• Journal of the Korean Chemical Society
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• v.55 no.4
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• pp.570-574
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• 2011

Large colorless single crystals of analcime with diameters up to 0.20 mm have been synthesized from gels with the composition of $3.00SiO_2$ : $1.50NaAlO_2$ : 8.02NaOH : $454H_2O$ : 5.00TEA. The fully $Na^+$-exchanged analcime have been prepared with aqueous 0.1 M NaCl (pH adjusted from 6 to 11 by dropwise addition of NaOH). The single-crystal structure of hydrated $|Na_{0.94}(H_2O)|[Si_{2.06}Al_{0.94}O_6]$-ANA per unit cell, a=13.703(3) ${\AA}$, has been determined by single-crystal X-ray diffraction technique in the orthorhombic space group Ibca at 294 K. The structure was refined using all intenties to the final error indices (using only the 1,446 reflections for which $F_o$ > $4{\sigma}(F_o))R_1/wR_2$ = 0.054/0.143. About 15 $Na^+$ ions are located at three nonequivalent positions and octahedrally coordinated. The chemical composition is $Na_{0.94}(H_2O)Si_{2.06}Al_{0.94}O_6$. The Si/Al ratio of synthetic analcime is 2.19 determined by the occupations of cations, 14.79, in the single-crystal determination work.

• Journal of the Mineralogical Society of Korea
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• v.23 no.1
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• pp.39-50
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• 2010

Zeolites were formed by the alteration of volcanic glass in the volcaniclastics including tuff cone/rings and subsurface Seoguipo Formation, Jeju Island. Phillipsite and analcime were identified by X-ray diffraction and electron microprobe analysis. Si/(Si+Al) atom ratios of analcime and phillipsite were similar to that of parent basaltic glass. In comparison with the simple chemistry of analcime, phillipsite showed a range of cavity cation compositions. Na is the major cavity cations of phillipsite in the Dangsanbong and Yongmeori tuffs bearing analcime, while K and Ca in core samples of Seoguipo Formation. Microtextural analysis by scanning electron microscope showed a general sequence that early phillipsite encrustification of pores was followed by later analcime infilling. Zeolites are abundant in the older tuff cone/rings but nearly absent in the younger ones.

• Journal of the Mineralogical Society of Korea
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• v.5 no.2
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• pp.61-71
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• 1992

Through the low-temperature(60-150${\circ}C$) hydrothermal treatment of perlite with the alkaline solution at various NaOH concentrations, the mode of volcanic glass alteration and resultant zeolite formation were investigated in a closed system. At a temperature of 80${\circ}C$ and alkalinities of pH range 8 to 12, corresponding to the natural environments of diagenetic zeolite formation, only weak dissolution of perlitic glass occurs without zeolite formation despite the residence time of 100 days. Activities of Si and Al increase progressively, as a consequence of increasing pH, whereas activity ratios of Si/Al decrease. Zeolites were synthesized from perlite in the alkaline solution at above 0.1M NaOH concentrations. Below the temperature of 100${\circ}C$ Na-P was mainly formed, whereas analcime was the dominant zeolite at the temperature range of 100-150${\circ}C$. During Na-P synthesis chabazite and Na-X were also formed as by-products in case of lower proportion of solution/sample(<10ml/g) and higher NaOH concentraion (>3M), respectively. The alteration modes of perlite in the zeolite synthesis reflect that the formation of synthetic zeolites occurs as an incongruent dissolution likely with the diagenetic formation of natural zeolites from volcanic glass. Considering much difference in reaction kinetics between natural and synthetic systems, however, the evaluated synthetic conditions in these experiments were not directly applicable to the natural diagenetic system.

• The Journal of the Petrological Society of Korea
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• v.25 no.4
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• pp.335-348
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• 2016

The fluvial Tamna Formation, consisting of conglomerate, sandstone and mudstone layers, is widely distributed in Jeiu Island. Various sizes of quartz crystals were identified from most of the Tamna Formation, including the mudstone layer. XRD analysis also shows that the mudstone layer is composed of various minerals, quartz, plagioclase, K-feldspar, mica, magnetite, hematite, olivine, amphibole, gibbsite, calcite, analcime and clay minerals such as illite, kaolinite, vermiculite, smectite, chlorite, $10{\AA}$-halloysite. There is a tendency showing that the more amount of kaolinite, vermiculite, and chlorite is present where the more amount of quartz crystals is present. It is likely that the main source materials contributing to the Tamna Formation were from the parental rocks containing abundant quartz grains, suggesting that the Tamna Formation could not be related to Jeju volcanic rocks, but possibly to pre-existing basement rocks. Thus, we propose that the Tamna Formation was formed from the materials derived from both pre-existing basement rocks and Jeju volcanic rocks, which were subsequently affected by diagenesis, hydrothermal alteration and weathering process.

• Economic and Environmental Geology
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• v.35 no.1
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• pp.13-23
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• 2002

The chemical compositions of groundwaters from the granite areas mainly belong to Ca-HC0$_{3}$ and Na-HC0$_{3}$type, and some of these belong to Ca-(CI+S0$_{4}$) and Na-(CI+S0$_{4}$) type. Spring waters and groundwaters from anorthosite areas belong to Ca-HC03 and Na-HC03 type, respectively. The result of reaction path modeling shows that the chemical compositions of aqueous solution reacted with granite evolve from initial Ca-CI type, via CaHC0$_{3}$ type, to Na-HC0$_{3}$ type. The result of rain water-anorthosite interaction is similar to evolution path of granite reaction and both of these results agree well with the field data. In the reaction path modeling of rain watergranite/anorthosite reaction, as a reaction is progressing, the activity of hydrogen ion decreases (pH increases). The concentrations of cations are controlled by the dissolution of rock-forming minerals and precipitation and re-dissolution of secondary minerals according to the pH. The continuous addition of granite causes the formation of secondary minerals in the following sequence; gibbsite plus hematite, Mn-oxide, kaolinite, silica, chlorite, muscovite (a proxy for illite here), calcite, laumontite, prehnite, and finally analcime. In the anorthosite reaction, the order of precipitation of secondary minerals is the same as with granite reaction except that there is no silica precipitation and paragonite precipitates instead of analcime. The silica and kaolinite are predominant minerals in the granite and anorthosite reactions, respectively. Total quantities of secondary minerals in the anorthosite reaction are more abundant than those in the granite reaction.