同源花岗岩谱系填图——内蒙古二连宝德尔石林花岗岩填图试点

    Pedigree mapping of cogenetic granitoids:A case study of Baoder Stone Forest granitic pluton in Erlian, Inner Mongolia

    • 摘要: 单元-超单元花岗岩谱系填图方法是以同源岩浆演化理论为指导思想建立发展的。该方法从20世纪80年代开始在中国推广和应用,然而,随着岩浆岩理论的不断发展及填图实践过程中遇到的问题,填图方法回归到早期的"岩性+时代"方法。在新的形势下,如何开展好新一轮的花岗岩填图工作,谱系填图是否仍具有适用性值得分析探讨。以中蒙边境地区出露的宝德尔石林花岗岩体填图试点成果为例,阐述岩浆岩填图试点方法的可行性。填图结果显示,该岩体为复式杂岩体,发育约160Ma和140~124Ma两期二长花岗岩,这两期二长花岗岩时代和岩石结构存在差别,野外的主要区别在于粒度。它们处于同一个区域性伸展背景,属于同源岩浆演化的产物。依据谱系划分方案,可以划分为晚侏罗世和早白垩世2个序列及5个单元,且可以进行区域对比。因此,基于岩浆演化规律,以解体岩体和进行岩石类型归并为精髓的谱系填图对于同源花岗岩仍是适用和必须的,但不可扩大化。

       

      Abstract: Unit and superunit mapping has been popularized in China after the development of the cogenetic magma from the 1980s. However, more and more problems cropped out in the mapping practice with the development of the magma theory, and the early stage mapping method of "litholiogy plus epoch" was used again. Whether the application of pedigree mapping in the new stage geological mapping is suitable or not is worth discussing. The Baoder Stone Forest granitic pluton on the border area of Mongolia and China was selected to perform mapping. It is shown that the rock types in this pluton are complicated, including~160Ma coarsemiddle grained porphyritic hornblende biotite monzogranite and 140~124Ma middle-fine grained monzogranite. The rock types are similar, but there are differences in the intrusive ages and mineral structures of these monzogranites, and the main difference is the grain size. They formed in the same regional extensional background by the evolution of the cogenetic granitic magma. They can be divided into two sequences of the Late Jurassic and the Early Cretaceous, as well as five units. Pedigree mapping is still applicable and necessary for the cogenetic granitoids with similar ages and homologous origin, but it must be carefully used and do not expand to practical mapping of all granitoids.

       

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