Whole-rock compositions of Precambrian iron formations and Phanerozoic ooidal ironstones: Comparative considerations and mineralogical differentiation of subtypes

摘要

Investigating 98 whole-rock analyses of iron-formations from 28 different localities and 102 analyses of ironstones from 7 localities it is shown that the proposed differentiation of James (1992) of these two types within the FeO-Fe_2O_3-SiO_2 diagram cannot be maintained. There are a lot of overlappings between them. However, it becomes obvious that the FeO-Fe_2O_3-SiO_2 diagram is a useful tool to differentiate the various subtypes within iron formations and ironstones as well.