonnam formation) of the Pyeonghae area located in northeastem part of the Yeongnam (Sobaeksan) massif. The Pyeonghae granite gneiss generally has higher abundance of mafic minerals (biotite etc.), and posesses higher ${Fe_2}{O_3}^t$, MgO, CaO, $TiO_2$, $P_{2}O_{5}$ contents but lower $SiO_2$ and $K_{2}O$ contents than the Hada leuco-granite gneiss which tends to have slightly high $Al_{2}O_{3}$ and $Na_{2}O$ contents and slightly high larger negative Eu anomalies. However both gneisses reveal very similar REE concentrations and chondrite-normalized patterns and apparently show differentiation trend affected by crystallization of biotite, plagioclase, apatite and sphene. Their peraluminous and calc-alkaline chemistry suggests tectonic environment of volcanic arc. SHRIMP Zircon U-Pb age determinations yield upper intercept ages of $1990{\pm}23\;Ma$ ($2{\sigma}$) and $1939{\pm}41\;Ma$ ($2{\sigma}$), and weighted mean $^{207}Pb/^{206}Pb$ ages of $1982{\pm}6.3\;Ma$ ($2{\sigma}$) and $1959{\pm}28\;Ma$ ($2{\sigma}$) for the Pyeonghae granite gneiss and the Hada leuco-granite gneiss respectively, showing overlapping ages within the error. Our study suggests that the Precambrian granitoids in this area intruded contemporaneously with the Buncheon granite gneissin volcanic arc environment.

• The Journal of the Petrological Society of Korea
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• v.24 no.1
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• pp.55-63
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• 2015

We investigated the zircon U-Pb ages of the metapelites from the Sungjeon-myeon Gangjin-gun, the southwestern Ogcheon belt, to provide geochronological constraints for the depositional age as well as the distribution of Late Paleozoic formation. Data from the detrital zircons are mostly concordant, yielding four major age groups: (1) Neoarchean (~2.5 Ga); (2) Paleoproterozoic (~1.86 Ga, Statherian); (3) Middle Devonian(~390 Ma); and (4) Late Paleozoic (~322 Ma, Serpukhobian). The youngest zircon age gives a weighted mean $^{206}Pb/^{238}U$ age of $322{\pm}4.8$ Ma (n=16, MSWD=4.9), indicating deposition age of Early Carboniferous(Serpukhobian) or after. Therefore, the metapelites is considered to be the lowest Formation of the late Paleozoic Pyeongan Supergroup correlated with the Manhang Formation of the Samcheock coal fields and the Oeumri Formation(the Middle to Late Carboniferous) of the Hwasun coal field.

• Proceedings of the KSEEG Conference
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• 2005.04a
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• pp.109-110
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• 2005

• The Journal of the Petrological Society of Korea
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• v.22 no.3
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• pp.235-249
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• 2013

The Gusandong Tuff (Kusandong Tuff), known as a very significant key bed in the Cretaceous Gyeongsang Basin, is divided into (1) Northern Gusandong Tuff (NKT), (2) Southern Gusandong Tuff (SKT), and (3) Sinsudo Tuff, which were derived from different vents. In order to suggest their more accurate eruption times and to contribute to establishing stratigraphy of the basin, SHRIMP U-Pb zircon ages were determined from the three tuffs. As a result, the virtually same ages of $103.0{\pm}1.2$ Ma and $104.1{\pm}1.3$ Ma were obtained from NKT and SKT, respectively, which mean that they simultaneously erupted during 103~104 Ma. The zircon ages obtained from the Sinsudo Tuff are however divided into two groups i.e. $103.4{\pm}2.1$ and $95.79{\pm}0.98$ Ma. Based on distinctive morphology and cathodoluminescence image of the younger zircons, the younger age, $95.79{\pm}0.98$ Ma, is much more reasonable as the eruption time of the Sinsudo Tuff.

• The Journal of the Petrological Society of Korea
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• v.27 no.2
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• pp.97-104
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• 2018

The U-Pb isotopic and rare earth element compositions of zircon were measured using a SHRIMP from a tonalitic gneiss sample DE43 in Daeijak Island, central Korea. Zircon crystals, up to ${\sim}300{\mu}m$ in diameter, rarely contain thin overgrowth rims. In contrast to Paleoproterozoic cores, the $^{206}Pb/^{238}U$ ages of $256{\pm}23Ma(1{\sigma})$, and $221{\pm}7Ma(1{\sigma})$ were yielded from two spot analyses on the overgrowth rims of zircon. The rims are geochemically characterized by low Th/U ratios (<0.01) and strongly depleted light rare earth elements. The Permian-Triassic apparent ages of zircon are consistent with the $^{208}Pb/^{232}Th$ ages dated from allanite ($227{\pm}7Ma(t{\sigma})$) in the same sample within uncertainties, indicating an equilibrium growth of allanite and zircon at ~227 Ma. On the other hand, the younger $^{208}Pb/^{232}Th$ and $^{206}Pb/^{238}U$ ages ($213{\pm}4Ma(t{\sigma})$ and $186{\pm}9Ma(t{\sigma})$, respectively) of allanite may result from Pb loss due to the infiltration of alkali fluids from Late Triassic and Jurassic granitoids nearby.