Structural and Mineralogical Characteristics of High-Grade BIF-Hosted Fe Mineralisation in the 3020 Ma Cleaverville Formation, North Pilbara Craton, Western Australia

The Banded Iron Formation (BIF)-dominated 3020 Ma Cleaverville Formation, exposed throughout the North Pilbara craton, hosts a number of high-grade (>70 wt. % Fe2O3) iron ore deposits of moderate size (<50 Mt Fe). The dominant structural and mineralogical controls involved in the formation of Fe ore deposits in this province remain poorly constrained. In this contribution, we examine the mineralogy and dominant styles of high-grade BIF-hosted Fe mineralisation in the 3020 Ma Cleaverville Formation throughout four iron camps. We show that the formation of iron ore results from the superposition of multiple hydrothermal alteration events involving both early hypogene and late supergene enrichment. In all camps, the formation of iron ore include the presence of: (i) thickening of BIF units during the North Pilbara Orogeny (referred to as D9 event, associated with regional metamorphism and transpressional deformation at ca. 2950 Ma), (ii) D9 fault zone-hosted, hypogene magnetite resulting in the formation of partly enriched ore, (iii) intensely developed, pervasive supergene alteration.