【作者】 郑中；

【导师】 黄智龙；

【作者基本信息】 中国科学院研究生院（地球化学研究所） ， 地球化学， 2006， 硕士

【摘要】 峨眉山大陆溢流玄武岩省(ECFB)是中国国内唯一被国际学术界认可的大火成岩省，其独特的地球化学特征和完整的岩浆演化序列，日渐引起了地学界的关注。但总体研究程度还很低，随着研究的推进，需要探讨以下问题：(1)对比ELIP各岩区的地球化学特征；(2)探讨ELIP岩浆岩演化趋势及其地球化学特征；(3)探索更多地幔柱成因证据；(4)分析其化学储库特征及其地球动力学指纹。本文从岩石地球化学、PGE地球化学、同位素地球化学和动力地球化学等方面作了较系统的探讨。 本文除了对峨眉山玄武岩活动时段、S不饱和特征、三大趋势及其氧逸度、两大序列、高镁岩浆岩等作了探讨外，还建立了一些新的微量元素、PGE和热动力熔融模拟图解，系统对REE、蛛网配分模式图进行了孔隙度动力熔融模拟，通过Sr—Nd—Pb同位素混合模拟较细致的研究了ELIP源区DM与EM组份比例。首次对ECFB的PGE含最作了定量模拟，表明ELIP起源于0.3—1％的外核物质+50％亏损上地幔+50—49.7％下部原始地幔的混合源区。 模拟还表明ELIP西岩区熔融源区在Gt橄榄岩到Sp二辉橄榄岩地幔内(熔融压力3.0～1.8GPa)，部分熔融度2—8％，部分小于＜2％；中岩区熔融源区在Gt—Sp二辉橄榄岩地幔内(熔融压力3.0—2.5GPa)，熔融度主要＜2％；东岩区熔融源区在Gt—Sp二辉橄榄岩内(熔融压力2.9～2.4GPa)，部分熔融小于1％。笔者认为从西到东，上覆岩石圈从薄的特提斯大洋盖层变为厚的扬子克拉通盖层环境，这导致熔融压力／深度的增加而平均熔融度降低，这与根据EFB中的La／Yb比值推测的岩石圈下熔融面地图基本一致。 通过Sr-Nd同位素动力学模式探讨了ELIP的组份异质性，认为亏损的镁铁质大洋板片携带泛古陆上地壳陆源沉积物，俯冲脱水后长期(约1Ga)储积在热边界层，沉积物与亏损古洋壳发生交代混合形成富集地幔(EM2)，并被峨眉山地幔柱捕获夹带入头部，并在P／Tr冲击登陆于扬子克拉通西缘，从而产出含有UCC(或TS或GLOSS)组份特征的ECFB。更多还原

【Abstract】 Emeishan continental floor basalts province （ECFB ）is one and only LIP in China which is approbatory by international academe. It has peculiar geochemistry features and complete magma evolutionary series, so is widely paying attention to geologists, but the degree of study on it is quiet low. Recently, through studies on ELIP advancing, four important things will be needed to researched: （1） to compare the geochemistry features with each rocky areas of ELIP; （2） to study the evolutionary trend and geochemistry features respectively; （3） to research more evidences about the mantle plume dynamic origin of ELIP; （4） to analyze the geochemistry reserves and geodynamic fingerprints of ELIP magma. So this paper researched and discussed systematacially ELIP from rock-, PGE-, isotope- and dynamic- geochemistry etc.Except that analyzing the problem of ECFB/ELIP magma as follows: basalts magma activity period of time, S- unsaturated character, three evolutionary trends and it’s fO₂, two evolutionary series, high-Mg magmas etc., this paper established some new trace element-, PGE-, porosity dynamic melting modeling diagrams, furthermore made modeling with porosity-dynamic melting model on REE- and Spider Web-patterns. I have studied the proportions of DM and EM of ELIP magma by means of some Sr-Nd-Pb isotope models. The quantitative modeling in this paper show ELIP magma origined from the mixture source 0.3-l%Outer Core + 50%DM + 49.7% PM, which is imply Emeishan traps resulted from deep mantle plume.The modeling in this paper show that the melting source zone of western ELIP is within Gt peridotite mantle to Sp lherzolite mantle （the melting pressure is 3.0～ 1.8GPa） , the degree of partial melting is 2 — 8%, partially <2%; the one of Middle ELIP is within Gt-Sp lherzolite mantle （3.0—2.5GPa）, the degree of partial melting is mainly <2%; the one of Eastern ELIP is within Gt-Sp lherzolite mantle（ 2.9～2.4GPa）, the degree of partial melting is <1%. So I think that up-laying lithosphere become thick from western thin paleotethys oceanic lid to eastern thicker Yangtze craton lid, this setting change caused the melting pressure/depth increased and the average degree of partial melting reduced, which accord with melting surface map inferred更多还原