• Economic and Environmental Geology
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• v.23 no.2
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• pp.245-259
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• 1990

Petrochemical analyses of granitic rocks including trace element, REE and oxygen isotope were carried out to understand petrogenesis of plutonic rocks from the Chungju, Wolaksan and Jecheon granite batholiths, which might be related with tungsten-base metal-fluorite mineralization in the Hwanggangri metallogenic province. Different geochemical characteristics such as major and trace elements were found between Jurassic Daebo granitic rocks (Chungju, Jecheon, Wonju, and Boeun granitic rocks) and Cretaceous Bulgugsa granitic rocks (Wolaksan, Muamsa and Sokrisan granitic rocks). Cretaceous granitoids are characterized by high $SiO_2$and $K_2O$ contents and low $TiO_2$, $Al_2O_3$, MgO and CaO contents. They also have relatively high contents of trace elements(Zn, V, Co, Cr, Sr, and Ba) in comparison with the Jurassic granitoids. (Eu)/($Eu^*$) and $(La/Lu)_{CN}$ ratios of Jurassic plutons vary from 0.78 to 1.13 and from 26.02 to 30.5, respectively, while the ratios of Cretaceous ones range from 0.22 to 0.28 and from 4.42 to 14.2, respectively. The REE patterns of the Cretaceous and Jurassic granitic rocks have quite different Eu anomalies: 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 deduced by Rayleigh fractionation model(Tsusue et al., 1987). Oxygen isotopic compositions of quartz for Daebo and Bulgugsa granitic rocks range from 9.98 to 10.51‰ and from 8.26 to 9.56‰, respectively. The Daebo granitic rocks enriched in $^{18}0$ suggest that the magma be undergone different partial melting processes from the Bulgugsa ones. Of the Bulgugsa granitoids, Wolaksan and Sokrisan mass have different contents of trace elements and ${\delta}\;^{18}0$ values of the silicate minerals, which indicate that they are not from the identical source of magma. Many mineral deposits are distributed in and/or near the Wolaksan and Muamsa granitic rocks, but a few mineral deposits are found in and near the Chungju and Jecheon granite batholiths. It might be depend on geochemisty of the related igneous rocks which have low contents of Ba, Sr, Co, V, Cr, Ni, Zn and high contents of Nb and Y, and on lithology of country rocks such as cabonate and noncarbonate rocks.

• Economic and Environmental Geology
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• v.28 no.2
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• pp.123-137
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• 1995

The Mesozoic Geumsan granitic rocks of various composition are distributed in the Geumsan district, the central part of the Ogcheon Fold Belt. About 40 ore deposits of $CaF_2{\pm}Au{\pm}Ag{\pm}Cu{\pm}Pb{\pm}Zn$ are widely distributed in this district and are believed to be genetically related to the granitic rocks. Based on their petrography and geochemistry, the granitic rocks in this district can be classified into two groups ; the Group I( equigranular leucocratic granite, porphyritic biotite granite, porphyritic pink-feldspar granite, seriate leucocratic granite) and the Group II(seriate pinkfeldspar granite, equigranular alkali-feldspar granite, equigranular pink-feldspar granite, miarolitic pink-feldspar granite, equigranular biotite granite). Interpreted from their isotopic dating data and geochemical characteristics, the Group I and the Group II are inferred to be emplaced during the Jurassic(~184Ma), and the Cretaceous to the early Tertiary period(~59Ma), respectively. Both Group I and Group II generally belong to magnetite-series granitoids. The Cretaceous granitic rocks of Group II are more highly evolved than those of the Jurassic Group I. The Rb-Sr variation diagram suggests that the granitic rocks of the Jurassic Group I and of the Cretaceous Group II be evolved mainly during the processes of fractional crystallization and partial melting, respectively.

