• The Journal of the Petrological Society of Korea
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• v.25 no.4
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• pp.349-360
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• 2016

The Bunam Stock ($29.5km^2$ area) is an outcrop of plutonic complex classified four facies: coarse-grained granite, quartz monzodiorite, granodiorite and fine-grained granite. Three facies except the last one exhibit very irregular boundaries with gradational compositional variations between both facies and show concentric zoning from the central quartz monzodiorite through granodiorite to outer coarse-grained granite. Mafic microgranular enclaves (MME) commonly occur in granodiorite. Some MMEs, have very fine-grained chilled margins and indentedly crenulate contacts, and display horizontally circular and vertically elongate shapes. Their shape and granularity indicate coeval flow and mingling of partly crystalline felsic and mafic magmas. MMEs exhibit dark fine-grained margins giving them a ellipsoidal form that has been attributed to undercooling of a mafic magma as blobs intruded into a felsic magma. The observed relations in the Bunam Stock identify that two endmembers are coarse-grained granite from a felsic magma and quartz monzodiorite from a mafic magma, and hybrid is granodiorite including MMEs. So they exhibit concentric zoning that lays the center on the mafic endmember due to magma mixing at the contacts of two magmas, when mafic magma injected into felsic magma. Thus the quartz monzodiorite may probably represent an ancient conduit of mafic magma transport through a granitic magma chamber. Mafic magma would rise through the conduit in which favorable conditions for magma mixing occurred. All these features suggest that they formed from mixing processes of calc-alkaline magma in the Bunam Stock.

• Korean Journal of Remote Sensing
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• v.21 no.6
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• pp.457-468
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• 2005

Increasing of impervious surface resulting from urban development has negative impacts on urban environment. Therefore, it is absolutely necessary to estimate and quantify the temporal and spatial aspects of impervious area for study of urban environment. In many cases, conventional image classification methods have been used for analysis of impervious surface fraction. However, the conventional classification methods have shortcoming in estimating impervious surface. The DN value of the each pixel in imagery is mixed result of spectral character of various objects which exist in surface. But conventional image classification methods force each pixel to be allocated only one class. And also after land cover classification, it is requisite to additional work of calculating impervious percentage value in each class item. This study used the spectral mixture analysis to overcome this weakness of the conventional classification methods. Four endmembers, vegetation, soil, low albedo and high albedo were selected to compose pure land cover objects. Impervious surface fraction was estimated by adding low albedo and high albedo. The study area is the Tanchon watershed which has been rapidly changed by the intensive development of housing. Landsat imagery from 1988, 1994 to 2001 was used to estimate impervious surface fraction. The results of this study show that impervious surface fraction increased from $15.6\%$ in 1988, $20.1\%$ in 1994 to $24\%$ in 2001. Results indicate that impervious surface fraction can be estimated by spectral mixture analysis with promising accuracy.

• Korean Journal of Remote Sensing
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• v.22 no.6
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• pp.553-563
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• 2006

This study aims to produce land-cover maps of Korean peninsula using multi-temporal MODIS (Moderate Resolution Imaging Spectroradiometer) imagery. To solve the low spatial resolution of MODIS data and enhance classification accuracy, Linear Spectral Mixture Analysis (LSMA) was employed. LSMA allowed to determine the fraction of each surface type in a pixel and develop vegetation, soil and water fraction images. To eliminate clouds, MVC (Maximum Value Composite) was utilized for vegetation fraction and MinVC (Minimum Value Composite) for soil fraction image respectively. With these images, using ISODATA unsupervised classifier, southern part of Korean peninsula was classified to low and mid level land-cover classes. The results showed that vegetation and soil fraction images reflected phenological characteristics of Korean peninsula. Paddy fields and forest could be easily detected in spring and summer data of the entire peninsula and arable land in North Korea. Secondly, in low level land-cover classification, overall accuracy was 79.94% and Kappa value was 0.70. Classification accuracy of forest (88.12%) and paddy field (85.45%) was higher than that of barren land (60.71%) and grassland (57.14%). In midlevel classification, forest class was sub-divided into deciduous and conifers and field class was sub-divided into paddy and field classes. In mid level, overall accuracy was 82.02% and Kappa value was 0.6986. Classification accuracy of deciduous (86.96%) and paddy (85.38%) were higher than that of conifers (62.50%) and field (77.08%).

