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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean earth science society
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Journal DOI :
The Korean Earth Science Society
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Volume & Issues
Volume 18, Issue 6 - Dec 1997
Volume 18, Issue 5 - 00 1997
Volume 18, Issue 4 - 00 1997
Volume 18, Issue 3 - 00 1997
Volume 18, Issue 2 - 00 1997
Volume 18, Issue 1 - 00 1997
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Fluid Inclusions within Granite in the Kwangyang district
Gwon, Sun-Hak ; So, Chil-Seop ;
Journal of the Korean earth science society, volume 18, issue 1, 1997, Pages 1~1
Diorite and granite porphyry of Cretaceous age in the Kwangyang district host the hydrothermal gold-silver mineralization. Fluid inclusion studies were undertaken for quartz in diorite stock and granite porphyry dyke. Four main types of fluid inclusions are found: Type I (liquid-rich, aqueous), Type II (vapor-rich, aqueous), Type III (halite±sylvite-bearing), and Type IV (liquid
bearing). Type III inclusions are found only in the granite porphyry which locally hosts the subeconomic Mo-W mineralization, and are thought to represent the earliest fluid trapped by the halite immiscibility (due to the pressure drop) during the postmagmatic evolution. Estimated salinites (wt.% NaCl + KCl eq.) of Type III inclusions in granite porphyry range from 55.6 to 61.6. Based on K/Na ratios, assuming the equilibrium between feldspar and fluids, trapping temperatures are inferred to be 680° to 700℃ and pressures are estimated to fall in the range 800- 1,000 bars. Within the diorite stock being cut by epithermal Au-Ag bearing quartz-carbonate veins are found only the Type I and Type II inclusions as primary inclusions. Liquid
- bearing (Type IV) inclusions occur along healed fractures in quartz from diorite, indicating their secondary origin, probably related to later hydrothermal Au-Ag mineralization.
Analysis on Slope Stability of Wedge Failure by Stereographic Projeetion Technique
Lee, Dong-U ;
Journal of the Korean earth science society, volume 18, issue 1, 1997, Pages 7~7
Stereographic projection technique was used to analyze the stability of wedge failure. Both the internal frictional angle and the strike and dip of joints were used to interprete the stability without considering the cohesion of rock. It suggests that the slope stability on steregraphic projection depends upon only the differential stress between driving and resisting forces. The stereographic projection is not suitable for unconsolidated material such as clay, soil, and highly weathered rock because of the assumption that cohesion strength acting on failure surface is negligible. The change of stability induced by seismic loading can be judged by proposed stereographic projection technique in this study.
A study on the Korean Geodetic System (1995) and World Geodetic System (1984)
Kim, Chang-Gyu ;
Journal of the Korean earth science society, volume 18, issue 1, 1997, Pages 12~12
World Geodetic System 1984, which is a geocentric datum with the origin of earth's center of mass, provides a reference system for Global Positioning System. Korean Geodetic System 1995 (KGS95) has been developed as a geodetic system adapted to WGS84 in Korea. The KGS95 networks consist of thirty one GPS stations with the Korean horizontal control point, and twenty nine stations including precise WGS84 coordinates and Bessel coordinates simultaneously in the KGS95 network are used and analyzed to determine the datum transformation parameters by the least square method. Transformations by seven parameter method, Molodensky Formulas, Multiple Regression Equations, and Universal Transverse Mercator method are investigated to calculate the inconsistancy with two datums. The datum transformation parameters are developed for the new KGS95, and updated results are represented in the distribution chart. A program is developed on the basis of datum transformation parameters. Using this program, geodetic coordinate and mapping coordinate could be calculated accurately.
The Depositional Environment of Southwestern area of the East Sea
Yu, Hwan-Su ; Lee, Yu-Dae ; Gang, Hyo-Jin ;
Journal of the Korean earth science society, volume 18, issue 1, 1997, Pages 20~20
The surface and core sediments taken on the ten sites of the sea bottom of southwestern area of East Sea have been analysed to study on the depositional environment. Surface sediments consists of muddy, sandy sediment and mixture of two type. From core sediments it is defined three different depositional facies: homogeneous mud, bioturbated mud, and massive sand. It is determined that four clay minerals: kaolinites, illites, smectites and chlorites which were terregineous materials or transported by the warm Tsushima Current, were occurred in sediments.
accumulation rates, 5.5 ㎜/year, are higher on the continental shelf of study area but decrease to 2.1 ㎜/year northward, and which provides evidence that some sediments were transported into the study area by warm current from southward. On the basis of silicoflagellates assemblages, eighteen species belonging to five genus including 3 varieties, it is suggested that the study area is dominant by warm current but on the southern slope of Ulleung Basin cold one is somewhat influenced. Accordingly it is considered that recent sediments, Holocene, transported from Nakdong river and relict sediments in glacial age are depositedin the study area, and relict sediments have been reworked and mixed.
