• 한국지구물리탐사학회:학술대회논문집
• /
• 2004.06a
• /
• pp.3-17
• /
• 2004

Space-borne Earth observation technique is one of the most cost effective and rapidly advancing Earth science research tools today and the potential field and micro-wave radar applications have been leading the discipline. The traditional optical imaging systems including the well known Landsat, NOAA - AVHRR, SPOT, and IKONOS have steadily improved spatial imaging resolution but increasing cloud covers have the major deterrent. The new Earth observation satellites ENVISAT (launched on March 1 2002, specifically for Earth environment observation), ALOS (planned for launching in 2004 - 2005 period and ALOS stands for Advanced Land Observation Satellite), and RADARSAT-II (planned for launching in 2005) all have synthetic aperture radar (SAR) onboard, which all have partial or fully polarimetric imaging capabilities. These new types of polarimetric imaging radars with repeat orbit interferometric capabilities are opening up completely new possibilities in Earth system science research, in addition to the radar altimeter and scatterometer. The main advantage of a SAR system is the all weather imaging capability without Sun light and the newly developed interferometric capabilities, utilizing the phase information in SAR data further extends the observation capabilities of directional surface covers and neotectonic surface displacements. In addition, if one can utilize the newly available multiple frequency polarimetric information, the new generation of space-borne SAR systems is the future research tool for Earth observation and global environmental change monitoring. The potential field strength decreases as a function of the inverse square of the distance between the source and the observation point and geophysicists have traditionally been reluctant to make the potential field observation from any space-borne platforms. However, there have recently been a number of potential field missions such as ASTRID-2, Orsted, CHAMP, GRACE, GOCE. Of course these satellite sensors are most effective for low spatial resolution applications. For similar objects, AMPERE and NPOESS are being planned by the United States and France. The Earth science disciplines which utilize space-borne platforms most are the astronomy and atmospheric science. However in this talk we will focus our discussion on the solid Earth and physical oceanographic applications. The geodynamic applications actively being investigated from various space-borne platforms geological mapping, earthquake and volcano .elated tectonic deformation, generation of p.ecise digital elevation model (DEM), development of multi-temporal differential cross-track SAR interferometry, sea surface wind measurement, tidal flat geomorphology, sea surface wave dynamics, internal waves and high latitude cryogenics including sea ice problems.

• Journal of the Korean earth science society
• /
• v.21 no.1
• /
• pp.67-80
• /
• 2000

We studied petrological and geochemical characteristics of the Mesozoic volcanic rocks in the Da Hinggan Ling area northeast China, and discussed tectonic settings and origin of the Mesozoic volcanic rocks in northeast Asia. Volcanic rocks in Da Hinggan Ling area are composed of alkaline to subalkaline basalt-basaltic andesite-andesite-dacite-rhyolite, showing typical BAR(basalt-andesite-rhyolite) association. However, most of the volcanic rocks are basaltic and rhyolitic in composition, and andesitic rocks are relatively rare, which shows bimodal characteristics. Rb, Ba, Th and other incompatible element contents in the volcanic rocks are enriched, but the contents decrease with increasing the compatibility. REEs are fractionated and REE patterns of volcanic rocks are characterized by a high LILE/HFSE. On the tectonomagmatic discriminant diagram of Hf-Th-Nb, they fall into the fields for subduction-related destructive plate margin basalts and its differentiates. We suggest that the tectonomagmatic setting of Da Hinggan Ling area was located at the continental margin arc related with subduction environment during the Mesozoic time or may be derived from mantle plume contaminated geochemically from subducting slabs, although it is, at present within the Asia continent.

• The Journal of the Petrological Society of Korea
• /
• v.15 no.2 s.44
• /
• pp.60-71
• /
• 2006

The Seokmodo consists mainly of biotite granite and granodiorite. The biotite granite is divided into the south and the north part by granodiorite. There occurs high temperature hot spring of which temperature is up to $72^{\circ}C$. The Rb-Sr isotopic data for the biotite granite define whole-rock isochron ages of $207{\pm}70$ Ma with initial Sr isotopic ratio of 0.7132 in north part and $132{\pm}50$ Ma with initial Sr isotopic ratio of 0.7125 in south part, suggesting that the magma be derived from the crustal source material. The geochemical characteristics of the biotite granite and hornblende granodiorite indicate that they were crystallized from calc-alkaline under syn-collisional tectonic environment. The samples of hot spring were collected at March 2005 and March 2006. The $^{87}Sr/^{86}Sr$ ratios of hot spring are 0.714507 and 0.714518, respectively and correspond to those oi the granite being occurred at the south part. The similarity of $^{87}Sr/^{86}Sr$ ratios between the granite and hot spring strongly suggests that the hot spring might be derived from the Seokmodo biotite granite.

