• 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.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.4
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• pp.339-347
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• 2020

We carried out the U-Pb age dating of zircon from basement rocks in the southern part of the Danyang National Geopark. Two migmatitic gneisses composed of biotite±sillimanite±garnet+feldspar+quartz were dated. Leucosomes in the samples were clearly distinguished from their melanosomes. The U-Pb isotopic compositions of zircon from sillimanite- and garnet-bearing migmatitic samples were measured using a secondary ion microprobe, yielding metamorphic ages, 1870±10 Ma (2σ)와 1863±6 Ma (2σ), respectively. 1.87~1.86 Ga metamorphic ages are consistent with those of the Paleoproterozoic low-P and high-T regional metamorphism (1.87~1.85 Ga) in the Yeongnam Massif. The maximum depositional age based upon the apparent 207Pb/206Pb ages of detrital zircon in the samples was estimated as 2.06 Ga, and thus sedimentation age of the protolith of the migmatitic gneisses ranges between 2.06 and 1.87 Ga.

• Economic and Environmental Geology
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• v.49 no.6
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• pp.433-444
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• 2016

The U-Pb ages of detrital zircons from the Baengnyeong Group were determined by LA-MC-ICPMS, yielding condensed age population in the range from 1100 Ma to 1800 Ma corresponding to the Mesoproterozoic to late Paleoproterozoic. However, detrital zircons of ca.1800-2000 Ma or ca. 2500 Ma ages, which appear frequently in the lower Paleozoic Joseon Supergroup and the upper Paleozoic Pyeongan Supergroup are lacking in the Baengnyeong Group. Such characteristics are identical to those of the Neoproterozoic Sangwon System of North Korea, suggesting that the Baengnyeong Group might be the southwestern extension of the Sangwon System. The zircon age distribution patterns from the Impi Formation in the Gunsan area closely resemble those of the Baengnyeong Group, implying possible correlation of the Impi Formation to the Sangwon System. Therefore, the Mesoproterozoic detrital zircons reported from the Hwangangni Formation of the Okcheon Metamorphic Belt and the Myobong, Sambangsan and Sesong Formations of the Taebaeksan Basin might be derived from the provenances within the Korean peninsula.

• Journal of the Korean earth science society
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• v.42 no.1
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• pp.11-38
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• 2021

Detrital zircon U-Pb dating of samples from the Baekseoktan (Iljik Formation), Mananjaam (Jeomgok Formation), and Sinseongri (Sagok Formation) geosites in the Cheongsong Global Geopark were carried out to estimate the depositional age and provenance of the Hayang Group in the Gyeongsang Basin. In the Iljik Formation, Jurassic and Triassic zircons are dominant with minor Precambrian zircons, with no Cretaceous zircon. In contrast, the Jeomgok and Sagok formations show very similar age distributions, which have major age populations of Cretaceous, Jurassic, and Paleoproterozoic ages. The weighted mean ages of the youngest zircon age groups of the Jeomgok and Sagok formations are 103.2±0.3 and 104.2±0.5 Ma, respectively. Results suggest that the depositional ages of the Jeomgok and Sagok Formations are Albian. The detrital zircon age spectra indicate a significant change in provenance between the Iljik and Jeomgok formations. The sediments of the Iljik Formation are thought to have been supplied from nearby plutonic rocks. However, the Jeomgok and Sagok sediments are interpreted to have been derived from relatively young deposits of the Jurassic accretionary complex located in southwest Japan.

• The Journal of the Petrological Society of Korea
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• v.26 no.1
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• pp.63-72
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• 2017

We report an Early Cretaceous zircon U-Pb age ($113.9{\pm}1.2Ma$) for the Heuksan-do granite located about 90km from Mokpo offcoast of the southwestern Korean peninsula. At this Aptian/Albian boundary, widespread igneous activities occurred not only in the Korean peninsula but also in the eastern China and Japan. We raise the possibility that the flat-slab subduction and delamination triggered such an episodic igneous activity over the large areas of East Asia.

