• Economic and Environmental Geology
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• v.52 no.5
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• pp.347-356
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• 2019

Various studies regarding the sedimentary environment, depositional age, provenance, and metamorphic history have been carried out on the Taean Formation in the western part of Gyeonggi Massif, since the unique detrital zircon age pattern was revealed. This review paper introduces the previous researches on the Taean Formation and discusses the depositional age and provenance. The Taean Formation was traditionally regarded as a Precambrian stratigraphic unit, but recently it is interpreted to be a middle or upper Paleozoic formation due to the occurrence of large amounts of Early to Middle Paleozoic detrital zircons. The Taean Formation consists of metasandstone, argillaceous schist, and phyllite which are mainly made up of quartz and mica. The protoliths are interpreted as turbidites deposited in deep sea fan environment. The Taean Formation has been interpreted to be deposited between the Devonian to Triassic ages given the age differences between detrital zircons and intrusive rocks. There are two opinions that the deposition age is close to the Devonian or the Permian period. The provenance of this formation is supposed to be South China block, Chinese collisional belt, or Gyeonggi Massif. Given the available detrital zircon ages of the Taean Formation and other Korean (meta)sedimentary rocks, the Taean Formation shares major source rocks with Yeoncheon Group and Pibanryeong Unit of the Okcheon Supergroup, but their source regions are not entirely consistent. Considering the existing hypotheses about the depositional timing and provenance, we put weight on the possibility that the Taean Formation was deposited between Permian and Early Triassic periods. However, further studies on the stratigraphy and sedimentary petrology are needed to clarify its definition and to elucidate the provenance.

• The Journal of the Petrological Society of Korea
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• v.23 no.3
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• pp.209-220
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• 2014

SHRIMP zircon U-Pb age dating is carried out for the Yeongju and Andong granite batholiths intruding the Precambrian metamorphic complex and Paleozoic sedimentary formations within the NE Yeongnam Massif, Korea. Dating of zircons from a hornblende-biotite tonalite and an equigranular biotite granodiorite in the Yeongju granite has yielded ages of ca. 187 Ma and ca. 186 Ma, respectively. Also, dating of zircons from a biotite granodiorite and a very coarse-grained biotite granite in the Andong granite has yielded ages of ca. 182Ma and ca. 186Ma, respectively. These data indicate that the main intrusions of the Yeongju and Andong granite batholiths occur almost at the same age. The oldest age of ca. 194 Ma has been determined on zircons from a hornblende gabbro in the Andong granite, and the youngest age of 175 Ma is obtained from the Chunyang granite pluton, mainly consisting of fine-grained two-mica granite, of the Yeongju batholith. These results indicate that Jurassic Daebo magmatism in the Yeongju-Andong area, NE Yeongnam massif, started early at the Early Jurassic with an intrusion of mafic magma, and followed by an emplacement voluminous granite magma during the middle of the Early Jurassic, and was finalized with the emplacement of relatively small amount of much evolved granite magma at the end of Early Jurassic.

• Journal of Conservation Science
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• v.36 no.6
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• pp.562-577
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• 2020

In this study, to conserve the clay seated Vairocana Buddha triad in Seonunsa temple, Gochang (Treasure 1752), the primary materials employed for creating the clay Buddha statues were scientifically analyzed. By analyzing the soil layer constituting the Buddha statues, it is observed that the said layer comprises sand having particle size greater than that of medium sand and soil having particle size smaller than that of fine sand, which were used in a ratio of 7:3, along with the bast fibers of paper mulberry (Broussonetia kazinoki). Hence, the aforementioned soil layer is composed of a mixture of sand and weathered soil, along with bast fibers to prevent scattering. By analyzing the tree species, it is found that the wooden materials constituting the bottom board and the interior of Buddha's sleeves of the Amitabha Buddha statue, Vairocana Buddha statue, and Medicine Buddha statue are hard pines (Pinus spp.). Additionally, three layers are found in the cross section of the gold layer. Furthermore, each of the hair sections of the Buddha statues is composed of earthy materials such as quartz, albite, microcline, mica, and magnetite, and the hair surface was painted by incorporating black materials containing magnetite.

