汉诺坝玄武岩及幔源包体对大陆地幔不均一性的指示

The heterogeneity of continental mantle:A perspective from the Hannuoba basalts and mantle xenoliths

了解大陆地幔的不均一性对于理解地壳成分再循环、壳-幔相互作用等过程至关重要。本文通过对华北克拉通北缘汉诺坝地区来自不同地幔深度幔源岩石(玄武岩及橄榄岩和辉石岩包体)的研究进行综述,探讨了地幔在垂向上成分的不均一性特征。汉诺坝玄武岩的研究揭示了汉诺坝地区软流圈顶部存在再循环的碳酸盐化榴辉岩以及岩石圈底部具有富集的古老洋壳和沉积物成分。另外,玄武岩携带的橄榄岩和多类型辉石岩包体记录了不同来源(蚀变洋壳、沉积碳酸盐岩、碎屑沉积物、拆沉下地壳、软流圈)且不同成分(硅酸盐、碳酸盐)的熔/流体活动。富集地壳来源的熔/流体加入明显影响了汉诺坝地区陆下地幔成分的均质性,使得陆下地幔在微米至千米尺度存在明显的成分不均一特征。汉诺坝地区陆下地幔不均一性的认识为了解地壳物质再循环提供了绝佳的窗口。

Understanding the heterogeneity of continental mantle is crucial for studying geological processes such as crustal component recycling and crust-mantle interaction.This study reviews the research of mantle-derived rocks(basalts,peridotites,pyroxenites)from different mantle depths beneath the Hannuoba region of the northern margin of the North China Craton,to investigate the continental mantle heterogeneity in the vertical direction.The study of Hannuoba basalts revealed the presence of recycled carbonated eclogites at the top of asthenosphere mantle and enriched ancient oceanic crust and sedimentary components at the bottom of lithosphere mantle beneath the Hannuoba region.Additionally,the peridotite and pyroxenite xenoliths carried by host basalts record multi-stage melt/fluid activities of different sources(altered oceanic crust,sedimentary carbonates,clastic sediments,delaminated lower continental crust,asthenosphere)and different compositions(silicate and carbonate).The addition of melt/fluid from enriched crustal materials significantly affected the homogeneity of sub-continental mantle beneath the Hannuoba region,and then sub-continental mantle displays chemical heterogeneity at the scale from micrometre to kilometre.The understanding of sub-continental mantle heterogeneity beneath the Hannuoba region provides an excellent window for studying crustal materials recycling.