• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.3
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• pp.95-100
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• 2006

Synthesis of the non-swelling property micas was carried out by hydrothermal method. In order to artificially induce the diffusion of ions, a rotating system was attached to the hydrothermal apparatus and by adding 0.7 mm zircon beads, synthesis of the non-swelling property micas could be performed in a low temperature area. The hydrothermal conditions for the preparation of micas were a reaction temperature of $260^{\circ}C$, for 72 hrs, using $1K_2O,\;1Al(OH)_3,\;4Mg(OH)_2\;and\;6SiO_2$ as the starting materials and a 8M-KOH solution as the hydrothermal solvent. The micas obtained under these conditions were a plate shape with a size of $2.89{\mu}m$ and showed a whiteness of over 97 %. Also, through the FT-IR analysis, because the absorption peak of the $Mg_3OH$ vibration was observed at approximately $3700cm^{-1}$, it could be known that it was phlogopite of non-swelling property showing the chemical composition of $KMg_3AlSi_3O_{10}(OH)_2$. This result was very consistent with the EDS analysis where O (41.34 %), Mg (3.88 %), Al (11.45 %), Si (17.62 %) and K (25.71%) elements were detected.

• Korean Journal of Materials Research
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• v.5 no.7
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• pp.888-896
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• 1995

In this paper the manufacture of shrinkage-free in situ Mullite-ZrO$_2$ceramics through the addition of Al base metal powder to the mixture of ZrSiO$_4$and A1$_2$O$_3$was attempt. The ZrO$_2$-strengthened mullite ceramics was prepared after the following reaction form, 3(Al+Al$_2$O$_3$)+2ZrSiO$_4$longrightarrow3A1$_2$O$_3$.2SiO$_2$+2ZrO$_2$Al metal powder was added from none to 30 weight percent to the A1$_2$O$_3$. The powders were mechanically mixed, isostatically pressed and reaction sintered at 1450-1$600^{\circ}C$ for 3hours. The specimens were sintered with and without intrim soaking time for 5 hours at 125$0^{\circ}C$ for the oxidation of Al-powder The addition of aluminium accelerates the reaction and compensate the shrinkage during the sintering through an increase in volume of oxidized Al. Because coarse flake type Al metal powders were not effectively milled, oxidized Al resulted in the relative large pore in the specimen.

• Economic and Environmental Geology
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• v.49 no.2
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• pp.147-153
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• 2016

SHRIMP U-Pb age determination was carried out for deformed granites in the Aneui quadrangle, SW Yeongnam Massif. Dating of zircons from a highly deformed mylonitic granite with banded structure and a relatively less deformed porphyritic to augenic granites, that were known as Precambrian gneisses, yielded the same age of ca. 195 Ma. On the basis of this result and previous age data, Early to Middle Mesozoic igneous activity around the Aneui area was interpreted as follows; Subduction-related granitic magmatism started with the intrusion of the Hamyang Granite in the middle Triassic (ca. 225-219 Ma) mainly in the west of the area and ended with syenitic intrusion at the end of Triassic period (ca, 220-210 Ma). After a relatively short period of quiescency, granitic magmatism restarted with the intrusion of magma forming deformed granites dated in this study at the Early Jurassic of ca. 195 Ma and continued to ca. 189 Ma and dioritic intrusion was associated around the late stage of granitic magmatism.

• 한국해양학회지
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• v.24 no.1
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• pp.39-51
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• 1989

A total of 139 surface sediment samples, collected from the continental shelf and slope off the southeastern coast of Korea, were analyzed in order to understand their grain-size, mineral composition and organic carbon content. Based on the grain-size characteristics, five surface sedimentary facies were distinguished: sand, clay, mud, sand-mud mixed, and sand-clay mixed facies. The sand facies appears to be composed mostly of relict sand. For mud, most of which seem to be of recent origin, two different sources were suggested, based principally on their areal distribution pattern and the local hydrographic conditions. Heavy mineral composition of the fine-sand size fraction allowed us to distinguish different sand populations from the study area. On the whole, the Hupo Bank sediments showed a high content of garnet, while the sediments from the northern part of the continental shelf were characterized by a relatively high content of metamorphic minerals (kyanite, sillimanite, andalusite, staurolite). Among clay minerals, the most abundant was illite, with chlorite, kaolinite and smectite following in decreasing order. Organic carbon contents in the sediments of the study area were generally high and showed an average value of 1.94%. The sediment grain-size exerted a strong influence on the organic carbon content. The highest organic carbon content, on the other hand, was found in the continental slope sediments.

