Origin of precious metals...

[Externet]

Hi.

Read somewhere that explosions or collisions of stars created much of the minerals that traveled trough space until stroke earth creating the deposits mined today.

Is it reasonable to believe all planets and moons that existed then and in the same neighborhood received a similar 'rain of imported' minerals/elements ?  Can soil similarities among planets tell they were nearby at that time; and dissimilarities mean they were then far apart ?

[exchemist]

49 minutes ago, Externet said:

Hi.

Read somewhere that explosions or collisions of stars created much of the minerals that traveled trough space until stroke earth creating the deposits mined today.

Is it reasonable to believe all planets and moons that existed then and in the same neighborhood received a similar 'rain of imported' minerals/elements ?  Can soil similarities among planets tell they were nearby at that time; and dissimilarities mean they were then far apart ?

I think most of the denser material ended up closer to the sun, though someone may correct me. But, while the gas giants are farther away, they also have rocky/metallic cores, I think, and I don't know the relative size of the cores compared to the rocky planets further in.

But as far as precious metals are concerned it seems to be only of academic interest, since I understand that mining them on another planet and transferring them to Earth would be uneconomic, due to the change in orbital velocity required. 

  

 

Edited July 18, 2022 by exchemist

[mistermack]

I'm no expert, but I believe that most of the heavy metals on the Earth didn't "rain" down from space, they existed in the vast cloud that collapsed to form the sun. When the Sun lit up with fusion ignition, it blasted away the remnants of the cloud, and that clumped together in orbit around the Sun, forming the planets. The heavier metals sank towards the core. The planets did experience a rain of smaller bodies in the early history of the solar system, I think that a lot of comets composed of mostly ice hit the Earth and formed the oceans. And the meteorite collisions are probably responsible for the metals available to us in the Earth's crust.

There is evidence of collisions of planets earlier in the Solar system's history. A lot of people think that the Earth was hit by a smaller planet, forming the Earth as we see it, and the moon. That kind of collision would blast a lot of material into space that orginated in the cores of the colliding planets, forming meteorites that are high in metals.

Gold is believed to form mainly in a collision of two neutron stars, which produces an explosive event to rival a supernova. The gold in the Earth's crust might well have rained down, in rubble from prior planetary collisions. But most of the gold on Earth was in the cloud that formed the solar system, and now sits deep in the core beyond our reach, due to its density.

[swansont]

15 hours ago, Externet said:

Can soil similarities among planets tell they were nearby at that time; and dissimilarities mean they were then far apart ?

Chemical differentiation plays a role, so one would not expect a great match between planets where the contributing factors are different. Some of the sources of metals came from impact events after planet formation (e.g. the iridium layer from the K-T impact event) And if the processes are the same (as they should be), one could have many similarities even if they are quite distant.

https://en.wikipedia.org/wiki/Planetary_differentiation

One can identify e.g. meteorites that came from Mars, based on composition differences with what we find on earth

https://en.wikipedia.org/wiki/Martian_meteorite

These meteorites are interpreted as Martian because they have elemental and isotopic compositions that are similar to rocks and atmospheric gases on Mars, which have been measured by orbiting spacecraft, surface landers and rovers. 

[studiot]

To the best of our knowledge (source Cambridge Handbook of Earth Science Data)

For every silicon (ie rocky) atom in our solar system there are 25,000 hydrogen atoms (mostly in the Sun) and 0.0000002 gold atoms.

[mistermack]

While gold is rare, there is a lot of it down below if only we could reach it. (which we never will).

One geologist geologist, Bernard Wood of Macquarie University in Australia reckons there's enough gold in Earth's core to coat its surface in 1.5 feet of the stuff. And six times as much of platinum. But even if we could reach it, it would probably cost more in energy costs to winch it up to the surface, than it would be worth in cash. 

Another surprising fact about gold is that China is the biggest producer, followed by Russia, and then Australia. Not what I would have guessed.  

https://www.discovermagazine.com/planet-earth/earths-inner-fort-knox   

[studiot]

I don't think we know enough about the composition of the minor elements deepr down (the mantle) laet alone in the core.

Here is the currently the mostl reliable information for the crust fromthe lates edition of Greenwood and Earnshaw "Chemistry of the Elements"

I have highlighted gold whose symbol is is Au

 

[mistermack]

That figure of .004 ppm seems reasonable. But you would expect the heavier elements to sink in the early days, when the Earth was molten all the way to the surface. So what's in the crust wouldn't be representative of the overall figure. By a coincidence, 0.004 ppm is the figure I recently read for the ocurrence in seawater. If it is coincidental. 

Edit :   Make that ppb.   

Edited July 19, 2022 by mistermack

[sethoflagos]

On 7/19/2022 at 7:09 PM, studiot said:

I don't think we know enough about the composition of the minor elements deepr down (the mantle) laet alone in the core.

Here is the currently the mostl reliable information for the crust fromthe lates edition of Greenwood and Earnshaw "Chemistry of the Elements"

I have highlighted gold whose symbol is is Au

 

Interesting to note that the last 10 positions on that list include all the Group VIII precious metals at typically 1 ppb whereas Thorium and Uranium despite being considerably heavier nuclei have over 3 orders of magnitude greater crustal abundance.  This is strong evidence that the dominant factor is not atomic weight but chemical affinity with the crust being heavily depleted in the siderophilic elements (those that have a chemical affinity for a metallic iron phase) relative to the lithophilic elements which are preferentially drawn to a silica rich phase. 

