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Geologists discussion thread!

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jman2007

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To all you Geo's lurking amongst ASF,

I thought we might be able to pool some of our knowledge together and basically discuss our ideas and experiences in the industry? This could include (but not exclusively) Exploration Geo's, Mine Geo's and Resource Modellers. I think it could be really ineteresting, as we could learn a lot from each other as well!

You could start by stating what sector you work in and a general description geographically of where you work (optional of course). Obviously specific company details and confidential reports would be strictly out of bounds.

It might help other ASF members who can get somewhat bamboozled by the technical mumbo-jumbo and who might want some help interpreting company information too.... hell, half the time even I have trouble understanding what they mean!

Cheers
jman
 
Mate, absolutely anyone who is interested is welcome to jump on board!

I thought this generalised diagram of the various JORC categories and their relationships would be a good start. This classifications sets out the basic framework for reporting tonnage and grade estimates to reflect varying levels of geological confidence and different levels of technical and economic evaluation.

Exploration Results in the early stages of exploration are generally insufficient to allow any type of Mineral Resource estimate to be made, hence they are excluded from the geen box.

Mineral Resources can mainly be worked out by a geologist, however, Ore Reserves which are a modified subset of Indicated and Measured Resources require consideration of numerous social, economic and many other factors....the so-called "modifying factors".

The code allows for a direct 2-way relationship between Indicated Mineral Resources and Probable Ore Reserves, and between Measured Mineral Resources and Proven Ore Reserves, reflecting the similar level of geological understanding required for each category.

Interestingly, the code allows for a conversion between Measured Mineral Resources and Probable Ore Reserves, reflecting a level of uncertainty in some of the modifying factors, but not a drop in the level of geological understanding. A Probable Ore Reserve can be upgraded to a Proven Ore Reserve once the uncertainties surrounding the modifying factors are removed.

Application of the Proven Ore Reserve category reflects the highest level of confidence possible, and under no circumstances can a Indicated Mineral Resource be directly converted to a Proven Ore Reserve. Ore Reserve estimates must never be combined with Mineral Resource estimates to report a single combined figure.

For a full explanation, visit the JORC website, you can download the JORC code there.

Cheers
jman

Source: The JORC Code, 2004 edition
 

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Well you may have answered one of my questions without me asking it. I was wondering if there was anyway to form a rough estimate of resource size from drill results announced. I can see some benefit only in assessing grades but even then it seems to be open to manipulation or on how a company "markets" these results. Sometimes wonder if they are of any real value to the market especially in gold. Iron Ore results seem to give a clearer picture.

On gold mining I have come to the following conclusions by way of google geology lol so would appreciate feedback on whether I may need to upgrade my research tools!

Epithermal deposits - exposed = very good

Banded Iron Formations = good

Refractory ore = very expensive to mine

Quartz vein = hard to define resource (as discussed on gold thread)


Thanks, appreciate it.
 
Spaghetti,

The JORC code is very clear when it comes to the reporting of Exploration results. Probably the key here is distinguishing discussion of Exploration results in terms of target size and type versus its misrepresentation as a Mineral Resource or an Ore Reserve. You cannot use the terms Resource(s) or Reserves(s) in this context.

"Any statement referring to potential quantity and grade of the target must be expressed as ranges and must include (1) a detailed explanation of the basis for the statement, and (2) a proximate statement that the potential quantity and grade is conceptual in nature, that there has been insufficient exploration to define a Mineral Resource and that it is uncertain if further exploration will result in the determination of a Mineral Resource" (JORC Code 2004).

What troubles me more is that you never really know what proportion of a Mineral Resource may be refractory in nature (Au deposits). I don't know if there are any restrictions or guidelines in terms of this type of reporting. I guess potentially a company good market it's deposit knowing that perhaps 40% of it is refractory. Refractory ore is bad news, it basically means that the gold is locked up in a lattice of sulfides, such as pyrite, and that conventional cyanide leaching is insufficient to liberate economic quantities of gold within normal residence times (Damn, a metallurgist would be great to have on this thread!...).

You can either use some kind of bio-leaching in which the "bugs" use the sulfides as "food" and liberate the gold or use a roaster like KCGM use outside Kalgoorlie for refractory Superpit ore. This basically bakes the ore up to 1000 deg celcius, driving off the carbon and sulfides. It would be prohibitively expensive to haul ore by road to a roaster, so most companies don't bother. I don't think you can build any more roasters now either.

