西藏羌塘地区印支期火山岩构造地球化学特征

西藏羌塘地区印支期火山岩主要分布在盆地北缘若拉岗日和羌塘中央隆起南缘肖茶卡—香琼火山岩地区。主要元素和稀土元素地球化学特征分析表明 ,若拉岗日区火山岩属富钠型的碱性系列玄武岩 ,肖茶卡—香琼火山岩为拉斑玄武岩。两区岩石系列和构造发育部位虽不同 ,却都是在海西期末闭合的裂陷带上再扩张过程中形成的 ,反映盆地北部和中央隆起处的两条板块缝合带有相似的演化特点。

TECTONO- GEOCHEMICAL CHARACTERISTICS OF INDO-CHINA EPOCH VOLCANIC ROCKS IN QIANGTANG AREA, TIBET

Indo-China epoch volcanic rocks in the Qiangtang area of the Tibetan plateau are mainly distributed in the Ruolagangri area in the northern marginal district of the Qiangtang basin and the Xiaochaka-Xiangqiong region in the Qiangtang central uplift. The geochemical analysis of major elements and rare earth elements shows that the Ruolagangri volcanic rocks belong to calc-alkaline volcanic suite with rich sodium and the Xiaochaka-Xiangqiong volcanic rocks belong to tholeiite. Although the rock type and tectonic setting are different, the volcanic rocks of the two regions were formed by the re-spreading process on the splitting belt which was closed in the last phase of Hercynian. It indicates that the two suture belts at the northern marginal Qiangtang basin and the central uplift of the Qiangtang basin have similar developing features.