滇西北碰撞型火山岩的地球化学特征

滇西北地区碰撞造山带中出露两个火山岩系，即中三叠世攀天阁组和晚三叠世崔依比组。对其地球化学研究表明：攀天阁组由酸性火山岩组成，来源于陆壳，是在陆－陆对接碰撞时期受强烈挤压促使壳发生深熔作用形成的；崔依比组是“双峰式”（玄武岩－流纹岩）火山岩特征，来源于亏损地幔，是碰撞后拉伸，由于深部的张裂促使地幔发生局部熔融生成原始岩浆，经结晶分离作用，在上升过程中有陆壳物质混染的情况下，以玄武岩和流纹岩相互交替

GEOCHEMICAL CHARACTERISTICS OF COLLISION TYPE VOLCANIC ROCKS FROM NORTHWESTERN YUNNAN

There are two series of volcanic rocks, the middle Triassic Pantian'ge formation and the late Triassic Chuiyibi formation, in the northwestern Yunnan collisional orogenic zone. The present study shows that the Pantian'ge formation is composed of acidic volcanic rocks, which were derived from the continental crust, as a result of the anatexis of the crust caused by intensive compression of continentcontinent collision. The Chuiyibi formation have features of "bimodal" (basalticrhyolite) volcanic rocks, originated from a depleted mantle source.Its formation involved local partial melting of the depleted mantle in a post-collision extensive zone, and fractional crystallization and crustal contamination of the primary magma during its upwelling, and final alternate eruption as basalt and rhyolite.