额尔古纳地区中生代火山岩形成的动力学环境

通过对额尔古纳地区中生代火山岩新的岩石化学、微量元素、构造等方面的分析， 表明该地区中生代火山岩（主要指塔木兰沟组（Ｊ_３ｔ）火山岩、上库力组（Ｋ_１ｓ）火山岩是形成在的明 显的挤压环境中；再结合区域构造、区域岩浆作用、古地磁特征和稳定同位素分析，笔者得出以 下认识；１、该区中生代火山岩岩浆来源较深（幔源）；岩浆是挤压背景下，“减压－剪切”作用的产 物，而不是裂谷环境中的产物，从而使得岩浆在演化过程中混入了大量的壳源物质；２、中生代火 山活动大致分两个亚族回，其中塔木兰沟组（Ｊ_３ｔ）火山岩和上库力组（Ｋ_１Ｓ）火山岩是同一岩浆亚 族回的产物，并构成一个完整的亚族回。

DYNAMIC BACKGROUND OF MESOZOIC VOLCANIC ACTIVITY IN ERGUN REGION

The Mesozoic volcanic rocks in Ergun region, which were formed mainly in the period of late Jurassic to early Cretaceous (150-100Ma), were formed in compressional surroundings apparently according to the analyses in petrochemistry, trace element and tectonics. Further studying in regional tectonics and magma activity, palaeo-magnetism as well as stable isotope etc., we concluded: 1 .The Mesozoic volcanic rocks were from the mantle, and were formed in compressional surroundings with"reduced pressure"-"shearing"process. That is why there are many materials of crust-source added in the Mesozoic volcanic rocks. 2. The Mesozoic volcanic activities can be divided into two subcircles. Among them, the volcanic rocks of Tamulangou formation(J_3t)and Shangkuli formation(K_1s)were formed in the same subcircle.