• Journal of the Mineralogical Society of Korea
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• v.31 no.3
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• pp.183-191
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• 2018

It is reported that Li-bearing minerals regarding as a promising battery industrial commodity occur in the Mogok metamorphic belt, Myanmar. Preliminary considerations on the mineralization of pegmatite occurrences within Mogok metamorphic belt such as Singu, Mogok and Momeik are as follows. In Singu area, lepidolite and rubellite occur together (Letpanhla No. 2 & 7 pegmatite) while rubellite only occur (Letpanhla No. 4 pegmatite). In Mogok area, lepidolite and rubellite occur together (Sakangyi pegmatite). In Momeik area, lepidolite and rubellite occur together (Pheyeou pegmatite) while rubellite only occur (Khetchel Ywar Thit pegmatite). In the future, it is estimated that it is necessary to implement the detailed exploration for the resource evaluation of lithium-bearing mineral targeted for the pegmatite of Mogok metamorphic belt.

• Journal of the Mineralogical Society of Korea
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• v.21 no.3
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• pp.261-269
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• 2008

A NYF-type (Nb-Y-Zr-F) Khaldzan-Buregtei pegmatite containing rare-earth metals occurs within alkali granitoid complex of the western Mongolia. The pegmatites are considered as differentiates of syenites and alkali feldpar granitic rocks, showing that their rare-earth element concentrations are enriched tens times higher than those from the adjacent alkali granitic rocks. It is suggested that econemic aspects of the pegmatites can be controlled by the magnitude of lateral and vertical extensions and local grade variation of REE-bearing pegmatites.

• Economic and Environmental Geology
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• v.46 no.5
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• pp.375-390
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• 2013

The Kenticha rare-element (Ta-Li-Nb-Be) mineralized zone is located in ophiolitic fold and thrust complex of southern Ethiopia and was firstly discovered by joint exploration program of Ethiopia-Soviet in 1980s. It includes Dermidama, Kilkele, Shuni Hill, Kenticha, and Bupo pegmatites from south to north. The Kenticha pegmatite intruded parallel to NS-striking serpentinite and talc-chlorite schist, and is exposed approximately 2 km length and 400-700 m width. The Kenticha pegmatite is internally zoned and subdivided into lower quartz-muscovite-albite granite, intermediate muscovite-quartz-albite-microcline pegmatite, and upper spodumene-quartz-albite pegmatite, based on their mineral assemblage. The major, trace elements (e.g., Rb, Li, Nb, Ta, and Ga), and element ratios (e.g., K/Rb, Nb/Ta, Mg/Li, and Al/Ga) suggest that the fractionation and solidification of pegmatite have progressed from the lower towards upper pegmatite. In contrast, unlike general magmatic fractionation, Mg/Li ratios of the Kenticha pegmatite tend to be increased towards the upper pegmatite. It may result from post-magmatic hydrothermal alteration and/or interaction with upper ultramafic rock. Rare-element mineralization in Kenticha pegmatite concentrates on the upper pegmatite, which contains up to 3.0 wt % $Li_2O$, 3,780 ppm Rb, 111 ppm Cs, 1,320 ppm Ta, and 332 ppm Nb. Ore minerals in Kenticha pegmatite mostly include tantalite, spodumene, and lepidolite, and tantalite has an association with coarser quartz-spodumene and relatively fine sacchroidal albite. The tantalite is classified into Mn-tantalite as a function of $Mn^*[Mn/(Mn+Fe)]$ and $Ta^*[Ta/(Ta+Nb)]$ values. Its compositions ($Mn^*$, $Ta^*$, and Nb/Ta) between coarse and fine tantalites are different and the former is strongly enriched in Ta and depleted in Nb compared to latter one. In conclusion, rare-element mineralization in the Kenticha pegmatite may has occurred in the latest stage of magmatic fractionation.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.2
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• pp.129-141
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• 2020

The Mogok metamorphic belt is a highland area mainly consisting of Archean crystalline rocks, where many ruby mines were distributed in the past, and jewelry has been identified in its alluvium as placer deposit. Minerals that are usually identified with ruby include spinel, garnet, and rubellite. The conglomerates that form the alluvium in which jewelry is found mainly consist of gneiss and clastic pegmatites. In Singu, Mogok, and Momeik areas, a number of pegmatites containing jewelry are distributed in the intrusions of Mogok metamorphic rocks, diorites, and granites. In Singu pegmatites, rubellite, goshenite, and blue and violet apatite occur as gems. In Momeik pegmatites, mushroom-type rubellite, petalite, hambergite, pollucite, and aquamarine can be found. In Mogok pegmatites, topaz, aquamarine, goshenite, and herderite occur are present.

