• Economic and Environmental Geology
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• v.35 no.5
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• pp.429-436
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• 2002

Core samples, drilled in the middle region of Bavaria, were analyzed to study the characteristics of organic matter in the Upper Jurassic Solnhofen limestone of southern Germany. The core (48$^{\circ}$53'N, 1-1$^{\circ}$19'E) contains Upper Jurassic Solnhofen strata ranging from the upper part of the Geisental Formation throughout the Solnhofen Formation to the lower part of the Mornsheim Formation. In the core, the Upper Jurassic lithologies consist of platy limestone, bedded limestone and massive limestone often interbedded with some chert layers. Geochemical variations (Carbon, Nitrogen and Total Organic Carbon) and Rock-Eval pyrolysis parameters (S$_2$ peak and Hydrogen Index) indicate that the organic matter in the Upper Jurassic limestone is mostly of marine origin. Particularly, the relation-ship of Hydrogen Index and S$_2$ as a function of Total Organic Carbon suggests that the upper formation of the core (Mornsheim Formation) was more influenced by terrigenous influx than the Solnhofen and Geisental Formations.

• The Journal of the Petrological Society of Korea
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• v.21 no.2
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• pp.113-128
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• 2012

The chemical composition of the continental crust play an important role in understanding of crustal formation and evolution and quantifying other processes taking place within continental crust. We summarized geochemical data reported in the previous literature for the crustal rocks in the Korean Peninsula and divided their chemical composition into geologic time scale. In the variation diagram normalized by average composition of the upper crustal rocks, the geochemical characteristics of the upper crust during Triassic period is different from those of the upper crustal rocks after Jurassic period or before Precambrian. However, the geochemical characteristics of the Jurassic and Precambrian period are similar each other. Our summarized data indicate that the source material of Triassic upper crust may be different from that of Jurassic or Precambrian upper crust.

• Proceedings of the KSEEG Conference
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• 2001.04a
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• pp.378-382
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• 2001

• Economic and Environmental Geology
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• v.34 no.3
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• pp.243-254
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• 2001

Variation in relative contents of clay minerals was used to genetically interpret depositional environment of the Upper Jurassic Solnhofen limestone. Mineralogical examination of whole rocks and clay fractions indicates that the faule and flinz beds are composed mainly of calcite and quartz with minor amount of clay minerals such as illite, kaolinite, and smectite. Smectite shows a trend of illitization: illite layers increase with increasing of burial depth. With increasing burial depth, relative abundance of kaolinite with quartz and illite increases. This implies that the Solnhofen basin was formed during the transgression based on reduce of terrigenous influx.

• Journal of the Korean earth science society
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• v.44 no.4
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• pp.307-317
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• 2023

We investigate the provenance of detrital garnets in Middle-Upper Jurassic sandstone of the Mino terrane, an accretionary complex in Southwest Japan, based on their chemical composition. The garnet grains in the Mino sandstone are mostly Fe-rich (almandine) and slightly Mg-rich (pyrope) species derived from high-grade metamorphic and intermediate to acidic plutonic rocks. The composition and interpreted origin of the garnets are generally consistent with those of metamorphic and igneous rocks of the Yeongnam Massif on the Korean Peninsula, a possible source region suggested in previous studies. In addition, two single grains of chromian spinel, an accessory mineral found in mafic to ultramafic rocks such as mantle peridotite, were found in one of the Mino sandstone samples. This finding suggests the possible presence of mafic to ultramafic rocks in the source area. The results of this study provide complimentary evidence for establishing a comprehensive tectonic and paleogeographical framework for the Mesozoic East Asian continent.

