Thanks for the link, Jacob.

Rio Tinto is the worlds (if memory serves) largest pyrite deposit. It's huge. And it is believed to be of hydrothermal origin.

Also, I watched the rebroadcast last night and two things caught my attention.

Bromine. Gotta think 'bout that.

MgSO4. Epsom salts. Kieserite. Very interseting.

Gypsum.

There were silicates, too.

This association should tell us about the local pH Eh conditions of this water and the concentration of the brine. Much to review.

They showed some nice APS graphs with some other interesting peaks. They've not posted them yet, hopefully they will soon.

Evaporite mineral deposition is very sensitive to things like original concentrations and volume of water/brine. As they get more and more concentrated, different mineral precipitate. Other outcrops could contain vastly different mineral assemblages. I'll have to think about the reduction of acid verses the concentration of variable amounts of water. It could have been a fairly steady-state environment.

Sorry, I don't have a link at hand and I'm pressed for time. Look up Evaporite Sequences. And/or supergene enrichment. And/or deposits related to weathering, laterites, etc. I'm just flipping through my "geology of Ore deposits" book (Guilbert + Park, 1986) and there is all kinds of stuff that I just don't have the time to post, but I will hopefully do so in a week or so.