• Economic and Environmental Geology
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• v.34 no.5
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• pp.437-446
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• 2001

Zoned epidotes formed by the propylitic alteration of the Bobae sericite deposit in western Pusan show complex compositional zoning patterns, such as multiple growth zoning, oscillatory zoning, patchy zoning and irregular zoning. The complex zoned epidote, in general, shows AI-rich cores and Fe-rich rims. Pistacite component (Ps) in the epidote ranges from 18.5 to 74.3 mot.%. Remnant textures in multiple growth zoning indicate that the earlier zone was partially resorbed prior to growth of later one. Multiple growth zoning and oscillatory zoning suggest that hydrothermal system underwent rapid changes and fluctuations in fluid chemistry, redox condition, or temperature.

• Journal of the Mineralogical Society of Korea
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• v.5 no.1
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• pp.42-47
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• 1992

The oscillatory zoning pattern in alunite from the Sungsan mine, Korea was studied by the back-scattered electorn(BSE) imaging and electron microprobe analysis. This zoning is not visible under the polarizing microscope, but is spectacularly illustrated in BSE image. Electron microprobe analysis reveals that the zoning is substantially due to the variation in the content of Na substituting for K in the A site of the alunite structure. With increasing brightess in BSE image, conternt of K increases but that of Na decreases. Delicate fine-scale zoning and sharp boundaries between adjacent zones suggest that the zoning would be ascribed to the variation in the composition of hydrothermal fluid around the growing alunite crystals. The effective factors for such a variation would be 1) the fluctuation in the composition of entering fluid. and/or 2) the rapid change in composition of fluid due to the rapid precipitation of more stable. Na-poor alunite.

• Journal of the Mineralogical Society of Korea
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• v.18 no.3 s.45
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• pp.227-236
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• 2005

Hydrothermal tourmaline occurs as aggregates or dissemination in the diaspore nodule from an aluminum-rich clay deposit, Milyang, southeastern Korea. Most crystals of tourmaline show complex textures that are finely zoned. The fine-scale chemical zonation of hydrothermal tourmaline reflects the fluctuation conditions that would be expected from fluid mixing in open systems. Oscillatory chemical zoning in tourmaline formed and showed similar patterns, regardless of its crystallographic directions. Mg was enriched in the early stage of crystal growth while Fe was enriched in the later stage, with fluctuations of the ratio of Fe to Mg. Chemical analysis, BSE images, and X-ray compositional maps confirm that the oscillatory Boning in tourmaline is exclusively controlled by the variations of Fe and Mg contents, but the contribution of boron to the zonation is insignificant. The fact that tourmaline altered to diaspore and dickite indicates that tourmaline was unstable with respect to these aluminous minerals as the B, Fe, and Mg activities decreased. Therefore, the aluminum activity may control the stability of tourmaline in the hydrothermal system.

• The Journal of the Petrological Society of Korea
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• v.23 no.2
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• pp.139-144
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• 2014

A series of the planar cathodoluminescence (CL) and backscattered-electron (BSE) images of magmatic zircon from the Paleozoic Yeongdeok pluton in the southeastern Korean Peninsula were taken using a scanning electron microscope for a 3D reconstruction of internal zonation of zircon. Seven zircon crystals mounted in epoxy were serially polished with average $3{\mu}m$ thickness to their disappearance. Their 3D reconstruction of zonation was performed using the Volume Viewer function in the ImageJ software. The 3D oscillatory zoning pattern of zircon was apparently shown in all the analyzed crystals. This method can further be applied to zircon crystals of multiple growth histories as well as other geological materials.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.2
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• pp.87-97
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• 2020

The compositions of the phenocrystic feldspars of the Sanbangsan trachyte range from labradorite(An_53.6) to andesine(An_35.4), and of the microphenocrysts and laths range from andesine(An_31.2) to oligoclase(An_18.7). Mantled feldspar which forms a thin rim around the phenocrysts and microphenocrysts, is anorthoclase(Or_20.5An_9.4) to sanidine(Or_49.2An_1.4). Phenocrystic plagioclase, which shows a distinct zonal structure, represents an oscillatory zoning in which the An content of the zone repeatedly increases or decreases between andesine (An_39.3) and labradorite (An_51.3) from the core toward the rim, and the rim of the phenocrysts is surrounded by alkali feldspar(Or_31.9-39.4Ab_63.2-57.0An_4.9-3.7), showing the antirapakivi texture. Microphenocryst which does not represent the antirapakivi texture, shows the normal zoning with a decreasing An content (An_36.4→An_25.6) as it moves outward from the center of a crystal. As a result of X-ray mapping of K, Ca, and Na elements for the feldspar phenocrysts representing the typical zonal structure, shows the oscillatory zoning that six zones show the distinctive compositional differences, and the rims are mantled by alkali feldspar to indicate the antirapakivi texture. The groundmass is composed of K-enriched, Ca-poor alkali feldspar. The antirapakivi texture of feldspar which appears in Sanbangsan trachyte, may have been formed in mixing systems as a result of the juxtaposition of near liquidus melt, rich in alkali feldspar components(trachytic magma), with plagioclase phenocrysts and microphenocrysts already crystallized in a more mafic system.

