• Korean Journal of Mineralogy and Petrology
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• v.35 no.3
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• pp.215-233
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• 2022

The zircon U-Pb and trace element analyses were performed for banded gneiss in the Euiam gneiss complex, central Gyeonggi Massif. An age of detrital zircon shows predominant age peaks at ca. 2500-2480 Ma with numerous ages ranging from Siderian to Rhyacian period. The youngest age peak of detrital zircon constrains the maximum deposition age of protolith of banded gneiss at ca. 2070 Ma. Meanwhile, the zircon rim yielded metamorphic age of ca. 1966 ± 39 Ma ~ 1918 ± 13 Ma. Based on the error range, degree of discordancy, and value of mean squared weighted deviation, we considered that the age of 1918 ± 13 Ma is the most reasonable age indicating the timing of metamorphism for banded gneiss. The zircon rims yield Ti-in-zircon crystallization temperature of 690-740℃. Therefore, we suggested that there was a high-grade metamorphic event in the Gyeonggi Massif at ca. 1918 Ma which is older than the metamorphic event that occurred in the Gyeonggi Massif during ca. 1880-1860 Ma.

• Korean Journal of Materials Research
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• v.26 no.4
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• pp.182-186
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• 2016

Zircon, having excellent thermal, chemical, and mechanical properties, is utilized in refractory materials, electronic materials, chemical machines, structural materials, etc. However, zircon generally shows thermal dissociation to zirconia($ZrO_2$) and silica($SiO_2$) around the sintering temperature of $1540^{\circ}C$, and when zircon particles are small and impurities are present, thermal dissociation is known to occur at around $1100^{\circ}C$. This reduces the mechanical properties of $ZrSiO_4$. In this research, the effect of adding $SiO_2$ and 3Y-TZP to $ZrSiO_4$ has been studied in order to suppress dissociation and improve the mechanical properties. Addition of $SiO_2$ suppressed the dissociation of $ZrSiO_4$ at lower temperatures. It also enabled optimum packing between the particles, resulting in a dense microstructure and good mechanical properties. When 3Y-TZP was added, recombination with the dissociated $SiO_2$ resulted in good mechanical properties by suppressing the generation of pores and the densification of the microstructure.

• The Journal of the Petrological Society of Korea
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• v.13 no.3
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• pp.119-125
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• 2004

Using a SHRIMP ion microprobe, we have dated zircon grains of a felsic meta-tuff from the so-cal1ed Munjuri Formation, Ogcheon metamorphic belt. The weighted mean $^{206}$ Pb/$^{238}$ U zircon ages obtained from 13 spot analyses of 10 grains provide an essentially concordant age of 747${\pm}$7Ma. This result corroborates the conventional U-Pb zircon age (756${\pm}$1Ma; Lee et al., 1998) for the Neoproterozoic bimodal volcanism in the Ogcheon belt. Thus, proto-basins associated with intracontinental, high-volcanicity rift in the Ogcheon belt are most likely to have formed at ca. 750 Ma.

• The Journal of the Petrological Society of Korea
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• v.14 no.2 s.40
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• pp.83-92
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• 2005

It has recently been proposed that granites can be divided into hot and cold ones by absence and presence of inherited zircon, respectively, which is closely related to zircon saturation temperature. The Phanerozoic granites in South Korea are divided into high- and low-Zr groups in a $SiO_2-Zr$ diagram, which appears to be related to their intrusive age. Most Triassic-Jurassic granites belong to low-Zr group, whereas most Cretaceous-Early Tertiary granites belong to the high-Zr group with the exception of geographically distinct Masan and Jinhae granites that belong low-Zr group. Calculated zircon saturation temperatures using major elements and Zr contents indicate that the Cretaceous-Early Tertiary granites $(608-834^{\circ}C,\;average\; 782\pm31^{\circ}C)$ except for the Masan and Jinhae granites $(average\;759\pm16^{\circ}C)$ show higher temperature than the Triassic-Jurassic granites $(642-824^{\circ}C,\;average\;756\pm31^{\circ}C)$. U-Pb zircon isotope data of the Triassic-Jurassic granites reported so far define discordia in a concordia diagram, which indicates presence of inherited zircon and agrees with their low zircon saturation temperatures. So the Triassic-Jurassic granites appear to belong to cold granite. On the other hand, presence or absence of inherited zircon has not been known for the Cretaceous-Early Tertiary granites with relatively high zircon saturation temperature, so that their classification into hot or cold granite awaits further study. Nevertheless, the Creatceous-Early Tertiary granites may have formed at higher temperature than the Triassic-Jurassic granites, since zircon saturation temperature reflects formation temperature of magma to a certain degree.

• The Journal of the Petrological Society of Korea
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• v.13 no.3
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• pp.126-132
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• 2004

This study provides detailed sample preparation methods for subgrain zircon analyses, and a simple mineral separation technique which overflows light mineral grains out of beaker using the running water from faucet. Excluding separation steps using of the Wilfley table and heavy liquid, this technique is faster and more efficient than conventional one, and remarkably suitable for collecting small amount of zircon for subgrain analyses.

• Journal of the Korean Ceramic Society
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• v.23 no.2
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• pp.50-54
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• 1986

Effects of additionof $NH_4Cl$, NaBr and LiF on the formation of Zircon and the synthesis of CdS-Se red stain were investigated by means of XRD, DTA and the color standard and color nomenclature. The red stain of CdS-Se system shows a little difference dependent on firing temperature on firing conditon. Consequently it forms a good soid-solution with red color under the ratio of CdS and Se 3.5 -4.1 at 58$0^{\circ}C$. But it changes to dark red as increasing Se. LiF is the most effective in mineralizer to preparae zircon with the equilbrant molar $SiO_2$ and ZrO Zircon makes a good preparation in 0.33 mole LiF from 90$0^{\circ}C$.

