• Economic and Environmental Geology
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• v.29 no.4
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• pp.483-493
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• 1996

The tectonic environment and source characteristics of the Daebo granitic batholith in the central Ogcheon Belt were investigated based upon major and trace element geochemistry. The batholith is comprised of three granite types; a biotite granite (DBBG), K-feldspar megacryst-bearing biotite granite (DBKG), and a more mafic granodiorite (DBGD). The variations of Na and K in the granites can not be explained by simple fractional crystallization from the same primary magma. The irregular behavior of these alkali elements indicates a variety of source materials or incomplete mixing of different source materials. The large ion lithophile (LIL) element enrichment and low Ta/Hf ratios of the granites are typical characteristics of normal, calc-alkaline continental arc granitoids. Based upon REE patterns of the granites, it seems to be unreasonable to regard the felsic DBBG as a late stage differentiate formed by residual melts after the fractionation of major constituent minerals of the more mafic DBGD. Inconsistent variations in ${\varepsilon}_{Nd}(t)$ and LIL element concentrations of the granites preclude a mixing model between primitive melt and LIL element-enriched upper crustal materials. The irregular geochemical variation of the granites is taken to be largely inherited from an already heterogeneous source region.

• Economic and Environmental Geology
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• v.27 no.4
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• pp.363-373
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• 1994

The Cretaceous granitic rocks show differences in rock types and chemical compositions according to metallogenic provinces of copper, lead zinc and molybdenum in the Gyeongsang basin. Jindong granites are of granodiorite~quartz diorite~diorite in Cu-province; Makeunsan/Yucheon-Eonyang granites, granodiorite~granite in Pb Zn-province; Onjeongri-Yeonghae granites, granodiorite~quartz diorite in Mo-province, and there is a trend that productive masses are less differenciated than barren masses in Cu and Pb-Zn provinces whereas productive masses are more differenciated than barren masses in Mo province. Metallogenic provinces are distinguishable by variations of major and trace elements. The Cretaceous granitic rocks are highest in the content of Ca, Mg and other basic major elements and lowest in the content of K and Na in Cu provicne; the variation trends are vice versa in Pb-Zn province. Trace elements such as Rb and Sr show variations related to K and Ca, and metallogenic provinces are also distinguishable by their ratios. The granitic rocks of Mo province have intermediate content of major and trace elements, but are clearly distinguishable from Jindong granites and partly overlapped by Yucheon-Eonyang granites. Chlorine content in biotites is higher in a productive mass than in a barren mass in Cu province. Therefore, the mineralogical and chemical compositions are applicable as geochemical index to distinguish the types of mineralizaion, and productive and barren masses of the Cretaceous granitic rocks in the Gyeongsang basin.

• Economic and Environmental Geology
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• v.24 no.3
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• pp.261-276
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• 1991

The main aspect of this study are to clarify igneous activity of igneous rocks, which is a member of various intrusives and volcanics exposed in Naju-Namchang area of southern central zone of Ogcheon Geosynclinal Belt, southern part of Youngdong-Kwangju depression zone of tectonic provinces in Korea. Naju-Namchang area are subdivided into three rock belts based on occuring of Cretaceous granites. Three rock belts consist of foliated granites, Jurassic granites and Cretaceous granites in central granitic rock belt (C-C), and acidic tuff and lavas in northwest volcanic rock belt(C-NW) and southeast volcanic rock belt(C-SE). Chemical composition of these igneous rocks show mostly similar trend to the Daly's values on Harker diagram and correspond to VAG + Syn-COLG region on Pearce's discrimination diagram. These igneous rocks vary wide range in total REE amount(37.4-221.3ppm) characterized by enriched LREE content and steep negative slope in Eu(-) anomaly. It is concluded each synchronous granites which composed of serveral rock facies is considered to formed by differentiation of co-magma at continental margin, and igneous activity of study area are two more Pre-Cambrian Orogenies, Songrim Disturbance, Daebo Orogeny and Bulkuksa Disturbance.

