下地壳的研究现状及展望
高山
摘要(Abstract)：
地球物理、地球化学及超深钻资料揭示出,下地壳无论在横向或垂向上都是极不均匀的,其中存在着众多的地震反射面、大型低角度逆掩断层及不同波速的层状构造.大陆地壳剖面由上至下显示出由绿片岩相→角闪岩相→麻粒岩相的变质分带现象.证实了Conrad面在横向上是不连续的及地球物理意义上的Moho面与岩石学和地球化学意义上的壳一幔界面之间存在着差异性.证实了下地壳中高导层的广泛存在.一般认为高导层主要是由自由的含水流体造成的.其成因的正确解释对于我们深入理解与岩石圈动力学有关的问题起着重要作用.关于下地壳的岩石类型,现已趋于认为主要由麻粒岩相岩石构成,可能还包括少量角闪岩相岩石.但关于下地壳的化学组成争议较大.已提出的成分模型范围可从基性—中性—酸性.同时还发现许多地区麻粒岩相岩石具有贫K、Th、U及其它LIL元素的特征.地球物理与同位素证据还表明,地壳的形成与演化只涉及上地幔.其结果是产生出贫化的上地幔,而下地幔仍处于原始状态.上、下地壳主要是通过壳内物质调整产生的.
关键词(KeyWords)：
基金项目(Foundation):
作者(Author): 高山
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