| 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,因此可以推断基本不存在不同性质的岩浆之间的直接混合作用。 |
| 关键词: 岩浆包裹体 岩石化学 酸性浮岩 冲绳海槽 |
| DOI： |
| 分类号: |
| 基金项目:国家自然科学基金重点资助项目49625609、49421007号;山东省自然科学基金资助项目Y2000e06号 |
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| THE PETROCHEMICAL FEATURE OF MELT INCLUSION IN ACID PUMICE IN THE OKINAWA TROUGH |
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YU Zeng-Hui, ZHAI Shi-Kui, ZHAO Guang-Tao
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Department of Marine Geosciences, Ocean University of Qingdao, Qingdao, 266003
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| Abstract: |
| 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 crystals grew. They can truly document the magmatic processes such as crystallization differentiation and magma mixing. The authors applied the microthermometry of melt inclusions to estimating the crystallization temperature and pressure of host crystals in pumices in the Okinawa Trough. To clearly reflect the compositions of initial melts and magmatic process, the chemical compositions of melt inclusions in acid pumice in the Okinawa Trough are systematically analyzed by the electron microprobe in this article. The results show that the melts from which the pumices grew are calc-alkalic dacitic or rhyodacitic magmas. The compositions mainly depend on the compositions of host crystals. Although there are differences between the melt inclusion compositions, the correlations among them demonstrates 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 crystallizing stages. Compared the chemical compositions of the melt inclusions with all 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 genesis. 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 not found in acidic host crystals, so there is no evidence to show the direct magma mixing. |
| Key words: Melt inclusion, Petrochemistry, Acid pumice, Okinawa Trough |