• Economic and Environmental Geology
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• v.55 no.1
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• pp.77-95
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• 2022

The Gonamsan gabbroic complex in the Pocheon area, northwestern region of South Korea consists of a variety types of gabbroic rocks and associated Fe-Ti oxide deposits caused by magmatic differentiation. Post-magmatic intrusions (i.e., gabbroic pegmatite and pyroxene-apatite-zircon rocks) partly intruded into the gabbroic rocks. The gabbroic pegmatite occurs in monzodiorite and oxide gabbro of the complex, intimately and spatially associated with high-grade lenticular Fe-Ti oxide mineralization. The pegmatite can be subdivided into plagioclase-amphibole and pyroxene-olivine pegmatite, in which the contact surface is sharp. The plagioclase-amphibole pegmatite comprises plagioclase and amphibole, with lesser amount of pyroxene, ilmenite, sphene, apatite, and biotite. The pegmatite shows plagioclase-amphibole intergranular texture, in which the open space formed by large plagioclase laths (An_2-26Ab_72-98Or_0-2) are infilled by amphibole. The pyroxene-olivine pegmatite is dark gray to black in color and also contains magnetite, ilmenite, spinel, apatite, and calcite as a minor component. The pyroxene (En_35-36Fs_8-9Wo₅₅) and olivine (Fo_84-85Fa_15-16) partly show a poikilitic texture defined by smaller euhedral olivine enclosed by coarser clinopyroxene. Fe-Ti oxide minerals consist mainly of magnetite and ilmenite that are found interstitially to earlier formed silicates. Subsequently, they are encompassed by reaction rim (almost of amphibole and biotite) along the boundary with surrounding silicate minerals. Under the microscope, magnetite contains a lot of oxyexsolved ilmenite (trellis type) and spinel, and thereby is weakly enriched in magnetite-compatible elements such as Ti, Al, Mg, and V. The structure and textures at the contact zone as well as mineralogical disequilibrium between gabbroic pegmatite and the host gabbroic rocks suggest that the pegmatite may form as a result of accumulation from Fe-rich melt (or liquid) that occurred somewhere rather than in situ form from the host gabbroic rock during the magmatic differentiation. Consequently, the preliminary study suggests that further study on the post-magmatic activities can not only help us improve our understanding on magmatic fractionation but also provide critical information on Fe-Ti oxide mineralization in gabbroic rocks resulting from the magmatic differentiation.

• Journal of the Mineralogical Society of Korea
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• v.24 no.2
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• pp.133-143
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• 2011

In Mujoo area, the granitic pegmatites are developed in the granitic gneiss complex with Jurassic gneissic granites, where Nb-Ta mineralization were reported. Pegmatites are mainly composed of large crystals of quartz, feldspars of end-member orthoclase and albite, and muscovite. Nb-Ta minerals in study area are columbite (Nb > Ta) in composition. Chemistry of muscovites shows post-magmatic in origin and they are closely related with columbite. Large columbite, in pegmatites occurred with quartz and feldspars, while microcrystalline columbite is associated with muscovite. The Nb contents in large columbite are relatively higher than those in microcrystalline ones. Two pegmatites, 4~15 m in width and 120 m, 250 m in extension respective1y, are developed. Five drilling cores with total 600 m in length are finally obtained and revealed no possible potential for economic rare metals of Na-Ta deposits.

