<p>Why are there no giant nickel porphyry deposits like those of copper, or SEDEX deposits, like those of zinc? Why is all the nickel found in direct magmatic intrusions from the mantle to the surface? Why isn't more nickel found from epithermal deposits in which water runs down to a deep seated magmatic intrusion, picks up the metals, and deposits them on the surface?
Also, as I understand it, the copper found in the Andean deposits are from water going down and picking up metal from the melting continental crust sitting above the subducting oceanic crust. It's not coming from any mantle rocks. Is that correct, and if so, why don't we get nickel deposits in the Andes too?</p>

CC BY-SA 4.0
2020-09-20T15:17:52.513Z
What is "porphyry"?
peterh
CC BY-SA 4.0
2020-09-20T19:32:58.697Z
Nickel is siderophilic, maybe?
Oscar Lanzi
CC BY-SA 4.0
2020-09-20T19:56:35.410Z
Presumably you mean enough nickel to be considered an ore ?
blacksmith37
CC BY-SA 4.0
2020-09-20T20:06:32.253Z
Yes, but given that nickel abounds in the core, and is about as heavy as iron, in the mantle too, you'd expect more of it on the surface. Copper is heavier and found in porphyry deposits....why not nickel?
hurreechunder
CC BY-SA 4.0
2020-09-21T02:05:25.727Z
Look into the age of the different types of deposits & what the geology of the Earth was like during those periods. Most nickel deposits I'm aware of are from the Archean (2.5-4.0 Ga) & are associated with ultramafic igneous material, komatiite & dunite. They were deposited when the Earth's geology was younger & different to later periods. Porphyry deposits tend to be younger, from the Phaerizoic period (from 541 Ma to the present).
Fred
CC BY-SA 4.0
2020-09-21T07:43:39.590Z
"the copper found in the Andean deposits are from water going down and picking up metal from the melting continental crust sitting above the subducting oceanic crust. It's not coming from any mantle rocks." This is not correct. There is a mantle wedge between the subducting oceanic crust and the continental crust. It is this mantle wedge that partially melts, or in some cases (adakites) the oceanic crust, but not the continental crust (although it can contaminate the magma from the mantle wedge as it rises).
Jean-Marie Prival
CC BY-SA 4.0
2020-10-07T09:18:38.920Z
"There is a mantle wedge between the subducting oceanic crust and the continental crust. It is this mantle wedge that partially melts, or in some cases (adakites) the oceanic crust, but not the continental crust (although it can contaminate the magma from the mantle wedge as it rises)"
Thanks for pointing that out. But this makes it even more strange that there are no nickel porphyries, since there's more nickel than copper in the mantle. Basically, the Andean copper belt should be an Andean nickel belt, but it's not.
hurreechunder
<plate-tectonics>
Nickel question - non geologist me
hurreechunder
# Nickel question - non geologist me

(Asked by: username_0 on 2020-09-20)

Why are there no giant nickel porphyry deposits like those of copper, or SEDEX deposits, like those of zinc? Why is all the nickel found in direct magmatic intrusions from the mantle to the surface? Why isn't more nickel found from epithermal deposits in which water runs down to a deep seated magmatic intrusion, picks up the metals, and deposits them on the surface?
Also, as I understand it, the copper found in the Andean deposits are from water going down and picking up metal from the melting continental crust sitting above the subducting oceanic crust. It's not coming from any mantle rocks. Is that correct, and if so, why don't we get nickel deposits in the Andes too?

**Tags:** plate-tectonics

> **Comments:**
> **username_1**: What is "porphyry"?  
> **username_2**: Nickel is siderophilic, maybe?  
> **username_3**: Presumably you mean enough nickel to be considered an ore ?  
> **username_0**: Yes, but given that nickel abounds in the core, and is about as heavy as iron, in the mantle too, you'd expect more of it on the surface. Copper is heavier and found in porphyry deposits....why not nickel?  
> **username_4**: Look into the age of the different types of deposits & what the geology of the Earth was like during those periods. Most nickel deposits I'm aware of are from the Archean (2.5-4.0 Ga) & are associated with ultramafic igneous material, komatiite & dunite. They were deposited when the Earth's geology was younger & different to later periods. Porphyry deposits tend to be younger, from the Phaerizoic period (from 541 Ma to the present).  
> **username_5**: "the copper found in the Andean deposits are from water going down and picking up metal from the melting continental crust sitting above the subducting oceanic crust. It's not coming from any mantle rocks." This is not correct. There is a mantle wedge between the subducting oceanic crust and the continental crust. It is this mantle wedge that partially melts, or in some cases (adakites) the oceanic crust, but not the continental crust (although it can contaminate the magma from the mantle wedge as it rises).  
> **username_0**: "There is a mantle wedge between the subducting oceanic crust and the continental crust. It is this mantle wedge that partially melts, or in some cases (adakites) the oceanic crust, but not the continental crust (although it can contaminate the magma from the mantle wedge as it rises)" Thanks for pointing that out. But this makes it even more strange that there are no nickel porphyries, since there's more nickel than copper in the mantle. Basically, the Andean copper belt should be an Andean nickel belt, but it's not.  

---

## 0 answers

