• Journal of Ecology and Environment
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• v.44 no.4
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• pp.212-221
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• 2020

Background: Rapid industrialization has caused various impacts on nature, including heavy metal pollution. However, the impacts of industrialization vary depending on the types of industrializing activity and surrounding environment. South Korea is a proper region because the rapid socio-economical changes have been occurred since the late nineteenth century. Therefore, in this study, we estimate the anthropogenic impacts on an ecosystem from a sediment core of Yonghwasil-mot, an irrigation reservoir on the western coast of Korea, in terms of heavy metal concentrations, nutrient influx, and pollen composition. Results: The sediment accumulation rate (SAR) determined by 210Pb geochronology showed two abrupt peaks in the 1930s and 1950s, presumably because of smelting activity and the Korean War, respectively. The following gradual increase in SAR may reflect the urbanization of recent decades. The average concentrations of arsenic (As), copper (Cu), and lead (Pb) during the twentieth century were > 48% compared to those before the nineteenth century, supporting the influence of smelting activity. However, at the beginning of the twenty-first century, the As, Cu, and Pb concentrations decreased by 19% compared to levels in the twentieth century, which is coincident with the closure of the smelter in 1989 and government policy banning leaded gasoline since 1993. The pollen assemblage and nutrient input records exhibit changes in vegetation cover and water level of the reservoir corresponding to anthropogenic deforestation and reforestation, as well as to land-use alteration. Conclusions: Our results show that the rapid socio-economic development since the twentieth century clearly affected the vegetation cover, land use, and metal pollutions.

• Economic and Environmental Geology
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• v.56 no.5
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• pp.557-564
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• 2023

Nuclear materials such as uranium are used as fuel for nuclear power generation, but there is a high possibility that they will be used for non-peaceful purposes, so international inspections and regulations are being conducted. Isotope analysis data of fine particulate obtained from nuclear facilities can provide important information on the origin and concentration method of nuclear material, so it is widely used in the field of nuclear safety and nuclear forensics. In this study we describe the analytical method that can directly identify nuclear particles and measure their isotopic ratios for fine samples using a large-geometry secondary ion mass spectrometer and introduce its preliminary results. Using the U-200 standard material, the location of fine particles was identified and the results consistent with the standard value were obtained through microbeam analysis.

• The Journal of the Petrological Society of Korea
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• v.21 no.2
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• pp.89-112
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• 2012

The Korean Peninsula consists of three Precambrian blocks: Nangrim, Gyeonggi and Yeongnam massifs. Here we revisited previous stratigraphic relationships, largely based on new geochronologic data, and investigated the crustal evolution history of the Precambrian massifs. The Precambrian strata have been usually divided into lower crystalline basements and upper supracrustal rocks. The former has been considered as Archean or Paleoproterozoic in age, whereas the latter as Paleoproterozoic or later. However, both are revealed as the Paleoproterozoic (2.3-1.8 Ga) strata as a whole, and Archean strata are very limited in the Korean Peninsula. These make the previous stratigraphic system wrong and require reconsideration. The oldest age of the basement rocks can be dated as old as Paleoarchean, suggested by the occurrence of ~3.6 Ga inherited zircon. However, most of crust-forming materials were extracted from mantle around ~2.7 Ga, and produced major portions of crust materials at ~2.5 Ga, which make each massif a discrete continental mass. After that, all the massifs belonged to continental margin orogen during the Paleoproterozoic time, and experienced repeated intracrustal differentiation. After the final cratonization occurring at ~1.9-1.8 Ga, they were stabilized as continental platforms. The Nangrim and Gyeonggi massif included local sedimentary deposition as well as igneous activity during Meso-to Neoproterozoic, but the Yeongnam massif remained stable before the development of Paleozoic basin.