• Korean Journal of Materials Research
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• v.13 no.9
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• pp.572-580
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• 2003

Synthesizing behavior and microstructural evolution of $CaZrO_3$and $m-ZrO_2$in a thermal reaction process of $ZrSiO_4$-$xCaCO_3$mixtures, where x is 7 and 19, were investigated to determine the addition amount of CaO in CaO:$ZrO_2$:$SiO_2$ternary composition. CaZrO$_3$-Ca$_2$SiO$_4$precursor prepared by the mixture of $ZrSiO_4$and CaCO$_3$in aqueous suspending media was controlled to the acidic (pH=4.0) condition with HCI solution to enhance the thermal reaction. The addition amount of dispersant into the $ZrSiO_4$-$xCaCO_3$slip increased with increasing mole ratio of $CaCO_3$, which was associated with the viscosity of slip. Decarbonation reaction was activated with an increase of the addition amount of $CaCO_3$, showing different final temperatures in $ZrSiO_4$-$7CaCO_3$and $ZrSiO_4$-$19CaCO_3$mixtures as about 980 and 116$0^{\circ}C$, respectively, for finishing decarbonation reaction. The grain morphology was changed to spherical shape for all samples with an increase of sintering temperature. The grain size and phase composition of the synthesized composites depended on the mixture ratio of Zrsi04 and CacO3 powders, indicating that the main crystals were m-ZrO2 ($\leq$3 $\mu\textrm{m}$) and $CaZrO_3$ ($\leq$ 7 $\mu\textrm{m}$) in $ZrSiO_4$$>-7CaCO_3$and $ZrSiO_4$-$19CaCO_3$mixtures, respectively.

• Economic and Environmental Geology
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• v.50 no.6
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• pp.467-476
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• 2017

Volcanic rocks related to the Guamsan cadera, which find in the southeastern Cheongsong, are divided into Volcanic breccia, Guamsan Tuff and Post-collapse intrusions. We determined their eruption, intrusion and caldera-forming timings based on SHRIMP U-Pb zircon dating. The dating results yield earlier eruption age of $63.77{\pm}0.94Ma$ from the lower ash-flow tuff and an later eruption age of $60.1{\pm}1.8Ma$ from the upper ash-flow tuff of the Guamsam Tuff, and intrusion age of $60.65{\pm}0.95Ma$ from the rhyolite ring dyke of the Post-collapse intrusions. The age data suggest that the Guamsan caldera is formed in 60.65~60.1 Ma between eruption of the upper ash-flow tuff and intrusion of the rhyolite ring dyke. The Guamsan cadera exhibits the volcanic processes of a perfect igneous cycle passing from ash-flow eruptions through caldera collapse to ring intrusions during 63.77~60.1 Ma.

• The Journal of the Petrological Society of Korea
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• v.9 no.1
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• pp.29-39
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• 2000

For the determination of metamorphic age of the metamorphic rocks distributed in the Ji-san area of Youngnam massif, Sm and Nd isotopic compositions were analyzed for the whole rock and garnet separates. As the result, we obtained 1799 + 11 Ma from the porphyroblastic gneiss, 1776 +30 Ma from the metapelite, 1714+35 Ma from the mafic granulite xenolith within the porphyroblastic gneiss, and 1776+30 Ma from the metapelite occurred as a xenolith within the quartzofeldspathic gneiss. There have been reports of geologic ages similar to such metamorphic ages of Jirisan area from the other portion of the Youngnam massif, which reveals that very intense metamorphism took place over the vast area of Youngnam massif during the period of 1.7-1.8 Ga ago. The granulite facies metomorphism of the Gyeonggi massif also shows the age similar to this period. Such resemblance in their metamorphic ages suggests that these massifs experienced similar tectonothermal events occurred at about the same Precambrian periods, which implies the possibility that the extension of the collision belt between the north and south China blocks does not extend through some places between the Youngnam and Gyeonggi massifs. On the other hand a quarzofeldspathic xenolith of porphyroblastic gneiss show 1928 +42 Ma which is older than above age of the metamorphism and is identical with the zircon U-Pb age of porphyroblastic gneiss indicating the formation age of the protolith of the porphyroblastic gneiss.

