The geology and genesis of high-grade hematite iron ore deposits

This paper presents a first summary of results of an ongoing study, started some two years ago, of high-grade iron ore deposits in South Africa, India and Brazil, including a comparison with the rather well-studied deposits of the Hamersley Province in Australia. Large, high-grade hematite iron ore bodies hosted by Precambrian banded iron formations are the world's most important source of iron ore. Despite their great economic importance, the origin of these deposits has remained rather enigmatic. Results of preliminary investigations into the geological setting, petrography and geochemistry of BIF-hosted high-grade hematite iron ore deposits in South Africa, India, Western Australia and Brazil reveal distinct similarities, suggest ing a very similar mode of hydrothermal and supergene-modified hydrothermal origin for most BIF-hosted highgrade hematite ore deposits. Differences between the deposits of this type are largely the result of varying intensities of supergene modification in Late Cretaceous to Tertiary times. Notable exceptions are the deposits in the Griqualand West region of South Africa, including the giant Sishen deposit, that are regarded to be of ancient supergene origin.