14. Tops and Bottoms of Porphyry Deposits featuring Richard Sillitoe

Richard Sillitoe and John Thompson talk about the evolution of the porphyry model from plate tectonics to lithocaps, mineral zoning, and the link to epithermal gold systems. How has the classic ‘tops and bottoms of porphyry deposits’ model changed and what have we learned over 50 years to guide our exploration.A prime example of the epithermal - porphyry connection is well known at the Lihir Gold Deposit, Papua New Guinea, operated by Newcrest Mining. We talk to Stephanie Sykora who studied the porphyry processes, alteration and mineralization about the evolution of the system and the challenges of working in an environment where the rocks and fluids are still hot.The last story brings it all together, with the discovery of the Onto Copper-Gold Deposit in Indonesia by Sumbawa Timur Mining, a subsidiary of Vale. Dave Burrows (Chief Geoscientist, Vale) takes us through what they achieved with their exploration strategy and the unusual features of this copper-gold system. New discoveries are still influencing how we view the tops and bottoms of porphyry deposits.Theme music is Confluence by Eastwindseastwindsmusic.comComing soon SEG Special Publication 23: Geology of the World’s Major Gold Deposits and Provinces. Editors: Richard H. Sillitoe, Richard J. Goldfarb, François Robert, and Stuart F. SimmonsCome join us in Salt Lake City, Utah for SEG 2026, September 30th to October 3rd. You can expect world-class technical content, including iconic ore deposits and the geological processes of North American Cordillera. The program balances applied case studies, framework geology, and technological innovation. The conference offers a unique opportunity to connect, learn, and help shape the future of economic geology. See you there.