• Journal of the Korean earth science society
• /
• v.34 no.4
• /
• pp.313-328
• /
• 2013

Jurassic granitoids in the northeastern part of the Yeongnam Massif are possibly the result of intensive magmatic activities that occurred in response to subduction of the proto-Pacific plate beneath the northeast portion of the Eurasian plate. Geochemical studies on the granitic rocks are carried out in order to constrain the petrogenesis of the granitic magma and to establish the paleotectonic environment of the area. Whole rock chemical data of the Uljin granitoids in the northeastern part of the Yeongnam Massif indicate that all of the rocks have the characteristics of calcalkaline series in subalkaline field. The overall major element trends show systematic variations in each granitic body, but the source materials of each granitoids seem to have different chemical composition. The Uljin granitoids are different from other granitic rocks, which distributed vicinity of the study area, in the contents of $Al_2O_3$ and trace elements such as Cr, Co, Ni, Sr, Y and Nb. The Uljin granitoids have geochemical features similar to slab-derived adakites such as high $Al_2O_3$, Sr contents and high Sr/Y, La/Yb ratios, but they have low Y and Yb contents. The major ($SiO_2$, $Al_2O_3$, MgO) and trace element (Sr, Y, La, Yb) contents of the Uljin granitoids fall well within the adakitic field. The Uljin granitoids have similar geochemical characteristics, paleotectonic environments and intrusion ages to those of the Yatsuo plutonic rocks of Hida belt located on northwestern part of Japan. Chondrite normalized REE patterns show generally enriched LREEs ($(La/Yb)_{CN}=10.6-103.4$) and are slight negative to flat Eu anomalies. On the ANK vs. A/CNK and tectonic discrimination diagrams, parental magma type of the granites corresponds to I-type and volcanic arc granite (VAG). Interpretations of the chemical characteristics of the granitic rocks favor their emplacement in a compressional tectonic regime at the continental margin during the subduction of Izanagi plate in Jurassic period.

• Journal of the Mineralogical Society of Korea
• /
• v.27 no.4
• /
• pp.169-181
• /
• 2014

Korea government has consistently investigated the development of economic mineral deposits in the Tofua volcanic arc, Tonga since 2008 for the secure of sea floor mineral resources. We studied the composition and distribution of minerals formed by hydrothermal activity around TA 25 seamounts of the Tofua volcanic arc, Lau Basin, Tonga, using X-ray diffraction analysis, scanning electron microscopy, X-ray fluorescence spectrometry, and inductively coupled plasma atomic emission spectrometry. We used 7 core samples and 9 surface sediment samples. Barite, sphalerite, and clinoclase are present in the most volcanic vent area. Gypsum, smectite, and kaolin mineral are distributed in vent A area, chalcopyrite, pyrite, smectite, and kaolin mineral are in vent B and C area, and gypsum, chalcopyrite, pyrite, and goethite are in vent D area. From the study of clay fraction, smectite and few kaolinite are detected in the most studied area except inner part of caldera, which suggest that argillic alteration are dominant in the volcanic vent areas. Various sulfide or arsenide minerals were found in the hydrothermal vent B, C, and D. The mineralogy and geochemistry suggest higher hydrothermal activities in volcanic vent B, C, and D compared to vent A and inner caldera area. Therefore higher probabilities of massive sulfide deposits may occur in hydrothermal vent B, C, and D.

• Journal of the Korean earth science society
• /
• v.30 no.4
• /
• pp.427-443
• /
• 2009

Cretaceous intrusive and extrusive rocks in the southwestern part of the Yeongnam Massif are possibly the result of intensive magmatism which occurred in response to subduction of the Pacific plate beneath the northeast portion of the Eurasian plate. Geochemical and petrological study on the granitic rocks were carried out in order to constrain the petrogenesis of the granitic magma and to establish the paleotectonic environment of the area. Whole rock chemical data of the granitic rocks from the study area indicate that all the rocks have characteristics of calc-alkaline series in the subalkaline field. The overall geochemical features show systematic variations in each granitic body, but the source materials of each granitic body are thought to have been different in their chemical composition. The granodiorites distributed around Donggyori in the Bognae area (DGd) are different from other granitic rocks within the study area in the contents and differentiation trends of $Al_2O_3$ and MgO as well as in the contents of the trace elements such as Ba, Sr, Pb, Ni, Cr and Y DGd have geochemical features similar to slab-derived adakites such as high $Al_2O_3$, Sr contents and high Sr/Y, La/Yb ratios, but low Y and Yb contents. The major and trace element contents of the DGd fall well within the adakitic field, whereas other Cretaceous granites in the study area are plotted in the island arc ADR area in Sr/Y vs. Y diagram. On the ANK vs. A/CNK and tectonic discrimination diagrams, parental magma type of the granites corresponds to I-type and volcanic arc granite (VAG). Interpretations of the chemical characteristics of the granitic rocks favor their emplacement in a compressional tectonic regime at continental margin during the subduction of Pacific plate. The geochemical and tectonic features reveal that adakite-like signatures of the DGd were generated by the interaction of mantle peridotite and subducted slab-derived adakitic melts (caused by the thermal effect of ridge subduction), and which slightly modified by crustal contamination during emplacement.

