大同火山群地质及岩石学特征

大同火山群以盆地为对称轴分布,中更新世晚期火山位于盆地的轴部,中更新世早期火山位于盆地两侧。计算的延伸和断裂速率分别为0.43cm/a和0.22cm/a。大同火山群主要属于碱性橄榄玄武岩系列,中更新世早期火山的一部分属于拉斑系列,夏威夷岩是大同火山岩的一个主要类型.中更新世早期火山岩的氧化物变异趋势可能是受高压下Ol+Opx的分离作用控制.中更新世晚期火山岩氧化物变异趋势暗示了是受岩浆混合作用的控制。

GEOLOGICAL AND PETROLOGICAL CHARACTERS OF DATONG VOLCANIC GROUP

The famous Datong volcanic group is located in Datong basin. The distribution of volcanoes is symmetrical to the axis of the basin, where late-Middle Pleistocene volcanoes are located in the axial area of the basin, early-Middle Pleistocene volcanoes are situated on the flanks of the basin. The calculated spreading and drifting rates are 0.43 cm/a and 0.22cm/a, respectively. Datong volcanic group mainly belongs to alkali olivine basalt series, a part of early-Middle Pleistocene volcanoes belong to tholeiite series. Hawaiite is a dominant type of Datong volcanic rocks. The oxide variation trend of early-Middle Pleistocene volcanoes may be controlled by the fractionation of O1+Opx at high-pressure. The oxide variation trend of the late-Middle Pleistocene volcanoes is suggested to be under the control of magma mixing rather than crystal fractionation.