Iron mineralisation at Razorback is hosted in the Braemar Iron Formation; click here for more details. The Razorback area covers an approximately 10 km continuum of Iron Prospects: Razorback West- Razorback Ridge-Interzone-Iron Peak Prospects.
The mineralisation within the Braemar Iron Formation forms a simple dipping tabular body with only minor faulting, folding and intrusives. Grades, thickness, dip, and outcropping geometry remain very consistent over kilometres of strike. While the bedded magnetite has the highest iron content, typically 19-35% Fe, the tillitic unit, at typically 15-26% Fe is diluted by the inclusion of lithic fragments, such as iron-poor granite and metasedimentary dropstones.
Razorback Ridge iron deposit is positioned on the north dipping (approximately 40o to 60o) limb of the Pualco Anticline. The Braemar Iron Formation at Razorback is spit into seven sedimentary packages, comprising members A to G, with a total thickness ranging from 480 m to 780 m. Of these, members A, B, D and G are of economic interest and all outcrop or sub-crop at the surface, with member B forming the prominent ridge. There are lower grade magnetite units within Unit C and E, which are also included in the JORC resource.
Both magnetite and hematite are observed at Razorback, with their distribution strongly linked to lithofacies, as well as weathering. The three predominant iron species observed at Razorback Project consist of:
1) individual hypidio-idiomorphic shaped magnetite grains in the size range of between 20 - 150 micron in diameter;
2) martitised replacements of these magnetite grains; and
3) microcrystalline hematite grains usually below 10 micron in diameter.
Hematite may also occur as subhedral intergrowths with magnetite (metamorphic in origin, rather than due to surface oxidation) and specular hematite associated with faulting or extreme weathering at surface.
Updated November 2013