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  • 館藏編號:NTUG010-T700087
  • 題名:岩石地球化學及地球的演化
  • 作者:孫賢鉥
  • 藏品形式:稿本
  • 尺寸:297X210(mm)
  • 簡述:第六講 島弧玄武岩, 板塊隱沒及大陸地殼的形成
  • 內容:

    11. Pb isotope compositions for island arcs built on the oceanic environment (Tonga-Kermadec, Mariana) indicate that involvement of the continental sediments decreases as island arc moves away into the oceanic environment. Some of the island arcs might not have any sediment component at all. However, the trace element over-abundances are not affected. These results imply that trace element over-abundances is not merely due to sediment subduction or crustal contamination. Contributon from the subducted oceanic crust, magma chamber contamination within the lithosphere might be important.
    12. Continuous melting of the subducted oceanic crust might be important to maintain the chemistry of the island arc volcanics derived from the mantle wedge above the subduction zone. Returning of the unconsumed lithosphere into the mantle convection system may have been important in creating the observed mantle chemical heterogeneity.