• The Journal of the Petrological Society of Korea
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• v.21 no.3
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• pp.309-333
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• 2012

Basalt having lots of feldspar phenocryst occurred at the northern and southern slope of the Mt. Halla, Jejudo. Among them, the Sioreum trachybasalt in southern slope consists of abundant phenocrysts of plagioclase in aphanitic groundmass. And the number of plagioclase grains are about 20 per $10cm^2$, and based on 667 grains the sizes are 13~0.7 mm (average 4.23 mm) in length and 8.6~0.5 mm (average 2.3 mm) in width. In according to modal analyses, Sioreum basaltic rock consists mainly of plagioclase (16~28%), olivine, clinopyroxene (1.5~6%) and opaque minerals (~0.1%) of magnetite and ilmenite as phenocryst and microphenocryst and groundmass (60~82%). The compositions of plagioclase, olivine and clinopyroxene are bytownite~andesine, chrysolite~hyalosiderite, augite respectively. Plagioclase phenocrysts show different type of zoning, namely, normal, reversal, patchy, oscillatory type. The An contents of zoned plagioclase mainly increase from core to rim. Those of oscillatory type from core to rim show variations of increase following decrease or decrease following increase, being more enriched in rim or almost same to core. Under the microscope, some plagioclase phenocrysts are especially melted in core part or marginal part, or found as only the remnant remain which resulted from reaction with melt. Some clinopyroxene are also corroded in margin part or found as irregular shape resulted from melting. The characteristics of petrography and compositional variation from core to rim of plagioclase and clinopyroxene, indicate that they are disequilibrium with melt and has been undergone geological environmental changes in magma batch during crystallization including magma mixing with replenishment of more mafic and high temperature melt.

• Economic and Environmental Geology
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• v.50 no.5
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• pp.325-340
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• 2017

The Seongdo Pb-Zn deposit, located in the northwestern part of the Ogcheon Metamorphic Belt, consists of skarn ore replacing limestone within the Hwajeonri Formation of Ogcheon Group and hydrothermal vein ore filling the fracture of host rock. Skarn minerals comprise mostly hedenbergitic pyroxene, garnet displaying oscillatory zonal texture composed of grossular and andradite, and a small amount of wollastonite, tremolite, and epidote, indicating reducing condition of formation. Ore minerals of skarn ore include sphalerite and galena with a small amount of pyrite, pyrrhotite, and chalcopyrite. In hydrothermal vein ore, arsenopyrite, sphalerite, chalcopyrite, and pyrite occur with a small amount of galena, native Bi, and stannite. Chemical compositions of sphalerite vary from 17.4 mole% FeS in average for dark grey sphalerite, 3.6 mole% for reddish brown sphalerite in skarn ore, and to 10.3 mole% FeS in hydrothermal vein ore. In comparison with representative metallic deposits in South Korea on the FeS-MnS-CdS diagram, skarn and hydrothermal vein ore plot close to the field of Pb-Zn deposits and Au-Ag deposits, respectively. Arsenic contents of arsenopyrite in hydrothermal vein ore decrease from 31.93~33.00 at.% in early stage to 29.58~30.21 at.% in middle stage, and their corresponding mineralizing temperature and sulfur fugacity are $441{\sim}490^{\circ}C$, $10^{-6}{\sim}10^{-4.5}atm$. and $330{\sim}364^{\circ}C$, <$10^{-8}atm$. respectively. Phase equilibrium temperatures calculated from Fe and Zn contents for coexisting sphalerite and stannite in hydrothermal vein are $236{\sim}254^{\circ}C$. Sulfur isotope compositions are 5.4~7.2‰ for skarn ore and 5.4~8.4‰ for hydrothermal vein ore, being similar or slightly higher to magmatic sulfur, suggesting that ore sulfur was mostly of magmatic origin with partial derivation from host rocks. However, much higher sulfur isotope equilibrium temperatures of $549^{\circ}C$와 $487^{\circ}C$, respectively for skarn ore and hydrothermal ore, than those estimated from phase equilibria imply that isotopic equilibrium has not been fully established.