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?

  • $\begingroup$ What is "porphyry"? $\endgroup$
    – peterh
    Sep 20 '20 at 15:17
  • 1
    $\begingroup$ Nickel is siderophilic, maybe? $\endgroup$ Sep 20 '20 at 19:32
  • $\begingroup$ Presumably you mean enough nickel to be considered an ore ? $\endgroup$ Sep 20 '20 at 19:56
  • $\begingroup$ 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? $\endgroup$ Sep 20 '20 at 20:06
  • $\begingroup$ 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). $\endgroup$
    – Fred
    Sep 21 '20 at 2:05

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