• Economic and Environmental Geology
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• v.31 no.2
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• pp.149-158
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• 1998

Volcanic rocks including rhyolitic tuff, rhyolite and welded tuff in the Bupyeong silver mine area form a topographic circular structure known as a resurgent caldera. Granitic rocks are emplaced inside and outside area of the circular structure. K-Ar dating and Nd-Sr isotope studies were carried out to invesitigate the origin and petrogenetic evolution of the rhyolitic and granitic magma in the Bupeong silver mine area. Whole rock K-Ar age ranges from 208 to 131 Ma for rhyolitic rocks. Radiometric ages for the granitic rocks are 167.6 Ma for pink feldspar biotite granite from inside granitic pluton of the circular volcanic body, 178.8 Ma for the Kimpo hornblende biotite granite and 111.8 Ma for the Songdo foliated granite from outside granitic plutons of the volcanic body. The radiometric age data indicates that the volcanic activities which are partly overlapped by granite plutonic activities in the Bupyeong mine area had recorded early Jurassic and early Cretaceous in age. Initial Sr and Nd isotopic ratios of the rhyolitic rocks ($^{87}Sr/^{86}Sr$=0.710~0.719 and $^{143}Nd/^{144}Nd$=0.5115~0.5118) are similar to those of granitic rocks ($^{87}Sr/^{86}Sr$=0.709~0.716 and $^{143}Nd/^{144}Nd$=0.5115~0.5116) from inside granite stock. This means that similar source materials of felsic magma responsibles for the Bupyeong volcanic rocks and inside plutonic rocks. Based on the Nd and Sr isotopic compositions, rhyolitic and granitic magmas in the Bupyeong area originated from the partial melting of the old continental crust which has Nd model age ranging from 1500 to 2900 Ma. This is analogous to those of the other Jurassic granitoids in South Korea.

• 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.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.4
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• pp.325-337
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• 2020

The Jurassic granitic rocks in the area of Gwangdeoksan located along the boundary between Hwacheon and Cherwon in northern Gyeonggi Massif consist of two-mica granite, garnet-bearing two-mica granite, mica-granite, and porphyritic biotite granite. These granitic rocks are calc-alkaline series and plotted in peraluminious domain in A/CNK vs. A/NK diagram. Petrographical and geochemical data indicate that the porphyritic biotite granite which intruded at the last period originated from distinct parental magma from two-mica granite, garnet-bearing two-mica granite, and mica-granite. On the basis of Rb/Sr vs. Rb/Ba diagram and Al2O3/TiO2 vs. CaO/Na2O, it is inferred the porphyritic biotite granite originated from protolith with less pelitic composition than 3 other granitic rocks. The enriched values of lithophile elements of Cs, Rb, and Ba and negative trough of Nb, P, Ti on spider diagram suggest that the peraluminous Jurassic granitic rocks in Gwangdeoksan area formed in subduction tectonic environment. Whole-rock zircon saturation thermometer indicates that the granitic rocks in the study area were melted at 692-795℃.

• Economic and Environmental Geology
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• v.28 no.4
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• pp.369-379
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• 1995

About forty ore deposits of $CaF_2{\pm}Au{\pm}Ag{\pm}Cu{\pm}Pb{\pm}Zn$ are widely distributed in the Geumsan district and are believed to be genetically related to the Mesozoic Geumsan granitic rocks. Based on their petrogeochemistry and isotopic dating data, the granitic rocks in this district can be classified into two groups ; the Jurassic granitic rocks(equigranular leucocratic granite, porphyritic biotite granite, porphyritic pink-feldspar granite, seriate leucocratic granite) and the Cretaceous granitic rocks(seriate pink-feldspar granite, equigranular alkali-feldspar granite, equigranular pink-feldspar granite, miarolitic pink-feldspar granite, equigranular biotite granite). Spatial distribution of fluorite ore deposits, fluorine contents of granitic rocks and fracture patterns in this district suggest that three granitic rocks(equigranular biotite granite, equigranular pink-feldspar granite, miarolitic pink-feldspar granite) of the Cretaceous period be genetically related to the fluorite mineralization. In these fluorite-related granitic rocks, fluorine is most highly correlated with Cs(correlation coefficient(r)>0.9), and also highly with MnO, U, Sm, Yb, Lu, Zn, Y, Li(r>0.7). Statistically the variation of fluorine in the fluorite-related granitic rocks can be explained in terros of only three elements, such as Lu, CaO and Cs, and the fluorite-related granitic rocks can be discriminated from the fluorite-nonrelated granitic rocks by a linear functional equation of La, Ce, Cs and F($Z_{Ust}=-1.38341-0.00231F-0.19878Ce+0.38169La+0.54720Cs$). Also, equigranular alkali-feldspar granite is classified into the fluorite-related granitic rocks by means of the linear functional equation($Z_{Ust}$).

