• Title/Summary/Keyword: K-Ar연대

Search Result 48, Processing Time 0.069 seconds

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
    • /
    • v.10 no.3
    • /
    • pp.172-178
    • /
    • 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.

  • PDF

K-Ar ages of the hydrothermal clay deposits and the surrounding igneous rocks in southwest Korea (한국 남서부의 열수점토광상과 주변암에 대한 K-Ar 연대 측정)

  • Kim In Joon;Nagao Keisuke
    • The Journal of the Petrological Society of Korea
    • /
    • v.1 no.1
    • /
    • pp.58-70
    • /
    • 1992
  • From the K-Ar age determinations for the clay deposits and their surrounded rocks in southwest Korea, the ages of the ore formation in all clay deposits fall in very narrow range from 78.1 to 81.4 Ma. K-Ar ages of clay deposits are slightly younger than those of the Cretaceous volcanic rocks (Hwangsan Formation, 81.4 to 86.4 Ma) and are slightly older than those of the Cretaceous granitic rocks (77.1 to 81.5 Ma). These results indicate that clay deposits were formed with genetical relation to late Cretaceous felsic magmatism. Weolgagsan granite, which has been previously considered to be Cretaceous, is proved to be formed its age in Jurassic (140.9 and 144.8 Ma). The close relationships of K-Ar ages between the clay deposits and Cretaceous granitic rocks suggest that the clay deposits were formed during the hydrothermal alterations caused by the thermal effects (hydrothermal circulation) of the granitic intrusions rather than by the hydrothermal activities associated with volcanic activities.

  • PDF

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
    • /
    • v.52 no.5
    • /
    • pp.449-457
    • /
    • 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 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
    • /
    • v.23 no.1
    • /
    • pp.11-21
    • /
    • 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.

  • PDF

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
    • /
    • v.23 no.1
    • /
    • pp.23-34
    • /
    • 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.

  • PDF

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
    • /
    • v.53 no.6
    • /
    • pp.645-654
    • /
    • 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.

Geology of the Kualkulun in the Middle Kalimantan, Indonesia: II. Mineralogy and Geochemistry (인도네시아 중부 칼리만탄 쿠알라쿠룬 지역의 지질: II. 광물 및 지구화학)

  • Kim In-Joon;Lee Gyoo Ho;Cho Deung-Lyong;Lee Seung-Ryeol;Lee Sa-Ro
    • Economic and Environmental Geology
    • /
    • v.37 no.5
    • /
    • pp.459-475
    • /
    • 2004
  • The geology of the Kualakulun area in Middle Kalimantan, Indonesia comprises Permian to Carboniferous Pinoh Metamorphic Rocks and Cretaceous Sepauk Plutonics of the Sunda Shield, late Eocene Tanjung Formation, Oligocene Malasan Volcanics, Oligocene to early Miocene Sintang Intrusives and Quaternary alluvium. Sepauk Plutonic rocks are classified as the calc-alkaline series and the S-type granite. Sintang Intrusive rocks are basic-intermediate and intermediate rocks, and consists of basalt, basaltic andesite, basaltic trachyandesite and trachyandesite. The Malasan Volcanics are characterized by intermediate dacitic pyroclasticl and minor lavas and belong to the subalkaline (calc-alkaline and tholeiitic) series. The whole-rock K-Ar ages of the fine-grained biotite granites and medium-grained granitoids were determined to be 100.5-106.5 Ma and 91.9-102.6 Ma, respectively. The whole-rock K-Ar age of the diorite is 89.1 Ma. K-Ar ages of the Malasan Volcanics and Shintang intrusives show 31.5-36.8 Ma and 24.6-34.5 Ma, respectively, and correspond to the Tertiary time.