• Title/Summary/Keyword: Mica

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Occurrence and Chemical Composition of Chlorite and White Mica from Drilling Core (No. 04-1) at Gubong Au-Ag Deposit Area, Republic of Korea (구봉 금-은 광상일대 시추코아(04-1)에서 산출되는 녹니석과 백색운모의 산상 및 화학조성)

  • Bong Chul Yoo
    • Korean Journal of Mineralogy and Petrology
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    • v.36 no.4
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    • pp.273-288
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    • 2023
  • The Gubong Au-Ag deposit, which has been one of the largest deposits (Unsan, Daeyudong, Kwangyang) in Korea, consists of eight lens-shaped quartz veins (a mix of orogenic-type and intrusion-related types) that filled fractures along fault zones within Precambrian metasedimentary rock. Korea Mining Promotion Corporation found a quartz vein (referred to as the No. 6 vein with a grade of 27.9 g/t Au and a width of 0.9 m) at a depth of -728 ML by drilling (No. 90-12) conducted in 1989. Korea Mining Promotion Corporation conducted drilling (No. 04-1) in 2004 to investigate the redevelopment's possibility of the No. 6 vein. The author studied the occurrence and chemical composition of chlorite and white mica using wallrock, wallrock alteration and quartz vein samples collected from the No. 04-1 drilling core in 2004. The alteration of studied samples occurs chloritization, sericitization, silicification and pyritization. Chlorite and white mica from mineralized zone at a depth of -275 ML occur with quartz, K-feldspar, calcite, rutile and pyrite in wallrock alteration zone and quartz vein. Chlorite and white mica from ore vein (No. 6 vein) at a depth of -779 ML occur with quartz, calcite, apatite, zircon, rutile, ilmenite, pyrrhotite and pyrite in wallrock alteration zone and quartz vein. Chlorite from a depth of -779 ML has a higher content of Al and Mg elements and a lower content of Si and Fe elements than chlorite from a depth of -275 ML. Also, Chlorites from a depth of -275 ML and -779 ML have higher content of Si element than theoretical chlorite. Compositional variation in chlorite from a depth of -275 ML was mainly caused by phengitic or Tschermark substitution [Al3+,VI + Al3+,IV <-> (Fe2+ or Mg2+)VI + (Si4+)IV], but compositional variation from a depth of -779 ML was mainly caused by octahedral Fe2+ <-> Mg2+ (Mn2+) substitution. The interlayer cation site occupancy (K+Na+Ca+Ba+Sr = 0.76~0.82 apfu, 0.72~0.91 apfu) of white mica from a depth of -275 ML and -779 ML have lower contents than theoretical dioctahedral micas, but octahedral site occupancy (Fe+Mg+Mn+Ti+Cr+V+Ni = 2.09~2.13 apfu, 2.06~2.14 apfu) have higher contents than theoretical dioctahedral micas. Compositional variation in white mica from a depth of -275 ML was caused by phengitic or Tschermark substitution [(Al3+)VI + (Al3+)IV <-> (Fe2+ or Mg2+)VI + (Si4+)IV], illitic substitution and direct (Fe3+)VI <-> (Al3+)VI substitution. But, compositional variation in white mica from a depth of -779 ML was caused by phengitic or Tschermark substitution [(Al3+)VI + (Al3+)IV <-> (Fe2+ or Mg2+)VI + (Si4+)IV] and direct (Fe3+)VI <-> (Al3+)VI substitution.

