加拿大地质调查所于1973年出版发行一种新型的地球化学图件——湖泊底沉积中的铜、铅、锌、镍、铀、铁、锰和钾的分布图。已出版的图件是根据加拿大西北地区3万6千平方哩的野外工作成果绘制的,它适用于矿产预测、普查和确定天然污染水平。在3万6千平方哩的图幅内,有1万8千平方哩还附有高灵敏度航空伽玛能谱测量的图件, The Geological Survey of Canada published and published in 1973 a new type of geochemical map of the distribution of copper, lead, zinc, nickel, uranium, iron, manganese and potassium in lake bottom sediments. Published maps are based on 36,000 square miles of fieldwork in northwestern Canada and are suitable for predicting, screening and determining natural pollution levels. Within the 36,000 square miles of maps, 18,000 square miles are accompanied by high sensitivity airborne gamma-ray spectrograms,