四川省昭觉地区峨眉山玄武岩地球化学特征

Geochemical Characteristics of the EmeishanBasalt in ZhaojueArea, Sichuan Province

四川昭觉地区峨眉山玄武岩组与上覆宣威组或飞仙关组呈平行不整合接触,与下伏阳新组呈火山喷发不整合接触,厚度大于1300m。玄武岩主要为基性岩系列碱性-亚碱性系列石英拉斑玄武岩,与我国基性火山岩玄武岩相比,明显高SiO_(2)、Fe_(2)O_(3)、TiO_(2),与西南地区峨眉山玄武岩相比,明显高Fe2O3,为典型的高铁玄武岩。具左高右低(右倾)平滑型的稀土配分模式,负铕异常不明显(δEu=0.85~1.20);富集Sr、K、Ba、Sm、Zr,亏损Rb、P、Ti、Y。结合野外产状、主微量元素特征及构造环境判别图解均表明,研究区玄武岩属于板内玄武岩。

The Emeisshan basalt Formation is in parallel unconformity contact with Xuanwei Formation or Feixianguan Formation in the overlying area of Sichuan Province,and is in volcanic unconformity contact with Yangxin Formation in the underlying area,with a thickness greater than 1300 m.Basalt is mainly basic rock series,alkali-subalkaline series of quartz tholeiite basalt.Compared with China's basic volcanic basalt,the contents of SiO2,Fe2O3 and TiO2 from Zhaojue are higher;compared with Emeishan basalt in southwest China,the contents of Fe2O3 is high,which is a typical high iron basalt.The rare earth partitioning pattern has a left-high and right-low(right-leaning)smooth pattern,and the Eu anomaly is not obvious(δEu=0.85~1.20).Sr,K,Ba,Sm and Zr were enriched,while Rb,P,Ti and Y were depleted.Combined with the field occurrence,major and trace element characteristics and tectonic environment discrimination diagrams,the basalts in the study area belong to intraplate basalts.