Jump to content

Ancient River Channels


Recommended Posts


That's a pretty good writeup with some nice diagrams. 

Usually people only talk about paleo placers in reference to California. One of my personal major pushes in the placer gold realm today is to locate these old channels in other states where they've been overlooked or ignored/unrecognized. I've found them in every state I prospect in. It's not just limited to gold though, I've found placer jade in Wyoming by concentrating on looking for older gravels from long extinct rivers. Sometimes the gravels themselves are mostly eroded away and difficult to locate, but there are still residual deposits of garnets or other heavies. In Colorado I found a bunch of heavy zircon sand which I used to trace an old channel. A pan can show the presence of minerals which could have only gotten to where they are at by stream transport at one time. In the case of the zircons, I was able to trace the formation which they originated from and thus was also able to find more parts of the long extinct and mostly invisible channel many thousands of feet elevation above and many miles distant. Things like this can be employed absent large visible paleo gravel deposits.

  • Like 8
  • Thanks 1
Link to comment
Share on other sites

I once met a guy who owned a book store in Elko, Nevada.  He told me that as a general rule all the ancient channels had run towards the west from the rocky mountains long before the Sierras.  At the time I didn't know what he was talking about.

They used this and of course a lot more information to discover gold in the Carlin Trend and some quite large nugget patches up that way.

I guess now when you find ancient river gold high in the Sierras he knew what he was talking about.

Link to comment
Share on other sites

1 hour ago, oneguy said:

Stumbled onto this interesting article form another site......  Not sure where to post this but Steve can relocate it where he see's fit?

Thanks for sending, great article and videos. Tertiary channels are plentiful here in the Sierra's. The problem is that some are rather deep with hundreds of feet of alluvial gravel covering the heavies. The trick when metal detecting is to find shallow channels. But those have practically all been mined already. 

  • Like 1
Link to comment
Share on other sites

More on California paleo channels...

  • The Tertiary Gravels of the Sierra Nevada of California 1911 USGS Professional Paper 73 by Waldemar Lindgren. A California geology classic. An account of the Tertiary formations of the Sierra Nevada Mountains and the origin and distribution of the gold-bearing (auriferous) gravels.
  • Like 5
  • Thanks 1
Link to comment
Share on other sites

25 minutes ago, Steve Herschbach said:

More on California paleo channels...

  • The Tertiary Gravels of the Sierra Nevada of California 1911 USGS Professional Paper 73 by Waldemar Lindgren. A California geology classic. An account of the Tertiary formations of the Sierra Nevada Mountains and the origin and distribution of the gold-bearing (auriferous) gravels.

Thanks, Steve. I was about to post the exact same document but thought people might not like it because of how old it is. However, it is a great read and a lot to learn in it. I am glad you posted it.

This one is also good, it shows all tert. channels and deposits (Clark, 1965-see attached pdf)TertiaryChannels Sierra Nevada.pdf

 

 

 

  • Like 1
Link to comment
Share on other sites

The extremely detailed 1961 Deb Chandra Special Report 67 is also a great resource for the American River tertiary gravels.

http://www.mylandmatters.org/Library/Item=172

In 2012 we managed to borrow one of the three remaining copies of the very large hand colored tertiary gravels map in the original 1890 Colfax Folio from the Federal Repository. We did digitize that map as well as the Lindgren, Clark, Olaf Jenkins and Deb Chandra reports to create the interactive geology mapping on the North and Middle Fork FootPrints.

 

 

  • Like 5
Link to comment
Share on other sites

This is a GIS based map of the "hydraulic mine pits of california" - has many unnamed small occurrences: Some you probably never knew was there.

https://www.sciencebase.gov/catalog/item/571976c2e4b071321fe22947

You can use different base maps.

When I left the USGS in 1995 I was at the time working with Warren Yeend on expanding the Tertiary Gravel study beyond Nevada County. One of the big unanswered questions is the primary source of the gold in the Tertiary Gravels? There have been proposals that there was a similar suture system to the current Mother Lode to the east that has been too deeply eroded: Garside at UNR (and others - some Aussies I can't remember) have proposed a possible source east of the current Sierra Nevada. For the Yuba/Feather area was it simply very rich pocket type occurrences like the 16:1? Lots of other proposed explanations.

Rich Goldfarb and Erin Marsh at the USGS in Denver took over much of this work, bringing in several grad students to work in the Mother Lode, but unfortunately the USGS lost its focus and any significant ore deposit research has long gone by the wayside.

  • Like 3
  • Thanks 3
Link to comment
Share on other sites

38 minutes ago, GeoBill said:

This is a GIS based map of the "hydraulic mine pits of california" - has many unnamed small occurrences: Some you probably never knew was there.

https://www.sciencebase.gov/catalog/item/571976c2e4b071321fe22947

You can use different base maps.

When I left the USGS in 1995 I was at the time working with Warren Yeend on expanding the Tertiary Gravel study beyond Nevada County. One of the big unanswered questions is the primary source of the gold in the Tertiary Gravels? There have been proposals that there was a similar suture system to the current Mother Lode to the east that has been too deeply eroded: Garside at UNR (and others - some Aussies I can't remember) have proposed a possible source east of the current Sierra Nevada. For the Yuba/Feather area was it simply very rich pocket type occurrences like the 16:1? Lots of other proposed explanations.

Rich Goldfarb and Erin Marsh at the USGS in Denver took over much of this work, bringing in several grad students to work in the Mother Lode, but unfortunately the USGS lost its focus and any significant ore deposit research has long gone by the wayside.

