• Journal of the Mineralogical Society of Korea
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• v.21 no.4
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• pp.373-382
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• 2008

First reported geochemical characteristics of mantle xneoliths (spinel peridotites) from Sunheul-ri, Jeju Island, provide important clues for understanding the lithosphere composition, equilibrium temperature, and the period of entrainment and transport of the xenoliths in the host magma. Core and rim of mineral phases in the xenoliths are constant chemical compositions as $Fo_{89-90}$ of olivines. The ranges of equilibrium temperature, obtained by two pyroxenes geothermometer, are about $951{\sim}1035^{\circ}C$ for Sunheul-ri spinel peridotite xenoliths and are similar to the range of equilibrium temperatures for the xenoliths from other sites in Jeju island. The period of entrainment and transport of the xenoliths in the host magma of Sunheul-ri mantle xenoliths is about 42 days.

• Journal of the Mineralogical Society of Korea
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• v.4 no.2
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• pp.129-140
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• 1991

Two illite polytypes, 2M1 and 1Md, have been identified from the sericite deposits of the Bobae mine, Kimhae, Kyungsangnam-do. Each polytype has characteristic grain size, chemical composition, and occurrence. 2M1 illite occurs predominantly in the sericitic alteration zone, while 1Md illite occurs predominantly in the propylitic alteration zone, implying that the former was formed in the higher temperature than the latter. Illites can be subdivided into two types based on their crystal sizes;(1) the $\mu\textrm{m}$-sized illite which is below 0.01mm(100$\mu\textrm{m}$) in size and consists of 2M1 and 1Md type, (2) the mm-sized illite which is above 0.01mm in size and consists only of 2M1 type. Especially illite below 1$\mu\textrm{m}$ is premominantly of 1Md type. Therefore, it seems likely that illite crystal size is to some extent related to the polytype. XRD data show that there is no interstratified layer in illites regardless of the crystal size and polytype. Activity of muscovite component of the $\mu\textrm{m}$-sized illite is 0.843 while that of the mm-sized illite is 0.790. However, the latter is more similar to muscovite in crystal structure than the former is. The mm-sized illite has less Al and more Kthan the $\mu\textrm{m}$-sized illite. In both illites, Si contents show a positive relation to octahedral Mg. Fluid inclusion study and mineral association show that the formation temperature of illite is $270-330^{\circ}C$. The major chemical processes leading to the formation of sericitic deposit as well as the alteration zones are the leaching of SiO2 from the country rock and the addition of Al2O3 and K2O into the sericitic ores.

• Journal of the Mineralogical Society of Korea
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• v.6 no.1
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• pp.38-47
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• 1993

Clinoptilolite and mordenite are important constituents of the Nuldaeri Trachytic Tuff and Guryongpo Dacitic Tuff of the Tertiary Janggi Group which were deposited in a lacustrine environment. The diagenetic cystallization sequences of zeolites in different tuffaceous sediments and their chemical behaviors have been studied to know the process of their formation. The paragenetic sequence established from textural observations and chemical data : Ca-smectite ${\leftrightarrow}$(Ca, K)-clinoptilolite${\leftrightarrow}$(K, Na)-mordenite, indicates that the chemical activities of alkalic ions and Si/Al activity ratio in pore fluids changed systematically with diagenetic alteration. The chemical trend of zeolite formation is characterized by decreasing Ca and Mg, non-variable Na and increasing K in the Nuldaeri Trachytic Tuff and by decreasing Ca and Mg, non-variable Na and increasing-decreasing K in the Guryongpo Dacitic Tuff. The paragenesis from glass via smectite to alkali zeolites indicates a sequence of incongruent dissolution reactions and subsequent crystallization. Inhomogeneity in chemical composition of each zeolite may be attributed to such processes.

