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    National Tsing Hua University Institutional Repository > 歷任校長 > 沈君山 (1994-1997) > 期刊論文 >  Rb-Sr Isotopic Study of Andesites from Lu-Tao, Lan-Hsu and Hsiao-Lan-Hsu, Eruption Ages and Isotopic Heterogeneity

    Please use this identifier to cite or link to this item: http://nthur.lib.nthu.edu.tw/dspace/handle/987654321/80842

    Title: Rb-Sr Isotopic Study of Andesites from Lu-Tao, Lan-Hsu and Hsiao-Lan-Hsu, Eruption Ages and Isotopic Heterogeneity
    Authors: C.Y. Lan;J.J. Shen;T. Typhoon
    教師: 沈君山
    Date: 1986
    Publisher: 中央研究院地球科學研究所
    Relation: Bulletin of the Institute of Earth Sciences, Academia Sinica, 中央研究院地球科學研究所, 第6卷, Dec. 1986, 第211-226頁
    Keywords: Andesites
    Rb-Sr isotopic study
    Eruption ages
    Isotopic heterogeneity
    Abstract: Rb-Sr radiometric ages and initial 87Sr/86Sr ratios have been measured for some volcanic samples erupted near the onset time of collision between the Luzon Arc and the Eurasian Piate at the islets of Lu-Tao, Lan-Hsu, and Hsiao-Lan-Hsu. Four Lu-Tao horn-blende-biotite andesites have ages 9.4, 2.9, 2.3, and 1.1 Ma based on data for coexisting biotite-plagioclase pairs. Two similar samples from Hsiao-Lan-Hsu show younger ages of ≦ 1.0 Ma. These ages are consistent with the K-Ar ages (Richard et al., 1986) but significantly expand the duration of dated magmatic activities. However, distinct isotopic heterogeneities observed in some of the coexisting amphibole separates render the oldest age in suspect. The younger ages imply that the magmatic activities lasted at least until two million years after the beginning of the collision, consistent with that inferred previously for the Coastal Range by paleontological and paleomagnetic means. The initial 87Sr/86Sr for the above six rocks range from 0.70478 to 0.70524 while a pyroxene andesite from Lan-Hsu yields a similar value of 0.70472. Such high ratios are unusual among intra-oceanic arcs. If no substantial exchange with seawater has occurred in the genesis of these andesites then the involvement of continental crustal material is implicated. Since these values are much higher than that reported for the Coastal Range in the northern section of the arc (< 0.7035, Shih, 1973), its Sr isotopic composition seems to be heterogeneous. There is no apparent correlation between the initial ratios and the eruption ages. We also describe our procedure for Rb-Sr isotopic analysis and demonstrate its capability.
    Relation Link: http://twgeoref.moeacgs.gov.tw/star/1986/19860438/EAB.PDF
    URI: http://nthur.lib.nthu.edu.tw/dspace/handle/987654321/80842
    Appears in Collections:[沈君山 (1994-1997)] 期刊論文
    [物理系] 期刊論文

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