118 posts in this topic

Okay, I think we can have a useful discussion about this.

 

Whether you like the wording of my little rule of thumb or not, the point which I am trying to make is that of targets identified by regional geophysical measurements, only a very small portion will end up becoming important discoveries, perhaps one to maybe a few percent (exact numbers vary of course, but they are something in that ballpark). Regional geophysical testing has been around for a long time, and while it is a very useful tool to exploration geologists, it is by no means a guarantee that a large percentage of the potential targets identified by this method will become valuable mineral discoveries.

 

Another poster in this same thread put forth the same concept a different way, he said: It takes 25,000 claims staked to find 500 worth diamond drilling to find one mine. Source: Lorne Ames. While his numbers are also just to make a point, the point remains the same. Many claims will be staked, much geophysical testing performed and a lot of drilling will be done to identify one deposit which can be mined on a profitable basis. Geophysical testing has not revoked this concept. You cannot have identified ore reserves based only on geophysical testing, actual drilling is still necessary to identify ore reserves.

 

You have an interest in pluton or intrusive related gold deposits. Let's take a look at those as exploration targets - I think they will make a good example. There are quite literally thousands of intrusive stocks, bosses and plutons in Alaska. Most of these bodies of intrusive rock do not contribute any significant gold to the streams which drain them. A small but significant number do have significant gold and very commonly there are placer deposits found in the streams around them. Although some are hidden, many are well enough exposed to have their locations fairly well identified. Because these intrusives are known sources of gold, many of these intrusive bodies have been explored previously and are well recognized by expiration geologists as attractive potential exploration targets. A significant number of these known, gold bearing targets have been explored by various companies to see if they contain economic hard rock deposits. Millions of dollars have been spent examining these targets by geophysical methods on a local scale, which gives data that is more detailed and accurate than the regional scale maps produced by DGGS. Many millions of dollars have been spent drilling these deposits to see if they contain ore bodies which could be mined at a profit. There is currently one mine in operation in all the state of Alaska processing this type of ore body. It is the Fort Knox mine near Fairbanks. There are some other bodies which have been identified to contain some gold reserves that are not currently being worked. These range from deposits which are really too small to work in Alaska because of the lack of infrastructure to larger deposits like Donlin which will probably eventually be worked once all the infrastructure problems are resolved. This scenario fits perfectly into my point that only a small percentage of exploration targets actually end up becoming viable discoveries that can lead to profitable hard rock mining operations. 
 

Even among known, gold bearing intrusive bodies, only a very small percentage will produce bodies of rock which can be mined by hard rock methods at a profit. Decades of exploration in Alaska has demonstrated this. The fact is that the bodies of intrusive rock which give rise to placer deposits in Alaska are for the most part very low-grade and spotty. The valuable placer deposits which are formed from the erosion of these bodies are created because the natural process of erosion and stream concentration produce bodies of gravel that are more concentrated than the original source rock host. There is no reason whatsoever to expect that intrusive bodies covered by shallow overburden will have an exploration record better than the intrusive bodies which are exposed and known to be shedding gold.

 

The surveys funded by DGGS are indeed serious efforts and useful to exploration geologists. They can help identify potential exploration targets worthy of further investigation. However they are by no means a guarantee and of the potential targets thereby identified, only a tiny percentage will result in valuable discoveries like Fort Knox or Donlin.

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 A dear old-timer friend of mine, long since passed away, had a great saying he liked to quote.

 

 " A lot of good ground has been ruined by prospecting"

 

So goes the State's geophysical surveys. The vast majority of those 'good spots' located would be

ruined by prospecting. In no way does that diminish the State's effort.

 

 I never for a minute took Chris's responses to be "rude" and most certainly not "uninformed" !

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Geo you are welcome to believe whatever you wish. You may believe your skills at interpreting regional scale geophysical maps far exceed those of the poor fearful geologists that you think are so intimidated by geophysics. Your claim the geologists are intimidated by geophysics is silly - the reality is quite different. Geologists employ geophysicists, both in the actual measurement and interpretation of the results. However if you think that all there is to state of the art, modern mineral exploration is geophysical testing, then you are woefully misinformed. There are a number of important specialties, only one of which is geophysics.

 

I am merely presenting only the facts and history of mineral exploration, including the state of the art in mineral exploration which includes geophysics, geochemistry and many other techniques.

The fact is, and you cannot debate this, only a small percentage of mineral deposit targets, no matter if it is identified by geophysics or other more traditional means, end up as successful discoveries that can be mined. You yourself said at the beginning of this thread that the DGGS maps could yield "possibly thousands of probable locations" - do you truly believe all or nearly all of the targets geophysical you identify are nearly certain to become viable mines?

 

Truly, I am not trying to trample your hopes and dreams. Again, you are free to believe whatever you like, but you should not present as fact claims which go against the science and history of mineral exploration. There are also folks who believe that they can look at a topographic maps and "see" with reliability where mineral deposits are. They are just as convinced in their opinions as you are in your beliefs. I don't argue with them either.

