摘要
报道了大兴安岭-太行山重力梯度带以西河北阳原和山西大同新生代玄武岩的元素和Sr-Nd同位素地球化学数据。含幔源包体的阳原早第三纪碱性玄武岩具有均一的Sr-Nd同位素组成(εNd≈5.7)和相似于OIB的微量元素特征,玄武岩主要来自软流圈地幔,岩浆起源较深。大同地区第四纪时期同时产出碱性和拉斑玄武岩,碱性玄武岩也主要来自软流圈地幔,岩浆起源深度小于阳原样品;拉斑玄武岩具有较低的εNd(1～4),可能是软流圈和岩石圈地幔相互作用的产物,岩浆起源较浅。大同两类玄武岩在空间上分野明显,可能与桑干河断裂对软流圈地幔上涌的控制以及区域上岩石圈-软流圈作用程度的变化有关。
Major and trace element composition s and Sr-Nd isotopes of the C enozoic b asalts from Yangyuan(Hebei Province)and Datong(Shanxi Province),w hich are located to west of the Da Hi nggan Ling-Taihangshan gravity gradient z one,are reported.The Early Tertiary alkali basalts from Yangyuan contain abund ant mantle xenoliths.They exhibit very homogeneous Sr-Nd isotopes with? Nd =5.7,and their trace elements resem ble those of ocean island basalts. Therefore,they mainly originated from the asthenospheric mantle at a relatively great dept h.At Datong,the Quaternary basalts include both alkali and tholei itic types.The Datong alkali basalts were also generated within the asthenosphe ric mantle but at a shallow depth compared to the Yangyuan alkali basalts.The D atong tholeiitic basalts exhibit l ow? Nd values(1～4),implying the effect of the asthenosphere-lithosphere inte ractions.These magmas were derived from a shallower depth than the a lkali basa lts.The distinct spatial distribution of the tholeiitic and a lkali basalts at Datong may be relate d to the effect of local lithospheric extension on the pass ive upwelling of asthenosphere and variable extents of interaction between litho sphere and asthenosphere.
出处
《地球化学》
CAS
CSCD
北大核心
2004年第1期75-88,共14页
Geochimica
基金
国家杰出青年基金项目(49925308)
关键词
岩石地球化学
新生代
碱性玄武岩
拉斑玄武岩
大同
Cenozoic
alkali basalts
tholeiit ic basal ts
geochemistry
Datong
Yangyuan
North China Craton
