本文对黑龙江省伊春市北部乌伊岭地区美丰组的一套以中基性为主的火山岩进行了矿物、岩石、地球化学方面的系统研究。根据其岩石具有富钾，富碱，w（Na2O+K2O）为3.90%~9.53%；贫钛，w（Ti2O）为0.37%~1.90%；高铝，w（Al2O3）为14.05%~18.24%，以及富集大离子亲石元素（Cs，Rb，Ba，Th）和轻稀土元素等特征，结合岩石基质中存在大量钾长石微晶、斜长石斑晶，见伊丁石化橄榄石斑晶等矿物学特点，确定乌伊岭地区的火山岩属钾玄岩系列，岩石组合为钾质粗面玄武岩、橄榄玄粗岩、安粗岩和粗面岩。采用锆石SHRIMP U-Pb年龄法，确定火山岩的同位素年龄为（105±1.5）Ma，时代归属早白垩世晚期。地球化学特征分析表明，低角度深俯冲的西太平洋板块的脱水作用是诱发发火山地幔源区熔融的主要因素，其形成的构造背景为板内拉张环境。%The intermediate-basic volcanic rocks of the Meifeng Formation were studied systematically to characterize its mineralogy, petrology and geochemistry in Wuyiling area, northern Yichun city of Heilongjiang Province. The rocks are characterized by high-K, high-alkali (w(Na2O+K2O)=3.90%-9.53%), low-Ti (w(Ti2O)=0.37%-1.90%), high-Al (w(Al2O3)=14.05%-18.24%) values, and are enriched in large ion lithophile elements (Cs, Rb, Ba, Th) and light rare earth elements. With the mineralogical features of micro-crystal potash feldspar texture and iddingsite olivine phenocrysts in the rock matrix, the volcanic rocks are identified as the shoshonite series, which are mainly composed of potassic trachybasalt, shoshonite, latite and trachyte. The zircon SHRIMP U-Pb dating is (105±5) Ma, which suggests that the volcanic rocks are formed during the late Early Cretaceous. Based on the geochemical features, the dehydration associated with the low-angle, deep subduction of the West Pacific plate caused melting of the mantle-derived source areas. The tectonic regime for the Meifeng Formation belongs to an intraplate extensional environment.
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