Well certainly the BIF is one of the key targeting criteia we use when coming up with exploration targets, in conjunction with many other tools such as pathfinder geochem, soil geochem anomalies etc. Because the BIF is so erosion resistant it can sometimes be mapped over large areas. There is a clear distinction between Au mineralization associated with sulfidization and silicified BIF and structurally controlled (a shear zone or a fold for example) sheared mafic volcanic rocks for example.

Structurally controlled Au can occur within almost any rock type, and is not bound by lithology (rock type), look at the Golden Mile Dolerite in Kalgoorlie compared to the conglomerate-hosted gold at Wiluna for example.... completely different rock types, yet both world-class systems! Granites for example, are generally (but not always) not as prospective for gold mineralization in most cases. A good hypothetical target could also include the intersection of a shear zone with a BIF.

Don't know much about epizonal gold deposits, have to get back to you on that. I mainly have experience in Archean Orogenic (means a period of mountain building) lode gold deposits, which is generally structurally controlled mineralization that can occur in any rock type.

Hope this helps
jman
 
Brilliant, thank you, such a great contribution. I almost understand it..which is great, wasn't long ago I would not have understood any of it.

I may give you a break before any more questions lol

cheers

Google geo aka spag
 
Eeek!!...:eek:

Er, slight error on my part folks, I referred to the "Wiluna Conglomerate" which is incorrect, it is actually the "Wallaby Conglomerate" I was thinking of (Mental rap over the knuckles...ouch!).

Thanks for the kind words of encouragement people, much appreciated. Have to fly up to NE Goldfields tomorrow to log diamond core, so might struggle to access ASF this week! :(

Hey think of me when you're sipping your after-work beers down by the waterfront while I'm swatting flies in 45 deg...:mad:

Over and out
jman
 
jman2007 said:
Eeek!!...:eek:

Er, slight error on my part folks, I referred to the "Wiluna Conglomerate" which is incorrect, it is actually the "Wallaby Conglomerate" I was thinking of (Mental rap over the knuckles...ouch!).Over and out
jman
Click to expand...

lol "A Freudian slip is like saying one thing, but meaning your mother."
 
Lurking Geo here.

Currently employed in the exploration sector, focussing on nickel sulphide exploration. With a junior atm, have worked with majors in Ni and Au exploration and Ni production.

One thing I have noticed, especially with respect to the plethora of juniors all fighting to get their piece of news to the market, is the standards of reporting. Some of what is reported sounds impressive, though when you have a working knowledge of the industry it is obvious that many things can be simply overstated or worse, grossly misrepresented. It is interesting how many exciting new projects or discoveries are reported on once or twice and are never covered again.

You need to read ASX releases with a very critical eye.

You need to look for the materiality of statements, that is, are grandiose statements backed up by hard physical evidence, or do a few surface grab samples constitute one of Australia's newest big discoveries?

Also transparency is an issue. Does the report contain sufficent information? is it clear and unambiguous? is it misleading? there are a lot of terms that sound great but have no significance wrt to JORC, such as hypothetical resources, insitu value, probable resources ...

It is hard to know what is a significant result, especially when you are unfamiliar with the exploration methods and commodities involved. It was very interesting watching the frenzy associated with uranium recently, every one was rushing to spin-off their potential U assets into new floats and ASX releases were thick and fast. The word around was if you have any historic U exploration results or access to a scintilometer, generate an anomaly and release it. My knowledge of U exploration is and was very limited and I didn't really know what was significant or not, though companies values would leap on announcement as everyone fought to get a piece of the U action.

Something I am really interested in is coal, oil and gas exploration and production. Though, it is also something that I have no working knowledge of and thus the significance of most terms and values wrt intersections are meaningless to me. Are there any coal-oil or gas geos out there that can give a quick rundown on significant exploration indicators?
 
derty said:
Lurking Geo here.

Currently employed in the exploration sector, focussing on nickel sulphide exploration. With a junior atm, have worked with majors in Ni and Au exploration and Ni production.
Click to expand...

Derty - I have a question for a nickel man/lady if you don't mind. How can I find out about the viability of nickel laterite deposits? I have often read that nickel sulphides are cost effective to mine but nickel laterite deposits are prohobitively expensive and thus not worth the risk. As with every rule of thumb, there will obviously be exceptions. So the geo question is what should you look for in laterite deposists or should they be shunned as a fools dream?

I am not sure how questions like this rate on the 'investment advice' scale so I guess a reference to a web site or a journal on the subject would be the most appropriate. As always, any info provided will be treated under the auspices of DYOR and IMO. Mods?
 
