• Title/Summary/Keyword: K-Ar age

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New K-Ar dating system in Korea Basic Science Institute: Summary and Performance (한국기초과학지원연구원에 도입된 K-Ar 연대 측정시스템: 개요 및 성능)

  • 김정민
    • The Journal of the Petrological Society of Korea
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    • v.10 no.3
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    • pp.172-178
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    • 2001
  • K-Ar dating system of Korea Basic Science Institute (KBSI) was installed in 1997 and has been used since then. The system consists of high temperature graphite furnace, gas purification system, and mass spectrometer with data acquisition system. K-Ar age is determined by the measurement of the concentrations of Ar and K through isotope dilution method using $^{38}Ar$ as spike and flame spectroscopy, respectively. The accuracy and reliability for the K-Ar age are checked using the several K-Ar standard materials. Although the exact age determination for young samples of less than 1 Ma is hampered by small fluctuations of sensitivity and mass discrimination, the present system yields the reliable K-Ar age compared to the standard materials of Tertiary and Mesozoic age. The measurements for the SORI93 biotite with the recommended K-Ar age of $92.6\pm$0.6 Ma and Bern4M muscovite of $18.5\pm$0.6 Ma yield the reliable age of $92.1\pm$1.1 Ma and $17.8\pm$0.2 Ma, respectively.

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K-Ar Age of the Keumseongsan Volcanic Rocks and Mineralization in the Southeastern Part of Euiseong, Gyeongsangbuk-Do, Republic of Korea (경북·의성 동남부에 분포하는 금성산 화산암류의 K-Ar연대와 그주변의 광화시기)

  • Lee, Hyun Koo;Kim, Sang Jung;Yun, Hyesu;Choi, Wyi Chan;Song, Young Su;Itaya, Tetsumaru
    • Economic and Environmental Geology
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    • v.26 no.4
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    • pp.445-454
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    • 1993
  • The Keumseongsan caldera is composed of the Cretaceous sedimentary rocks of the Gyeonesang Supergroup, volcanic rocks of the Yucheon Group and basic dykes. The Keumseongsan caldera is formed by subsidence of volcanic rocks, and arc fault developed late. Also, synistral strike-slip fault ($N60^{\circ}W$) developed. Volcanic rocks belong to subalkaline rocks and calcalkaline magma series. First tuffaceous breccia erupted before 71.4 Ma and cavity of magma chamber caused subsidence, which formed arc fault. Basaltic lava erupted at 71.4 Ma and residual fluids containing Fe, As, Pb, Zn and Cu metal elements built the Ohto deposits, which are dated to be 70.5 Ma based on K-Ar age for sericite. Tuffaceous breccia and tuff erupted between 70.5 and 67 Ma. When volcanic eruption became weakened, cavity in site of magma chamber brought subsidence. Rhyolite intruded and erupted at 67 Ma, and intrusive rhyolite intruded according to arc faults, also. Hydrothermal fluids containing Fe, As, Pb, Zn, Cu, Sb, Bi, Au and Ag formed the Tohyeon deposits. K-Ar age for sericite from the Tohyeon mine gives 66.0 Ma. Results of field exploration, geochemical analyses of volcanic rocks support mineralization possibility by volcanism. Especially, age of volcanism and mineralization are well in coincidence with results of K-Ar age dating. By these results, Ohto Cu mineralization is regarded to be associcated with basaltic rocks, while Tohyeon Cu mineralization with rhyolitic rocks.

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An Engineering Geological Study of Moryang Fault for Tunnel Design (터널설계를 위한 모량단층의 지질공학적 연구)

  • 방기문;우상우
    • The Journal of Engineering Geology
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    • v.10 no.3
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    • pp.237-245
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    • 2000
  • This study was for characterizing the engineering geological properties of Moryang Fault, and providing the basic data for tunnel design. Land-sat image analysis, geologic surveys, resistivity prospecting and 3-dimensional analysis for results of resistivity prospecting, core boring, mineralogical identification and chemical analysis for the bedrock, and K-Ar age dating for fault clay were carried out for the study of Moryang Fault which is located at Duckhyunri Sangbukmyun Uljinkun Ulsan metropolis. As a result of the study, it was shown that strike/dip was N20-3$0^{\circ}C$E/70-9$0^{\circ}C$NW, width of fault ranged from 20 to 60m(maximum 80m), and depth was more than 50m. K-Ar age dating results of fault clay were 5,700$\pm$1.129Ma and 1,900$\pm$0.380Ma. Hydraulic fracturing test results showed the principal stress direction similar to the strike of Moryang Fault.