• Economic and Environmental Geology
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• v.25 no.4
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• pp.435-446
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• 1992

REE, major and trace elements analyses of the Jurassic Daebo granite and Cretaceous Bulguksa granite were carried out to interpet their petrogenesis and relationships between petrogenesis and tectonics. Analytical results are summarized as follows. (1) $SiO_2$ content of the Bulguksa granite (aver. 74.6%) are significantly higher than those of the Daebo granite (aver. 68.1%). Major elements of $TiO_2$, $Al_2O_3$, $P_2O_5$, CaO, MgO, Total FeO, and trace elements of Co, V and Sr are negatively correlated with $SiO_2$. Incompatible elements such as Ba, Sr, Y, Zr and HREE are contained differently in the Bulguksa granites distributed in between Okchon folded belt and Kyongsang sedimentary basin. (2) Trace element abundances show a good discrimination between two goups of granitic rocks. Ba, Sr and V are enriched in Daebo granites, while Zn and Cr are depleted in them. (3) Jurassic granites have quite different Eu anomalies and REE patterns from those of Cretaceous granites: Large negative Eu anomaly in the former and mild or absent Eu anomaly in the latter. The large Eu negative of Cretaceous granitic rocks are interpreted as a differentiated product of fractional crystallization of granitic magma from the upper mantle. Meanwhile, the Daebo plutonic rocks was resulted from the partial melting of subcrustal material or crustal contamination during ascending granitic magma from the mantle. Senario of igneous activities of Mesozoic age in South Korea was proposed based on Kula-Pacific ridge subduction model.

• Economic and Environmental Geology
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• v.20 no.1
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• pp.35-60
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• 1987

The geochemical characteristics including minerals, major and trace elements chemistries of the Proterozoic, Jurassic and Cretaceous granites in Korea are systematically summarized and intended to decipher the origin and crystallization process in connection with the tectonic evolution. The granites in Korea are classified into three different ages of the granites with their own distinctive geochemical patterns: 1) Proterozoic granitoids; 2) Jurassic granites(cratonic and mobile belt); 3) Cretaceous-Tertiary granites. The Proterozoic granite gneisses (I-type and ilmenite-series) formed by metamorphism of the geochemically evolved granite protolith. The Proterozoic granites (S-type and ilmenite-series) produced by remobilization of sialic crust. The Jurassic granites (S-type and ilmenite-series) were mainly formed by partial melting of crustal materials, possibly metasedimentary rocks. The Cretaceous granites (I-type and magnetite-series) formed by fractional crystallization of parental magmas from the igneous protolith in the lower crust or upper mantle. The low temperature ($315{\sim}430^{\circ}C$) and small temperature variations (${\pm}20{\sim}30^{\circ}C$) in the cessation of exsolution of perthites for the Proterozoic and Jurassic granites might have been caused by slow cooling of the granites under regional metamorphic regime. The high ($520^{\circ}C$) and large temperature variations (${\pm}110^{\circ}C$) of perthites for the Cretaceous granites postulate that the rapid cooling of the granitic magma. In terms of the oxygen fugacity during the feldspar crystallization in the granite magmas, the Jurassic mobile belt granites were crystallized in the lowest oxygen fugacity condition among the Korean granites, whereas the Cretaceous granites in the Gyeongsang basin at the high oxygen fugacity condition. The Jurassic mobile belt granites are located at the Ogcheon Fold Belt, resulting by closing-collision situation such as compressional tectonic setting, and emplaced into a Kata-Mesozonal ductile crust. The Jurassic cratonic granites might be more evolved either during intrusion through thick crust or owing to lower degree of partial melting in comparison with the mobile belt granites. The Cretaceous granites are possibly comparable with a continental margin of Andinotype. Subduction of the Kula-Pacific ridge provided sufficient heat and water to trigger remelting at various subcrustal and lower crustal igneous protoliths.

• Journal of the Korean earth science society
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• v.40 no.2
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• pp.163-176
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• 2019