• The Journal of the Petrological Society of Korea
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• v.10 no.3
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• pp.190-201
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• 2001

Isotope Dilution Mass Spectrometry(IDMS) is one of the analytical method which uses enriched isotope spikes and analyzes the abundance of element by comparison of the spectrum between spiked mass and non-spike mass. Especially, the Thermal Ion Mass Spectrometry with isotope dilution technique (in general ID-TIMS) is the most accurate method of the chemical analysis, which enables us to obtain the data better than 1% in accuracy and precision. In IDMS, enriched isotope spike is one of the most important factor in order to obtain the best data. For rare earth elements, in general, a mixture of /sup 138/La, /sup 142/Ce, /sup 145/Nd, /sup 149/Sm, /sup 151/Sm, /sup 151/Eu, /sup 157/Gd, /sup 163/Dy, /sup 167/Er, /sup 171/Yb, and /sup 176/Lu is used as composite spike. IDMS is very useful in geochronology and REE geochemistry. Especially, it is very effective in studying the “tetrad effect” of rare earth elements in natural samples.

• The Journal of the Petrological Society of Korea
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• v.4 no.2
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• pp.153-167
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• 1995

Emplacement ages for the granite plutons of the Jurassic and the Cretaceous times in the central Ogcheom Fold Belt were determined by Rb-Sr whole rock and mineral isocheon methods. In addition mineral ages for the plutons were determined by K-Ar and fission track methods. In turn, thermal histories and uplifting rates of the granitic bodies are elucidated from the isotopic ages. The Jecheon(~203 Ma) and Mungyeong(at lest~200 Ma) granites of the Jurassic and the Muamsa, Wolagsan and Daeyasan granites(~110 Ma) of the Cretaceous show high strontium initial ratios [$(^{87}Sr/^{86}Sr)_1$0.7100],suggesting that the granitic magmas have been generated by partial melting of crustal materials (S-type), or by mixing of mantle and crustal materials. Only mineral ages of the Sogrisan and Hyeongjebong granites (~90 Ma) were determined by K-Ar method, and petrogenesis of them were not defined yet. The two Jurassic granite plutons were cooled rapidly down to $300^{\circ}C$, right after the plutons were slowly cooled down since then, due to their deep emplacment. During the Middle Cretaceous period, the Jurassic Mungyeong granitic pluton was intruded and thermally affected much by the surrounding Wolagsan and Daeyasan granites. Accordingly the Rb-Sr mineral age, K-Ar hornblende and biotite ages of the Mungyeong granite appear to be reduced or reset due to the thermal effects above their blocking temperatures. All the cretaceous granites have been cooled much ore simply and rapidly down than the Jurassic ones below $300^{\circ}C$, owing to their shallow emplacement.

• The Journal of the Petrological Society of Korea
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• v.20 no.4
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• pp.191-206
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• 2011

The emplacement ages, whole-rock geochemistry and Sr-Nd isotopic compositions of granitoid rocks from Cheongju area, South Korea, were investigated for delineating their petrogenetic link to the Jurassic Daebo granitoid rocks. Zircon crystals were collected from the diorite, biotite granite and acidic dyke samples in a single outcrop. Cross-cutting relationships show that the emplacement of diorite was postdated by the intrusion of biotite granite. Both rocks have been subsequently intruded by acidic dyke. The U-Pb isotopic compositions of zircon from the diorite, biotite granite, and acidic dyke were measured using a SHRIMP-II ion microprobe, yielding the crystallization ages of $174{\pm}2Ma$, $170{\pm}2Ma$, and $170{\pm}5Ma$, respectively, with 95% confidence limits ($t{\sigma}$). The emplacement ages are consistent with those determined from the above relative ages. The major and trace element patterns of the rocks are consistent with those of the Jurassic Daebo granitoid rocks, possibly suggesting a subduction-related I-type granite. The geochemical signature is, however, betrayed by the Sr and Nd isotopic compositions of these rocks. The isotopic signatures suggest that the rocks were produced either by the partial melting of lower-crust or by the mantle-derived magma contaminated by the basement rocks during its ascent and/or emplacement. In addition, the inherited ages of zircons of the rocks (ca. 2.1, 1.8, 0.8 and 0.4 Ga) suggest a possible assimilation with crustal rocks from the Gyeonggi massif and Ogcheon metamorphic belt.

