摘要
系统地分析了冲绳海槽酸性浮岩中玻璃质岩浆包裹体的岩石化学成分 ,探讨了包裹体的岩石化学成分特征及其在岩浆起源及结晶演化过程中的指示意义 ,并结合前期及前人工作讨论了冲绳海槽不同岩石类型之间的成因联系及演化关系。结果表明 ,斑晶结晶时岩浆熔体为钙碱性英安质或流纹质岩浆 ,是来自地幔的拉斑玄武质岩浆充分结晶分异作用的产物。尽管各斑晶矿物中玻璃质岩浆包裹体的化学成分有所差异 ,但根据包裹体的岩石化学成分特征可以断定包裹体所代表的岩浆具有同源性 ,其差异只是反映了岩浆结晶演化的不同阶段或不同矿物结晶期 ,为进一步详细研究浮岩岩浆的结晶演化过程提供了最直接的资料。对比冲绳海槽酸性浮岩与玄武岩等不同岩石类型的岩石化学特征 ,可以证明这些岩石类型之间存在着密切的成因联系 ,包括同源性与继承性 ,它们分别是岩浆作用不同阶段的产物。另外 ,包裹体的成分主要取决于包裹体所在斑晶矿物的种类与成分 ,分析中未发现岩石化学性质明显不同的岩浆包裹体共存的现象 ,也没有在中酸性矿物中发现基性玻璃质岩浆包裹体 。
Melt inclusions are the melts trapped by host crystals when they were formed. The microanalysis of melt inclusions is a powerful tool for estimating the compositions of melts from which the host cry stals grew. They can truly document the magmatic processes such as crystallizati on differentiation and magma mixing. The authors applied the microthermometry of melt inclusions to estimating the crystallization temperature and pressure of h ost crystals in pumices in the Okinawa Trough. To clearly reflect the compositio ns of initial melts and magmatic process, the chemical compositions of melt incl usions in acid pumice in the Okinawa Trough are systematically analyzed by the e lectron microprobe in this article. The results show that the melts from which t he pumices grew are calc-alkalic dacitic or rhyodacitic magmas. The composition s mainly depend on the compositions of host crystals. Although there are differenc es between the melt inclusion compositions, the correlations among them demonstr ates that the melts from which the host crystals grew are related in origin, and the differences reflect that they were formed at different evolving and crystal lizing stages. Compared the chemical compositions of the melt inclusions with al l kinds of whole rocks in the Okinawa Trough formed at different magma evolving stages, it can be found that these rocks are interrelated and inherited in genes i s. In addition, it is not found that the melt inclusions with distinct chemical features coexist in the same host crystals, and the basic melt inclusions are no t found in acidic host crystals, so there is no evidence to show the direct magm a mixing.
出处
《海洋与湖沼》
CAS
CSCD
北大核心
2001年第5期474-482,共9页
Oceanologia Et Limnologia Sinica
基金
国家自然科学基金重点资助项目 4 962 5 60 9
4 94 2 1 0 0 7号
山东省自然科学基金资助项目 Y2 0 0 0e0 6号。