The Potosinian geological basement in central Mexico is comprised of the Upper Paleozoic metamorphic rocks, which crop out on the Sierra de Catorce nucleus located in the northeastern part of the state. The sedimentary sequence that covers unconformably the Paelozoic basement is represented by an Upper Triassic marine sedimentary sequence, correlating to the Zacatecas Formation and the Upper Triassic continental Huizachal Formation red beds, which in turn are covered either by La Joja Formation Jurassic red beds or by Upper Jurassic marine sediments. This sequence is overlain by the conformable Cretaceous calcareous marine sedimentary rocks in all the state of San Luis Potosi. The Cenozoic sequence unconformably covers some of the aforementioned rocks and is represented by undifferentiated volcanic rocks as well as by marine clastic rocks. The existing intrusive igneous rocks are felsic to intermediate composition, and they intrude the metamorphic basement and sedimentary rocks. Conglomerates with evaporitic sediments were deposited during the Pleistocene. The Quaternary sequence includes basalt flows, piedmont deposits, alluvium, and occasionally evaporites and caliche layers. In the state of San Luis Potosi, a great diversity of mineral deposit types is known as both metallic and nonmetallic. The host rocks of these deposits vary from one another including formations that represent from Paleozoic up to Tertiary. The mineralization age corresponds approximately to Tertiary (75%), and is mainly epigenetic. Conclusively, the data on geology and mineralization in San Luis Potosi, Mexico are helpful to predict a hidden ore body and select promising mineralized zone(s) when the domestic company makes inroads in the mining sector of Mexico.

• Economic and Environmental Geology
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• v.1 no.1
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• pp.35-46
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• 1968

Some of geologists in Korea recently postlated that Okchon system previously known to be precambrian age was the metamorphosed sediments of post-Chosen (Ordovician and pre-Kyeongsang (late Jurassic to Cretaceous) periods, or even definitely of Triassic period simply on the basis of the fact that Okcheon system overlies the Great Limestone series of Chosen system of Camber-ordovician age, and of other few assumptions of minor importance. As a result of such correlation, thick series of metasediments and Okcheon system of unknown age were established in this particular region and vaguely correlated to Paleozoic and Mesozoic sediments. Recent study done by the author reveled that: 1) only the upper Okcheon bed of S. Nakamura was true Okcheon system, and the middle and lower Okcheon beds were excluded, because they were correlated to Cambrian and Permian sediments resfectively, 2) Sangnaeri, Seochangri, and rengam formations of unknown age, and Baekhwasan, Jobong, and Ihwaryeong formations of Okcheon system of also unknown age were the metamorphosed Yangdeok system of Cambrian age, all of these formations were differentiated by the previous workers and were equivalent to the middle Okcheon system of S. Nakamure, and. 3) These metamorphosed Yangdeok system overlaid apparently the Great Limestone series in forms of overthrust and klippe which were produced by the orogeny took place during post-Daedong and pre-Kyeongsang period (probably middle to the Jurassic). The Sobaeksan Range, folded mountain Chains was also formed by this orogeny. Thus, Okcheon system newly defined by the author is precambrain age and consists in ascending order of Kemyenogsan, Hyangsan dolomite, and Daehangsan quartzite formation which were previously classified into metasediments of unknown age, and Munjuri, and Hwangkanri, formations which were differentiated into Okcheon system unknown age by the previous workers, but are of reversed sequence. Myeongori and Bukrori formations of Okcheon System are regard by the author as part of Hwangkanri formation. Few other assumption of minor important taken by the previous workers as their positive evidences are carefully explained that they were misinterpreted.

• The Journal of Engineering Geology
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• v.28 no.4
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• pp.661-672
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• 2018

Radon concentration was measured in a total of 5,453 groundwater samples from wells across Korea. The radon concentrations showed the values ranging from 0.1 Bq/L to 7,218.7 Bq/L, with a median of 48.8 Bq/L which is lower than those of other countries having similar geological conditions. The distribution of radon concentrations was lognormal. The median value is high in the granite areas (63.5-105.1 Bq/L) while it is low in the sedimentary rocks and Cheju volcanic area (16.0-20.3 Bq/L). When grouping the groundwater with well depth, the median radon value is high in weathering and/or upper bedrock zone (61.4 Bq/L) while it is low in alluvium and/or weathering zone (28.5 Bq/L). About 17.7% of the total samples exceeded 148 Bq/L of USEPA guideline value. The exceeding radon ratio more than 148 Bq/L in groundwater is highest in Jurassic granite area, however, the exceeding radon rates more than 300 Bq/L and 500 Bq/L are highest in CGRA area.