Ann: Gold Extraction Results from Ema and Tres Estados, page-180

Hi ainsleym,

Yes you are correct in respect of the garimpeiros. My point was that given the potential that is implied for the amount of gold and PGM mineralisation that might exist at these prospects one would probably expect significantly more native forms of gold to exist both within the weathered zone and also within the deposit itself.

The occurrence of gold and platinum group metals together in such abundance is highly unusual and so it is natural to try and compare these prospects to the closest simila example one can find. This takes us back to the Serra Pelada Au-Pd-Pt Deposit in Northern Brazil.

As mentioned before most of the gold and Pd-Pt at Serra Pelada is located in the weathered horizon of the rock and as mentioned before the main deposit exists within sediments that are thought to have formed a "cap" over a dioritic intrusion and created the right Ph and oxygen fugacity conditions for the deposit to form. We don't seem to have these same diorites or host sediments currently at Tres Estados and Ema, instead the gold is being recovered from a fresh (unweathered) gabbro which is also an intrusive rock like a diorite, it just has a more mafic (is richer in magnesium and iron) composition.

"Diorite is an intrusive igneous rock composed principally of the silicate minerals plagioclase feldspar, biotite, hornblende, and/or pyroxene. The chemical composition of diorite is intermediate, between that of mafic gabbro and felsic granite."

Most (and this is good news for BBX story) of the gold and Pd-Pt in the weathered zone at Serra Pelada is not considered to have come from supergene enrichment processes.
It occurs as a dominantly as a gold-Pd alloy. This however is not to say native gold doesn't exist within the deposit.

http://econgeol.geoscienceworld.org/content/97/5/1127

"The occurrence of gold dominantly as an Au-Pd alloy, the abundant selenide and arsenide inclusions in palladian gold, and the characteristic mercury signature point to an origin of the near-surface bonanza ore from a sulfur-deficient hydrothermal system, with apparently only minor supergene precious metal enrichment."

Some of the grades from Serra Pelada are truly spectacular.

"A historic drill core from the Serra Pelada open pit was only recently assayed and has spectacular gold, palladium, and platinum grades over a 43-m-depth interval (4,709 g/t Au, 1,174 g/t Pd, 204 g/t Pt). The Au-Pd-Pt mineralization in a bonanza-grade interval (54.5–55.0 m @ 132,000 g/t Au, 11,400 g/t Pd, 359 g/t Pt) consists of coarse-grained, up to several centimeter-large, dendritic palladian gold aggregates (Au₇Pd) with abundant inclusions of guanglinite (Pd₃As), "stibio-guanglinite" (Pd₃[As,Sb]), sudovikovite (PtSe₂), palladseite (Pd₁₇Se₁₅), and an unnamed Pd-Pt-Se alloy. The palladian gold aggregates are often coated by goethite and are embedded in a powdery, ferruginous, clay-rich matrix with fragments of vein quartz. Iron and manganese oxides occur as vug fillings in palladian gold and are associated with native palladium and Pd-oxygenated compounds."

So as you can see from this example even though we might have a complex form of ionic gold wrapped up in unusual alloys at the BBX prospects we should still be able to find abundant amounts of metallic alloys in the weathered zone that due to their weight should easily pan out of soils and or clay or clayey rock. What's more, so far in my investigations I haven't been able to find any reference to these Au-Pd alloys at Serra Pelada not being amenable to standard assay schemes. If anyone can find any evidence of this please let me know as that would help support our story.

The problem with the BBX story for me is that there has been very little attempt to try and explain what this statement means

"a complex style of multi-element mineralisation where metals are present in an ionic form"

The types of metallic alloys that I've referenced above at Serra Pelada are not ionic solids, ie they are not created through ionic bonds, they are metallic solids not unlike a normal metal. Alloys are essentially just like any other pure metal. They are just a mixture of metals where the less dominant metal either substitutes for the more dominant metal in the crystal lattice or it forces its way into gaps in the lattice. Alloys are also created at high temperatures so if these are true alloys they wouldn't fit easily with models for mineralisation that involved low temperatures like epithermal mineralisation or low temperature hydrothermal deposits. It could be that they are not true alloys, more so aggregates of the constituent metals.

The words "ionic form" from my understanding can only be interpreted in three ways. The first being that the metal has formed an ionic bond. This can occur with a non-metal in the rock or in the case of gold with extremely reactive metal like Ce or the very rare metalloids like Tellurium. Below is a link to site which describes all the groupings and compounds of gold. You can steer through this site to find similar information for Pt and Pd.

https://www.mindat.org/min-1720.html

The second is that the metal exists in the rock as an ions (an ion is an atom, or a molecule, in which the total number of electrons is not equal to the total number of protons, giving the atom or molecule a net positive or negative electrical charge). Generally ions only like existing in solutions where there is nothing to find to bind to (not in rocks). The third and more contentious and it might be what the reference to relativistic chemistry was trying to allude in this statement


is where you have a compound (ionc solid) of Au, Pt or Pd that behaves like it is an ion due to relativistic effects stemming from the high energies of its orbital electrons. Frankly I have read the reference that Jeff Mckenzie has made to this paper

http://www.sciencedirect.com/science/article/pii/S129325580500230X

and can't see any explanation in it myself for how this ionic form of metal occurs or why it would not be amenable to conventional assay techniques. In fact when reading on this subject it seemed clear that the these relativistic effects in chemistry can be considered to be perturbations, or small corrections, to the non-relativistic theory of chemistry and I don't seem like likely candidates for the problems with the assaying and metallurgy that we see here IMO. And before anyone tells me to ring Jeff to find out, remember he comes form a banking background so would have no fundamental knowledge of the workings of relativistic chemistry, I on the other hand have a degree in physics and mathematics so understand how the orbital states of electrons in atoms come to be explained. Esh