Bushman, I think that's a fair question, but I suspect the question relates into the process of recovering the metal as opposed to geology. I'm sure they'll be able to help somewhat...
 
jman2007 said:
Hey think of me when you're sipping your after-work beers down by the waterfront while I'm swatting flies in 45 deg...:mad:

Over and out
jman
Click to expand...

Roger that Jman.

Shouldn't that be sitting in the air-conditioning in the 'cruiser with your Engel listening to an ipod though?;)

Don't let any of those smelly drillers do unspeakable things in your sample bucket .............

As the hatchetman said- great idea for a thread, look forward to it.

Whatyousee - loved the freudian slip thing :) I'm going to use that
 
Bushman said:
I have often read that nickel sulphides are cost effective to mine but nickel laterite deposits are prohobitively expensive and thus not worth the risk.
Click to expand...

Wonder if you are thinking of the same company I am? Anyways, not a geo but I agree with Doctorj...I think that's a metallurgical question. Would be great to get one here. Many thanks for this thread.
 
Yes, a question best posed to a metallurgist, but I can lay some ground work. Being a sulphide explorer I spend most of my time trying to avoid the confusion that lateritic enrichment of nickel creates in the regolith (the stuff between fresh air and fresh rock) when targeting sulphides.

Basically during the weathering of ultramafic rock nickel can be concentrated in various parts of the weathering profile and in various minerals. The nickel to be enriched is originally contained within the mineral olivine and does not have a sulphide origin.

Nickel laterites come in 3 varieties.
1. Hydrous silicate laterites - Ni is contained in Mg-Ni silicates such as garnierite, hosted in the lower part of the weathering profile. Forms in well-drained tropical areas, generally higher grade (1.8-2.5% Ni). e.g Goro deposit in New Caledonia.
2. Clay silicate laterites - Ni is hosted mainly within smectitic clays and is hosted within the lower-saprolite (middle of weathering profile). Common in Australia, lower grade (1-1.5% Ni) e.g. Murrin Murrin, Bulong.
3. Oxide laterites - Ni is mainly hosted within goethite (Fe oxyhydroxide) in the upper saprolite (upper part of the weathering profile). Common in Australia, lower grade (ave 1.2% Ni) though grade can be significantly improved by screen removal of free silica (benification). e.g. Cawse, Ravensthorpe.

In Australia, a deposit usually has both clay silicate and oxide laterite, though one will usually dominate.

Costs for setting up processing facilities for Ni-laterites are huge (billions $) and the processing plants are largely ore-type dependant. The lead time from resource definition to commissioning a plant are 5-10 years and someone with very deep pockets needs to be involved.

The appearance of heap leach technologies can provide a faster route to production for the smectite-type ores. The costs involved in setting these up appear to be in the order of 100's of millions and not billions. HRR's Jump Up Dam project is an example of this in the pipeline.

As for what makes a prospective laterite play? It is a complicated question. Those with smectite ores can pursue the relatively cheaper heap leach options. Either way a very large amount of finance is involved. The processing requires large volumes of water and acid so sources for these must be acquired. While it sounds like laterite ores are huge continuous homogeneous blankets, they often have high localised variability of grades and ore types that can complicate mining and processing.

I'm sure a metallurgist will be able to make this more clear as I have at best a poor understanding of the details of the extraction processes involved.
 
Thanks for the detailed reply Derty. Very informative. It sounds like the capex for a laterite deposit is prohibitive after all.
 
derty said:
Lurking Geo here.

Currently employed in the exploration sector, focussing on nickel sulphide exploration. With a junior atm, have worked with majors in Ni and Au exploration and Ni production.
Click to expand...

Hey Derty,

Great to have you contributing to the thread, you also raised some really good points re interpretation of Exploration results as well.

Mate the Goldfields flies are still out in force, I'm sure I recognised some of the same little buggers from last time! :p:

jman
 
Derty..or anyone who knows!

Looking at a map atm prospective for nickel. It shows a legend and the area surrounding drill target is described as ultrabasic. Is this the same as ultramafic? However the drill target area is described as pyroxenite. sort of an outcropping I guess....so could this be suphide sort of nickel? Or could this also be laterite. Once again I ask forgiveness if totally ignorant question.

And once again can say how much appreciate all this. Going forward in this market I think we will need a far better understanding of what we are buying than we have had in the past.

Cheers
 
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