• The Journal of the Petrological Society of Korea
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• v.16 no.1 s.47
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• pp.1-11
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• 2007

CHIME (chemical Th-U-total Pb isochron) geochronology were made for Precambrian rocks from Goseong-Ganseong area, northeastern part of the Gyeonggi massif. Zircon and/or monazite grains from orthogneisses give $1672{\pm}69\;to\;1414{\pm}36Ma$ ages, and monazite grains from paragneisses yield similar ages ranging from $1703{\pm}70\;to\;1395{\pm}97Ma$ suggesting that $1.7{\sim}1.4Ga$ igneous intrusions and coeval metamorphisms were occurred over the area. Together with reported prevailing $1.9{\sim}1.8Ga$ igneous activities and regional metamorphism from the Cyeonggi massif, our age data from Goseong-Ganseong area would be potentially correlated with long-lived $(1.8{\sim}1.3Ga)$ global tectonotermal events in marginal outgrowth of supercontinent Columbia which was finally assembled by collisional orogenies at ${\sim}1.8Ga$. Petrological and geochmical studies, however, should be followed to confirm this tectonic interpretation.

• The Journal of the Petrological Society of Korea
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• v.26 no.1
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• pp.13-43
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• 2017

In the Hapcheon area, hypersthene-bearing monzonite (mangerite) and syenite are recognized. The main minerals of syenite are alkali feldspar, plagioclase, amphibole, biotite, and quartz. Anhedral hornblende and biotite are interstitial between feldspar and quartz, indicating that the hydrous minerals were crystallized later on. Based on petrochemical studies of major elements, syenite is alkaline series, metaluminous, and I-type. The variation patterns in the trace and rare earth elements of mangerite and syenite show the features of subduction-related igneous rock such as depletion of HFSE, relative enrichment in LILE to LREE, and negative Nb-P-Ti anomalies. Based on the experimental data and petrographic characteristics of the syenite, Hapcheon syenitic magma is considered to be formed by partial melting in a dry system. SHRIMP U-Pb zircon data yield the Triassic age as $227.4{\pm}1.4Ma$ in mangerite, $215.3{\pm}1.2Ma$ in syenite, and $217.9{\pm}2.6Ma$ in coarse-grained syenite, respectively. The mangerite age is similar to those of post-collisional plutonic rocks in Hongseong (226~233 Ma), Yangpyeong (227~231 Ma), and Odaesan (231~234 Ma) areas in the Gyeonggi Massif. Syenites were intruded after about 10 Ma. The features seen in the mangereite and syenite rocks can be explained by models such as the continental collision and slab break-off and the lithosphere thinning and asthenosphere upwelling model.

• The Journal of the Petrological Society of Korea
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• v.23 no.4
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• pp.311-324
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• 2014

The Hongjeom formation of the Pyeongan Supergroup in the Munkyeong coalfield mainly consists of metapsammite and metapelites. Metampelites occur as slate preserving chloritoid+chlorite+muscovite and andalusite+biotite+chlorite+muscovite mineral assemblages. Chloritoid and andalusite occur as porphyroblast, and the matrix composed of fine-grained micas. Metamorphic P-T conditions for these mineral assemblages are $510-520^{\circ}C$ and 3.0-3.5kbar based on P-T pseudosection in $MnO-K_2O-FeO-MgO-Al_2O_3-SiO_2-H_2O(MnKFMASH)$ system and isopleth intersections of Fe/(Fe+Mg) ratios in chloritoid and chlorite. The medium temperature and low pressure metamorphism resulted from a higher geothermal gradient ($40-45^{\circ}C/km$) condition than that of burial metamorphism. The youngest (SHRIMP U-Pb age; ca. 327-310 Ma) detrital zircon grains from the Hongjeom formation display oscillatory zoning and relatively high Th/U ratio (0.60-1.12). Based on the previous sedimentary, paleontological, and geochronological studies in the Taebaeksan basin together with results of this study, we suggest that (1) initial deposition of the Hongjeom formation was contemporaneous with a magmatic activity in the provenance, (2) the Pyeongan Supergroup was deposited in an arc-related basin at an active continental margin during the Carboniferous to Permain, and (3) magmatic activities occurred repetitively in relatively short interval in the active continental margin had continuously supplied sediments to the basin.