• Economic and Environmental Geology
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• v.29 no.4
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• pp.455-470
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• 1996

Mesozoic granitic rocks in the Korean peninsula contain $H_2$, $CH_4$, CO and rare $C_2H_6$. The Jurassic Daebo granites mostly belonging to the ilmenite series are predominated in $CH_4$. Meanwhile, the magnetite series Bulguksa granites of Cretaceous age in the Kyongsang basin and Okchon zone are relatively enriched in $CO_2$. The older granites have a wide variation of $CH_4/CO_2$ ratios (0.1~1.0) compared to those of the younger ones (0.1~0.5). This characteristics of gas compositions suggest that the Jurassic granites are principally derived from the partial melting of metasedimentary rocks with much reducing materials in the lower continental crust. On the other hand, the mantle source granitic magmas might be responsible for the Cretaceous granites characterized by dominant and homogeneous $CO_2$ gas compositions. Liquid-vapor homogenization temperatures of quartz in the Jurassic and Cretaceous granites range from 108 to $539^{\circ}C$ (av. $324^{\circ}C$) and 160 to $556^{\circ}C$ (av. $358^{\circ}C$), respectively. Their salinities are between 0.2 and 16.3 wt.% NaCl for the Jurassic granites and 0.4, and 15.6 wt.% NaCl for the Cretaceous ones. Fluid inclusions with solid daughter minerals lying on or near the halite equilibrium curve represent inclusion fluids from the magmatic stage. The type I and II fluid inclusions which are plotted apart from the equilibrium curve are considered to trap in late hydrothermal alteration stage with a increasing influx of metedric water.

• 보존과학연구
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• s.13
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• pp.14-36
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• 1992

The investigation has been made on the rocks consisting the pagoda(12), Buddhist Statues(9) Buldaejwa and cakra(2, rewpectively), stele(5), and Flagpole wupport and stupa(6) which are stood in Weonju city, Weonju-gun, Hwoengseong-gun and Hongcheon-gun, Kangweondo. These rock-monuments range mostly in age from late Shilla Kingdom to middle Korye Kingdom. The geology around this region is mainly composed of Precambrian metamorphic rocks and mesozoic granitic rocks. The granitic rocks are largely divided into Jurassic and cretaceous ones which are slightly different in rock phase. The main rock phase consisting the monumentsare are coarse biotite granite with minor amount of hornblende in Jurassic age. Variation in rock phase is abserved even in part of the stone used in the monuments. Inclusions composed of biotite and hornblende, porphyritic texture with microcline phenocryst, igneous lineation and exfoliation according to weathering are observable in all rocks in these monuments. In the case of stele whose a body and a capstone is remained, one is composed of black slate and the other white limestone. But the turtle shaped pedestal is constituted of coarse biotite granite. These stone-monuments are strongly weathered and exfoliated out about 1∼2mm.In case of exfoliated weathering along igneous lineation, some are taken off about 3∼5mm thick. In some monuments, the degree of weathering is somewhat different according to position, grade of sculpture, and biological activity.

• Proceedings of the Petrological Society of Korea Conference
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• 1998.09a
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• pp.22-22
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• 1998

• Journal of the speleological society of Korea
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• v.42 no.2
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• pp.33-40
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• 1995

The Cheonbo gold mine is located approximately 8km northeast of Cheonan in southern part of Korean peninsula. The Cheonbo gold deposits are composed of parallel-filling quartz veins that are associated wi th the Cheonan granite which intruded the surrounding Precombrian metamorphic country rocks. Rb/Sr date of the granitic intrusion is 170${\pm}$0. 3m.y., suggesting a middle Jurassic age for gold mineralization.