摘要
吕梁山中部的古元古代吕梁群 (2 3 0 0Ma)和野鸡山群 (2 10 0Ma)均由下部的碎屑建造和上部的火山建造组成。在火山建造中以基性火山岩为主 ,酸性火山岩较少。该区的玄武岩中MgO和P2 O5含量低 ,而Feo ,K2 O +Na2 O和LREE含量高 ,类似于大陆溢流玄武岩。酸性火山岩则以LIL和ΣREE富集和高 (La/Yb) N 比值为特点。沉积环境和火山岩的地球化学特征表明 ,吕梁群和野鸡山群火山岩形成于陆内或大陆边缘裂谷环境。正的εNd(tDM)值 (+ 3 .0左右 )说明玄武岩的母岩浆来源于亏损地幔 ,而近于零的εNd(tFM)值则表明原始岩浆曾受到大陆地壳物质的混染。古元古代裂谷型火山作用的出现意味着在此之前 (太古宙末 )
The Paleoproterozoic Luliang Group(～2 300 Ma) and Yejishan Group (～2 100 Ma) in central Luliang Mountains of Shanxi Province mainly consist of detrital formation in the lower part and volcanic formation in the upper part. The volcanic formation is dominated by basic volcanics (basalt) with less acidic volcanics (rhyolites). The basalts in the area, which have low MgO and P 2O 5 content but contain abundant FeO *,K 2O+Na 2O and LREE,are similar to continental basalts. The acidic volcanics are characterized by high LIL and ΣREE values as well as large (La/Yb) N ratios. The sedimentary environment and geochemical characteristics of the volcanics indicate that the volcanic rocks of the Luliang Group and Yejishan Group were erupted in intracontinental or epicontinental rift type tectonic setting. The positive ε Nd ( t DM ) value (～+3.0) suggests that the parental magma of the basalts in both group was derived from depleted mantle source, and the lower ε Nd ( t FM ) value (about zero) shows that the parental magma was contaminated by continental materials. The existence of the Palaeoproterozoic rift-type volcamism implies that a considerable continental crust was formed in the North China Craton at the end of Archean.
出处
《地球学报》
EI
CAS
CSCD
北大核心
2003年第2期97-104,共8页
Acta Geoscientica Sinica
基金
国家自然科学基金 (4 0 0 72 0 60
49832 0 30 )
原地质矿产部"九五"科技项目 (95 0 116)资助