• Geomechanics and Engineering
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• v.15 no.1
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• pp.631-643
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• 2018

The estimation of the strength and other mechanical parameters characterizing the tensile behavior of granites can play an important role in civil engineering tasks such as design, construction, rehabilitation and repair of existing structures. The purpose of this paper is to apply data mining techniques, such as multiple regression (MR), artificial neural networks (ANN) and support vector machines (SVM) to estimate the mechanical properties of granites. In a first phase, the mechanical parameters defining the complete tensile behavior are estimated based on the tensile strength. In a second phase, the estimation of the mechanical properties is carried out from different combination of the physical properties (ultrasonic pulse velocity, porosity and density). It was observed that the estimation of the mechanical properties can be optimized by combining different physical properties. Besides, it was seen that artificial neural networks and support vector machines performed better than multiple regression model.

• Economic and Environmental Geology
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• v.19 no.3
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• pp.179-192
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• 1986

In the Bupyeong district, Mesozoic pyroclastic rocks, intrusive breccia, granites and felsic porphyries comprise a volcano-plutonic complex, overlying and intruding the Precambrian Gyeonggi gneiss complex. pyroclastic rocks, consisted mainly of rhyolitic welded tuffs, form a topographic circular structure about 10 kilometers in diameter. Granites and felsic porphyries which intruded the pyroclastic rocks are distributed in the inner side and also along the outer margin of the circular structure. K-Ar ages of two granite bodies(biotite), 162 and $148{\pm}7$ Ma, and that of the intrusive rhyolite (whole rock), $121{\pm}6$ Ma indicate that a series of volcano-plutonic igneous activity occurred between Jurassic and early Cretaceous age. Petrochemical characteristics suggest that the pyroclastic rocks, granites and felsic porphyries were originated from the comagmatic source. From the evidences of field occurrence, petrochemical and geochronological characteristics of igneous rocks and the geologic structures, it is believed that the igneous rocks in the Bupyeong district were formed during a Jurassic to early Cretaceous resurgent caldera evolution.

• Economic and Environmental Geology
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• v.26 no.1
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• pp.83-96
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• 1993

Kwangju granite body located in vicinity of Kwangju city consist of three rock bodies-Kwangju rock body, Jangsung rock body and Youngkwang rock body. Petrochemistry of Kwangju granite is as follows: Kwangju granite body is igneous complex which compose of a series of differential products of a magma. Kwangju granites are divided into four rock facies based on the geologic age, mineralogical and chemical constituents and texture: Triassic hornblende-biotite granodiorite and biotite granite, and Jurassic porphyritic granite and two mica granite. Harker and other variation diagrams of Kwangju granites plot on trend of calc-alkali rock series and range of peraluminous granite. Parental magma type of Kwangju granites correspond to I-type, Syn-Collision type in compressive stress field by collision movement between both rock block. In chondrite normalized REE patterns of Kwangju grnites, LREE enriched than HREE in REE amount and have more steep negative slope with slightly (-) Eu anormaly.

• 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.

• The Journal of the Petrological Society of Korea
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• v.13 no.1
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• pp.1-15
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• 2004

