Jaehyung Yu

Mineralogy and Chemical Compositions of Dangdu Pb-Zn Deposit

The Dangdu Pb-Zn deposit is located at approximately 10 km south of Jecheon, Korea. Geology of Dangdu deposit area consists of Pre-cambrian metamorphic rocks, Ordovician sedimentary rocks, Jurassic and Cretaceous igneous rocks. The ore deposit is developed along the fracture trending in Ordovician limestone and is considered to be a skarn type ore deposit. The shape of ore bodies developed in the Dangdu ore deposit can be divided into lens-form(two ore bodies of -30 m level adit and one ore body of -63 m level adit) and pocket-form developed in -30 m level adit. Ore minerals observed in the ore deposits are magnetite, pyrrhotite, pyrite, chalcopyrite, sphalerite, galena, cosalite, marcasite, hessite, native Bi and bismuthinite. Chemical composition of sphalerite ranges FeS 14.14~18.08 mole%, CdS 0.44~0.70 mole%, MnS 0.52~1.13, 1.53~2.09 mole%. Galena contains a small amount of silver with an average of 0.54 wt.%. An average composition of cosalite is Ag 2.43 wt.%, Bi 44.36 wt.%, Pb 35.05 wt.% which results the chemical formula of cosalite as . Skarn minerals consist of epidote, garnet, pyroxene, tremolite, quartz and calcite. The zoning pattern of the ore deposit can be subdivided into epidote-clinopyroxene zone, epidote-clinopyroxene-chlorite zone and epidote-garnet-clinopyroxene zone from the central part of the ore body towards the wall rocks. The chemical composition of garnet shows an increasing trend of grossular from epidote-clinopyroxene zone to epidote-garnet-clinopyroxene zone. Clinopyroxene occurs as a solid solution of diopside and hedenbergite, and the ratio of johannsenite increases from epidote-clinopyroxene zone to epidote-clinopyroxene-chlorite and epidote-garnet-clinopyroxene zones. The mineralization of the ore deposit is considered to be one stage event which can be separated into early skarn mineralization stage, middle ore mineralization stage and late low temperature mineralization stage. The temperature estimation from the low temperature mineralization range from which is considered to be representing the temperature of late mineralization.

Spectral characteristics of minerals associated with skarn deposits: a case study of Weondong skarn deposit, South Korea

This study examined the spectral characteristics of minerals occurring at Weondong skarn deposit located in South Korea and assessed the effectiveness of VNIR-SWIR spectroscopic approaches in zone definition characterizing skarn deposits based on XRD, XRF, and petrographic studies. The spectroscopic analyses identified intrusive rock, garnet-clinopyroxene skarn, clinopyroxene-garnet skarn, W-ore, and host rock zones. The assessment results for VNIR-SWIR spectroscopy in skarn exploration illustrated that the spectral approaches would be very useful for attaining skarn mineral information such as calcite, chlorite, clinopyroxene, garnet, scapolite, vesuvianite, and wollastonite and clay minerals. Furthermore, the rock-forming minerals such as K-feldspar, plagioclase, quartz, fluorite, and tungsten-bearing minerals like scheelite may require supplementary mineral analysis. A combined analysis of spectrometry, XRD, XRF, UV lamp scanning, and petrographic studies reveals that the skarn mineralization of the study area related to W mineral of the study core is defined as proximal endoskarn to proximal exoskarn, which could be defined by spectroscopic approaches.

Typhoon Impact on a Pure Gravel Beach as Assessed through Gravel Movement and Topographic Change at Yeocha Beach, South Coast of Korea