• Korean Journal of Materials Research
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• v.21 no.4
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• pp.220-224
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• 2011

Zircon has excellent thermal, chemical, and mechanical properties, but it is hard to make a dense sintered product because of dissociation during the sintering process. This study analyzes how the addition of $SiO_2$ and $Al_2O_3$ affects the mechanical properties of sintered zircon, particularly in regards to reducing the thermal dissociation and improving the mechanical properties of $ZrSiO_4$. Zircon specimens containing different amounts of $SiO_2$ and $Al_2O_3$ were prepared and sintered to observe how the mechanical properties of $ZrSiO_4$ changed according to the differing amount of $SiO_2$ and $Al_2O_3$. The $ZrSiO_4$ that was used for the starting material was ground by ball mill to an average particle size of 3 ${\mu}m$. The $SiO_2$ and $Al_2O_3$ that was used for additives were ground to an average particle size of 3 ${\mu}m$ and 0.5 ${\mu}m$, respectively. Adding $SiO_2$ resulted in transformation in the liquid phase at high temperatures, which had little effect on suppressing the thermal dissociation but enhanced the mechanical properties of $ZrSiO_4$. When $Al_2O_3$ was added, the mechanical properties of $ZrSiO_4$ decreased due to the formation of pores and abnormal grains in the microstructure of the sintered zircon.

• The Journal of Advanced Prosthodontics
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• v.13 no.6
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• pp.396-407
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• 2021

PURPOSE. Zirconia has exceptional biocompatibility and good mechanical properties in clinical situations. However, finite element analysis (FEA) studies on the biomechanical stability of two-piece zirconia implant systems are limited. Therefore, the aim of this study was to compare the biomechanical properties of the two-piece zirconia and titanium implants using FEA. MATERIALS AND METHODS. Two groups of finite element (FE) models, the zirconia (Zircon) and titanium (Titan) models, were generated for the exam. Oblique (175 N) and vertical (175 N) loads were applied to the FE model generated for FEA simulation, and the stress levels and distributions were investigated. RESULTS. In oblique loading, von Mises stress values were the highest in the abutment of the Zircon model. The von Mises stress values of the Titan model for the abutment screw and implant fixture were slightly higher than those of the Zircon model. Minimum principal stress in the cortical bone was higher in the Titan model than Zircon model under oblique and vertical loading. Under both vertical and oblique loads, stress concentrations in the implant components and bone occurred in the same area. Because the material itself has high stiffness and elastic modulus, the Zircon model exhibited a higher von Mises stress value in the abutments than the Titan model, but at a level lower than the fracture strength of the material. CONCLUSION. Owing to the good esthetics and stress controllability of the Zircon model, it can be considered for clinical use.

• The Journal of the Petrological Society of Korea
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• v.8 no.2
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• pp.71-80
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• 1999

We report zircon morphology of granitoids in the Mt. Keumjeong district, Pusan. There are a series of granitoids in the study area of the late Cretaceous: granodiorite, hornblende granite, adamellite, tonalite, biotite granite, and micrographic granite. Generally, the shapes of zircon crystals are short prismatic to middle prismatic and are dominant in {loo) prism and {101) pyramid in total average morphological data of the granitoids. The crystal forms of zircon in the granitoids can be distinguished by the PPEF diagram and the prism index (PI). The prism index values of zircon crystal forms in granodoirite and hornblende granite are higher than those of tonalite and micrographic granite. The finishing temperature range ($820~800^{\circ}C$) for crystallization of zircon crystals in granodoirite and hornblende granite is higher than the temperature ($790~770^{\circ}C$) at which the zircon crystals are created in tonalite and micrographic granite. The last differentiates (biotite granite and micrographic granite) have mainly intermediate zircon ({110)={100)) crystals, respectively. As differentiation proceeds, the zircons of granitoids become from short prismatic to middle prismatic in the each granitoid types.

• The Journal of the Petrological Society of Korea
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• v.27 no.2
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• pp.97-104
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• 2018

The U-Pb isotopic and rare earth element compositions of zircon were measured using a SHRIMP from a tonalitic gneiss sample DE43 in Daeijak Island, central Korea. Zircon crystals, up to ${\sim}300{\mu}m$ in diameter, rarely contain thin overgrowth rims. In contrast to Paleoproterozoic cores, the $^{206}Pb/^{238}U$ ages of $256{\pm}23Ma(1{\sigma})$, and $221{\pm}7Ma(1{\sigma})$ were yielded from two spot analyses on the overgrowth rims of zircon. The rims are geochemically characterized by low Th/U ratios (<0.01) and strongly depleted light rare earth elements. The Permian-Triassic apparent ages of zircon are consistent with the $^{208}Pb/^{232}Th$ ages dated from allanite ($227{\pm}7Ma(t{\sigma})$) in the same sample within uncertainties, indicating an equilibrium growth of allanite and zircon at ~227 Ma. On the other hand, the younger $^{208}Pb/^{232}Th$ and $^{206}Pb/^{238}U$ ages ($213{\pm}4Ma(t{\sigma})$ and $186{\pm}9Ma(t{\sigma})$, respectively) of allanite may result from Pb loss due to the infiltration of alkali fluids from Late Triassic and Jurassic granitoids nearby.