• The Journal of the Petrological Society of Korea
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• v.27 no.4
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• pp.207-222
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• 2018

Celestial Chart Stones (original and reproduction) in the National Palace Museum are representative scientific cultural heritage of Korea. Material analysis and nondestructive deterioration assessment were conducted for long-term preservation of these stones. Material analysis revealed that the original was composed of slate and the reproduction was made of dolostone. The original consists of quartz, mica, dolomite minerals, while the reproduction was made up of dolomite, calcite and forsterite. Major deterioration factors of the original stone were cracks and breakouts. In case of the reproduction, scratches and artificial materials were mainly observed. The green and black surface contaminants present at the sides and back of the two celestial chart stones were interpreted as resin-based paint materials. The physical property evaluation using ultrasonic velocity showed a low velocity in the upper left side of the original, while the front right side of the reproduction showed a weak property. Meanwhile, the To-Tc method using ultrasonic velocity was applied to major cracks that impede stability of the original. As a result, it has been calculated that the beginning and the center of the crack are the deepest.

• Economic and Environmental Geology
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• v.52 no.4
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• pp.275-290
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• 2019

Geochemical study was conducted to elucidate the origin of fluorine (F) distributed in the rocks within the four areas of Yongyudo and Sammokdo, Incheon, which have been used as the source area of land reclamation for the $3^{rd}$ and $4^{th}$ stage construction sites of the Incheon International Airport. The main geology of the study area is Triassic biotite granite. Fluorine is contained at high levels in biotite granite, mylonite, and dykes (andesite and, basaltic-andesite). Furthermore, the higher concentrations of fluorine in the biotite granite can be contributed to fluorite. The results of microscopic analyses reveal that the fluorite was mostly observed as small vienlets together with quartz. This features support that fluorite was naturally formed due to the secondary process of hydrothermal fluids. In addition, fluorine was investigated to be highly enriched in a large amount of mica within the veins. In the case of mylonite, a high levels of fluorine was contributed to a large amount of sericite. The sericites contained in the mylointe, differently to those of the biotite granite, filled the micro-fractures of quartz formed as a result of mylonitization and included small cataclastic quartz grains. This indicates that fluorine was naturally enriched due to the alteration of hydrothermal fluids filling fractured zones formed by mylonitization. Consequently, the results of petrological and mineralogical study confirm that the fluorine distributed in the rocks within the Yongyudo and Sammokdo originated naturally.

• Economic and Environmental Geology
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• v.52 no.1
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• pp.91-106
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• 2019

The Donghachong tomb from Royal Tombs at Neungsanri is composed of 15 sides including the floor, and the most highly proportion of rock, two-mica granite, are used on the 7 sides (46.6%). Also, augen gneiss consist with another 3 sides (20.0%), and each of the remaining 3 sides (6.7%) are made up of granodiorite, gneissous granite and leucocratic granite, all of which were used to comprise the tabural stone. Meanwhile, the two floors of the burial chamber and the front chamber, are made up of brick-shaped amphibole schist (13.3%). These rocks are occurred in the Buyeo area and their provenance sites are located at the side of Guemgang river. The Memorial Stone for Liu Renyuen in Tang China is a typical augen gneiss showing distinct schistosity and augen texture. This rock has the same petrographic characteristics with the rocks used to build the Donghachong tomb, Sanjikri dolmens and Setapri pagoda in Buyeo. This augen gneiss is distributed from the Jeungsanri in Buyeo to Dukjiri in Gongju as a large scaled rock body, and where currently are the quarries to produce stone aggregates, garden and landscape rocks. Thus, it is highly probable that the site around Buyeo was the source area of augen gneisses since the Bronze Age. However, while augen gneiss is easier to form into shapes it should have disadvantages when it comes to painting on the tomb wall because of their petrographic characteristics of low strength and dark color. Therefore, it is very intriguing to investigate which transportation method the people of Baekje chose with consideration of the distance and terrain, efficiency and convenience.