ABSTRACT Han, M.; Yang, D.Y.; Yu, J., and Kim, J.W., 2017. Typhoon impact on a pure gravel beach as assessed through gravel movement and topographic change at Yeocha Beach, south coast of Korea. This study investigated sediment movement and topographic change using radio frequency identifier (RFID) tracers and real-time kinematic (RTK)–global positioning system (GPS) data to examine the response of a gravel beach under typhoon conditions. Yeocha Beach, the study site and a pure gravel beach, was affected by strong wind and waves produced by Typhoon Goni on 24–26 August 2015. On 26 August, the main direction of the tracer movement was toward the upper part of the beach and toward the west relative to the onshore-offshore and alongshore directions. The average movement distance of the tracers differed according to the insertion points. The tracers inserted in the beach face showed a longer average movement distance of 12.07 m compared with 1.89 m for those inserted in the storm berm. In addition, the tracers inserted in the beach face showed an average movement of 0.44 m in height toward the upper part of the beach. The result of topographic change showed that sedimentation was dominant within most parts of the beach. Moreover, this study clarified sediment movement patterns according to various patterns of localized topographic changes and tracer movement. This study investigated the relationship between tracer properties and movement distance and found that significant statistical differences did not occur under the typhoon conditions; thus, the beach gravel moved collectively rather than individually under strong wave energy conditions. In addition, 3 months after the typhoon, the beach recovered back to its original topography under normal wave conditions. The beach response and recovery indicate that the pure gravel beach exhibited an outstanding natural seawall effect. However, this study investigated the beach response based on a single typhoon; future research is necessary to understand the response under various environmental conditions.

Mapping the moisture content of coastal sediments using ASTER data for spectroscopic and mineralogical analyses: a case study in South Korea

Mineralogical characteristics of coastal sediments and their spectral characteristics related to moisture content were analysed for South Korea in this study, and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) short-wave infrared (SWIR) remote sensing approaches for moisture content mapping based on conventional SAM module were proposed in this study. The mineral composition included the major minerals of quartz, alkali feldspar, plagioclase and calcite and the accessary minerals of mica and clay. The absorption features of coastal sediments studied occurred at wavelengths of 1.900 μm for clay minerals and water, 2.200 μm for clay minerals and 2.350 μm for micas and calcite. The spectral signature changed with increased moisture content as the absorption feature at 2.200 μm and 2.350 μm faded out. The fading absorption features shifted the resampled laboratory spectra in a spectral vector space and enabled the use of a SAM module for the ASTER SWIR data. The SAM method effectively distinguished not only the absolute moisture content distribution using the reference spectra but also the relative moisture content distribution without the actual reference spectra for coastal sediments. Given that mineral composition and absorption feature behaviours with regard to the moisture content of soil samples are similar to coastal sediments, this method may be applicable for soil moisture mapping.

Site Selection for Geologic Records of Extreme Climate Events based on Environmental Change and Topographic Analyses using Paleo Map for Myeongsanimni Coast, South Korea

This study selected optimal sites in Myeongsasimni located in west coast of Korea for stratigraphic research containing extreme climate event during quaternary period by spatio-temporal analyses of changes in sedimentary environment and land use employing 1918 topographic map, 2000 digital terrain map, 1976 and 2012 air photographies. The study area shows no significant changes in topographic characteristics that hilly areas with relatively large variations in elevation are distributed over north and south part of the study area, and sand dues are developed along the coast line. Moreover, flat low lying areas are located at the back side of the sand dues. The movement of surface run off and sediment loads shows two major trends of inland direction flow from back sides of sand dunes and outland direction flow from high terrains inland, and the two flows merge into the stream located in the center of the study area. Two sink with individual area of 0.2 km 2 are observed in Yongjeong-ri and Jaryong-ri which are located in south central part and south part of the study area, respectively. In addition, sea level change simulation reveals that 3.4 km 2 and 3.64 km 2 are inundated with 3 m of sea level rise in 1918 and 2000, respectively, and it would contribute to chase sea level change records preserved in stratigraphy. The inundated areas overlaps well with sink areas where it indicates the low lying areas located in south cental and south part of the study area are identical for sediment accumulation. The areas with minimal human impact on sediment records over last 100 years are 3.51 km 2 distributed over central and south part of the study area with the land use changes of mud and rice field in 1918 to rice field in 2012. The candidate sites of 0.15 km 2 in central part and 0.09 km 2 in south part are identified for preferable locations of geologic record of extreme climate events during quaternary period based on the overlay analysis of optimal sedimentary environment and land use changes.