• Korean Journal of Remote Sensing
• /
• v.24 no.2
• /
• pp.189-194
• /
• 2008

Middle-infrared (MIR) spectral region between 3.0 and $5.0\;{\mu}m$ in wavelength is useful for observing high temperature events such as volcanic activities and forest fire. However, atmospheric effects and sun irradiance in day time has not been well studied for this MIR spectral band. The objectives of this basic study is to evaluate atmospheric effects and eventually to estimate surface temperature from a single channel MIR image, although a typical approach utilize split-window method using more than two channels. Several parameters are involved for the correction including various atmospheric data and sun-irradiance at the area of interest. To evaluate the effect of sun irradiance, MODIS MIR images acquired in day and night times were used for comparison. Atmospheric parameters were modeled by MODTRAN, and applied to a radiative transfer model for estimating the sea surface temperature. MODIS Sea Surface Temperature algorithm based upon multi-channel observation was performed in comparison with results from the radiative transfer model from a single channel. Temperature difference of the two methods was $0.89{\pm}0.54^{\circ}C$ and $1.25{\pm}0.41^{\circ}C$ from the day-time and night-time images, respectively. It is also shown that the emissivity effect has by more largely influenced on the estimated temperature than atmospheric effects. Although the test results encourage using a single channel MR observation, it must be noted that the results were obtained from water body not from land surface. Because emissivity greatly varies on land, it is very difficult to retrieval land surface temperature from a single channel MIR data.

• Journal of the Mineralogical Society of Korea
• /
• v.32 no.3
• /
• pp.163-172
• /
• 2019

A long core (RS15-LC48) was collected at a site in the continental rise between the Southern Ocean and the Ross Sea (Antarctica) during the 2015 Ross Sea Expedition. The mineralogical characteristics and the origin of clay minerals in marine sediments deposited during the Quaternary in the Ross Sea were determined by analyzing sedimentary facies, variations in grain size, sand fraction, mineralogy, clay mineral composition, illite crystallinity, and illite chemical index. Core sediments consisted mostly of sandy clay, silty clay, or ice rafted debris (IRD) and were divided into four sedimentary facies (units 1-4). The variations in grain size distribution and sand content with depth were very similar to the variations in magnetic susceptibility. Various minerals such as smectite, chlorite, illite, kaolinite, quartz, and plagioclase were detected throughout the core. The average clay mineral composition was dominated by illite (52.7 %) and smectite (27.7 %), with less abundant clay minerals of chlorite (11.0 %) and kaolinite (8.6 %). The IC and illite chemical index showed strong correlation trends with depth. The increase in illite and chlorite content during the glacial period, together with the IC and chemical index values, suggest that sediments were transported from the bedrocks of the Transantarctic Mountains. During the interglacial period, smectite may have been supplied by the surface current from Victoria Land, in the western Ross Sea. High values for IC and the illite chemical index also indicate relatively warm climate conditions during that period.

• Korean Journal of Remote Sensing
• /
• v.38 no.5_1
• /
• pp.447-460
• /
• 2022

It is well known that satellite synthetic aperture radar interferometry (InSAR) has been widely used for the observation of surface displacement owing to earthquakes, volcanoes, and subsidence very precisely. In wetlands where vegetation exists on the surface of the water, it is possible to create a water level change map with high spatial resolution over a wide area using the InSAR technique. Currently, a number of imaging radar satellites are in operation, and most of them support a ScanSAR mode observation to gather information over a large area at once. The Cienaga Grande de Santa Marta (CGSM) wetland, located in northern Colombia, is a vast wetland developed along the Caribbean coast. The CGSM wetlands face serious environmental threats from human activities such as reclamation for agricultural uses and residential purposes as well as natural causes such as sea level rise owing to climate change. Various restoration and protection plans have been conducted to conserve these invaluable environments in recognition of the ecological importance of the CGSM wetlands. Monitoring of water level changes in wetland is very important resources to understand the hydrologic characteristics and the in-situ water level gauge stations are usually utilized to measure the water level. Although it can provide very good temporal resolution of water level information, it is limited to fully understand flow pattern owing to its very coarse spatial resolution. In this study, we evaluate the L-band ALOS-2 PALSAR-2 ScanSAR mode to observe the water level change over the wide wetland area using the radar interferometric technique. In order to assess the quality of the interferometric product in the aspect of spatial resolution and coherence, we also utilized ALOS-2 PALSAR-2 stripmap high-resolution mode observations.