Geophysics at the Hawsons Iron Project, NSW ? Eastern Australia?s new magnetite resource

Abstract

A JORC inferred resource of 1.4 billion tonnes at a magnetite Davis Tube Recovered Grade of 15.5% was defined at The Hawsons Iron Project near Broken Hill in western New South Wales making it the largest magnetite iron ore resource identified to date in eastern Australia. Reconnaissance surface exploration in 2009 identified the area?s potential for magnetite iron ore fifty years after it was last considered an iron ore play prior to the discovery of Mt Tom Price. Neoproterozoic Braemar Ironstone Facies sediments host the magnetite mineralisation which generates aeromagnetic anomaly amplitudes greater than 6000 nT. Five target areas for magnetite iron ore were identified from the open-file aeromagnetics. A realistic Exploration Target was estimated from selective 2.5D magnetic modelling and image processing of the airborne aeromagnetic data. The inferred resource was established within 18 months of commencing the exploration program drilling 72 holes into the five aeromagnetic targets. The monotonous sedimentary host sequence of siltstones and sandstones with few marker beds makes detailed geological interpretation extremely difficult. A magnetic stratigraphy was constructed from recognizable patterns in wireline magnetic susceptibility traces and correlations of the mineralisation could then be established down dip and across strike.