On the stratigraphy and petrography of the Tuomivaara iron formation in Sotkamo, northern Finland

[摘要] The Tuomivaara iron formation is an example of a chemically sedimented, strata bound occurrence of Pre-Cambrian age. It is characterized by a relatively large volume of silicate facies, while the economically important oxide facies is in a subordinate position. The general stratigraphy of the Tuomivaara area is given, and the petrography of the iron formation horizon is described in more detail. Some economic aspects are presented. The origin of iron formations is discussed.