Mindoona Detrital Modelling, The Pilbara, Western Australia

Mindoona, part of the South Jimblebar Iron Ore Hub, is situated 40 km east of the town of Newman. The deposit is located on a faulted east-west striking ridge abutting the granite-greenstone outcrop of the Sylvania Inlier along the Painkiller Bore Fault. The north-dipping strata are partially buried by Cenozoic detritals up to 200 m thick.

PSM was engaged to model Cenozoic detritals into geotechnically significant sub-units following from the precedent study undertaken at Mining Area C.

Variability in the rock mass strength required defining the sub-units and determining whether sub-divisions were co-relatable at the drill-hole spacing of  50 m.

Most drill-holes were drilled within the ore-body zone, with less available for characterisation of the final wall area. Undertaking a comparative study between assay results and new technology Hylogger geochemical assessment.

Following rigorous assessment and modelling, PSM’s tailored approach included:

• Review of cored data and exposures to assess typical lithological composition of each unit
• Understanding of mineralogy to assess what elements should be elevated and which low for each unit based on the compositional assessment
• Use of geochemical data from RC holes adjacent to cored holes to correlate typical geochemistry
• Extrapolation of geochemical interpretations to the site as a whole
• Completion of a comparative study between assay results and new technology Hylogger geochemical assessment
• Development of 3D wireframe surfaces representing each unit
• Development of a 3D model correlating geochemical signatures of the various units across 20 sections including interpretations of 40 cored and 700 non-cored boreholes.

The project significantly increased geotechnical understanding of the hanging wall materials and provides an excellent basis for future analytical studies, stability analyses and slope design.

PSM and BHP Billiton Iron Ore expanded their collaboration into geotechnical differentiation of Cenozoic detritals and introduced the concept to additional Pilbara sites. This represented the first geotechnical modelling of detrital for the Mindoona site and the first where data from the new Hylogger method of geochemical analysis was used.

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