Awesome, thanks GeoBill! I have downloaded the kml file, works great with Google Earth. Now, if we would just have a modern good PI detector that could discriminate. The amount of trash I usually collect in hydraulic pits is mind-boggling. These areas are prime territories for the GM or Nox 8. SDC/Zed completely useless. 

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Similar Content

    • By oldmancoyote1
      You have had a lot of success over the years.  I imagine you have found some wonderfully large masses of gold.  Think about each of those for a few moments, especially those in the lower 48.  Does anything appear as a common feature of their locations?  Surely not everything would fit the same mold, but was there anything present frequent enough to indicate one location might be a little bit more likely to yield big gold than another?
      Thanks
    • By afreakofnature
      The Mystery Formation of Extremely Rich Gold Veins Might Finally Be Solved
      MICHELLE STARR 24 MAY 2021 Gold, for all its wonderful uses, isn't hugely abundant in Earth's upper layers. For each ton of crust material, there's an estimated just 0.004 grams of the precious metal.
      Yet somehow, there are regions that contain "bonanza" abundances - hyper-enrichment, in the scientific parlance. How these gold veins form in time spans as short as days from hydrothermal systems that only contain trace amounts of the metal has been a geological mystery.
      It's one that now has an answer, from the most unlikely of clues: the separation and clumping of fat particles in soured milk.
      "Scientists have long known that gold deposits form when hot water flows through rocks, dissolving minute amounts of gold and concentrating it in cracks in the Earth's crust at levels invisible to the naked eye," geoscientists Anthony Williams-Jones and Duncan McLeish of McGill University in Canada stated in a Q&A.
      "In rare cases, the cracks are transformed into veins of solid gold centimetres thick. But how do fluids with such low concentrations of gold produce rare ultrahigh-grade gold deposits? Our findings solve the paradox of 'ultrahigh-grade' or 'bonanza' gold formation, which has frustrated scientists for over a century."
      Milk is an aqueous solution made up of several components, one of which is microscopic globules of fat. At the pH level of fresh milk - very close to neutral - these fat particles have a negative charge, which causes them to repel each other.
      The souring process involves bacteria in the milk converting lactose to lactic acid, lowering the pH level accordingly. This causes the surface charge on the fat particles to break down, and the fat particles separate from the milk serum and clump together with each other via coagulation, forming a sort-of gross decomposing milk fat jelly.
      Williams-Jones, McLeish and their colleagues found a similar process when using transmission electron microscopy to study gold deposits from the Brucejack Mine in British Columbia. This is one of the spots around the world where bonanza-grade mineralization can be found, up to 41,582 grams per ton.
      It's long been accepted that gold is transported by way of fluid through Earth's crust. However, in order to reach the abundances found in hyper-enrichment zones, previous studies suggested that the gold may have been dissolved in high concentrations in fluids containing chlorides or bisulfides, and transported and deposited that way.
      The other possibility is a colloidal solution, with solid nanoparticles of gold dispersed throughout hydrothermal and geothermal fluids. Since the gold nanoparticles hold a charge (like milk fat), they repel each other. When the charge breaks down, the gold particles clump together in a process similar to coagulation, known as flocculation.
      This has been indirectly demonstrated in the past; now, McLeish and colleagues have observed how it actually happens.
      "We produced the first evidence for gold colloid formation and flocculation in nature and the first images of small veins of gold colloid particles and their flocculated aggregates at the nano-scale," Williams-Jones and McLeish said.
      "These images document the process by which the cracks are filled with gold and, scaled up through the integration of millions of these small veins, reveal how bonanza veins are formed."
      For this process, the concentration of gold in the geothermal fluids only has to be a few parts per billion. It flocculates to form a jelly-like substance, which gets trapped in cracks in Earth's crust to form rich gold veins.
      This finding suggests that rich gold deposits may be more common than we thought, and may have occurred in several other contexts than previous estimates had allowed for. If other studies and further examination can back it up, the research could give us a new toolkit for understanding and locating gold deposits around the world.
      "We suspect that the colloidal processes that operated at Brucejack and other bonanza gold systems may also have operated to form more typical gold deposits. The challenge will be to find suitable material to test this hypothesis," Williams-Jones and McLeish said.
      "The next step will be to better understand the reasons why colloid formation and flocculation occurred on the scale observed and reconstruct the geological environment of these processes."
      The research has been published in PNAS.
    • By RiverRat
      I'm interested in any information on how gold veins/ lode deposits become offset and how to attempt to predict the amount of offset.
      Anyone have information on this?
      Thanks,
      RiverRat
    • By Libertas
      Interesting! Will be useful when we eventually have a colony there.
       
    • By Dances With Doves
      I only  went real nugget hunting one time in Stanton,Arizona in march 2002 because the late Charlie Wilson of Wilson metal   detectors took us as guests for a week.I was   using a Minelab gold machine he lent me that ran at 3  different freq.You had to choose one.I really envy you guys that get to do this in your area.I loved doing it even though I found no gold since i was  new at this type of hunting.The owner of the   Johnson mine even gave us permission to hunt his land which I thank him for.I  met Chris  Gholson and his  father and they were fantastic people.  
    • By mn90403
      So what caused it to break away?  Here is more on that theory.
       
      https://www.sciencemag.org/news/2021/03/remains-impact-created-moon-may-lie-deep-within-earth 
×
×
  • Create New...