Geochronology and Petrochemistry of Foliated Granites between Damyang and Jinan (담양(潭陽)-진안(鎭安)사이에 분포(分布)하는 엽리상화강암류(葉理狀花崗岩類)에 대(對)한 지질시대(地質時代)와 성인(成因)에 관(關)한 연구(硏究))

  • Kim, Cheong Bin;Kim, Yong Jun
    • Economic and Environmental Geology
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    • v.23 no.2
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    • pp.233-244
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    • 1990
  • Plutons of Damyang-Jinan area consist of gray feldspar granite gneiss, biotite granite gneiss, foliated granites, Namweon granites, gabbro, biotite granite and Ogangri granite in term of mineralogical, texture and field evidence. From Isotope data of study area, chronological order of the Plutons are the Pre-cambrian gray feldspar granite gneiss(Ar39-Ar40, hornblende, $1998.4{\pm}8.3Ma$), middle to late Triassic Daegang foliated granite(Rb/Sr, whole rock, $288{\pm}4Ma$), foliated hornblende biotite granodiorite(K/Ar, hornblende, $198.7{\pm}9.9Ma$), Sunchang foliated granodiorite(Rb/Sr, whole rock, $222{\pm}4Ma$), foliated two mica granite, Samori foliated granite and Namweon granite(Rb/Sr, whole rock, $211{\pm}3Ma$: K/Ar, hornblende, $203{\pm}10.2Ma$), middle Jurassic Gabbro(K/Ar, hornblende, $180.7{\pm}9MA$) and biotite granite, and Cretaceous Ogangri granite. According to variations diagrams of $Al_2O_3$ versus normative PI(100 An)/(Ab+An), Daegang foliated granite is plotted on tholeiitic series, and other foliated granites on calc alkaline rock series which are consider to be formed by magmatism at continental margin and island arc region. And alkalinity versus $SiO_2$ shows that Daegang folited granite and Samori foliated granite are correspond to alkaline region, foliated hornblende biotite granodiorite and Sunchang foliated granodiorite to calc alkaline region, and foliated two mica granite to both regions. According to ACF diagrams, Daegang and Samori foliated granites are plotted on S-type. Foliated hornblende biotite granodiorite and Sunchang foliated granodiorite on I-type, and foliated two mica granite on both type. Foliated granites are a series of differentiated products from cogenetic magma, and effected under ductile sheared zone. Characteristic foliation of foliated granites are considered to be generated by dextral strike slip faulting and ductile shearing.

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Mechanical and Thermal Properties of Epoxy/Organically Modified Mica Type Silicate (OMTS) Nanocomposites (에폭시/유기치환된 실리케이트 나노복합체의 기계적 및 열적 성질에 관한 연구)

  • 노진영;김진환
    • Polymer(Korea)
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    • v.25 no.5
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    • pp.691-698
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    • 2001
  • Nanocomposites based on epoxy acid nanoclay were prepared employing organically modified mica type silicate (OMTS), diglycidyl ether of bisphenol A (DGEBA) type epoxy. curing agent (dicyandiamide; DICY), and catalyst (benzyl dimethyl amine; BDMA). Both melt mixing and solution mixing were und for the sample preparation and structural developments with curing reaction were analyzed using X-ray diffractometer (XRD) and small angle X-ray scattering (SAXS). Because of the different curing rate between extra-gallery and intra-gallery reactions of epoxy mixtures, only intercalated structure was observed for the sample prepared by melt mixing while fully exfoliated structure was observed for the sample prepared by solution mixing. Mechanical properties of exfoliated epoxy nanocomposite were investigated using a dynamic mechanical analyzer (DMA). The dynamic storage modulus of the nanocomposite in both glass and rubbery plateau regions were increased with increasing OMTS contents, but glass transition temperatures ($T_g$) remained unchanged. Thermal properties of epoxy nanocomposite were investigated using thermogravimetric (TGA) and limit oxygen index (LOI) methods. Thermal decomposition onset points and LOI values were increased with increasing OMTS contents due to barrier effects of OMTS sheets.

