摘要
华北克拉通内部前寒武纪麻粒岩地体和新生代火山岩的麻粒岩捕虏体的研究表明,前寒武纪下地壳与现今下地壳的组成是不同的。下地壳的主要置换发生在中生代。这表明,华北克拉通中生代的构造重大转折,不仅使得盆山格局发生了变化,而且下地壳和上地幔的组成和结构也发生了变化。已发表的关于东部岩石圈减薄的机理有拆沉作用、幔柱构造等模式,均与造山带的演化相联系。本文注意到,华北克拉通最下部地壳的部分或大部都已被中生代的下地壳置换,它们不仅发生在克拉通边部,而且发生在克拉通内部。因此华北克拉通中生代的地幔上涌造成前寒武纪的下地壳被中生代的下地壳取代的作用,可称为华北克拉通中生代换底作用。中生代时期的华北克拉通下可能存在有规模的地幔柱,强烈的壳幔交换是换底作用的主要方式,热侵蚀和化学侵蚀的细节还不清楚。但可以推测这与造山带的演化没有直接关系,和造山带岩石圈根部的拆沉作用及一般意义的底侵作用不同。
The study of Precambrian granulite terrain in the North China craton and the granulite xenoliths in Cenozoic volcanic rocks shows that there are differences between the Precambrian lower crust and the present lower crust. This study further shows that the Mesozoic tectonic inversion in the North China craton not only causes changes in basin-range system but also changes in the composition and texture of the lower crust and upper mantle. There have been many models suggested, such as delamination,mantle-root structure etc, for the mechanism of thinning of the eastern lithosphere, all are related to the evolution of orogenic belt. We have noted in our work that most or all of the lowermost crust of the North China craton has been substituted by the Mesozoic lower crust. This has been occurred not only the edge of but also within the craton. Therefore, the processes of the North China craton mantle uplifting and the quick thinning of the Paleozoic lithosphere may be seen as the replacement of bottom crust in the North China craton. An upwelling mantle plume possibly existed during Jurrasic-Cretaceous, and strong crust-mantle interaction is a major way of replacement of bottom crust, while the details of thermal and chemical corrosion is still not clear. However, it may be inferred that this has no direct relationship with the evolution of orogenic belt and is different from the lithosphere delamination at the root of orogenic belt.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2002年第1期1-8,共8页
Acta Petrologica Sinica
基金
国家重点基础研究规划项目G1999043207
国家自然科学基金40072061
中国科学院重大创新项目KZCX1-07的研究成果
关键词
华北
中生代
下地壳
置换作用
Mesozoic
lower crust
replacement of bottom crust
North China
