摘要
南极菲尔德斯半岛岛弧火山岩,除个别明显受蚀变影响的样品外,大多数样品的δ^(18)O值变化范围为4.81-7.59‰,显示出其玄武岩浆为上地幔衍生岩浆,结晶分异起着主导的作用。在同一类型的岩石中,δ^(18)O值的差异与岩石的蚀变程度有关,δ^(18)O值随蚀变的增强而升高。
The island are volcanic rocks of Cenozoic era are widely distributed in Fildes Peninsula, Antarctica. This set of volcanic rocks is characterized by lower K-higher Al. Though they have some characters of tholeiitic series, however, they are essentially of calc-alkaline series.
The range of δ18O-values varies between 4.85 and 7.59 ‰ for most of samples of volcanic rocks in the area, showing that the basaltic magma is characterized by derived magma of the upper mantle. The range of variation indicates also that the fractional crystallization was of main effect in the evalutional process of magma from basalt to basaltic andesite, up td andesite series rocks. The δ18O-values raise with the intensification of alteration of rocks of the same type. The oxygen isotopic composition shows positive correlation with SiO2wt% and negative with MgO wt%.
The 87Sr/ 86Sr, 143Nd/ 144Nd and Eu / Eu * ratios, and the relations between δ18O-87Sr / 86Sr, ∈ Sr- ∈ Nd diagram aslo show that magma was derived from the upper mantle.
出处
《资源调查与环境》
1990年第1期54-66,共13页
Resources Survey & Environment