Inference of Atmospheric Thermal State from Satellite Data: Global Temperature Trends
Yu, Jeong-Mun ;
Journal of the Korean earth science society, volume 18, issue 1, 1997, Pages 40~40
Monthly mean brightness temperature (
) anomalies at nadir which have been derived from the channel 1 at 50.3 GHz and channel 2 at 53.74 GHz of the microwave sounding unit (MSU) on board NOAA satellites are examined for the global and hemispheric thermal trends, and for local trends over Korean Peninsula during the 9 years of 1980-88. To make the intersatellite correction for temperature differences due to different solar times of the morning and afternoon orbits, anomalies from different satellites were compared during the periods of overlap between satellites to find the time-averaged offsets relative to NOAA-6. The anomalies are computed with respect to the global and hemispheric averages in the following three zones; ocean, land, and both ocean and land. A good agreement in the channel 2 brightness temperature (T₂) anomalies between this study and Spencer and Christy (1990) is found in the global and hemispheric trends with correlation coefficient r=0.8-0.9. However, comparisons between monthly T₂ anomalies and corresponding thermometer-measured anomalies for the global reveal a little lower correlation (0.7). This may result from both poor thermometer sampling of remote regions and weak coupling of surface and mid-tropospheric temperature anomalies in tropical ocean areas due to mainly hydrometeors. Analysis of the 9 years of
anomalies in this study indicates a global warming of 0.2℃/9yr, consistent with independent results of IPCC (1992) and Kerr (1991), particularly showing strong warming of 0.35℃/9yr in the southern hemispheric ocean. The warmest years were 1987, 1988 and 1983 in descending order, while the years 1984 and 1985 were the coolest. In the meantime, the significant correlation (0.5) between T₂ anomalies near Korean Peninsula and thermometer-measured anomalies in Seoul has been obtained. Global
trend for the same period generally agrees with that of T₂ (r=0.7), showing a higher correlation (0.8) over northern hemispheric land. Here the warmest years were 1983, 1981 and 1987, while the years 1984 and 1985 were the coolest. The thermal trends in both T₁ and T₂ anomalies responded well to two major El Nino events for 1982 - 83 and 1986 - 87. It is necessary for global atmospheric temperatures estimates to be accurate for monitoring of possible greenhouse warming, evaluation of numerical model for climate studies, and for systematic understanding of climate change.
Origin of Graded Cherty Beds containing Skolithos ichnosp. from the Cretaceous Yucheon Group in Mt. Hwangryeong Area, Pusan, Korea
Kim, Jeong-Ryul ;
Journal of the Korean earth science society, volume 18, issue 1, 1997, Pages 51~51
Graded cherty beds containing abundant trace fossils, Skolithos ichnosp. from the Cretaceous Yucheon Group of Mt. Hwangryeong area, Pusan, Korea were described and interpreted as storm-originated deposits. A graded cherty bed is composed of basal graded sandstone, parallel-laminated cherty sandstone, cherty sandstone with hummocky cross stratification (HCS), and flat-laminated cherty siltstone in ascending order. The basal graded sandstone comprises tuffaceous sands and has sharp erosive lower contact and sole marks. It shows mostly normal grading and occasionally contains cross bedding in the lower part. Parallel-laminated cherty sandstone which gradationally overlies the basal graded sandstone is characterized by parallel lamination and sporadically contains dish structure in the lower part and syndepositional fold in the upper part. The abundance of trace fossils (mostly Skolithos ichnosp.) increases from the basal graded sandstone to cherty sandstone with HCS. Uppermost flat-laminated cherty siltstone contains horizontal trace fossils including Palaeophycus ichnosp. On the basis of erosional surface with sole marks, generally upward-fining grain size distribution, upward-increasing degree of bioturbation, and distribution of physical sedimentary structures including HCS and trace fossils, graded cherty beds are interpreted to be formed by rapid deposition of tuffaceous sediments which was transported by storm currents into a lake margin environment. The trace fossils of the graded cherty beds are the only known biogenic evidence of the Yucheon Group by this time and they are characterized by low diversity and high density. They are interpreted to have been produced by opportunistic animals in the storm events.
