Powder Gold identification on site, help required

[Hann]

Hi everyone, really looking for some help with this problem, firstly I took out a lease for its hematite prospectivity a couple of years ago in the NT.
The Iron ore prices tumbled so that was the end, I went and relooked at my XRF assays and noticed a elevation in Arsenic levels along a faultline I then decided to fire assay all the samples with high Arsenic levels, I was blown away with a 60 ppm Au level and silver around 8 ppm.
Problem is the gold when analysed under a electron microscope proved to be between 4 to 50 Nanos so totally invisible to the eye and too small to pan, so this gold located in about 40% hematite/Goethite ore is presenting me a problem to find again as this particular bag of pulps tested had it's id number worn away, but we do know its from an area 200 metres long where the fault line pushes out. I believe this is hydrothermal and its just sticking its nose out by perhaps a area as small as a coffee table, after 2 trips and fire assaying 60 samples I have not been able to locate it as there is no way of seeing the gold and crushing and panning on site doesn't work with this material, the million $ question is DOES ANYONE OUT THERE KNOW A WAY THAT I CAN IDENTIFY ON SITE THAT I HAVE GOLD PRESENT IN THE ROCK?? otherwise I may have to physically take a 1000+ samples and hope that among them there is one that constitutes the window to the deposit?
Last week I spent $10.000 on air fares car hire accommodation and a hire of a Niton hand held XRF which turned out to be totally useless when using in a rich Fe area, I was hoping to follow the Arsenic trail using the Niton, so this was a total lost week in that respect, thank you rental company for letting me know that for this purpose the XRF is totally useless...
Any Ideas anyone? this could be the first Carlin type deposit in the southern hemisphere...
Thank you John

 

[jethro]

Can you narrow your search by discounting all pulp sample bags that still have a legible number but dont show high
As , Au levels.

 

[Hann]

Thanks Jethro,
Yes, done that which now narrows it to a 200x100 meter area, highest Au in this area from testing is 0.07ppm not close yet

 

[jethro]

Im not a geo, but would rock chip geochem samples at 10m intervals narrow the search?

 

[Hann]

Thanks Jethro, yes I think that will be our next move but perhaps in 5m spacing as I believe the footprint will be on the small side, rock chips will have to be at least 100 grams to be able to send to fire assay and keep an in-house sample, wish there were a way though to ascertain the rocks for gold content before taking them for a 3 kilometres hike back to the 4wd that would save considerable cost on fire assays etc., but this looks like may be the only way.
Cheers

 

[jethro]

why not run a 15 metre grid spacing to start with and see if you get lucky. you can always fill in with a closer spacing between you first grid if nothing definiive turns up.

 

[Chewy]

Just thinking outside the box, I have no idea if this would work or not, but would a thermal imaging camera be of use? Used at night it may disclose groundtemp differences. You mentioned it may be hydrothermal.

 

[ILikeGold]

Google 'gold hunter test kit' should do what your after.

Would be easier to just get a decent fieldy in there then waste $10k stuffing around. Im not sure of your ground conditions there, but it sounds like your getting your sampling methods mixed up. Trying to pan a 100g rock sample is pointless and not going to tell you nothing. Why not just drill it?

 

[Tathradj]

If that deposit is in a hydro thermal area, Wouldn't the Au bearing deposit be subtle in colour or composition. ??
It is a stupid thing I suppose but what about plotting the other samples then refer to Google Earth to study your different ground characteristics.
If the area the sample came from was the size of a coffee table, You would be looking for a pipe. The surrounding soil would be significantly changed.
Think Target Rings.
Like a Molybdenite Pipe.
Another Lasseters Reef situation happening. LOL
Good Luck in your endevoures.

 

[Flitgold]

You can always use other pathfinder elements such as bismuth cobalt silver etc have a look back through your assays and see if higher arsenic correlates with other elements that are elevated ...over here in nsw in the central west exploring for shear hosted structurally controlled systems high arsenic bithmuth tellurium and copper are great indicators of hydrothermal fluid movement along faults/shears etc

Study those results! ! Pick out any relationships with elements and whats out on the ground

Unfortunately gold can be associated with sulphides and not visible to the eye

Hopefully ive given you a bit of help

 

[Barra_Mad]

Stat by looking for the alteration zone on the fault. follow that along strike sampling. in order to provide answers more information will be needed like where is it located, what is the host rock in the area. Photos of ore samples could help depends on quality. geochemistry results would be great too.

 

[Metamorphic]

Yeh its a tough one Hann!

This is the way i see it mate.

Gold in very minute quantities of PPM is virtually everywhere......its known as 'Background Gold'

Its most likely in your backyard, your nature strip etc etc.

Such small quantities dont mean a deposit of substantial benefit in terms of economical extraction, lay's near by!

A decent deposit that proves its worth for economical extraction value (ie. in assay;s of grams per tonne), would be shedding gold every day/month/year if it were nearby.

This would ofcourse mean good visible gold to the eye, enabling it to be panned for color, thereby meaning an ability to zero in on any deposit.

The minute quantities you are concerned with would require expensive extraction chemical processes which would make it unviable to the small ML holder in my opinion.

Regards

Meta

 

[goldtrapper]

Is not 60ppm 60 grams/ ton? Near 2oz? Surley worth attention.

 

[user 4485]

Yes but you would need to prove that you were getting similar results to that consistently over an area for it to be feasible.
The further testing returning a high reading of 0.07ppm isn't very promising!

 

[user 4386]

Hi everyone, really looking for some help with this problem, firstly I took out a lease for its hematite prospectivity a couple of years ago in the NT.
The Iron ore prices tumbled so that was the end, I went and relooked at my XRF assays and noticed a elevation in Arsenic levels along a faultline I then decided to fire assay all the samples with high Arsenic levels, I was blown away with a 60 ppm Au level and silver around 8 ppm.
Problem is the gold when analysed under a electron microscope proved to be between 4 to 50 Nanos so totally invisible to the eye and too small to pan, so this gold located in about 40% hematite/Goethite ore is presenting me a problem to find again as this particular bag of pulps tested had it's id number worn away, but we do know its from an area 200 metres long where the fault line pushes out. I believe this is hydrothermal and its just sticking its nose out by perhaps a area as small as a coffee table, after 2 trips and fire assaying 60 samples I have not been able to locate it as there is no way of seeing the gold and crushing and panning on site doesn't work with this material, the million $ question is DOES ANYONE OUT THERE KNOW A WAY THAT I CAN IDENTIFY ON SITE THAT I HAVE GOLD PRESENT IN THE ROCK?? otherwise I may have to physically take a 1000+ samples and hope that among them there is one that constitutes the window to the deposit?
Last week I spent $10.000 on air fares car hire accommodation and a hire of a Niton hand held XRF which turned out to be totally useless when using in a rich Fe area, I was hoping to follow the Arsenic trail using the Niton, so this was a total lost week in that respect, thank you rental company for letting me know that for this purpose the XRF is totally useless...
Any Ideas anyone? this could be the first Carlin type deposit in the southern hemisphere...
Thank you John

Fine gold in ironstone is common, especially at surface (and sadly is not diagnostic of Carlin style). If the area is only 200 m long you won't need to take many samples for analysis (between 10 and 20 perhaps, at equal spacings)? If you can't detect gold in samples taken 20 m apart there is unlikely to be enough there to be of interest (it will usually be detectable over some distance, especially in ironstone). If you have taken 60 equally-spaced samples and got nothing high it does not sound at all interesting. No, there is no easier way....

And sometimes an individual assay can be wrong - did you independently re-assay that sample?