• The Journal of the Petrological Society of Korea
• /
• v.15 no.1 s.43
• /
• pp.39-48
• /
• 2006

U-Pb ages were determined from the granitic rocks from central and northeastern parts of Yeongnam massif. Porphyritic granite of Seosang-myeon, Hamyang-gun near the boundary with Anui-myeon shows age of $225.4{\pm}4.1Ma$. Foliated granodiorites of Anui-myeon, Hamyang-gun and Sinwon-myeon, Geochang-gun are $195.6{\pm}1.8Ma$ and $194.2{\pm}2.4Ma$ old respectively. Granites from Hari-myeon and Buksang-myeon of Geochang-gun show almost identical ages of $198.4{\pm}2.5Ma$ and $194.6{\pm}2.6Ma$ respectively, while foliated granodiorite of Yeongju shows an age ot $171.3{\pm}2.3Ma$. Combining with previously reported results, Triassic granitoids were emplaced almost identically at ca. 225 Ma throughout the areas of Hamyang and Sangju oi Yeongnam massif and Baengnok, Jeomchon and Goesan of Okcheon metamorphic belt. There were significant gap of non-magmatism before the resume of granitic activities over the large areas of Hamyang-gun, Geochang-gun, Gimcheon-si and Seongju-gun from Triassic-Jurassic boundary to early Jurassic, 200-194 Ma. Igneous activity within the Yeongnam massif of this period has not been reported from the Okcheon belt or Gyeonggi massif and may reflect distinct tectonic environment. Around 170 Ma, when Yeongju granodiorite was emplaced, there were active granitic magamtism throughout the Yeongnam massif, Okcheon belt and also Gyeonggi massif.

• Economic and Environmental Geology
• /
• v.39 no.5 s.180
• /
• pp.567-581
• /
• 2006

The Au-Ag lode deposits in South Korea are closely associated with the Mesozoic granitoids. Namely, the Jurassic deposits formed in mesozonal environments related to deep-seated granitoids, whereas the Cretaceous ones were developed in porphyry-related environments related to subvolcanic granitoids. The time-space relationships of the Au-Ag lode deposits in South Korea are closely related to the changing plate motions during the Mesozoic. Most of the Jurassic auriferous deposits (about $165{\sim}145$ Ma) show fluid characteristics typical of an orogenic-type gold deposits, and were probably generated in a compressional to transpressional regime caused by an orthogonal to oblique convergence of the Izanagi Plate into the East Asian continental margin. On the other hand, strike-slip faults and caldera-related fractures together with subvolcanic activity are associated with major strike-slip faults reactivated by a northward (oblique) to northwestward (orthogonal) convergence, and probably have played an important role in the formation of the Cretaceous Au-Ag lode deposits (about $110{\sim}45$ Ma) under a continental arc setting. The temporal and spatial distinctions between the two typical Mesozoic deposit styles in South Korea probably reflect a different thermal episodes (i.e., late orogenic and post-orogenic) and ore-forming fluids related to different depths of emplacement of magma due to regional changes in tectonic environment.

• The Journal of the Petrological Society of Korea
• /
• v.14 no.4 s.42
• /
• pp.212-225
• /
• 2005

This study has been designed to elucidate the morphology of Jisagae columnar joints and the petrography and petrochemistry of Daepodong basalt in Jeju Island, distributed along the 3.5 km-long coast from Seongcheonpo to Weolpyeongdong. Colonnade of the Jisagae columnar joint typically occurs within the upper part of a flow and consists of relatively well-formed basalt columns. Most columns are straight with parallel sides and diameters from 100 cm to 205 cm, $130\~139\;cm$ in maximum. Length of the columns extends up to 20 m. Most columns tend to have 6 or 5 sides but sometimes they have as few as $3\~4$ or as many as 7 or 8 sides. The Daepodong basalt consists of plagioclase, olivine, orthopyroxene, clinopyroxene, ilmenite and magnetite. Plagioclase is labradorite, clinopyroxene is augite, orthopyroxene is bronzite and olivine is chrysolite and hyalosiderite. The Daepodong basalt shows porphyritic texture with matrix of mainly intersetal texture. The Daepodong basalt is plotted into alkali rock series on the TAS diagram. The tectonic setting of the Daepodong basalt represents within plate environment.

• The Journal of the Petrological Society of Korea
• /
• v.4 no.1
• /
• pp.20-30
• /
• 1995

We report major element chemistry of the Chuncheon amphibolite in the Precambrian Kyonggi massif and discuss its origin. On the basis of areal distribution and chemical difference, the Chuncheon amphibolite can be divided into the Gubongsan arnphibolite in the Gubongsan Group east of Chuncheon city and the Sangguli amphibolite in the Yongduri gneiss complex occurring to the southeast of the Gubongsan Group. Overall major element characteristics of the Chuncheon amphibolite indicate an igneous precursor, although it shows concordant relationship with metasedimentary rocks in many cases. The parental rock of the amphibolite has tholeiitic composition with 45-53wt% $SiO_2$. The Sangguli amphibolite has lower MgO than the Gubongsan one. The difference in $TiO_2$/P_2O_5 ratio between the two amphibolites suggests that they are not genetically related. In MgO variation diagrams, $Na_2O$, $Fe_2O_3$ and $Al_2O_3$ show scattered pattern, while MgO has positive correlation with CaO and negative one with $SiO_2$, $TiO_2$, $P-2O_5$ and $K_2O$. These variations can be interpreted as the result of differentiation of basaltic magma with fractionation of olivine, pyroxene, and plagioclase. Tectonic discrimination using major elements generally suggest withinplate environment for the Chuncheon amphibolite which is similar to that of the amphibolite in the Ogcheon belt.

