摘要
采用主量元素、微量元素、Sr-Nd同位素地球化学研究手段和大地构造分析方法,对临清坳陷中新世玄武岩的地球化学特征进行了研究。结果表明:中新世馆陶组(N1g)玄武岩为碱性玄武岩和碱性粗面玄武岩,呈现轻稀土富集型分布模式,无Eu异常,稀土总量较低。大离子亲石元素富集,蛛网图显示负斜率较大的右倾曲线,并有不同程度的Nb-Ta和Sr元素富集以及Zr、Ti和Y元素的轻度亏损,含量较低的不相容元素基本上呈平滑分布。Sr-Nd同位素组成较为均一,玄武岩岩浆主要来自亏损软流圈地幔,同时存在轻微的岩石圈地幔混染作用。包括临清坳陷在内的渤海湾盆地是地幔上隆而造成岩石圈伸展减薄的产物,是太平洋板块向欧亚板块之下俯冲形成的陆内扩张盆地。
The whole rock analyses including major element, trace-REE (rare earth element) and strontium-neodymium isotopic methods were used to show the geochemical features of the Miocene basalts in Linqing Sag and to discover the original geodynamic background of Bohai Bay Basin. The basaltic rock samples from three members of Guantao Formation (N1g) during the Miocene belong to alkaline basalt and alkaline trachybasalt. All samples show the enrichment distribution pattern of light rare earth element (LREE) and have no any uranium abnormality. The total content of REE is relatively low. The large iron lithophile element (LILE) of the basalts are generally enriched. The spider diagram shows a negative slope curve. The niobium-tantalum and strontium elements display different enriched degree, but zirconium, titanium and yttrium are lightly depleted relatively. In addition, the incompatible element basically shows a smooth pattern. The homogeneous strontium-neodymium isotopic component suggests that the basalts probably derived from asthenosphere depleted mantle and slightly lithosphere mantle contamination. The conclusion drawn from field geology and geophysics is that Bohai Bay Basin including Linqing Sag is both products of lithosphere extensional attenuation resulted from mantle upwelling and the inner-continental extensional basin generated from Pacific tectonic plate under-riding into Asia-Europe tectonic plate.
出处
《石油学报》
EI
CAS
CSCD
北大核心
2005年第4期5-11,共7页
Acta Petrolei Sinica
基金
中国科学院知识创新工程项目(KZCXZ-SW-117)资助。
