多布伦地区前寒武纪流纹熔接凝灰岩(图1,2),几年以前 Einarsson(1979)和 Lindroos 及 Smellie(1979)作过描述,它是由熔接的或部分熔接的流纹岩和火山灰落或火山灰流成因的凝灰岩组成。熔接凝灰岩单元约有60米厚,延伸长度达4到5公里,包括三个主岩流,各岩流均被1到10米厚的砾岩层隔开。底部岩流分布范围最广。而整个单元在横向上向东尖灭。 Precambrian rift-fused tuffs in the Dobruun area (Figures 1 and 2), described by Einarsson (1979) and Lindroos and Smellie (1979) a few years ago, consist of fused or partially fused rhyolite and volcanic ash Or volcanic ash tuff formation. The fused tuff unit is about 60 meters thick with an extension of 4 to 5 kilometers and consists of three main rock flows, each separated by conglomerates of 1 to 10 meters. The bottom of the rock flow distribution of the most extensive. And the entire unit in the horizontal to the east sharp extinguished.