中国东部壳-幔、岩石圈-软流圈之间的相互作用带:特征及转换时限

Zones of crust-mantle and lithosphere-asthenosphere interaction in eastern China:Characteristics and timing of transformation

中国东部中—新生代,下部岩石圈存在壳与幔、岩石圈与软流圈两个相互作用带,它们是重要的岩浆源区,在层圈相互作用中,热和物质的交换及其动力学过程是引起中、新生代岩石圈内部层圈间的厚度调整、岩石圈不均匀减薄以及区域构造-岩浆-成矿作用的重要机理。大陆内部的壳-幔作用有3种类型:地幔来源的底侵熔体与下地壳的作用;下地壳拆沉进入弱化(weakening)了的岩石圈地幔二者发生的作用以及陆-陆碰撞深俯冲带的壳-幔相互作用。它们形成的火山岩组合有一定的差别,但源区都含有地壳组分。岩石圈-软流圈的作用带也是重要的岩浆源区,源区是以软流圈地幔为主,基本不含地壳组分。东部岩石圈的减薄时间大体与出现大规模软流圈来源的玄武岩喷发的时间一致,也与上述两类层圈作用转换的时间一致,大约在100Ma以后。

There exist Meso-Cenozoic crust-mantle and lithosphere-asthenosphere interaction zones in the lower lithosphere beneath eastern China, which are also two important magma sources. The heat and material exchanges between crust and mantle and between lithosphere and asthenosphere in the interactions and their dynamic processes are the critical mechanisms for thickness readjustment in the interior of the Meso-Cenozoic lithosphere, lithospheric uneven thinning and tectono-magmatic mineralization. Three types of crust-mantle interaction can be recognized in the interior of the continent; they are the interactions between mantle-derived underplating melts and the lower crust, between the delaminated lower crust and weakening lithospheric mantle and between the deeply subducted crust and mantle wedge in the continental-continental collision zone. Although the volcanic rock associations formed by the three types of crust-mantle interaction are somewhat different, their magma sources all contain crustal components. The lithosphere-asthenosphere interaction zone is also a major component of the magma source, which consists predominantly of asthenospheric mantle and in the main contains no crustal component. Lithospheric thinning was largely coeval with large-scale asthenospherederived basalt eruption and also with transformation of the two types of interaction. It occurred about 100 Ma later.