华北东部中、新生代岩石圈地幔的不均一性：来自橄榄石的组成填图结果

华北中、新生代玄武质火山岩和基性脉岩携带的地幔橄榄岩捕虏体中橄榄石和/或橄榄石捕虏晶系统的组成填图显示华北东部中、新生代岩石圈地幔存在明显的时空分布规律和不均一性。这与通过岩石圈地幔源基性岩石的地球化学反演获得的华北中生代岩石圈地幔的时空不均一性及其块体特征完全一致。太行山和鲁皖地区新生代岩石圈地幔的差异演化主要反映古老地幔橄榄岩与熔体相互作用时熔体性质和来源的不同。同时,橄榄石 Fo 填图还揭示了郯庐断裂对华北东部中、新生代基性岩浆活动及其岩石圈地幔演化的重要制约作用。而且,华北东部中生代岩石圈减薄后尚存古老岩石圈地幔残留。因此,华北东部岩石圈减薄的整体拆沉模式很难成立。

Heterogeneity of Mesozoic and Cenozoic lithospheric mantle beneath the eastern North China Craton: evidence from olivine compositional mapping

Systematical compositional mapping of olivines from mantle peridotitic xenoliths and/or xenocrysts entrained in basaltic rocks and mafic dykes from eastern North China Craton demonstrates that an apparently temporal and spatial distribution and heterogeneity exist in the Mesozoic and Cenozoic lithospheric mantle.This is entirely consistent with the temporal and spatial heterogeneity and block feature of Mesozoic lithospheric mantle beneath the eastern North China Craton as revealed by the geochemistry of the lithospheric mantle-derived mafic rocks.Different evolution of the Cenozoic lithospheric mantle between the Taihang Mountains and Shandong-Anhui regions mainly reflects the difference in the nature and composition of the melt involved in the interaction between the old refractory lithospheric mantle and the infiltrated melt.Simultaneously,olivine Fo mapping also reveals that the Tan-Lu Fault played an important role in both the Mesozoic and Cenozoic mafic magmatism and the lithospheric evolution in the eastern North China Craton.Furthermore,olivine composition indicates that there still exist some old lithospheric mantle remnants beneath the eastern North China Craton after the lithospheric thinning.Thus,tbe wholesale delamination model for the lithospheric thinning in the eastern North China Craton is difficult to reconcile the available data.