USGS Circular# 609 "Mercury in Soil Gas and Air ~~~~~"

[Cubfan64]

Beth - I found another interesting paper by J. Howard McCarthy Jr. in the Journal of Geochemical Exploration 1 : 143-162 (1972) entitled "Mercury Vapor and Other Volatile Components in the Air as Guides to Ore Deposits."

If you or anyone else would like a copy, let me know and I can forward it to you.

It has small sections on exactly what you were suggesting as "variables" in the testing for mercury vapor such as weather conditions, atmospheric pressure, recent precipitation, altitude, etc...

In the "conclusions" section, he states the following:

"Geochemical anomalies in soil gas can be useful guides to ore deposits, and may be espectially valuable in covered areas. Anomalies in near-surface air require great care in interpretation, and airborne anomalies require even more. All can be useful - none will be foolproof."

This statement is a reasonably good summary of why I'm leary of drawing too many conclusions from the USGS circular 609 report. Not saying it might not indicate precious metal deposits in the Superstitions, just that it doesn't present enough information to prove it to me is all.

[Oroblanco]

Cubfan wrote

This statement is a reasonably good summary of why I'm leary of drawing too many conclusions from the USGS circular 609 report. Not saying it might not indicate precious metal deposits in the Superstitions, just that it doesn't present enough information to prove it to me is all.

That makes very good sense to me and is a reasonable view. It is still interesting (to me) that such high mercury vapor results were obtained while flying over the Superstitions, but we ought not attach too much weight to those results for a number of reasons.

Joe - $10k for a hand-held vapor sampler? Say amigo how would you feel about investing say, $9,995 in a "sure thing" type of investment/loan? (heh heh)

<kidding of course>

Roy

[Mike McChesney]

Now to throw a little gasoline on this fire:

A friend in the business just emailed me regarding this subject. He is more on the research side than the mining side. He told me that since Mercury comes in seven different isotopic forms (Hg196, Hg198, Hg199, Hg200, Hg201, Hg202, and Hg204). Different isotopes found while analyzing the samples could mean different things (some of the isotopes could mean gold, some could mean silver, and some could mean mercury). He will check into it for me.

It just gets better and better. What he did tell me for an absolute fact is that mercury vapor testing is (and has been for a long time) used to find valuable precious metal deposits by the mining industry. That is not a fact in question.

Best-Mike

[Cubfan64]

Mike,

Could you ask your friend what the source generally is for the mercury vapor that leads to the precious metal deposits?

As Beth and I mentioned, cinnabar doesn't decompose at typical temperatures into elemental Hg and sulfur, so the vapor wouldn't be coming from unworked cinnabar deposits.

So is the mercury vapor coming from elemental mercury that has been added in those locations by previous prospectors and/or miners - thus the precious metals deposits are being "rediscovered" from vapor analysis?

Another option is that cinnabar deposits could be geologically related to precious metal deposits, so if the cinnabar has been roasted/processed in the same area, elemental mercury could still be present and again leads to being the source of the Hg vapor?

Is there any chance at all that the Hg is being vaporized at higher temperatures underground and carried out of faults and cracks in rocks?

It would be wonderful if we could get a geologist to visit the forum for this topic and provide some input.

What's odd to me is if mercury vapor testing has been used for a long time to lead to precious metal deposits, why would the USGS come out with the circular in 1969 using saying it's a "potential tool?" Could it be that this is a case similar to dowsing where the industry has used the tool for a long time without really doing a study to figure out why or how it works - just the fact that it works is good enough?

Thanks Mike

[Mike McChesney]

Personally for me, knowing that the mining industry has been using mercury vapor testing to find valuable deposits is enough for me. While I understand most of what is involved and the science behind it, I don't need to know every miniscule detail as I don't work in the field.

This is an answer to my question:

"Hg vapor sampling has been utilized to indicate the presence of precious metal deposits. Typically, mercury occurs above Au and Ag deposits but may, also, be localized or anomalous within the precious metal concentrations. Some areas don’t have precious metal deposits where mercury occurs. There are numerous examples in CA adjacent to old mercury mines. The McLaughlin mine (Homestake Mining Company) was discovered beneath an old mercury mine; however, the mercury occurrences on the Livermore ranch out of Napa valley have no known gold deposits. Thus, the presence of anomalous mercury (particularly on low-atmospheric pressure days) simply indicates that you have unusual Hg that may have other metals at depth."

That was from the Dept. Head of a prestigious School of Mines. What he said was that more often than not, the presence of larger than background mercury vapor levels indicate precious metal deposits, and occasionally it just indicates mercury. He wouldn't put a percentage on it.

Best-Mike

[Cubfan64]

It's interesting to read a little of the history of the McLaughlin Mine - the folks that worked for Homestake Mining Co. who ended up discovering it were specifically looking for mercury deposits (I assume cinnabar) associated with hot springs.

Thanks for the information Mike - I understand you may not be interested in more detailed explanations, but I always find that stuff interesting and it almost always leads me to further studying that leads to me learning useful things.

[Mike McChesney]

Paul,

Its not that I don't do it. I find myself doing too much of it. When you start getting in too much detail once you arrive at a conclusion, you wind up spending too much time in research and not enough outside. HAHAHA

Best-Mike

[Cubfan64]

True, but like I've told Jim Hatt a few times when he complains that I'm getting caught up in details that won't help find the Lost Dutchman...

Until I live close enough to the Superstitions that I can go exploring anytime I want, I'm limited to reading and research and I never know what I'll stumble across that might be important.

Don't be surprised if I'm rarely seen on forums anymore once we get out there for good

[Mike McChesney]

HAHAHA Aint that always the truth,

Mike