Sulfidation State of Fluids in Active and Extinct Hydrothermal Systems: Transitions from Porphyry to Epithermal Environments

To be honest, I am surprised to find myself addressing a meeting of the Society of Economic Geologists—being neither a geologist nor economic. And looking at the title of my paper, I wouldn’t be offended if people told me that I may be going to talk about something I know nothing about. After listening to some of this afternoon’s talks, however, it is clear to me that I wouldn’t be the only one. With this I don’t mean that the previous speakers were inept but that there are still quite a few basic problems which have to be solved before we may safely say, we know what’s going on in hydrothermal systems. And by basic, I mean basic.The title of my talk links two processes: magma degassing, something I have been studying now, from the gases’ point of view, for more than 20 years, and mineral deposition, something I had my nose rubbed into by living in close vicinity to some of the biggest gold freaks like Kevin Brown, Jeff Hedenquist, Dick Henley, and Terry Seward. I myself had, quite early on, declared gold a four letter word and had vowed never to use it in any of my papers, together with other uncouthities, such as zinc or lead. Now that the above have dispersed, each into his corner of the globe, I think myself free to reconsider my earlier pledge.