• Korean Journal of Heritage: History & Science
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• v.50 no.2
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• pp.40-61
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• 2017

This study investigated material characteristics of composition and variable strength measurement using physicochemical and petrographic analysis for lime-soil mixture barrier tombs of Guri Galmae site in Joseon Dynasty. The tomb barriers are composed mainly of microcrystalline calcite, quartz, feldspar and mica with lime matrix. The lime matrix shows compact sheet texture, and some samples show hydration aggregates with needle-shaped textures. Gypsum occurred as a secondary process where carbonization reactions were poor. Concentrations of CaO in the tomb barrier very widely ranged from 4.43 to 36.19 wt.%, specific gravity and absorption ratio of the materials show of 1.35 to 1.62 and 20.1 to 32.6%, respectively. As the rebound hardness, the materials ranged from 10.0 to 28.4 (mean 15.7). The values are higher in the $-90^{\circ}$ direction rather than in the $0^{\circ}$ direction with the consequence that the values indicate more strength toward the vertical direction. Difference in strength by directions was caused by the directions of the tomb barriers, which is related to the processes in each stage. In the tomb barriers, ultrasonic velocity and unconfined compressive strength ranged from 1,049.2 to 1,728.9m/s and under 5.00MPa, respectively. Variation patterns between the two are very similar in values. As the result of composition and strength, the materials of higher contents on CaO are higher in strength values. Generally, techniques and skills to make the lime-soil mixture barriers are interpreted as low qualities in relatively.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.1
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• pp.26-32
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• 2021

Powder type sericite has been actively researched in the area of chemistry and mineralogy in terms of waste recycling. It is a material that can be obtained relatively inexpensively with a low thermal conductivity like general mica, so in order to improve the thermal conductivity of the mortar, powder type sericite was used in this work. Compressive strengths of mortar before and after high temperature exposure were compared and evaluated to determine the fire resistance of mortar with powder type sericite. According to the experimental results, it was found that the compressive strength decreased when powder type sericite was replaced with cement, but the decrease in compressive strength with the increasing amount of powder type sericite was insignificant. When powder type sericite was incorporated, the thermal conductivity decreased, and the residual strengths of the mortar specimens which were heat treated at 600℃, 900℃, and 1,200℃ were higher than that of plain mortar. From the comprehensive evaluation of the experimental results, it can be concluded that the powder type sericite has the potential to be used as a refractory material for cement composites.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.47 no.2
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• pp.163-170
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• 2021

This study was conducted to create a technology to remove acne bacteria with human-friendly materials. First, the Cutibacterium acnes (C. acnes) were adsorbed to the mica disc to grow, and then the biofilm was checked through an atomic microscope to see if the biofilm had grown. Based on the topographic image, the shape changed round, the size was 17% longer on average, and the phase value of the resonance frequency separating materials was observed as a single value, the biofilm grown by covering the extracellular polymeric substrate (EPS). As a result of processing 50 mM of amino acids in the matured biofilm, the concentration of C. acnes decreased when valine, serine, arginine and leucine were treated. Scanning with nanoindentation and AFM contact modes confirmed that the hardness of biofilms treated with Valine (Val) increased. This indicates that an AFM tip measured cell which may have more solidity than that of EPS. The experiment of fluorescent tagged to EPS displays an existence of EPS at the condition of 10 mM Val, but an inhibition of growth of EPS at the 50 mM Val. Number of C. acnes was also reduced above 10 mM of Val. Weak adhesion of biofilm generated from an inhibition of EPS formation seems to induce decrease of C. acnes. Accordingly, we elucidated that Val has an efficiency which eliminates C. acnes by approach of an inhibition of EPS.

• Journal of Conservation Science
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• v.36 no.6
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• pp.494-504
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• 2020

Ten historic sites (denoted as A- J in this study) of a tomb were found during the construction of the east-west expressway in District 2 of Hyangnam, Hwaseong, which is implemented by the Gyeonggi-do headquarters of the Korea Land & Housing Corporation. Thetombswere first detected at siteH, and further investigations revealed various tombs from the Three Kingdoms period; artifacts such as gilt-bronze shoes and caps were excavated from wooden coffins in the tombs. The pottery examined in this study was the only pottery artifact excavated from the site. Its raw clay was soft and loose, reddish brown, and had quartz and feldspar particles of < 1 mm, which appeared to have been added as reinforcing agents. The firing temperature of the pottery was estimated to be under 800-870 ℃ as the mica remains and tridimite, which is the phase transition mineral of quartz, was not produced; a slight endothermic peak was also detected because of the hydration of sericite at 800 ℃. The condition of the artifact was severely weakened because of various factors, such as soil pressure from the stratum formed over the site and repeated freezing and thawing. The artifact could not be collected alone, and thus, surrounding soil that had attached to the artifact was also collected; the artifact was transported to the laboratory and conservation treatment was conducted in a safe and systematic manner.