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Axial Seamount Basalts in P3 Segment of Phoenix Ridge, Drake Passage, Antarctica: K-Ar Age Determination and Geochemistry (남극 드레이크 해협 피닉스 해령 P3구역 축부 해저현무암: K-Ar 연대측정과 지구화학)

  • Lee, Jong-Ik;Hur, Soon-Do;Lee, Mi-Jung;Kim, Kyu-Jung;Nagao, Keisuke
    • Ocean and Polar Research
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    • v.25 no.1
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    • pp.107-118
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    • 2003
  • The axial seamount basalts in the P3 segment of the Phoenix Ridge were obtained from dredging and the K-Ar age determination and whole-rock geochemical analyses have been done for understanding their origin. The K-Ar ages for PRS basalts sampled from 1,000m below sea level are 2.6-2.2 Ma and those for PR3 basalts from 800m are 1.6-1.5 Ma. The younger ages towards the crest of the seamount indicate that this submarine volcano has been grown by central eruptions. The youngest age of about 1.5 Ma for PR3 basalts corresponds to the final eruption period of this volcano. The seamount basalts contain small amounts of normative quartz and olivine. They have transitional geochemical nature between alkaline- and subalkaline-series basalts. Trace and rare earth elements compositions of the seamount basalts are very similar to those of ocean island basalts (OIB), and indicate that this seamount has been formed by a hotspot activity, not in association with a seafloor spreading. The melting degree from the source has decreased with time, and finally the volcanic activity has stopped when the basaltic magma reached mild alkaline composition.

K-Ar Age and Geochemistry of Hydrothermal Alteration in the Barton Peninsula, King George Island, Antarctica (남극 킹조지섬 바톤반도의 열수변질작용에 관한 K-Ar 연대와 지구화학)

  • Hur, Soon-Do;Lee, Jong-Ik;Hwang, Jeong;Choe, Moon-Young
    • Ocean and Polar Research
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    • v.23 no.1
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    • pp.11-21
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    • 2001
  • K-Ar ages of the altered rocks from the Barton Peninsula are belows; altered tuffaceous andesite from southwestern part is 42 Ma, altered rocks contacted with quartz vein from southern part are 28 and 33 Ma, and advanced argillic altered andesite from northeastern part are 33 and 35 Ma. Those K-Ar ages are 10 My younger than granitic rocks of the Barton Peninsula. Hydothermal alteration of the Barton Peninsula was originated from mixing of magmatic water from parent magma of granitic rocks with meteoric water. The Al content in the hostrock is relatively constant during hydrothermal alteration, on the contrary the Mg content is in proportion to total alkali. The variation of total alkali and Mg contents in hydrothermal alteration indicates that those elements was washed out during hydrothermal alteration. The sequences of hydrothermal alteration of the Barton Peninsula is chloritization of amphiboles, sericitization of feldspars and kaolitization of sericite.

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Geochemistry and K-Ar Age of Alkali Basalts from Weno Island, Caroline Islands, Western Pacific (서태평양 캐롤라인군도 웨노섬 알칼리 현무암류의 지구화학 및 K-Ar 연대)

  • Lee, Jong-Ik;Hur, Soon-Do;Park, Byong-Kwon;Han, Sang-Jun
    • Ocean and Polar Research
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    • v.23 no.1
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    • pp.23-34
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    • 2001
  • Geochemical and Sr-Nd isotopic compositions and K-Ar ages are analyzed in volcanic rocks from Weno Island, Caroline Islands. Seven Weno lava samples of alkali basalt and basaltic trachyandesite are aphyric or sparsely phyric comprising olivine, plagioclase, and clinopyroxene phenocrysts. Whole-rock geochemical variation of Weno lavas reflects main fractional crystallization of olivine and Cr-spinel phenocrysts. Newly determined K-Ar ages of Weno lavas range from 6.7 to 11.3 Ma (late Miocene), indicating their formation during primary volcanic stage of Chuuk Islands. Trace element compositions of Weno lavas are very similar to those of typical ocean island basalts (OIBs), suggesting their formation during intra-plate mantle plume activity. The plume composition is isotopically very similar to that of Hawaiian hot spot. However, the age span of Chuuk volcanism is longer than that of the other individual volcanoes in the Pacific.