Cost-effective reflectance calibration method for small UAV images

ABSTRACT We introduce a cost-effective reflectance calibration method for small unmanned aerial vehicle (sUAV) images using ethylene-vinyl acetate (EVA) greyscale reference panels. The goal is to test if such light-weight and low-cost panels can provide sufficient calibration accuracy to support UAV survey projects. The universal calibration equations to convert red-green-blue (RGB) digital number (DN) values of UAV images to surface reflectance values were constructed based on the relationship between RGB values measured by a colour digitizer and surface reflectance values measured by a spectrometer. We compared the calibration results for UAV ortho-mosaic images acquired at three different illumination conditions in late autumn to the results derived from high-cost commercial panels. The comparison showed high degree of agreement between our method using the EVA panels with the traditional methods using the commercial panels. The Mann–Whitney U test verified our method was statistically more significant at all illumination conditions tests. In addition, the calibration results applied for two different sensors and three different flight altitudes acquired in early summer were satisfactory. This method is transferable to various illumination conditions and flight altitudes as long as the effects of shades and the bidirectional reflectance distribution function (BRDF) are minimal. We expect our research could expedite sUAV image calibration by lowering its cost and levelling its availability.

Relationship between spectral reflectance and metal content of Korean pine needles as a metal contamination indicator

This study investigated variations of spectral characteristics of Korean pine needles associated with heavy metal contamination at an abandoned Pb-Zn mine. XRF analysis revealed that the pine needles are mainly polluted by Zn and As. Among the contaminants, As content showed highest correlation with surface reflectance in visible and near infrared spectrum where positive relationship in visible and negative relationship in near infrared are detected. Especially, NIR reflectance and As content have the highest correlation with R2 of 0.9241. This study would contribute for development of remote sensing based exploration techniques of As contamination for large area over the world if further experiments follows.

Analysis of Quaternary Sedimentary Environment based on 3D Geological Modeling for Saban-ri, Haeri-myeon, Gochang

Haein Shin, Jaehyung Yu*, Sungji Bae, Dongyoon Yang and Min Han Department of Astronomy, Space Science, & Geology, Chungnam National University Department of Geology and Earth Environmental Sciences, Chungnam National University Geological Research Division, Korea Institute of Geoscience and Mineral Resources Graduate Program, Department of Geography Education, Seoul National University (Received: 30 June 2016 / Revised: 24 August 2016 / Accepted: 25 August 2016)

Detection of an Impact Flash Candidate on the Moon with an Educational Telescope System

At the suggestion of the NASA Meteoroid Environment Office (NASA/MEO), which promotes lunar impact monitoring worldwide during NASA`s Lunar Atmosphere and Dust Environment Explorer (LADEE) mission period (launched Sept. 2013), we set up a video observation system for lunar impact flashes using a 16-inch educational telescope at Chungnam National University. From Oct. 2013 through Apr. 2014, we recorded 80 hours of video observation of the unilluminated part of the crescent moon in the evening hours. We found a plausible candidate impact flash on Feb. 3, 2014 at selenographic longitude and latitude . The flash lasted for 0.2 s and the light curve was asymmetric with a slow decrease after a peak brightness of . Based on a star-like distribution of pixel brightness and asymmetric light curve, we conclude that the observed flash was due to a meteoroid impact on the lunar surface. Since unequivocal detection of an impact flash requires simultaneous observation from at least two sites, we strongly recommend that other institutes and universities in Korea set up similar inexpensive monitoring systems involving educational or amateur telescopes, and that they collaborate in the near future.

Assessment of Rocks and Alteration Information Extraction using ASTER data for Övörkhangaii Province, Mongolia

This study examined the possibility to extract potential alteration zones and lithologic information based on ASTER band ratio techniques for mineralized area located in province, Mongolia, and the effectiveness of remote sensing as a preliminary exploration tool for mineral exploration was tested. The results of ABRLO, PBRLO, and PrBRLO models indicated that the detection of argillic zone requires the verification of the samples to verify hydrothermal alteration minerals as clay minerals can formed by weathering process, whereas phyllic-propylitic zones were considerably related to the spatial distribution of the intrusive bodies, geological structures, and ore distribution. QI and MI results showed that QI is more useful for sedimentary rocks such as conglomerate and sandstone than meta-sedimentary like quartzite, and MI faced relatively uncertain in detection of felsic or mafic silicate rocks. QI and MI may require additional geologic information such as the characteristics of samples and geological survey data to improve extraction of lithologic information, and, if so, it is expected that remote sensing technique would contribute significantly as a preliminary geological survey method.