华北克拉通破坏的物理、化学过程:地幔橄榄岩证据

本文对比了华北东部不同时代、不同位置捕虏体/地质体橄榄岩的地幔属性,讨论了华北克拉通破坏的物理、化学过程。结果表明,拆沉作用不能很好地解释古老难熔、过渡型和新生饱满地幔并存的事实;单纯的熔体-橄榄岩相互作用也不易解释中、新生代岩石圈巨大减薄和新生饱满地幔Cpx中LREE亏损现象,即具复杂演化历史的克拉通地幔向演化历史简单的"大洋型"岩石圈的转换。华北东部克拉通破坏作用包括地幔伸展、熔-岩作用、侵蚀置换等复杂的物理、化学过程。岩石圈先大幅减薄、后小幅增厚实现了最终的地幔置换和岩石圈整体减薄过程。喷发时代为100 Ma的阜新玄武岩所捕获的橄榄岩主体是饱满的,说明华北东部部分地区在此之前有过地幔置换作用。

Physical and Chemical Processes of the Destruction of the North China Craton: Evidences from Peridotite

This paper has compared the subcontinental lithospheric mantle(SCLM) properties reflected by xenolith and terrane peridotites occurred in different times and locations in the eastern part of the North China Craton,and discussed the physical and chemical processes of the destruction of the North China Craton.The the lithospheric delamination is hard to interpret the coexistence of the SCLM with refractory,transitional and fertile affinity beneath the same area.Pure peridotite-melt interaction is also difficult to interpret the thinning of the Mesozoic and Cenozoic lithospheric mantle and the LREE depletion of clinopyroxene in Cenozoic lithospheric mantle,which means the transitions of the cratonic mantle (with complicated evolution history) to the oceanic lithosphere(with simple evolution history).The destruction of the eastern North China Craton includes various complicated physical and chemical processes of mantle extension,melt-rock interaction,metasomatism and replacement.The earlier large scale lithosphere thinning and the later small scale lithosphere thickening resulted in the mantle replacement and the total lithosphere thinning of the North China Craton lithosphere.The fertile peridotite xenoliths trapped in the 100 Ma Fuxian basalts indicate that the early mantle replacement beneath the eastern North China Craton occurred locally before 100 Ma.