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Laboratory Weathering Experiment on Mica and Feldspar and Their Mineralogical Characteristics (운모와 장석의 실내 풍화실험 및 광물학적 특성)

  • Lee, Seung-Yeop;Kim, Soo-Jin;Cho, Won-Jin
    • Journal of the Mineralogical Society of Korea
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    • v.19 no.2 s.48
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    • pp.63-69
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    • 2006
  • When rocks are exposed to the near surface environment, they are broken down due to several factors such as physical and chemical weathering during the geologic time. The feldspar and mica, which are the main rock-forming minerals, are easily broken down relative to other minerals. In order to reproduce some weathered minerals similar to the ones exist in natural weathered granite, there was an experimental interaction between fresh minerals and acidic solution. In low pH condition, biotite initially dissolved and its surface structure broke down, whereas plagioclase dissolved and had a needle-shaped dissolved morphology with some precipitates composed of Al element. The minerals were deeply dissolved in a strong acid condition, showing the prominent dissolved structure. Some etch pits and dissolved textures developed on the natural mineral surfaces are similarly found in our experiment, suggesting the development of mineral dissolution and weathering texture by the influence of the mineral's intrinsic nature.

Geochemistry of Granitoids in the Kwangyang-Seungju Area (광양-승주지역에 분포하는 화강암류의 암석화학)

  • Lee, Chang Shin;Kim, Yong Jun;Park, Cheon Young;Lee, Chang Ju
    • Economic and Environmental Geology
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    • v.25 no.1
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    • pp.51-60
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    • 1992
  • The pluton rocks in Kwangyang-Seungju area consist of two mica granite, hornblende diorite, Rimunri quartz diorite, grnodiorite porphyry and granophyre. The analysis of the geochronological data by the methods of K-Ar for the hornblende from Rimunri quartz diorite and hornblende diorite show that the ages are found to be $86{\pm}3.3$ Ma and $108{\pm}4$ Ma, respectively, and K-Ar age for chlorite from the altered two mica granite which intruded by the hornblende diorite of the Bonjeong mine shows $108{\pm}4$ Ma; K-Ar age for sericite from the greisenized hornblende diorite, which is closely associated with the Bonjeong ore deposits, is dated as $94.2{\pm}2.4$ Ma. They correspond to the igneous activity of the Bulgugsa Disturbance periods in the area. In chemical feature for oxides versus silica and AFM triagular diagrams of the pluton rocks in the study area, there is a suggestion of the possibility that these rock facies area a Calc-alkali series of differentiated products by low-pressure crystal fractionation processes in $SiO_2$-undersaturated suites. Compared with hornblende diorite, andesite and granodiorite porphyry, two mica granite, Rimunri quartz diorite and granophyre exhibit a wider range of normalized REE abundance and negative Eu anomalies. Such anomalies imply more extensive feldspar fractionation during crystallization. The Rimunri quartz diorite and hornblende diorite occurring in the margin of four mines(Bonjeong, Okdong, Soungchei and Saungyeul) of this area have high contents of As, Sb, Cu and Zn which have been shown as the best indicators in hypogene gold deposits and low contents of Ba, Cr served as more sensitive indicators. And the granitoids are regarded as the rocks associated with gold and sulfide mineralization of the area.

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Characterization of Poly(vinyl alcohol) Nanocomposite Films with Various Clays (다양한 점토를 이용한 폴리(비닐 알코올) 나노 복합체 필름의 특성 연구)

  • Ham, Miran;Kim, Jeong-Cheol;Chang, Jin-Hae
    • Polymer(Korea)
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    • v.37 no.2
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    • pp.225-231
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    • 2013
  • Poly(vinyl alcohol) (PVA) hybrid films containing 5 wt% pristine clay mineral were synthesized in the water solution. The various PVA hybrid films were synthesized from structurally different pristine clays: saponite (SPT), montmorillonite (MMT), hectorite (SWN), hydrophilic bentonite (PGV), and mica (Mica). The thermo-optical properties and morphologies of the PVA hybrid films were evaluated with various pristine clays. The nanostructure of the hybrid films was observed using transmission electron microscopy, which showed that the clay layers were well dispersed into the matrix polymer, although some clusters or agglomerated particles were also detected. The addition of pristine clay was more effective with regard to improving the thermal properties and gas barrier characteristics, whereas the optical transparency of the PVA hybrid films deteriorated with pristine clay.