关于A型花岗岩判别过程中若干问题的讨论

    A discussion on how to discriminate A-type granite

    • 摘要: 自A型花岗岩提出(1979年)30年来,其内涵和外延相对于原始定义而言已发生了很大的变化。主要针对A型花岗岩的各种判别方法(尤其是判别图解)的有效性和局限性进行了讨论。这些判别方法对于A型花岗岩的判定并不总是奏效,所以在实践过程中不能过于依赖判别图解,否则就很容易得出错误的结论。 实际上,A型花岗岩最本质的特征很可能在于它是一种高温花岗岩(相对于I型和S型花岗岩),因此较高地温梯度下的各种地球动力学背景均有利于这一类型花岗岩的发育。

       

      Abstract: 30 years have passed since the term of “A-type granite” was firstly proposed, since then the recognition of A-type granite has changed a lot in terms of connotation and denotation compared to its original definition. This paper mainly focuses on the validities and limitations of various kinds of methods to identify A-type granite (especially geochemical discriminating diagrams), and we find that these are not always available. Thus, it should be prudential when they are applied to help discriminate the types of granite. Actually, the essence of A-type granite is very likely to be its relatively high temperature (cf. I- and S-type granite), regardless of the geodynamic settings.

       

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