赤峰市平庄—元宝山盆地汉诺坝玄武岩的地球化学特征及其构造背景

对分布于赤峰东部平庄—元宝山盆地的汉诺坝玄武岩进行了岩石学、地球化学研究.结果表明,研究区内火山岩主要岩石类型为玄武岩及少量沉凝灰岩.玄武岩岩石成分较均一,主量元素变化不大,富钛、贫铝,富Na2O,低K2O.玄武岩稀土元素总量低,轻稀土元素富集,铕、铈异常不明显.玄武岩富集大离子亲石元素Rb,Ba,Th,K,Ta和LREE,高场强元素U相对亏损,相容元素Cr,Co,Ni含量较低.本区汉诺坝玄武岩属于拉斑玄武岩系列,火山岩的源区是软流圈上地幔,玄武岩形成于大陆裂谷的拉伸环境,是大陆板块内部稳定构造环境的产物.

Geochemical Characteristics and Tectonic Setting of Hannuoba Basalts from Pingzhuang-Yuanbaoshan Basin in Chifeng

Petrology， geochemistry characteristics of the Hannuoba basalts distributed in Pingzhuang—Yuanbaoshan basin in eastern of Chifeng， Inner Mongolia were studied. The results showed that the volcanic rocks are dominated by basalts and minor sedimentary tuff. The petrologic compositions of basalts are homogeneous， content of the main elements change rarely， the basalts is characterized by higher titanium， lower aluminum and high Na₂O content，lower K₂O content. The total amounts of REE are lower， LREE is enriched， and there are weak Eu and weak Ce negative anomaly for Hannuoba basalts. The basalts are obviously enriched inlithophile elements (Rb，Ba，Th，K，Ta， LREE etc.)， and depleted in high field-strength element(U，HREE)as well as compatible elements (Co， Ni， Cr etc.). The Hannuoba basalts belong to the tholeiitic basalt series， and the source region of volcano rock is the asthenospheric upper mantle.The Hannuoba basalt formed in a continental rift tensile environment which is the product of continental intraplate stable tectonic environment.