• The Journal of the Petrological Society of Korea
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• v.19 no.1
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• pp.89-101
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• 2010

To constrain the depositional ages of the Gyeongsang sedimeantary formations, SHRIMP U-Pb ages were determined from detrital zircons in three samples: (1) a pebble-bearing sandstone from the lowermost Jinju Formation of the Sindong Group and (2) two conglomerates from the Silla Conglomerate of the Hayang Group. Their concordia ages are $112.4{\pm}1.3(2{\sigma})$ Ma and $110.4{\pm}2.0(2{\sigma})$ Ma respectively. Such ages represent the maximum deposition ages for the lowermost Jinju Formation and Silla Conglomerate, indicating the deposition of the Jinju Formation started from late Aptian and lasted to early Albian, then deposition of the rather thin Chilgok Formation and Silla Conglomerate was followed during the Albian. The age distribution of the analyzed detrital zircons indicates the presence of protoliths, or zircons derived from them, regarding a wide span of igneous activities from Mesozoic to Archean. Among such ages, there are Mesoproterozoic, Neoproterozoic and Paleozoic igneous activities, which have not been known or seldom reported from Korean peninsula. These ages further suggest the possible presence of rocks with such ages during the deposition periods or their derivation through a long river system developed into the continents at the time of deposition.

• The Journal of the Petrological Society of Korea
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• v.23 no.4
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• pp.393-403
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• 2014

U-Pb ages were determined from the Yongyudo biotite granites from western parts of Gyeonggi massif. The results show that the emplacement age of the Yongyudo biotite granite is ca. 227-230 Ma. Such age result that is somewhat older than previous reported ages, suggesting further investigations for the timing and evolution of the Jurassic granites of the western Gyeonggi massif.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.3
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• pp.215-233
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• 2022

The zircon U-Pb and trace element analyses were performed for banded gneiss in the Euiam gneiss complex, central Gyeonggi Massif. An age of detrital zircon shows predominant age peaks at ca. 2500-2480 Ma with numerous ages ranging from Siderian to Rhyacian period. The youngest age peak of detrital zircon constrains the maximum deposition age of protolith of banded gneiss at ca. 2070 Ma. Meanwhile, the zircon rim yielded metamorphic age of ca. 1966 ± 39 Ma ~ 1918 ± 13 Ma. Based on the error range, degree of discordancy, and value of mean squared weighted deviation, we considered that the age of 1918 ± 13 Ma is the most reasonable age indicating the timing of metamorphism for banded gneiss. The zircon rims yield Ti-in-zircon crystallization temperature of 690-740℃. Therefore, we suggested that there was a high-grade metamorphic event in the Gyeonggi Massif at ca. 1918 Ma which is older than the metamorphic event that occurred in the Gyeonggi Massif during ca. 1880-1860 Ma.

• The Journal of the Petrological Society of Korea
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• v.26 no.1
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• pp.73-82
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• 2017

We determined SHRIMP U-Pb ages of the detrital zircons separated from the Bangnim Group of the Pyeongchang area to constrain its depositional age. As the result, the minimum age group yielded $^{206}Pb/^{238}U$ age of $450.3{\pm}4.2Ma$ (n=3), suggesting depositional age younger than Late Ordovician. Therefore, the Bangnim Group cannot be a Precambrian sedimentary formation but is younger than Myobong Formation of the Early Paleozoic Joseon Supergroup of the Taebaeksan basin. Such a depositional age implies that the Bangnim Group and structurally overlying Jangsan Quartzite should be in fault contact, suggesting that the Jangsan Quartzite, Myobong Formation and Pungchon Limestone thrusted over the Bangnim Group. The zircon U-Pb age distribution pattern of the Bangnim Group resembles those of the Early Paleozoic Myobong and Sambangsan Formations of the Taebaeksan basin and seemingly Middle Paleozoic Daehyangsan Quartzite and the Taean Formation. However, detrital zircon U-Pb age patterns of the Late Paleozoic Pyeongan Supergroup are quite distinct from them, suggesting drastic change in provenance of the detrital zircon supply. Therefore, we suggest that the Bangnim Group was deposited before the Pyeongan Supergroup.

• 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.