摘要
南秦岭元古宙火山岩主要由两大类岩石构成 ,一类为SiO2 4 5 %～ 5 7%的基性火山岩系 ,另一类为SiO2 6 7%～ 78%的酸性火山岩系 ,主要岩石类型为细碧岩、玄武岩和石英角斑岩、流纹岩。基性火山岩整体上属拉斑玄武岩系列 ,酸性火山岩属钙碱系列。火山岩强烈富集稀土元素 ,尤其是轻稀土元素 ,酸性火山岩和基性火山岩有相似的稀土元素特征 ,显示了源区特征的不同。基性火山岩富集强不相容元素 ,相对亏损Nb和Ti,形成于大陆裂谷环境 ,具有大陆拉斑玄武岩的特征。同位素特征表明基性火山作用与地幔柱活动密切相关。南秦岭的中。
The Proterozoic volcanic rocks in South Qinling are dominated by basic volcanic rocks with SiO 2 45%～57% and acid volcanic rocks with SiO 2 67%～78%. The basic volcanic rocks with spilites and basalts as the major types are close to tholeiite series, whereas the acid rocks with quartz_keratophyre as the major type are close to calc_alkaline series. Both the basic and the acid volcanic rocks are enriched with REE, especially LREE, indicating that they were derived from different sources. Primitive mantle_normalized trace element patterns of the basic volcanic rocks exhibit the continental tholeiitic characteristics with highly_enriched incompatible elements and moderately_depleted Nb and Ti, suggesting that they were formed in the continental rift. According to the Sr_Nd isotopic study, the basic volcanism was closely related to the mantle plume upwelling. All the features demonstrate that the continental rift in South Qinling region was formed in Middle-Late Proterozoic, and the mantle plume activity was the precursor of the break_up of the ancient Qinling Ocean.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
2001年第3期255-262,共8页
Acta Petrologica et Mineralogica
