摘要
产出于北淮阳地区晓天盆地的早白垩世玄武岩的主量元素具有碱性系列和亚碱性系列过渡的特征。其微量元素特征表现为Rb、Ba、Th、K、Pb的显著富集和Nb、Ti的亏损。锶和钕同位素的初始比值分别为0.7076,0.7080和-13.9,-12.7。这些特征表明所研究玄武岩来自富集的源区,很可能是古老的扬子型岩石圈地幔。与长江中下游和大别造山带中同时代幔源岩石相比表明,虽然总体上都表现为富集特征,但具有明显的不均一性。长江中下游地幔源区最亏损,可能反映来自亏损的软流圈地幔和富集的岩石圈地幔的物质的混合。大别造山带的源区最富集,代表古老岩石圈的贡献。北淮阳地区玄武岩的源区特征与大别造山带的非常相似,但富集程度略低。
Early Cretaceous basalts occurring in Xiaotian basin, North Huaiyang region show transitional character of alkaline to subalkaline series. The basalts show enrichment in Rb, Ba, Th, K and Pb and depletion in Nb and Ti. The rocks give initial Sr isotopic ratios of 0.7076, 0.7080 and εNd(t) of -13.9, -12.7. These features indicate that these basalts were derived from an enriched source region, very likely the old Yangtze lithospheric mantle. Comparing with mantlederived rocks in the Middle and Lower Reaches of the Yangtze River and the Dabie orogenic belt, it is suggested that the mantle sources are highly heterogeneous although they all show enriched characteristics. The mantle beneath the Middle and Lower Reaches of the Yangtze River is the most depleted, reflecting mixing between materials from depleted asthenospheric mantle and enriched lithospheric mantle. The mantle of the Dabie orogenic belt is the most enriched, representing contribution of the old lithosphere. The initial isotopic ratios of the source region of the basalts from the North Huaiyang overlap that of the Dabie orogenic belt, but are slightly more depleted.
出处
《矿物岩石地球化学通报》
CAS
CSCD
2003年第1期26-31,共6页
Bulletin of Mineralogy, Petrology and Geochemistry
基金
国家自然科学基金资助项目(49573172)