• Economic and Environmental Geology
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• v.21 no.2
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• pp.171-174
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• 1988

A muscovite and a sericite altered from plagioclase taken from the Sungyeong tin-bearing pegmatite near the Sangdong mine are dated by K-Ar method. The muscovite and the sericite yield $1546.94{\pm}29.4\;Ma$ and $187.80{\pm}4.19\;Ma$,respectively. The muscovite age can be assumed to become younger than the previously reported K-Ar muscovite ages of the pegmatites around this area, because radiogenic argon in the muscovite could be partially lost by the heat of later hydrothermal activities which caused the plagioclase to be sericitized in the Jurassic time (about 190 Ma).

• Economic and Environmental Geology
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• v.50 no.3
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• pp.181-193
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• 2017

Mn-Fe phosphate mineral complexes included within the pegmatite are observed at Jurassic Cheolwon two-mica granite in Gyeonggi Massif, South Korea. The genetic evolution between the Cheolwon two-mica granite and pegmatite, and various trend of Mn-Fe phosphate minerals is made by later magmatic, hydrothermal, and weathering process based on mineralogical, geochemical analysis. The Cheolwon two-mica granite is identified as S-type granite, considering its chemical composition (metaluminous ~ peraluminous), post-collisional environment, low magnetic susceptibility, and existence of biotite and muscovite. The K-Ar age (ca. 153 Ma) of pegmatite is well coincident with age of the Cheolwon two-mica granite ($151{\pm}4Ma$). It indicates that these two rocks are originated from the same magma. Pegmatite indicates the LCT geochemical signature, and was classified as muscovite-rare element class / Li subclass / beryl type / beryl-columbite-phosphate subtype pegmatite. The triplite $\{(Fe^{2+}{_{0.4}},Mn_{1.6})(PO_4)(F_{0.9})\}$ is dominant phosphates in later magmatic stage which partly altered to leucophosphite $\{KFe^{3+}{_2}(PO_4)_2OH{\cdot}2H_2O\}$ and jahnsite $\{(Fe^{3+}{_{0.7}},Mn_{2.3})(PO_4)_2OH{\cdot}4H_2O\}$ by hydrothermal alteration. In particular, near fractures, the triplite has been separatelty replaced by the phosphosiderite ($Fe^{3+}PO_4{\cdot}2H_2O$) and Mn-oxide minerals during weathering stage.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.3
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• pp.283-298
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• 2022

In this study, we investigated the mineral geochemistry of the albite-spodumene pegmatite, associated exogreisen, and wall rock from the Boam Li deposit, Wangpiri, Uljin, Gyeongsangbuk-do, South Korea. The paragenesis of the Boam Li deposit consists of two stages; the magmatic and endogreisen stages. In the magmatic stage, pegmatite dikes mainly composed of spodumene, albite, quartz, and K-feldspar intruded into the Janggun limestone formation. In the following endogreisen stage, the secondary fine-grained albite along with muscovite, apatite, beryl, CGM(columbite group mineral), microlite, and cassiterite were precipitated and partly replaced the magmatic stage minerals. Exogreisen composed of tourmaline, quartz, and muscovite develops along the contact between the pegmatite dike and wall rock. The Cs contents of beryl and muscovite and Ta/(Nb+Ta) ratio of CGM are higher in the endogreisen stage than the magmatic stage, suggesting the involvement of the more evolved melts in the greisenization than in the magmatic stage. Florine-rich and Cl-poor apatite infer that the parental magma is likely derived from metasedimentary rock (S-type granite). P₂O₅ contents of albite in the endogreisen stage are below the detection limit of EDS while those of albite in the magmatic stage are 0.28 wt.% on average. The lower P₂O₅ contents of the former albite can be attributed to apatite and microlite precipitation during the endogreisen stage. Calcium introduced from the adjacent Janggun formation may have induced apatite crystallization. The interaction between the pegmatite and Janggun limestone is consistent with the gradual increase in Ca and other divalent cations and decrease in Al from the core to the rim of tourmaline in the exogreisen.

• The Journal of the Petrological Society of Korea
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• v.24 no.2
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• pp.65-75
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• 2015

Around Harar in the northeastern part of the Ethiopia, the Precambrian granitic gneiss and gabbro bodies are developed with several pegmatites. The rock bodies in this area have been deformed by ductile and brittle deformations developing fold and ductile shear structure, and thrust and fault.