大兴安岭北部上护林盆地恩和大岭火山机构主要由白音高老组酸性熔岩、火山碎屑岩、次火山岩及火山- - 沉积岩组成。实测剖面显示，该火山机构由侵出相、溢流相、爆发相、次火山岩相及火山沉积相构成，不同岩性、岩相围绕火山口大致呈对称分布，产状外倾，为中心式喷发的穹状火山。溢流相的流纹岩和次火山岩相的正长斑岩锆石 U- -Pb 测年结果分别为 (115. 3 ± 2. 3) Ma 和 (114. 3 ± 1. 6) Ma，表明恩和大岭火山机构形成于早白垩世晚期。该火山机构为一次简单的火山喷发旋回一个喷发期次，大致的火山活动过程可分为四个阶段，第一阶段为早期岩浆溢流阶段，形成溢流相流纹岩夹少量流纹质角砾凝灰岩; 第二阶段为晚期火山爆发阶段，产生大量的爆发相火山碎屑岩; 第三阶段为岩浆侵入阶段，分别形成侵出相松脂岩、次火山岩相正长斑岩等; 第四阶段为火山活动的间歇阶段，形成火山沉积相火山- - 沉积岩。

Enhedaling volcanic edifice from Shanghulin Basin in northern Great Xing'an Range is mainly com- posed of acid lavas，pyroclastic rocks，sub- volcanic rocks and volcanic sedimentary rocks of Baiyingaolao Forma- tion． The measured section shows that the volcanic edifice is made up of extrusive facies，overflow facies，explosive facies，sub- volcanic facies and volcanic sedimentary facies． Different lithology and facies distribute around the cra- ter approximate symmetrically with outward tilt of rock strata，which belong to dome shaped volcano of the central type eruption． Zircon U- - Pb dating results of rhyolite with overflow facies and syenite porphyry with sub- volcanic fa- cies are (115. 3 ±2. 3) Ma and (114. 3 ±1. 6) Ma，respectively，indicating that Enhedaling volcanic edifice was formed in the later Early Cretaceous． The volcanic edifice is a simple volcanic eruption cycle- a volcanic eruption period，the possible process of volcanic activity can be divided into four stages， the first stage is the early magma o- verflow，formed overflow rhyolite with a small amount of rhyolitic breccia tuff; the second stage is the late volcanic eruption，produced a large amount of explosive facies pyroclastic rocks; the third stage is magmatic intrusion， formed extrusive facies pitchstone and sub- volcanic facies syenite porphyry，etc; the fourth stage is the intermittent period of the volcanic activity，produced volcanic sedimentary rocks of volcanic sedimentary facies．