藏北沉鱼湖-向阳湖一带石坪顶组火山岩特征、形成时代及环境

沉鱼湖—向阳湖一带的石坪顶组火山岩大地构造位置属巴颜喀拉-可可西里地块和南部的若拉岗日裂谷带,岩石结构类型比较简单,以粗面安山岩为主,粗面岩、玄武粗安岩、粗面英安岩次之,以钾质太平洋型钙碱性系列为主.火山岩轻、重稀土分馏程度均较高,重稀土分馏程度比轻稀土稍低一些,具轻稀土富集,重稀土亏损的特点,时代属中新世.K2O/Na2O>1,说明成矿物质为深部幔源物质混合了壳源物质,属大陆板内造山晚期演化的火山岩类型.

TIME AND ENVIRONMENT OF FORMATION AND GEOCHEMICAL CHARACTERISTICS OF THE CHENYUHU TO XIANGYANGHU SHIPINGDING GROUP VOLCANIC ROCKS IN NORTHERN TIBET

The Chenyuhu to Xiangyanghu Shipingding group volcanic rocks are located north of the Hoh Xil Mountains-Bayan Har massif and south of the Ruolagangri Rift Valley Belt. Rock types are simple: trachyandensite, the trachyte, basalt-trachyte, trachyandensite and are typical of the Pacific Ocean calcium alkali series. The volcanic rock is light; the degree of heavy rare earth fractionation is all high and compared to the light rare earth is slightly lower; has light rare earth concentrates and; the heavy rare earth loses are characteristic. The age is Miocene Epoch. K2O/Na2O is greater than 1 and the ore forming material consists of deep seated mantle derived material mixed with crust-derived material. The volcanic rocks formed and evolved during continent intraplate orogeny.