• The Journal of the Petrological Society of Korea
• /
• v.8 no.3
• /
• pp.149-170
• /
• 1999

The volcanic lavas in the Janggi area are plotted on basalt, basaltic andesite and andesite field (SiO$_2$; 48-61 wt.%) in the TAS diagram and belong to subalkaline series. Nineteen chenmical analyses of lavas show two distinct differentiation trends; tholeiitic and calc-alkaline. Calc-alkaline basaltic andesites composed of plagioclase and two-pyroxenes (cpx, opx) in their phenocrysts. Tholeiitics basaltic lavas can be classified into two sub-types. The one is porphyritic basalts composed of plagioclase, clinopyroxene and olivine phenocryst, and the other is aphyric basalt and more evolved lavas (aphyric basaltic andesite) with the same mineral phases. Incompatible elements and REE patterns show the enrichment of LILE and depletion of HFSE. This characteristics indicate that these lavas are evolved from the magmas related to subduction. Howeverm calc-alkaline basaltic andesite lavas show that slightly higher enrichment of LILE and the depletion of HFSE than those of tholeiitic basaltic lavas. On the tectonic discriminant diagram such as Ba/Th and La/Th ratios, calc-alkaline basaltic andesite lavas belong to orogenic medium to high-K suites, whereas tholeiitic basaltic lavas belong to medium-K suites and MORB. On the other diagram, such as La/Yb vs. Th/Yb, the volcanic lavas in the study area plotted in the field of oceanic arc basalt. Tholeiitic basaltic lavas are located in more prinitive environment than calc-alkaline andesitic lavas.

• Geophysics and Geophysical Exploration
• /
• v.9 no.3
• /
• pp.241-249
• /
• 2006

Due to the long tectonic history and the very complex geologic formations in Korea, the anisotropic characteristics of subsurface material may often change very greatly and locally. The algorithms commonly used, however, may not give sufficiently precise computational results of traveltime data particularly for the complex and strong anisotropic model, since they are based on the two-dimensional (2D) earth and/or weak anisotropy assumptions. This study is intended to develope a three-dimensional (3D) modeling algorithm to precisely calculate the first arrival time in the complex anisotropic media. Considering the complex geology of Korea, we assume 3D TTI (tilted transversely isotropy) medium having the arbitrary symmetry axis. The algorithm includes the 2D non-linear interpolation scheme to calculate the traveltimes inside the grid and the 3D traveltime mapping to fill the 3D model with first arrival times. The weak anisotropy assumption, moreover, can be overcome through devising a numerical approach of the steepest descent method in the calculation of minimum traveltime, instead of using approximate solution. The performance of the algorithm developed in this study is demonstrated by the comparison of the analytic and numerical solutions for the homogeneous anisotropic earth as well as through the numerical experiment for the two layer model whose anisotropic properties are greatly different each other. We expect that the developed modeling algorithm can be used in the development of processing and inversion schemes of seismic data acquired in strongly anisotropic environment, such as migration, velocity analysis, cross-well tomography and so on.

• Journal of the Mineralogical Society of Korea
• /
• v.17 no.4
• /
• pp.365-383
• /
• 2004

Granitic rocks in the southeastern Gyeongsang Basin can be classified into three groups. The group I contains various mafic microgranular enclave (MME) and/or mafic clot which implies magma mixing or mingling. The group II show the feature of shallow depth emplacement at low pressure, and the group III is characterized by A-type granite implying extensional tectonic environment. Mineralogical characteristics of the granitic rocks have showed systematic variations in perthite exsolution temperatures and biotite compositions according to their rock facies, although they do not show any distinctively different trend in geography and textures or rock facies. Amphiboles from Group I are calcic-amphibole and they were formed at 0.4 ～ 2.8 kb in pressure based on the amphibole geobarometry. Amphiboles from group ill are riebeckite, whileas amphiboles were not observed in Group II. The chemical composition of biotite defined in clusters showing a continuous spectrum between group I to ferric-annite of group ill. The composition of plagioclase generally plotted in albite, oligoclase, and andesine area without any distinctive differences among their geography or rock facies. The exsolution temperatures by perthite geothermometry are calculated as $300～400^{\circ}C$ in Group I, and 500～$600^{\circ}C$ in equigranular granite of group II and alkali-feldspar granite of group III.