Gold From Meteorites?

[mn90403]

I just came back from a trip to Gold Basin.  As we know there are meteorites there.  I found one about 80 grams.

When it was washed off and brushed I could see some tiny yellow shinny spots.  I've found lots of Gold Basins but I don't remember and of them with gold in them so I did a search.  That search introduced me to a concept that many have that much of our mineable metals, including gold came to earth with meteor showers.  If true this could explain a lot of unexplainable patches in different areas.

Here is a primer from one of the AI tools, Copilot.

This is new for me and might take a while to have my brain wrap around it after all of the info about gold being molten and coming up with eruptions.

Someone help me understand this.

Did meteorites bombard Earth with gold? | EarthSky 

https://earthsky.org/earth/did-meteorites-bombard-earth-with-gold/ 

[Clay Diggins]

ALL the elements on earth come from meteorites. Earth is a ball of accreted matter from space.

After the material accreted it was processed by the standard geological processes - pressure, heat and erosion in the form of vulcanism, plate movement, convection and sedimentation. It was those geological processes that concentrated gold into veins that eventually eroded into placer deposits. Those same processes created our atmosphere which acts to slow and deflect the arrival of new meteorites. All those same processes continue today.

The article made those same points except the one about our atmosphere. The theory proposed in the article is based on the spike of one element's occurrence in earth's timeline. The theory seems plausible but it's just one theory attempting to explain earths metallic abundance.

The gold you find in placer deposits all came from meteorites but no measurable amount of that gold in a placer deposit or a vein was deposited directly by meteorites.

[GB_Amateur]

Not quite sure what you are asking, but here are some info (in some cases with numbers) that may help.

1) According to the scientific work that the article was based upon, they're referring to something that happened *very* early in the earth's history.  To put this in relative terms, compare the earth's age with a human who lives 90 years.  Right now the earth is middle aged -- equivalently about 45 years old.  This meteorite bombardment occurred when the earth was (equiv.) 0.2 years (a few months) old.  Needless to say the place was a lot different then!  (The work referred to was done with 3.8 billion year old rocks from Greenland -- some of the oldest rocks on earth.  The human equivalent age of the earth for those -- 7 years old.)

2) The mass of those meteorites is estimated at 2x10^19 (think 2 followed by 19 zeros) tons or 2x10^22 kg.  The mass of today's earth is 6x10^24 kg, so this meteorite bombardment is about 1 part in 300 of the earth's current mass.  (BTW, you can think of mass as weight -- true at the earth's surface anyway.)

3) Meteorite compositions have a ballpark (there's a range but this number is good for getting our heads around it) mass ratio for Fe to Au of 1 million (1x10^6).  For the average earth's surface (crust) composition is about four times that high, so meteorites on average are a bit more concentrated in gold than other rocks/dirt/etc, but not ridiculously so.

People have speculated regarding mining asteroids.  IMO those stories tend to be exaggerated.  But here is a decent article on the subject.  Basically, though, they're still talking about ppm of precious metals, it's just that some asteroids are (relative to earth's mines) large and you can pick the ones that are primarily metals.  I.e. you don't need to clear overburden and get rid of all the worthless silicon, oxygen etc. -- the early solar system already did that for you.

The earth was formed from the solar nebula.  So were the sun, the other planets, natural satellites (aka 'moons') the asteroids, and comets.  The nascent sun had enough mass to collect the dominant elements:  hydrogen in particular, plus helium) while the planets' lower masses let those go and mostly kept the heavy stuff.  So no magic here, at least no more than has been known for quite a while.  Precious metals are rare and even when concentrated (e.g. nuggets) that's still the case.

[mn90403]

I knew you guys would save me time!

The idea that gold patches we hunt now were caused by different falls seems to be unfounded.  😁

[MSC]

Early in Earth history it was molten, all heavy elements sank to the center, (could be lots of gold there) as the Earth cooled and a crust formed it continued to be bombarded with meteorites which is where much of the metals and elements that are mined today come from.   

[mn90403]

I wasn't able to get a photo of the fleck but here is the meteorite.

[jasong]

I inherited a few boxes of of older publications from an old oil well log library. Among them is a booklet by the DOI called "Gold in Meteorites and the Earth's Crust". I don't think it's available online though.

No scanner here, so here is a photo of the chart from this paper on the general gold content in many types of meteorites, just for general interest. 1ppm = 1 gram/ton more or less. 

So it seems the iron meteorites are the ones that tend to have the highest gold content.

[Swegin]

10 minutes ago, jasong said:

Gold in Meteorites and the Earth's Crust

Is this it?    https://pubs.usgs.gov/circ/1968/0603/report.pdf

 

[jasong]

Yep that's the one, thanks.

[Gold Seeker]

5 hours ago, jasong said:

I inherited a few boxes of of older publications from an old oil well log library. Among them is a booklet by the DOI called "Gold in Meteorites and the Earth's Crust". I don't think it's available online though.

No scanner here, so here is a photo of the chart from this paper on the general gold content in many types of meteorites, just for general interest. 1ppm = 1 gram/ton more or less. 

So it seems the iron meteorites are the ones that tend to have the highest gold content.

 

That publication can be found here....

https://pubs.usgs.gov/circ/1968/0603/report.pdf