• The Journal of the Petrological Society of Korea
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• v.7 no.2
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• pp.77-97
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• 1998

We analyzed geochemical and radiogenic isotope data to investigate the genesis and source characteristics of the Onjeongri granite in the northern part of the Gyeongsang Basin. Field observation and K-Ar ages confirm late Cretaceous intrusion (ca. 87 Ma) of the Onjeongri granite. The hornblende geobarometery gives less than 2 kbar for the emplacement pressure of the Onjeongri granite. Geochemical and isotopic compositions suggest that the Onjeongri granite was formed in a relatively immature arc system. $SiO_2$ contents show a negative linear relationship with initial $^{87}Sr/^{86}Sr$ ratios, and an apparent positive correlation with $^{207}Pb/^{204}Pb$ ratios, suggesting an incomplete mixing or assimilation. However, the isotopic data known for any exposed rocks of the study area do not fit as an endmember, implying that the contaminant might reside in the lower crust. A review of published isotopic ages, geochemical, and Sr and Nd isotopic data for the Cretaceous to Tertiary granites in the Gyeongsang Basin indicates the followings. 1) Granitic magmatism in the Gyeongsang Basin were episodic. 2) Granitic rocks in the basin were derived from young (< 0.9 Ga) lower crust, and their isotopic signatures reflect heterogeneous source region. Geochemical and isotopic signatures of granitic rocks in the basin are difficult to explain by upper crustal contamination. 3) Granites in the Gyeongsang Basin have closely related to those in the San in Belt of the Inner Zone of Southwest Japan in terms of age, petrography, and isotopic and geochemical composition. 4) Sr-Nd isotopic signatures of the Onjeongri granite are relatively primitive compared with granitic rocks in the other parts of the Gyeongsang Basin and in the Inner Zone of Southwest Japan.

• Korean Journal of Mineralogy and Petrology
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• v.34 no.3
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• pp.157-167
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• 2021

Lead (Pb) is one of the key trace elements, exhibiting a peculiar partitioning behavior into silicate melts in contact with minerals. Partitioning behaviors of Pb between silicate mineral and melt have been known to depend on melt composition and thus, the atomic structures of corresponding silicate liquids. Despite the importance, detailed structural studies of Pb-bearing silicate melts are still lacking due to experimental difficulties. Here, we explored the effect of lead content on the atomic structures, particularly the evolution of silicate networks in Pb-bearing sodium metasilicate ([(PbO)_x(Na₂O)_1-x]·SiO₂) glasses as a model system for trace metal bearing natural silicate melts, using ²⁹Si solid-state nuclear magnetic resonance (NMR) spectroscopy. As the PbO content increases, the ²⁹Si peak widths increase, and the maximum peak positions shift from -76.2, -77.8, -80.3, -81.5, -84.6, to -87.7 ppm with increasing PbO contents of 0, 0.25, 0.5, 0.67, 0.86, and 1, respectively. The ²⁹Si MAS NMR spectra for the glasses were simulated with Gaussian functions for Qⁿ species (SiO₄ tetrahedra with n BOs) for providing quantitative resolution. The simulation results reveal the evolution of each Qⁿ species with varying PbO content. Na-endmember Na₂SiO₃ glass consists of predominant Q² species together with equal proportions of Q¹ and Q³. As Pb replaces Na, the fraction of Q² species tends to decrease, while those for Q¹ and Q³ species increase indicating an increase in disproportionation among Qⁿ species. Simulation results on the ²⁹Si NMR spectrum showed increases in structural disorder and chemical disorder as evidenced by an increase in disproportionation factor with an increase in average cation field strengths of the network modifying cations. Changes in the topological and configurational disorder of the model silicate melt by Pb imply an intrinsic origin of macroscopic properties such as element partitioning behavior.