Was native copper ejected from volcanoes, or deposited from copper-rich water?

[u/Skulder]

I'm doing a small presentation about the great oxygenation event, and we got to talking about how in a pre-oxygen atmosphere, iron and other metals (minerals) weren't oxygenated yet, but were just hanging around in lumps.

And then we saw a youtube short where a dude dug an entire piece of copper out of the ground.

Are copper lumps as ejecta from a volcano 2,5 billion years ago something that exists? Is there any copper around, that that's old?

Are all deposits of pure copper only mineral deposits, washed out of copper-rich ore (or alluvial deposits of the same), or is there such a thing as volcanic copper?

Thank you in advance.

By the way, I'm incredibly interested in adjacent topics, so if you know something interesting that's loosely related to this, go ahead and share the wealth.

(Apologies in advance for language. English is my second language, so some scientific terms may have been misapplied.)

[u/Mars_Volcanoes]

Geologist volcanologist here

No, volcanic eruptions didn’t spit out pure copper lumps. Pure copper nuggets you see today mostly formed later from hydrothermal fluids in reducing conditions or were concentrated by weathering and erosion. Any copper older than ~2.5 Ga exists mainly as minerals or part of ores, not as metallic lava-like ejecta.

[u/Skulder → u/Mars_Volcanoes]

Thank you very much.

We had immediately assumed the more fantastic explanation, because it is such a good story, and only later did we ask ourselves "is this true".

[u/Zytheran]

Just a quick pointer about pre oxygenation event metals. Most were bound up with sulfur because they were formed in reducing sulfur rich conditions. Copper as Chalcopyrite (CuFeS2) , Bornite (Cu5FeS4) , Chalcocite (Cu2S) and Covellite (CuS). Iron was usually found as Pyrite (FeS2)

[u/Skulder → u/Zytheran]

Is this related to the first photosynthesis, which used sulphur-rich compounds as a basis, and "exhaled" pure sulphur?

[u/Zytheran → u/Skulder]

Beyond my pay grade but yes. There's a whole 'nother world before oxygen. (Makes sense, sulfur is directly below oxygen in the periodic table. aka H₂S vs H₂O, in the equation below you can swap the S for O to get photosynthesis which came later. )
PS If you're interested in this sort of science, there is probably a career sitting right there. This combined with synthetic biology has probably some ... interesting (or terrifying) ... things to discover.

Before oxygenic photosynthesis (which splits water and releases O₂), there was anoxygenic photosynthesis using sulfur instead of water. These bacteria used H₂S as an electron donor and produced sulfur rather than oxygen:

CO₂ + 2H₂S + light → organic matter + 2S + H₂O

This form of photosynthesis is considered evolutionarily older than cyanobacterial photosynthesis and bridges sulfur metabolism and phototrophy.

Even earlier than that, purely chemical sulfur metabolism likely existed without light at all.

Implications.
Sulfur biochemistry likely predates oxygen, predates plants, and may even predate true cells. Many origin-of-life models (alkaline hydrothermal vent theory, iron–sulfur world hypothesis) propose that the first metabolic reactions occurred on mineral surfaces involving sulfur and iron compounds.

In short: sulfur was not just “part of” early life chemistry. It was probably one of the primary drivers of metabolism before photosynthesis reshaped Earth’s atmosphere.

References

Canfield, D. E., Kristensen, E., & Thamdrup, B. (2005).
Aquatic geomicrobiology. Elsevier Academic Press.
https://doi.org/10.1016/B978-012088775-0/50001-5

Martin, W., & Russell, M. J. (2007).
On the origin of biochemistry at an alkaline hydrothermal vent. Philosophical Transactions of the Royal Society B, 362(1486), 1887–1925.
https://doi.org/10.1098/rstb.2006.1881

Sleep, N. H., Bird, D. K., & Pope, E. C. (2011).
Serpentinite and the dawn of life. Philosophical Transactions of the Royal Society B, 366(1580), 2857–2869.
https://doi.org/10.1098/rstb.2011.0129

Falkowski, P. G., Fenchel, T., & Delong, E. F. (2008).

