【摘要】 通过对藏北祖尔肯乌拉山地区大面积分布的新生代火山岩的 4 0 Ar- 39Ar同位素测年结果分析表明 ,火山岩 4 0 Ar- 39Ar同位素年龄介于 4 5 Ma～ 39Ma之间 ,集中于 4 0 Ma左右 ,属始新世。火山岩 4 0 Ar- 39Ar同位素年龄的精确限定 ,不仅为该区生物化石缺乏的新生代陆相红层沉积时代上限提供了同位素年代学依据 ,而且为藏北 EM 型富集地幔形成时限提供了同位素年代学的约束。更多还原

【Abstract】 Isotopic ages of the Cenozoic volcanic rocks from Zuerkengwula mountain area, Northern Tibetan Plateau, have bean determinated by using ⁴⁰Ar-³⁹Ar isotopic dating technique.The ages of the volcanic rocks range from 45 Ma to 39 Ma with most of ages about 40 Ma, which are of Eocene ages.The accurate dating of volcanic rocks provide not only isotopic chronology basis for the upper limit of Cenozoic continental redbeds sedimentary, but also isotopic chronology limit of enriched EMⅡ mantle formation in Northern Tibetan Plateau.更多还原