北昆仑火山岩亚带阿勒坦凝灰岩地质特征

Petrochemistry and Age of the Aletan Tuff from the North Kunlun Volcanic Subzone

位于青海境内的昆仑山火山岩较为发育,区内不同构造单元中火山岩岩石类型、岩石组合及岩石地球化学特征、形成时代各不同,在区域矿产调查中在北昆仑火山岩亚带发现非正式示填图单位新元古代阿勒坦凝灰岩(Pt3A^tf)。通过野外地质剖面测量、镜下分析以及获得的锆石对凝灰岩分析,采用LA-ICP-MS法锆石U-Pb测年获得958.4±5.3Ma的年龄值,反映凝灰岩活动时代为新元古代青白口纪;根据岩石化学特征及区域资料,火山岩为过铝质-钙碱性系列岩石,凝灰岩应为岛弧相火山岩,为揭示反演东昆仑造山带形成演化和岩浆作用提供一定依据及观点。

Volcanic rock was well developed in the Kunlun Mountains in Qinghai. This paper has a discussion on petrochemistry and age of the Aletan tuff (Pt3A^tf from the north Kunlun volcanic subzone. Petrochemical study indicates that the tuff is an island arc volcanic rock of peraluminous-calcium alkali series. The tuff yields zircon U-Pb ages of 958.4 ± 5.3 Ma, belongning to the Neoproterozoic Qingbaikou Period.