In this study we propose that the ‘enclaves’ which occur in the granites should be translated into ‘Po-yu-am’in Korean. Also we suggest some criteria to discriminate the mafic microgranular enclaves (MME) of igneous origin from the xenoliths, which possibly come from the plutonic, volcanic and sedimentary country rocks. The color of the MME is gray green∼dark gray and the mineral grains are fine and equigranular. The MME are generally of ellipsoidal shape and can be easily found within the granites. They do not show any evidence of contact metamorphism by granite host. On the other hand. the xenoliths are generally of angular shape and are of the same mineral assemblage and texture as the country rocks around the granites. The distribution of the xenoliths is mostly concentrated along the intruding plane of the granites near the country rocks. The xenoliths were partly metamorphosed by the granite intrusion. The xenoliths from the plutonic rocks are easily distinguished from the MME in terms of their angular shape and coarser grain size, but they do not have any metamorphic mineral assemblage and texture. The xenoliths from the tuffaceous rocks show angular shape and porphyritic and pyroclastic textures. Large size xenoliths from the sedimentary rocks specifically preserve bedding structure which are indicative of the sedimentary strata. However, the sedimentary xenoliths of small size are often difficult to distinguish from the MME. Metamorphic minerals and texture are a useful key to discriminate the small-sized sedimentary xenoliths from the MME. In summary the xenoliths in the granites can be megascopic ally distinguished from the MME by comparing their color, shape, grain size and remnant original structure like bedding. Additionally the metamorphic mineral assemblage and texture are microscopic discriminators between the xenoliths and the MME in the granites.

• The Journal of the Petrological Society of Korea
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• v.16 no.1 s.47
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• pp.12-26
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• 2007

We have studied orientational characteristics of vertical rift and grain planes developing in 108 quarries for Mesozoic granites. Orientations of these planes vary in different localities. In general, orientations of these planes are predominantly NNE in South Korea. From the regional distribution chart, orientations of these planes show three dominant sets in terms of frequency orders: (1) $N2{\sim}10^{\circ}E(1st-order),\;(2)\;N15{\sim}25^{\circ}E(2nd-order),\;(3)\;N45{\sim}70^{\circ}E,\;N10{\sim}30^{\circ}W\;and\;N70{\sim}80^{\circ}W(3rd-order)$. These granite quarries are classified by the relative difference in the easiness of rock splitting between horizontal and vertical quarrying planes into: R-type, G-type, and H-type. The results showed that quarries for Triassic granites belong to R and G-types;those for Jurassic granites belong to R, G and H-types. In addition, quarries for Cretaceous granites belong mainly to R-type. Among these quarry types, the most diverse type was identified in the quarries for Jurassic granites. R-type (77.8%) shows a higher distribution ratio compared with G and H-types (22.2%). In general, anisotropy of physical properties is found in granitic rocks and there exists close correlation between orientations of granitic rock splitting planes and those of the open microcracks. Meanwhile, it has been reported that preferred orientations of open microcracks suggest maxinum principal stress orientations.

• The Journal of the Petrological Society of Korea
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• v.17 no.4
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• pp.222-230
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• 2008

Intruding ages for the Jurassic(${\sim}Triassic$) granites in South Korea can be reestablished as $210{\sim}170\;Ma$ and $180{\sim}160\;Ma$ according to the tectonic provinces of magma emplacement. Most Jurassic granites in the Gyeonggi massif have the intrusion ages of $180{\sim}160\;Ma$, indicative of middle Jurassic igneous activity. On the other hand the intrusion ages ($210{\sim}170\;Ma$) for the Jurassic granites in the Yeongnam massif represent late Triassic to middle Jurassic igneous activity. Using the concept of granite suite/supersuite, the Jurassic granites in South Korea can be hierarchically divided into two supersuites and two suites. Huge batholith of NE-SW direction in the Gyeonggi massif could be designated to be 'Gyeonggi Supersuite', which was originated from the mixture of igneous protolith and more evoloved crustal materials and formed in the post-orogenic environment after collision of the north China and south China blocks. There are one supersuite and two suites in the Yeongnam massif 'Yeongnam Supersuite' could be designated from the NE-SW trend batholith in the massif. This supersuite was originated from the mixture of igneous protolith and evolved crustal materials. Granitic rocks between Andong and Girncheon areas could be defined as 'Andong Suite'. This suite was originated from the mixture of depleted mantle and igneous protolith. The Daegang and Hamchang granties could be designated as 'Daegang Suite'. This suite was formed in the anorogenic environment which was different from the orogenic environment of the other supersuite/suite in the Yeongnam massif.