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华北陆块岩石圈经历了中-新生代强烈的岩石圈减薄和随后的地幔增生作用.来自山东莒南和青岛晚白垩世玄武岩中橄榄石捕虏晶和地幔包体橄榄石的原位氧同位素分析结果显示,它们总体上具有低δ18O的特征,其中莒南橄榄石捕虏晶和地幔包体橄榄石的Fo=87.5～89.8,δ18O=4.1‰～5.2‰,平均值为4.8‰;青岛玄武岩中地幔包体的橄榄石Fo=89.0～89.9,δ18O=4.1‰～5.2‰,平均值为4.8‰.前人的矿物学和地球化学研究资料显示,这些橄榄岩包体具有饱满的岩石化学特征和亏损的Sr-Nd同位素组成,类似于亏损的MORB型地幔.因此,这类低δ18O的地幔橄榄岩可能为经历了俯冲板片高温流体或熔体交代的地幔楔.结合近年来报道的新生代低δ18O玄武岩和代表残留洋壳的低δ18O石榴石辉石岩包体,我们认为华北大陆岩石圈中-新生代地幔演化过程中存在俯冲大洋地壳的贡献.
The lithosphere of the North China terrane experienced intense Mesozoic-Cenozoic lithospheric thinning and subsequent mantle accretion. Oxygen in situ from the olivine xenoliths and mantle enclaves olivine from the Late Cretaceous basalts in Junan, Shandong The results of isotope analysis showed that they all have the characteristic of low δ18O. Among them, Fo = 87.5-89.8 and δ18O = 4.1 ‰ -5.2 ‰ of Peridot olivine xenoliths and mantle enclaves olivine, with an average of 4.8 ‰; Qingdao The basalts contain olivine in the mantle enclaves with Fo = 89.0 ~ 89.9 and δ18O = 4.1 ‰ ~ 5.2 ‰ with an average of 4.8 ‰. Previous mineralogical and geochemical data show that these peridotite inclusions have full petrochemistry Characteristic and depleted Sr-Nd isotopes, similar to the depleted MORB mantle.Therefore, such low δ18O mantle peridotites may be mantle wedges that have undergone subducting slab hydrofluids or melt substitution.With the recent reports of Low Cenozoic δ18O basalts and low δ18O garnet pyroxenites representing the remnant oceanic crust, we believe that there is subduction oceanic crustal contribution during the Mesozoic-Cenozoic mantle evolution of the North China continent.