• Economic and Environmental Geology
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• v.42 no.3
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• pp.247-259
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• 2009

This study is focused on the relationship between whole rock boron contents and metamorphic P-T conditions of metasedimentary rocks from northeastern Yeongnam massif around Samcheok area, Korea. Metamorphic P-T conditions of sillimanite and garnet zones based on the Ti-biotite geothermometer is 553-687$^{\circ}C$ and 582-722$^{\circ}C$ at 4-6 kbar, respectively. In the metasedimentary rocks, boron contents in whole rock decrease with increasing metamorphic grade, from sillimanite zone (9.60-189 ppm B) to garnet zone (2.63-15.97 ppm B), except one sample (90.9 ppm B) from garnet zone containing graphites. Boron depletion in garnet zone has relation with mode of tourmaline which are broken down with increasing metamorphic temperature. Boron contents are indirectly proportional to major and trace elements such as $Al_2O_3$, MgO, $Fe_2O_3$, $K_2O$, Li, Ba, Sc, Co, Cr, Rb and Cs that are abundant in tourmalines. In conclustion, tourmalines and graphite are modulator of boron contents in metasedimentary rocks. In the biotite granitic gneisses, boron contents (2.62-12.2 ppm B) are similar or lower than those of metasedimentary rocks and have no relation with metamorphic P-T conditions.

• The Journal of the Petrological Society of Korea
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• v.16 no.1 s.47
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• pp.1-11
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• 2007

CHIME (chemical Th-U-total Pb isochron) geochronology were made for Precambrian rocks from Goseong-Ganseong area, northeastern part of the Gyeonggi massif. Zircon and/or monazite grains from orthogneisses give $1672{\pm}69\;to\;1414{\pm}36Ma$ ages, and monazite grains from paragneisses yield similar ages ranging from $1703{\pm}70\;to\;1395{\pm}97Ma$ suggesting that $1.7{\sim}1.4Ga$ igneous intrusions and coeval metamorphisms were occurred over the area. Together with reported prevailing $1.9{\sim}1.8Ga$ igneous activities and regional metamorphism from the Cyeonggi massif, our age data from Goseong-Ganseong area would be potentially correlated with long-lived $(1.8{\sim}1.3Ga)$ global tectonotermal events in marginal outgrowth of supercontinent Columbia which was finally assembled by collisional orogenies at ${\sim}1.8Ga$. Petrological and geochmical studies, however, should be followed to confirm this tectonic interpretation.

• The Journal of the Petrological Society of Korea
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• v.14 no.1
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• pp.1-11
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• 2005

Sphene U-Pb ages were determined for the granodiorites from Gimcheon, Seongju and Anui areas of the middle Yeongnam massif. The determined ages were in the narrow range of 195.7±2.4∼200.8±1.9(2σ) Ma that are approximately coincident with the boundary between Triassic and Jurassic. Even though the studed plutons are aerially separated, they reveal quite similar major element compositions and almost identical ages, suggesting that they were generated from the similar source materials under the identical tectonic environment and thus they can be considered to form a single suite. Considering the age and spatial distribution of the Triassic to Lower Jurassic plutons of the Yeongnam Massif and Okcheon Belt, it seems that there were episodic changes in tectonic environment in both areas with relatively short intervals. In general, the compressive environment of active continental margin was prevailed. However, the tensional environment of within-plate was also appeared several times intermittently. In conclusion, Yeongnam Massif and Okcheon Belt experienced distinct tectonic environments during Triassic to Lower Jurassic, providing important clue to reveal the crustal evolution of the Korean Peninsula.

• The Journal of the Petrological Society of Korea
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• v.24 no.3
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• pp.273-289
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• 2015

This study used the petrological features and the whole rock susceptibility characteristics suggest ways to determine the domestic dimension stones and Chinese similar dimension stones. In addition, this study compare the intrusive period by measuring the zircon U-Pb age of these stones. Result of comparing the petrological feature, with the exception of Macheon stone and Boryeong stone to show the differences in mineral composition and texture under a microscope, the domestic dimension stones and Chinese similar dimension stones exhibit substantially the same petrological feature. According to the measurement results for the whole rock magnetic susceptibility, Goheong, Iksan, Pocheon stones are the similar as Chinese dimension stones, and other stones are easily distinguished. The zircon U-Pb age results for Geochang, Iksan, and Pocheon stones are equivalent to the Jurassic Daebo granites and G603, G633, G655 are the Cretaceous granites. Therefore, the domestic dimension stones and Chinese similar dimension stones can be clearly determined by the zircon U-Pb age results.