简单混合、AFC混合和花岗岩同位素数据解释

SIMPLE MIXING,AFC MIXING AND ISOTOPE DATA EXPLANATION OF GRANITOIDS

本文介绍Sr、Nd、O同位素体系的简单混合和AFC混合的区别和应用。前者产生于岩浆混合、同位素交换、幔源壳源岩石互层或混合物的熔融等情况下,后者代表幔源岩浆同化地壳围岩的过程。不同混合机制的辩认有助于了解花岗岩类岩石的形成过程。但仅当AFC过程发生在地壳浅部时才表现最显著。

Mixing Processes can be divided into two main types, two-end member simple mixing and assimi- lation coupled with fractional crystallization (AFC) -type mixing, based on Sr, Nd and Oisotopic system- atics. Generally, simple mixing is represented by magma mixing, isotope exchange or remelting of a mixture made of mantle-derived and crustal materials. The AFC mixing is represented by a process in which mantle-derived magma assimilates crustal country rock and crystallizes in the same time, which is most clearly shown when the process happens in the shallow level of the crust. It is important to distinguish different mixing machanisms in understanding petrogenesis of granitoids.