Basic volcanic rock-banded magnetite puartzite-carboncaceous-siliceous slate(siliceous graphiuc schist)formation which should be put under Upper Archaeozoic to Lower Proterozoic Erathem is in existence in the Hekou Group.

• 河口群中存在基·性火山岩、条带状磁铁石英岩、碳硅质板岩（硅质石墨片岩）三组合建造，应属晚太古代未－早元古代地层。