太平洋洋中脊火山玻璃主量元素地球化学特征

Geochemical characteristics of major elements in Pacific mid-ocean ridge volcanic glass

洋中脊火山玻璃代表地幔源区熔体成分,携带了岩浆作用和洋壳形成的大量信息。通过研究太平洋洋中脊火山玻璃的主量元素地球化学特征,探讨了岩浆作用过程的元素分配特征,结果表明：洋中脊火山玻璃的主量元素成分呈现规律性演化,从基性向中酸性演化过程中,Na_2O的含量从2%逐渐升高至6%,K_2O从〈1%逐渐升高至5%;而Ca O含量从10%~13%逐渐降低至1%,Fe O从9%~13%逐渐降低至3%,Al_2O_3从18%逐渐降低至13%。洋中脊火山玻璃中主量元素分配特征揭示了其分配的不均一性,这可能是受到宏观上地幔不均一性的影响;在同一洋中脊中的火山玻璃成分也存在不均一性,可能是岩浆作用过程中局部动力学机制差异引起的元素分配不均一。

The mid-ocean ridge volcanic glass is of mantle partial melting carrying lots of information on formation of oceanic crust and its magmatism. The major element geochemical characteristics of mid-ocean ridge glass from Pacific mid-ocean ridge system is studied,and the element distribution characters of magma is discussed in this paper. Results indicate that the major element composition of glass displays normal evolution,with Si O_2 increasing,the Na_2 O increasing from 2% to 6%,K_2 O increasing from 1% to 5%,but Ca O decreasing from10%- 13% to〈 1%,Fe O decreasing from 9%- 13% to 3%,and Al_2O_3 decreasing from 18% to 13% when Si O_2 increasing. The distribution pattern of major elements suggests the heterogeneity of magma,which was likely caused by mantle heterogeneity. Moreover,the glass from same mid-ocean ridge system also shows the composition heterogeneity,which is probably due to the locality geodynamic difference（ es） inducing from major element heterogeneous distribution.