沂沭裂谷及其邻区下白垩世火山熔岩地球化学特征

沂沭裂谷及邻区下白垩世火山熔岩以碱性系列的玄武粗安岩、粗安岩、粗面岩为主。而亚碱性系列以钙碱性为多。碱性系列以钾质亚系列为主，其中鲁东、鲁西基本上是钾质亚系列，而沂沭裂谷内有一定数量的钠质亚系列。稀土元素标准化曲线均呈向右陡倾斜，其斜率相似，为典型的富轻稀土，而亏损重稀土的型式。多数δＥｕ在０．７８－１．２８之间。

PETROLOGY AND GEOCHEMICAL CHAPACTERICS OF THE LOWER CRETACEOUS VOLCANIC ROCKS IN THE YISHU RIFT ZONE ANDJACENT AREA

Thec early Cretaceous volcanic rocks in the Yishu rift zone and its adjacent area are mainly basaltic trachyandesite,trachyandesite,and trachyte of alkaline series,as well as some rhyolite,dacite and andesite according to the chemical classification of volcanic rocks(Le Maitre,1989). The rocks of alkaline series are mainly of potassic sub series,in particular,those in easternand western Shandong regions are essentially the potassic sub series whereas some sOdic sub series rocks are present in the Yishu r...