• Journal of the Mineralogical Society of Korea
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• v.22 no.4
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• pp.307-312
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• 2009

Motukoreaite and quintinite-3T, Mg-Al layered double hydroxides, were found in the Sinyangri Formation of Jeju Island. They fill the pores of basaltic volcaniclastic sediments in globular and botryoidal aggregates of fine platy particles. Globular aggregates of quintinite-3T were crusted with the parallel overgrowth of motukoreaite plates. X-ray diffraction data and chemical composition are consistent with those reported in literature, while the Mg/Al ratio of motukoreaite is higher. Structural formula of motukoreaite and quintinite-3T derived from electron microprobe analysis are $Na_{1.6}Ca_{0.1}Mg_{40.7}Al_{20.7}Si_{0.9}(CO_3)_{13.6}(SO_4)_{7.4}(OH)_{108}56H_2O$, and $Mg_{3.7}Al_{1.9}Si_{0.2}(OH)_{12}(CO_3)_{0.8}(SO_4)_{0.2}3H_2O$, respectively. Motukoreaite and quintinite-3T were formed by reaction between seawater and basaltic glass, and contributed to the cementation and lithification of the volcaniclastic sediments.

• Korean Journal of Soil Science and Fertilizer
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• v.32 no.4
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• pp.421-428
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• 1999

Potassium (K) released from weathering of biotite in soils has been recognized as one of major K-sources for plant growth. Sand size biotite in a soil-saprolite-parent rock profile developed under temperate climate was studied in terms of morphological, mineralogical, and chemical changes according to depth employing petrographic and electron microscopes. X-ray diffraction, and electron microprobe. Biotite showed discoloring from black to goldish white and loss paleochroism with decreasing depth. Both edge and layer weatherings of biotite showed in this study. Hexagonal holes and cracks on (001) plane of weathered biotite grains were observed and their members increased with increasing weathering degree. Biotite was altered to kaolinite with or without intermidiate products such as hydrobiotite, degraded biotite, and illite. Average chemical composition of weathered biotite changed to that of katolinite with decreasing depth: increasing concentrations of silicon (Si) and aluminum (Al) and decreasing concentrations of potassium (K), iron (Fe), magnesium (Mg), manganese (Mn), and taitanium (Ti).

• Korean Journal of Mineralogy and Petrology
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• v.36 no.4
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• pp.337-343
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• 2023

Olivine is a complete solid solution of fayalite and forsterite that is abundant in Earth and extraterrestrial materials such as rocky planets, meteorites, asteroids, and interplanetary dust. Due to the wide range of olivine compositions, diverse olivine standards are required for quantitative mineralogical analysis of olivine-bearing materials. Olivine standards were synthesized using an electric furnace and stainless steel tubes at temperatures ranging from 1000~1100 ℃. Overall, olivine was synthesized covering the full range of composition, with some synthetic impurities and unreacted material. The synthesized olivine showed a linear increase in the unit cell dimension in proportion to the molar ratio of fayalite in the starting materials, and the diffraction intensity was consistent with that of natural olivine. However, iron-rich synthetic olivine samples tend to have a higher content of impurity, suggesting that not all synthetic olivine can be used as a standard material yet, and improvements in the synthesis process, such as using high purity starting materials and control of reaction time and temperature, are required.

• Journal of the Mineralogical Society of Korea
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• v.32 no.3
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• pp.163-172
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• 2019

