甘肃宕昌一带中生代火山岩岩石地球化学特征及构造环境探讨

GEOCHEMICAL FEATURES AND TECTONIC SETTING OF MESOZOIC VOLCANIC ROCKS IN TANCHANG AREA OF GANSU PROVINCE

甘肃宕昌彭都—簸箕一带中酸性火山岩的岩石化学研究表明为钙碱性火山岩系列,具富钾,低钛特点。稀土总量较高,轻稀土分馏明显,铕具负异常。微量元素K、Rb、Ba、Th等强不相容元素强烈富集,Sc、Cr等相容元素亏损。岩石地球化学特征表明火山岩形成于一个正常陆壳或形成于双倍陆壳的中上部。形成的构造环境为陆内碰撞构造环境。同位素研究表明其形成时间为早中侏罗世。

The intermediate-acid volcanic rocks existing in Tanchang area of Gansu Province is classified as calc-alkaline series with K-rich and Ti-low. The total amount of REE is relatively higher, with fractionated light REE and negative anomaly of europium. The trace elements such as K, Rb, Ba, Th are strong enrichment, while Sc, Cr depletion. The volcanic rocks formed on the middle and top section of a normal or double continental in the tectonic setting of intra-continental collision. The study of isotope show the age of formation is in earl middle Jurassic Epoch.