I am assuming they are using SIBX than another collector...

I am assuming they are using SIBX than another collector anion  i may be wrong. But most of these xanthates and similar metal salts of organic 

Sodium isobutyl xanthate (SIBX) is typically used when the collector needs to be stronger than SEX (sodium ethyl xanthate )without compromising too much on selectivity, for instance in some copper-gold, copper-zinc and nickel operations. It is therefore used for flotation of almost all sulphide minerals where high selectivity is not required. It can be successfully applied at flotation of sulphide minerals containing gold, silver or native gold in the process of selective flotation of zinc mineral, after activating of sphalerite or mormolite by copper sulphate.

reading on collectors and how they function with relation to pyrites etc and dissolved oxygen blabla. Looks to be big business. SIBX $1650 USD per ton. very cheap at $1.65 per kg. I would suggest they use around 0.1kg per ton to make the flotation of the sulfide ore work effectively. . https://www.tandfonline.com/doi/abs/10.1080/01496396908052266

 cf with PIO:ASX just exporting pollucite - Na's big brother Caesium and that stuff is worth $$$$$$$.

https://www.911metallurgist.com/blog/flotation_collectors gives a very good introduction into flotation separation of gold ore by this process, although as it has been OCRd some words are bung ....acids reads as adds. 

Cant find much about the DOW 250 - but Dow are producing gold specific selective resins for picking it up from the leach process. - http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_0043/0901b803800434b0.pdf

And the copper sulphate may be there as a redox acceptor or to interfere with other minerals present etc.

the pyrite seems to be mainly quartz from the photos but could have galena and covellite or some such; as As,Pb and Sb are often with Au and Ag. Bizzo you may know more about this. 

What they havent detailed throughout all this time is what they are going to do with the enriched gold ore once post flotation/drying.
No detail of acid /pressure/ cyanide or electrowinning detail. I was kind of hoping that a green chemistry was going to be dropped for this area or a bit of new research was going to be busted out. I figure they are going to sell it to a refinery for the first bit.

Id be putting down some electrolytic research on the refined gold ore. "Ah we found that we could fuse the ore in the pots at Tiwai and produce extremely pure Au by fusion of the ore and running 10000A at 6/32 V Dc through it and Ah we signed a contract with rio tinto to hire one of their out of use pots for the next 6 years". We might look at starting up our own one in 4 years time...