A long core (RS15-LC48) was collected at a site in the continental rise between the Southern Ocean and the Ross Sea (Antarctica) during the 2015 Ross Sea Expedition. The mineralogical characteristics and the origin of clay minerals in marine sediments deposited during the Quaternary in the Ross Sea were determined by analyzing sedimentary facies, variations in grain size, sand fraction, mineralogy, clay mineral composition, illite crystallinity, and illite chemical index. Core sediments consisted mostly of sandy clay, silty clay, or ice rafted debris (IRD) and were divided into four sedimentary facies (units 1-4). The variations in grain size distribution and sand content with depth were very similar to the variations in magnetic susceptibility. Various minerals such as smectite, chlorite, illite, kaolinite, quartz, and plagioclase were detected throughout the core. The average clay mineral composition was dominated by illite (52.7 %) and smectite (27.7 %), with less abundant clay minerals of chlorite (11.0 %) and kaolinite (8.6 %). The IC and illite chemical index showed strong correlation trends with depth. The increase in illite and chlorite content during the glacial period, together with the IC and chemical index values, suggest that sediments were transported from the bedrocks of the Transantarctic Mountains. During the interglacial period, smectite may have been supplied by the surface current from Victoria Land, in the western Ross Sea. High values for IC and the illite chemical index also indicate relatively warm climate conditions during that period.

• Journal of the Korean GEO-environmental Society
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• v.17 no.5
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• pp.17-25
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• 2016

The rocks exposed on the surface undergo expedite weathering process due to the effects of climatic process, etc. and the weathering process changes the properties of minerals, thereby lowering the stability of rocks. Therefore, it is important to examine the composition of minerals in order to investigate the resistance of rocks against weathering, which is performed by weathering sensitivity analysis. And microscopic flaking test was performed for the bored samples in this study and the composition of minerals that are vulnerable to weathering was measured through mode analysis. The lithological and mineralogical weathering factors were evaluated through this process. Furthermore, the degree of progress of weathering was identified by quantitatively measuring the actual mineral composition of rocks through X-Ray diffraction analysis and identifying the secondary minerals through observation with a scanning electron microscope. This analyzing the weathering sensitivity was analyzed to be capable of determining appropriate indicators that can determine weather resistance and predicting the weathering grade using chemical weathering speed.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.4
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• pp.427-437
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• 2020

Manganese nodules, which are evaluated as potential metal resources, have been found in the Arctic Ocean as well as in the abyssal plains of the Pacific and Indian Oceans. Manganese nodules exhibit strong variations in the morphology, internal texture, chemical composition and mineralogy as they grow. The relationship between the texture and chemical elemental composition during the growth process is well documented, but the mineral composition variation during the growth process is not. Because the manganese oxide minerals in nodules are fine-grained and poorly crystalline, quantitative analysis for the mineral composition is challenging for the bulk nodule sample. This study investigated the internal texture and Mn-oxide mineral composition of manganese nodules obtained from the East Siberian Sea. Semi-quantitative analysis was attempted for three main Mn-oxide minerals constituting the manganese nodules (i.e., todorokite, buserite and birnessite) using the peak area ratio of X-ray diffraction analysis graphs. In the East Siberian Sea manganese nodules, birnessite is more abundant than buserite or todorokite, and no correlation is found between the mineral composition and the internal texture. Instead a correlation is found between the relative content of todorokite and the lamellae depth. The todorokite content tends to increase from the surface to the core of the nodules, which can be attributed to a recrystallization process or difference in the growth rate within the nodule. This study shows that semi-quantitative analysis of manganese oxide minerals using the peak area ratio is useful in the mineralogical study of manganese nodules.

• Economic and Environmental Geology
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• v.45 no.2
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• pp.157-167
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• 2012

This study aimed to interpret the provenance and firing temperature of pottery from Chipyeongdong site in Gwangju, Korea though mineralogical and geochemical methods and also investigated the post-depositional alteration of pottery in burial environments. It is also presumed that they were made of soils near the site because they have similar mineralogical composition and same geochemical evolution path. Based on the results of mineralogical analysis, the pottery samples are largely divided into 2 groups; $700^{\circ}C$ to $1,000^{\circ}C$ and 1,000 to $1,100^{\circ}C$. At some pottery fired at over $1,000^{\circ}C$, it is thought that the refinement of raw materials were processed to remove macrocrystalline fragments. However, it was found that phosphate in soil environments formed amorphous aggregates with Al and Fe within the pores and voids on pottery fired at the low temperature. It indicates the contamination of pottery after burial.