【摘要】 大陆火山的复杂性是一个普遍关注的全球性问题,也是一个长期以来悬而未解决的地质问题。长白山火山位于亚洲板块东部的活动边缘,受到西太平洋俯冲的影响,新生代构造和火山活动活跃,为探讨大陆火山成因及其地幔源区特点提供了极佳的天然实验室。天池火山和龙岗火山是长白山地区两个重要的新生代火山区,其火山岩分布具有空间相邻、火山活动时代相似的特点,本文通过对基性火山岩的岩石学和地球化学对比研究,指出天池火山和龙岗火山具有明显的地球化学不均一性,包括微量元素不均一性和 Sr、Nd、Pb 同位素不均一性,来自于不同的地幔源区,天池火山和龙岗火山火山岩分布相邻,覆盖范围东西最大不过100多公里,因此这是典型的小尺度地幔地球化学不均一的特点。Sr、Nd 同位素特征显示龙岗火山来自于原始地幔,而天池火山来自于原始地幔和富集地幔混合源区。不相容元素 Nb、Ta 显示,天池火山 Ta 元素含量很低(主要落在0.17～2.15 ppm 的范围),具有明显的负 Ta 异常和明显的 Nb/Ta 分异(Nb/Ta=10～50,个别达到100以上),可能是板片部分熔融产物与金红石等副矿物反应的结果,暗示了西太平洋板块俯冲机制的影响;而龙岗火山没有明显 Nb、Ta 亏损或者分异。更多还原

【Abstract】 The complexity of continental volcanism is a global phenomenon,which has confused the geologists for a long time.The Changbaishan Volcanic Province(CVP),located at the active margin of the eastern Asia Plate with large scale volcanic and tectonic activity,provides a natural laboratory for exploring continental volcanisms and their mantle sources.Tianchi Volcanic field(TV)and Longgang Volcanic field(LV)are two important parts of the CVP.Comparison on petrology and geochemistry indicates that volcanic rocks from the TV and the LV came from different mantle sources,the LV came from primary mantle source,while the TV came from hybrid mantle sources of primary mantle and enriched mantle.Distance between LV and TVP is only about 40km,so the mantle source of CVP has small scale heterogeneity.Volcanic rocks of TV have strong negative Ta abnormity and significant fraetionation of Nb/Ta (Nb/Ta=10～50,some basahs even over 100).This fact,combined with the Sr,Nd and Pb isotopic data,indicates that the TV mantle source experienced reactions between melts from partial melting of the subducted slab and minor minerals,such as rntile,while LV has no geochemical signals of such contamination.更多还原