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Every prospector must be an optimist to think that he or she can find a bonanza although the odds are not in their favor. Somehow, whether by by their knowledge. skills, tools, system, hard work, luck, or the will of God they will be able to find a deposit that others have overlooked for hundreds of years. 


Before coming to Alaska about 30 years ago I spent a half hour looking at generalized geologic map of the state and picked 10 targets that I felt had “favorable geology” based on no other information other than my theory that large intrusives into sedimentary rocks such as impure limestones, muddy or limey shales, etc. had the highest potential for precious metal lodes. As my research later showed all 10 areas that I chose had seen historic lode production. Of course with greater knowledge, a little work, and a “better system” I could have further narrowed my search to the what would have to be the mother of all mother lodes - but at that point it would still be a “prospect”. 


Mineralized rock is just rock and ore needs to be proven.


Of the “lodes” mentioned by Geowizard, which one has the highest potential reward to risk ratio? Remember it is better to take risks if you stay close to the road and use other people’s money.

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Also, I would add, Chris, the geophysical data is NOT "regional" as you have stated. It is specific data that applies to a discrete bedrock or alluvial conductor!

 

You don't seem to understand the difference between the two, so let me explain to you how that works. When you are covering a large regional area like the DGGS is doing, you fly widely separated data lines in order to cover a large area. Yes the data collected is real, and the actual values collected are no different,  but with smaller, property scale geophysical testing, you will fly much tighter lines. The difference is in the interpolation between data points.

No geophysical testing is done by taking a reading at every possible point in space, and the data which is collected along specific lines is put into a computer program which estimates the values between the data points. There are various methods of interpolating like inverse distance squared, but those details are really beyond the scope of what I am trying to point out. Although the computer uses math to give a best estimate, you really never know for sure what is happening between the data lines being flown. If the lines are very close together (perhaps 100 meters or less) the chances for unexpected geologic conditions to occur between the lines is much less than than if you are flying data lines 500 or 1000 meters apart.

This is why exploration geologists will use regional geophysical maps like the ones produced by DGGS in a general way, but if they have a specific property block they are interested in, they will have the geophysical data re-flown with much tighter data lines, perhaps 50 meter or 100 meter data line separations. This results in a more accurate map with fewer uncertainties caused by interpolation. As an example, the DGGS data for the 40 mile you refer to is done on a 1/4 mile separation. A lot can happen geologically speaking in a quarter mile. Apparent anomalies can indeed be created in the interpolation of the data to fill in the space between the lines, so some apparent anomalies will go away when more data lines are flown.

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I don't recall having said that every geophysical anomaly would become a viable mine.

My rule of thumb was one in one hundred, and you found that rude and insulting. So be honest and plain and say what percentage you so think. You point out there are 9,033 EM anomalies in the 40 mile area. Roughly speaking what percentage of these would you estimate would become viable mines? 80%? 50%? I have repeatedly asked this question, and you just wont give an answer. So if you find a one percent estimate rude, tell us - what is your number?

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Geo - I asked you this question:

 

You have pointed out there are 9,033 EM anomalies in the 40 mile area. Roughly speaking what percentage of these would you estimate would become viable
mines?

 

 And you completely avoided the point. The point is that only a very tiny percentage of these 9,033 geophysical anomalies will turn out to be valuable discoveries, and that
is not an irrelevant fact. It is an important fact that is unavoidable. Why are you having such difficulty with this very simple fact?

 

Geophysical conductive anomalies can be many things which are not valuable mineral deposits. Mineral exploration is in part about determining which few of the thousands of anomalies are actually valuable. This is why mineral exploration is a very high risk business.

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I am not going to continue to try to educate you on this as it is quite apparent you really don't want to learn.

 

However:

Anton H needs to give me a call.

I will remind you that advertisement for, or solicitation of investors is not permitted on this forum. It is considered the same as advertising to sell products or services.

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Fisher spent many years and millions of dollars finding all sorts of iron trash on the ocean floor - and some treasure too. He lost one of his sons during the years of searching for treasure amongst the huge amount of trash. Some other treasure explorers have not had the same success. If he were still alive, I am sure he'd be the first to agree with me that his geophysical equipment found thousands of targets, but only a small number of these were of value.

In the same way, the earth has many thousands of geophysical anomalies only a tiny few of which are valuable. That's the truth behind a saying like geophysical data find 1000 of the next 10 valuable discoveries.

 

Geophysical data is a useful tool, but the existence of an anomaly does not guarantee a valuable find. Mineral exploration is a high risk business.

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Excellent discourse gentlemen.  

 

I can see the avoidance of geo to acknowledge a 1% success rate.  You'll need to state a number or say "I don't know".

 

Chris has explained a sound history of geophysical testing results.  1% looks accurate.

 

We want to obtain better than 1% and might be able to IF we can prove even the 1%.  "I don't know" is an untrue statement, given the vast experience and application of current scientific data.

 

Fess-up geo,  what percentage do you ascribe to?

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