Stable Isotope Study of Gold-Silver Deposits in the Muju-Youngdong Area
Yun, Seok-Tae ;
Journal of the Korean earth science society, volume 18, issue 1, 1997, Pages 60~60
The Yonghwa, Weolseong, Soowang and Kilyoung Au-Ag deposits in the Muju-Youngdong area are emplaced along the fissure of Ns-25W direction in middle Cretaceous porphyritic granite or Precambrian Sobaegsan gneiss complex. Sulfur, carbon, oxygen, hydrogen isotope studies were carried out for stage I, II, III and IV mineral assemblage. The δ
values of sulfides fall in a very narrow range throughout the paragenesis with the total range for sphalerite, galena and pyrite +0.9‰, to 5.5‰ The sulfur isotope data indicate a deep-seated source for the hydrothermal sulfur. δ
values in the carbonates range from - 8.7‰ to - 3.5‰ during postote deposition. The carbon isotope data was probably derived from a deep-seated source. The δ
of the hydrothermal fluid was determined from δ
values of quartz and calcite. δ
of most of the hydrothermal fluids in each mineralization stage range from - 6.3‰ to - 2.0‰, in stage I, from - 10.4‰ to - 5.6‰ in stage II, from - 9.3‰ to - 5.3‰ in stage III and from - 3.8‰, to + 4.8‰, in stage IV. δD values of sericites range from - 93.1‰, to - 89.8‰. Oxygen and hydrogen isotope studies reveal that meteoric water dominate over ore-bearing fluid.
The Petrochemistry and Geochronology of Cretaceous Plutonie Rocks in the Koheung Area, Chonnam
Park, Yeong-Seok ; Kim, Jeong-Bin ; Yun, Jeong-Han ;
Journal of the Korean earth science society, volume 18, issue 1, 1997, Pages 70~70
Plutonic rocks of the Koheung area are composed of a granitic gneiss, a diorite, a biotite granite and a granophyre. These rocks are distinctly different in terms of their field occurrence, mineralogy and petrochemistry, as well as their isotopic ages. The granitic gneiss is Precambrian in minimum age, has a U-Pb zircon age 1890±6 Ma. The diorite, the granophyre and the biotite granite are much younger, having K-Ar whole rock ages 70.1±1.9 Ma, 67.2±1.0 Ma and 67.0±0.9 Ma respectively, which are Late Cretaceous ages. On the basis of normative Qz-Or-PI, Or-Ab-An diagrams and D.I., the diorite plots from diorite through quartz diorite to quartz monzodiorite region while the biotite granite and the granophyre plot in a granodiorite to a granite region. On the A-M-F diagram all the diorite, the biotite granite and the granophyre are a calc-alkalic rock series. The diorite has high chalcophile, ferromagnesian and low REE, lithophile and HFS elements. One the other hand the biotite granite and the granophyre have high chalcophile, HFS elements, REE, ferromagnesian and low lithophile. In terms of the REE characteristics the ∑LREE/∑REE is 0.90 for the diorite and 0.89 to 0.90 for the biotite granite to the granophyre. Chondrite normalized REE trend is for the diorite, the biotite granite and the granophyre show a decrease in LREE while the HREE pattern is essentially constant. For the diorite the ∑REE, [La/Lu]CN and Eu/Eu* are 128 ppm, 9.3, 1.0 respectively which classifies it as a continental andesite. The same parameters for the biotite granite and the granophyre are 134 ppm to 173 ppm, 6.8 to 5.9 and 0.3 to 0.7 with a small to moderate Eu (-) anomaly and thus indicates a monzo- to syenogranite composition. On alkalinity-silica diagram the diorite plots in calc-alkaline while the biotite granite and granophyre fall in the alkaline field. But on the alkali-silica diagram all plutonic rocks plot in the calc-alkaline field. Based on the silica vs. trace element diagrams the diorite, the biotite granite and the granophyre could have formed near a volcanic arc or a plate collision environment.