张双悦.天水地区丹凤群中火山岩的地球化学特征及地质意义[J].甘肃地质,2013,22(1):24-29
天水地区丹凤群中火山岩的地球化学特征及地质意义
Geochemical Characteristic and Geological Significance of the Volcanic Rock in Danfeng Group of Tianshui Area, Gansu Province
  
DOI:
中文关键词:  天水地区  丹凤群  火山岩地球化学特征  形成环境  岛弧
英文关键词:volcanic rock  formation environment  island arc  Danfeng Group  Tianshui area
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作者单位
张双悦 甘肃省地矿局第一地勘院甘肃 天水 741020 
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中文摘要:
      丹凤群分布于天水市南部,向东延入陕西凤县。通过原岩恢复,其下部层位的岩石以变玄武岩为主,夹安山岩、石英岩、大理岩,中部为变石英砂岩夹玄武岩、薄—微层状石英岩夹安山岩、英安岩,上部为玄武岩、玄武安山岩、安山岩、石英砂岩、大理岩夹流纹岩及硅质条带。火山岩为碱性—拉斑系列,锶同位素初始比值低,地球化学特征与岛弧玄武岩的地球化学模型相似。通过对丹凤群火山岩地质特征、岩石组合、岩石地球化学特征的综合分析,认为丹凤群的沉积环境,处于当时的秦岭古陆南侧的古大洋岛弧。
英文摘要:
      Danfeng Group exists in the southern Tianshui area, extends eastwards into Fengxian County of Shaanxi Province. Based on the restoration of original rock in Danfeng Group, it is known that the Lower rock layer mainly consists of meta-basalt with andesite, quartzite and marble, the Middle rock layer consists of quartz sandstone with basalt, thin-microlayer bedded quartz sandstone with andesite and quartz andesite, the Upper rock layer consists of basalt, andesibasalt, rhyolite with siliceous banding and quartz sandstone, and marble with rhyolite and siliceous banding. The volcanic rock belongs to alkalic-tholeiitic series with low initial ratio of Sr isotope, its geochemical characteristic is similar to the geochemical model of the island arc basalt and the continental rift basalt. According to the combining analysis of geologic feature, rock association feature and geochemical feature of the volcanic rock in Danfeng, the formation of Danfeng Group mainly deposits in the contact place of the Qinling ancient land and the ancient ocean which lies in south Qinling ancient land, and is caused by the ancient ocean subduction to the Qinling ancient land.
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