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位于太行山重力梯度带西侧的河北阳原第三纪碱性玄武岩中产有大量幔源包体,包括二辉橄榄岩、方辉橄榄岩和辉石岩.在橄榄石含量-橄榄石成分图解上,阳原橄榄岩偏离大洋趋势线,多数落在太古宙和元古宙地幔范围;部分富集LREE的样品具有EMI型的Sr-Nd同位素特征(εNd=?6.9~?10.6,87Sr/86Sr=0.7044~0.7047),而另一些富集LREE的样品的εNd值(+5.7)与亏损LREE的样品相类似.这说明阳原上地幔经历了多期地幔交代作用.由于EM1型同位素组成常见于典型古老克拉通下岩石圈地幔,因此阳原包体为华北西部存在古老岩石圈地幔提供了新的证据.
A large amount of mantle-derived inclusions, including lherzolite, harzburgite and pyroxenite, are found in the Tertiary alkaline basalts located in the Yangyuan area, Hebei Province, west of the gravity gradient zone of the Taihang Mountains. In the olivine content-olivine composition diagram , Most of the proterozoan peridotites deviate from the oceanic trend line, and most of them fall in the Archean and Paleozoic mantle. Partially enriched LREE samples have the Sr-Nd isotopic characteristics of EMI (εNd = 6.9 ~ 10.6, 87Sr / 86Sr = 0.7044 ~ 0.7047), while the εNd values (+5.7) of other LREE-enriched samples are similar to that of the depleted LREE samples, indicating that the mantle of the Yangyuan experienced multi-stage mantle metasomatism.Because the EM1 isotope composition is common in the typical The ancient craton under the lithospheric mantle, so the Yangyuan crate provides a new evidence for the existence of ancient lithospheric mantle in western North China.