Almost as if the crust had been washed 99.9% clean of siderophiles by a descending wave of iron heading for the core.  

[paulsutton]

Once we start running more sample return missions we may get a better picture.  However IIRC the current mission to collect Mars samples is more to do with finding evidence of life than perhaps determine mineral composition.   We may not know  until those samples are returned successfully.

[Ken Fabian]

Enough magma convection and volcanic activity still goes on to keep bringing up some minerals from deeper down; it isn't a placid one way sinking of heavier minerals towards the core. I live on the remnants of an extinct volcano, on the rim of what was once it's crater. Whilst not a major deposit, it coughed up enough gold, copper and silver to attract the attention of gold rush prospectors in the late 1800's and mining companies ever since. Not a lot of actual, profitable mining but they keep looking, with hopes of prices going high enough to be economic. The last eruption was 23 million years ago - very recent in geological terms.

 

9 hours ago, sethoflagos said:

This is strong evidence that the dominant factor is not atomic weight but chemical affinity with the crust being heavily depleted in the siderophilic elements (those that have a chemical affinity for a metallic iron phase) relative to the lithophilic elements which are preferentially drawn to a silica rich phase. 

Is this about the density of the mineral compounds they form or otherwise bind to?

[sethoflagos]

56 minutes ago, Ken Fabian said:

Is this about the density of the mineral compounds they form or otherwise bind to?

Other than the top 6 or 7 commonest crustal elements, it's more about the density of the rocks of which they are a minor/trace component. ie less than 1% by weight of the local rock formation and having negligible impact on the bulk density.

[paulsutton]

In terms of Origins of Elements I found this posted on Twitter I think the other day which may be helpful    Lighter elements were formed in stars,  heavier elements seemed to have been formed when stars explode, or undergo changes during their life time / end of life. 

 

[Sensei]

@paulsutton"This periodic table depicts the primary source on Earth (...)" ... Helium on Earth is formed by radioactive decay, alpha decay..

[paulsutton]

3 minutes ago, Sensei said:

@paulsutton"This periodic table depicts the primary source on Earth (...)" ... Helium on Earth is formed by radioactive decay, alpha decay..

Is that not right then,  i thought Helium was produced from the fusion of Hydrogen in stars.    Hence the name is derived from Helios (sun)

On 8/18/2022 at 1:13 PM, paulsutton said:

Once we start running more sample return missions we may get a better picture.  However IIRC the current mission to collect Mars samples is more to do with finding evidence of life than perhaps determine mineral composition.   We may not know  until those samples are returned successfully.

They have recently grown plants from returned moon soil, which may imply that there could be some nutrients in that soil  If I understand things plants need Nitrogen and other elements found in soil to grow properly.  I know peas use a lot of Nitrogen and can't generally be planted in the same place each year as time is needed for the level of Nitrogen to recover (I could be wrong here)

https://www.universal-sci.com/article/plants-grown-in-moon-soil

Important step and opens up more fields of research.

Paul

[Sensei]

On 9/27/2022 at 9:58 PM, paulsutton said:

i thought Helium was produced from the fusion of Hydrogen in stars.    Hence the name is derived from Helios (sun)

Scientists who found a new unknown element in the Sun's spectrum did not yet know about fusion. The name was given only because it was found on the Sun (its spectral lines).

[Ken Fabian]

On 9/28/2022 at 5:58 AM, paulsutton said:

They have recently grown plants from returned moon soil, which may imply that there could be some nutrients in that soil 

The link also said -

Quote

After the sixth day, however, it became apparent that the lunar soil plants were not as rugged as the aforementioned control group. Instead, the lunar plants grew at a slower rate and had stunted roots; in addition, some had discolored pigmentation and stunted leaves.

Sound like about the time the plants had ceased to rely on the nutrients that came in their cotyledons they had problems. Stunted roots is an especially bad sign. Likely that some nutrients are present but some important ones are either not present or insufficient.

 

[paulsutton]

6 hours ago, Ken Fabian said:

The link also said -

Sound like about the time the plants had ceased to rely on the nutrients that came in their cotyledons they had problems. Stunted roots is an especially bad sign. Likely that some nutrients are present but some important ones are either not present or insufficient.

 

Sounds like a step in the right direction,   we are treading on new ground   experimentation -> learning and ten revision of what we can do, but also what we can't do.

Even if the plants fail to grow as long as we can learn and then find a way to try different things we should eventually get to the point where we can grow things.

[Lacedaemonian]

The first elements to be created were Hydrogen and Helium. First-generation stars consisted of these two elements. The fusion inside these stars created the heavier elements and when the stars exploded these elements created the soup in which the second-generation stars were made, which were higher in metallicity. Metallicity for the asrophysicists is the content of a star in elements higher than Hydrogen and Helium. The Sun has high metallicity because was made from the remains of a first-generation star. Because Earth was created in the same planetary disk of dust that the sun was made has metals in the interior. Also, some metals come from asteroid impacts. The K-T extinction asteroid caused a layer of Iridium in the global stratigraphy.