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Paleomagnetism and K-Ar Age of Volcanic Rocks from Guryongpo Area, Korea (구룡포에서 산출(産出)되는 화산암(火山岩)에 대(對)한 고지자기(古地磁氣)와 K-Ar연령(年齡))

  • Kim, Kwang Ho;Won, Jong Kwan;Matsuda, Jun-ichi;Nagao, Keisuke;Lee, Moon Won
    • Economic and Environmental Geology
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    • v.19 no.3
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    • pp.231-237
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    • 1986
  • Samples of porphyries, andesites, decites and sandstones were collected from 14 sites in order to study paleomagnetism and to determine K-Ar age in Guryongpo area. K-Ar age dating indicates that porphyries and volcanic rocks formed 41.7 and 22.7~19.4Ma, respectively. The mean direction of remanent magnetization for each site was generally well grouped after alternating field demagnetization. Both normal and reversed directions are present. The mean magnetic direction of the porphyries of Late Eocene and that of the volcanic rocks of Late Oligocene to Early Miocene have similar, easterly declinations. Overall magnetic direction is $Dm=43.8^{\circ}$, $Im=53.5^{\circ}$, ${\alpha}95=12.2^{\circ}$. the reliability of the observed paleomagnetic directions is ascertained by the presence of normal and reversed polarities. This is also conformed by the similarity of the declinations of the normal and reversed polarities. Observed easterly declinations in this area are attributed to local clockwise rotation of the land mass by approximately 40~50 degrees since early Miocene.

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Reactivated Timings of the Yangsan Fault in the Yeonghae area based on the Mineralogical Characteristics of Fault Clays (단층암 점토광물 특성에 기초한 영해지역 양산단층의 단층활동연대 결정)

  • Hong, Seongsik;Sim, Ho;Choi, Sung-Ja;Song, Yungoo
    • Economic and Environmental Geology
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    • v.53 no.6
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    • pp.645-654
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    • 2020
  • We present the K-Ar age dating results of <0.1㎛ fraction of the selected fault rocks from the Yangsan fault in the Yeonghae area. Based on the mineralogical characterization, the <0.1㎛ fractions were mostly composed of 1Md illite polytype, or I-S interstratified mineral, which should be formed by fault activation. Therefore, we determined the timings of fault activation events by analyzing K-Ar age-dating for the <0.1㎛ fractions. Accordingly, the activation timings of Yangsan Fault in the Yeonghae area were determined as 45.5±1.1 Ma, 50.9±1.2 Ma, 58.2±1.3 Ma, 60.8±1.4 Ma, 65.3±1.6 Ma, 66.8±1.5 Ma, 67.1±1.5 Ma, and 75.1±1.7 Ma. These results indicate that at least 5-times of major fault events occurred in the Yangsan fault from late Mesozoic to Cenozoic Era. In the outcrop, age dating results tend to be younger age from the location of the oldest sample(75.1±1.7 Ma) toward to the both sides. From the results, it suggests that the fault activation extends from the location of oldest age saple to both sides. This geochronological research of the multiple fault activation ages for the Yangsan Fault will provide crucial information for establishing the tectonic evolution model in the southeastern part of the Korean Peninsula.

K-Ar Age-dating Results of Some Major Faults in the Gyeongsang Basin: Spatio-temporal Variability of Fault Activations during the Cenozoic Era (경상분지 내 주요단층의 K-Ar 연대: 신생대 단층활동의 시·공간적 특성)

  • Song, Yungoo;Sim, Ho;Hong, Seongsik;Son, Moon
    • Economic and Environmental Geology
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    • v.52 no.5
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    • pp.449-457
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    • 2019
  • We present the K-Ar age-dating results of the bulk and the less than $0.1{\mu}m$ fraction of the fault gouges collected from some major faults in the Gyeongsang basin. We try to determine the timings of fault activation based on the mineralogical characteristics, and to interpret the spatio-temporal variability of the major fault events during the Cenozoic Era by considering together with the previous results. We propose at least the 3-times of major fault events at about 50 Ma, and just after 30 Ma and 20 Ma in the Gyeongsang basin, which were inferred from the combined approach of the K-Ar ages and the clay mineralogy of the bulk fault gouges and the <$0.1{\mu}m$ fractions. The fault activation timings of the Yangsan fault tend to be younger in the northern part than in the southern part. In particular, the inferred fault events just after 30 Ma and 20 Ma are mainly detected in the Ocheon fault and the related faults, and the fault in the Gyeongju area. The fault activation timings of the major faults can be revised accurately by using illite-age-analysis(IAA) method. These geochronological determinations of the multiple events of the major faults in the Gyeongsang basin are crucial to establish the tectonic evolution in the southeastern part of the Korean Peninsula during the Cenozoic Era.

K-Ar Age Detwermination of a Lava Stalagmite in Manjang Cave Jeju Island Korea

  • Okada, Toshinori;Itaya, Tetsumaru;Sawa, Isao;Hong, Shi-Hwan
    • Journal of the speleological society of Korea
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    • v.42 no.2
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    • pp.17-28
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    • 1995
  • THE K-AR METHOD of age determination is commonly used to date rocks from Pleistocene volcanoes in Japan (e.g. Kaneoka et al. 1980, Itaya et al. 1984, Shimizu et al. 1988, Itaya et al. 1989). However. there are still many problems with K-Ar dating of the young volcanic rocks, as reviewed by Itaya and Nagao (1988).(omitted)

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