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乔治王岛第三纪火山岩含大量斜长石斑晶。斜长石的主元素、稀土和微量元素分析表明，它们主要为中长石—钙长石。斜长石种类与寄主岩之间有较好对应关系，即玄武安山岩和安山岩中以中长石和拉长石为主，而高铝玄武岩中为倍长石和钙长石；它们的ＲＥＥ、Ｌａ／Ｙｂ和δＥｕ等之间也有明显对应关系。但不同种类的斜长石之过渡金属元素特征相近，反映了过渡金属元素在斜长石中的含量和分异趋势主要受制于斜长石的晶体结构。综合研究表明，斜长石成分取决于其母岩浆成分，并反映了区域岩浆演化的趋势。
Tertiary volcanic rocks in King George Island contain a large amount of plagioclase phenocrysts. The main elements of plagioclase, rare earth and trace element analysis show that they are mainly feldspar - calcium feldspar. There is a good correspondence between the plagioclase type and the host rock, ie, the basaltic andesite and andesite are mainly feldspar and labialite, while the high-aluminum basalts are palygorskite and anorthite; and their REE, La / Yb and δEu also have a clear correspondence between. However, the transition metal elements of different types of plagioclase are similar in character, reflecting that the content and differentiation of transition metal elements in plagioclase are mainly controlled by the crystal structure of plagioclase. The comprehensive study shows that the composition of plagioclase depends on its parent magmatic composition and reflects the trend of regional magmatic evolution.