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    花岗岩类与大陆地壳生长初探——以中国典型造山带花岗岩类岩石的形成为例

    A preliminary study of the relationship between granitoids and the growth of continental crust: a case study of the formation of key orogen granitoids in China

    • 摘要: 提要:本文主要基于东昆仑造山带、秦岭造山带、兴蒙造山带、阿尔泰造山带、燕山造山带以及华南过铝花岗岩带等花岗岩类形成的研究成果,讨论中国大陆内几个造山带的花岗岩类形成与大陆地壳生长方式和过程,我们的初步认识是:软流圈(对流地幔)的热和物质向大陆的输入(input)是大陆地壳生长和再改造的根本。大陆地壳的形成演化和再改造(reworking)主要通过岩浆作用完成,岩浆的形成、运移和定位是大陆地壳生长的基本过程。幔源玄武质岩浆底侵(underplating) 于大陆地壳底部和内侵(intraplating)于地壳内部,是软流圈注入大陆的基本形式。造山带镁铁质下地壳的拆沉作用是致使陆壳总组成为中性火成岩(安山岩和闪长岩,或粗面安山岩和二长岩质的)的主要原因。收缩挤压构造作用使陆壳加厚达≥50 km,是诱发镁铁质下地壳拆沉作用的必需条件。火成岩构造组合及其时间序列是识别大陆地壳从软流圈地幔中分出,直至最终形成的过程的关键记录。

       

      Abstract: Abstract:Based on the achievements concerning the formation of granitoids in the East Kunlun orogenic belt, Qinling orogenic belt, Xingmeng orogenic belt, Altay orogenic belt, Yanshan orogenic belt and South China peraluminous granitoids, this paper has dealt with the formation of key orogenic zone granitoids in mainland China and the continental crust growth and reached some preliminary conclusions: the input of the asthenosphere(mantle convection)thermal materials to the mainland made up the foundation of the growth and reworking of the earth's crust. The formation, evolution and reworking of the continental crust mainly underwent magmatism, whose formation, migration and positioning made up the basic process of continental crust growth. Mantle-derived basaltic magma underplating on the bottom of the continental crust and intraplating within the crust constituted the basic form of the input of the asthenosphere to the mainland. Delamination of mafic orogenic belt in the lower crust was the key mechanism, which made the continental crust composition chemically intermediate (andesite and diorite, or trachyte andesite and monzonitic rock). The contraction extrusion tectonism thickened the continental crust to ≥50 km, which was the necessary prerequisite for inducing delamination of the mafic lower crust. The igneous tectonic assemblage and its time series seem to be the key to identifying the separation of the continental crust from the mantle asthenosphere until the eventual formation

       

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