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  CWEDG Technical MeetingTUESDAY 20 August 2024 Discovery of the Gamsberg East Broken Hill-Type Deposit, Northern Cape, South AfricaBroken Hill type deposits remain something of an enigma in economic geology, despite their highly characteristic features and economic value. Discoveries are rare (eg Cannington 1991), and their geological origins are still debated. The brownfields discovery of Gamsberg East in 2005 was the culmination of decades of mapping, interpretation, analysis, and drilling at Gamsberg near Aggeneys in Northern Cape Province in South Africa. However, the eventual discovery was driven at the time by limited exploration funds, a need to re-evaluate exploration strategy, new technology, and a Saturday afternoon paper maps and sections light table discussion in the Anglo American Exploration office at Aggeneys. The public Inferred mineral resource at Gamsberg East is 32.2Mt @ 9.83% Zn (7% Zn COG), with lesser Pb and Zn credits. Upside-down metamorphism at Broken Hill NSW, Broken Hill. Structure/metamorphism no longer done and dustedDetailed mapping of the andalusite-sillimanite isograd at Broken Hill indicates that metamorphic grade decreases up stratigraphy whether the stratigraphy is right way up or overturned. Previous structural/metamorphic models do not explain this. There are two alternatives: either sillimanite grade metamorphism took place prior to folding, or sheath-like F2 folds caused the overturning of stratigraphy and metamorphic grade Join us for the meeting, drinks, nibbles and dinner. For more information: cwedg@aig.org.au Speakers:Ian Willis Ian Willis has worked as a technical specialist, consultant and manager in geoscience and minerals exploration for more than 50 years. Ian learned his geoscience trade during an early field-based mapping career with the GSNSW (1973-1988), principally in Broken Hill and New England areas of NSW. Barney Stevens Barney worked for the Geological Survey of NSW for a lifetime, “retiring” in 2007 and taking on contract work with exploration companies at Broken Hill and Bathurst-Orange district and elsewhere. Barney’s first job was creation of the Bathurst 1:250,000 Metallogenic Map, the first of the series in NSW. He went on to lead the Broken Hill mapping and metallogenic project.
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