南秦岭勉县-略阳结合带变质火山岩岩石地球化学特征

Petrology and Geochemistry Features of theMetamorphic Volcanic Rocks in Mianxian Lueyang Suture Zone,South Qinling

勉县－略阳结合带变质火山岩以基性和中基性岩石为主体，见有少量英安质火山岩。可区分为两种岩石－构造组合类型：一类为低钾高钛、轻稀土亏损的拉斑玄武岩，Ｔｉ／Ｖ、Ｔｈ／Ｔａ、Ｔｈ／Ｙｂ、Ｔａ／Ｙｂ表明其应属于ＭＯＲＢ型玄武岩；另一类为岛弧火山岩组合，以钙碱性安山岩类为主体，并有少量岛弧拉斑玄武岩类。

The metamorphic volcanic rocks in Mianxian Lueyang suture zone are mainly basalts and andesite as well as a small amount of dacite.They can be divided into two types of petrotectonic association.The mid ocean ridge basalts in this region exhibit a LREE depletion but a HREE enrichment showing low K 2O and high TiO 2· Their ratios of Ti/V,Th/Ta,Th/Yb and Ta/Yb indicate that they belong to MORB type basalt.The island arc volcanic rocks in this region can be divided into tholeiitic and calc alkaline associations.