Diversity in iron ore deposits in Western Australia

Iron ore deposits hosted by Banded Iron Formation (BIF) in the Weld Range greenstone belt record five main iron ore types: (1) 'Residual' ore formed as a result of two generations of hypogene alteration of BIF. The first alteration phase replaced silica-rich bands with carbonates; the second phase involved the removal of carbonate gangue minerals and the concentration of residual Fe oxide-rich bands in the BIF via volume reduction. The product is a high-grade, high-tonnage Fe orebody, with minor contaminants. (2) Magnetite-bearing shear and fault zones cut BIF along lithological contacts and produce narrow, high-grade magnetite-rich ore zones with high levels of contaminants (e.g. SiO2, Al2O3). (3) Specular hematite quartz-bearing shear and fault zones cut residual orebodies and magnetite-bearing structures. (4) Goethite-hematite supergene ore zones are controlled by brittle faults that cut BIF. (5) Detrital deposits comprise transported BIF fragments and are intensely goethite-hematite supergene-altered. Similar iron ore types and their relative timing relationships are expressed by other BIF-hosted iron ore deposits located throughout the Murchison Domain of the Yilgarn Craton (e.g. Windarling and Koolyanobbing). A "mineral systems" approach to understanding controls on iron ore formation will lead to a more predictive exploration strategy for targeting iron orebodies.