摘要
西藏羌塘中部角木日地区出露有大量的二叠纪玄武岩,岩石由拉斑玄武岩和碱性玄武岩组成,SiO2含量在43.87%～54.25%之间,K2O含量较高,平均为0.58%,TiO2含量中等偏高,平均为1.60%,P2O5含量也较高,平均为0.48%,Zr/Y比值平均为6.04,Zr/Nb比值平均为9.88,明显具有富集地幔的特征;∑REE平均为147.5×10-6,轻稀土轻微富集,LaN/SmN比值平均为1.98。这些特征和三江地区的准洋脊型玄武岩一致。综合玄武岩岩石学和地球化学特征,认为二叠纪玄武岩可能形成于准洋中脊环境。
Permian basalt is widespread in the Jiaomuri area, central Qiangtang, Tibet. According to petrological and geochemical studies, the basalt consists of tholeiite and alkali basalt. Its content of SiO2 ranges from 43.87 to 54.25%; the content of K2O is high, averaging 0.58%; the TiO2 content is slightly above medium, averaging 1.60%; the P2O5 content is also high, with an average of 0.48%; the ratios of Zr/Y and Zr/Nb average 6.04 and 9.88 respectively, evidently showing the features of the enriched mantle; the ∑REE averages 147.5×10^-6, with LR.EE slightly enriched; the ratio of LaN/SmN averages 1.98. All these characteristics accord with those of MORB-like basalt in the Sanjiang region. Therefore, the authors think that the Permian basalt may have originated in an environment of the MORB-like.
出处
《地质通报》
CAS
CSCD
北大核心
2006年第12期1419-1427,共9页
Geological Bulletin of China
基金
国家自然科学基金项目(编号:40672147)
中国地质调查局项目(编号:1212010561605
200313000054)联合资助
关键词
西藏
羌塘
角木日
玄武岩
地球化学
构造意义
Tibet
Qiangtang
Jiaomuri
basalt
geochemistry
tectonic significance