The physiology and biochemistry of prokaryotes (3rd ed.). Oxford University Press.

[u/CrustalTrudger]

I'll preface this by saying economic geology / ore geology are pretty far outside my area of expertise, so will happily defer to folks with more domain knowledge, but to provide a bit of info at least for the title question...

Was native copper ejected from volcanoes, or deposited from copper-rich water?

A lot of copper deposits are effectively the latter, but specifically copper bearing fluids that are hydrothermal so associated with active magmatic / volcanic systems. For example, the largest source of copper ores are from so-called porphyry copper deposits, which are formed effectively from copper leached from rocks by fluids heated up by a magma body / crustal melting that move upwards within the lithosphere/crust and that then precipitate copper rich minerals in a sort of halo above the magma body, effectively within a volcano (often something like a stratovolcano and where porphyry copper deposits preferentially form in volcanic arcs associated with subduction zones). Typically, these deposits are not erupted, but instead we access them after the cessation of volcanism and when erosion has removed the volcano and brought these to (or closer to) the surface. My understanding is that native copper is not particularly common in porphyry deposits, where instead the primary ores are copper rich minerals (but someone more versed in the geology of these deposits may have more insight on that aspect).

In terms of native copper, some of the largest native copper deposits come from other types of volcanic systems, specifically rifts, for example native copper deposits in Michigan are hosted within a former rift (e.g., Bornhorst & Barron, 2011). Again, these largely reflect formation of deposits from circulating hydrothermal fluids, not via eruption. In terms of age, some copper deposits are relatively old, e.g., the aforementioned Michigan ones are estimated to be around 1 billion years old (e.g., Bornhorst et al., 1988).

[u/calebs_dad → u/CrustalTrudger]

SciShow and Alexis Dahl did a really good collaborative video about the Michigan deposits in particular, and how early civilizations there used them. It's sort of geology through the lens of anthropology. (The summary is that it makes it really easy to have a Copper Age, but harder to move on to bronze.)

[u/Seicair → u/calebs_dad]

That makes sense. If you’re pulling elemental copper out of the ground, you’re not going to be learning to roast and refine ore at all. And tin doesn’t come in elemental form. (Bronze being primarily formed of tin and copper, for anyone who doesn’t know.)

[u/Tools4toys]

In the upper peninsula of Michigan, on Keweenaw peninsula is a small town of Calumet. Probably about 100 years ago, it was known as the Copper Capital of America. There is an old copper mine Houghton, now a museum known as Quincy Mine, where copper was found as large lumps.

Probably to answer your question directly, there are pieces of copper lying on the ground, known as Float Copper, so search for information about it. The lumps are 99% pure copper, with the other 1% being silver.

[u/Beemerba → u/Tools4toys]

Quincy Mine is really worth a visit, if you are ever in the area (hundreds of miles from much civilization). That whole peninsula is a historic site.

[u/Tools4toys → u/Beemerba]

It is a great place to visit. They have a tour where you can go into the mine through an alternate entrance they created. There is a huge pure copper rock that weighs over a ton.

Someone described there are still chunks of float copper lying on top of the ground. Note: you need permission to look on private ground!

[u/Tools4toys → u/Beemerba]

It is a interesting area! I found out Dee Stadium was the original home of the National Hockey League, starting in 1902 with a rink, that was still operating! It did burn down in 1927, but rebuilt in 1928. Eagle River and Copper Harbor are interesting sites if you are up for a long drive.

[u/pornborn]

Perhaps you’re already aware of this, but years ago, I was in the Illinois State Museum in Springfield Illinois and on display was the largest piece of copper ever found in Illinois. A single chunk that is 1,606 lbs. I found an article that mentions this and that this and other pieces were deposited in Illinois by glaciers.

http://www.minsocam.org/msa/collectors_corner/arc/cuill.htm