How deep do ore bodies go?

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Offline Atomic-S

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How deep do ore bodies go?
« on: 02/10/2013 04:10:19 »
Contemplating the fact that, to feed the world appetite for copper, two controversial new mines are likely to open, I began to wonder, given the difficulty of finding politically suitable sites to mine any more, how much metal could be gotten out of existing mines? That would depend on, among other things, how deep the ore goes. I began to wonder how deep it  does go. Mines eventually "run out"; but I began to wonder if this running out is absolute or there could be much more there at very great depths. How far down do ores go?


Offline Bass

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Re: How deep do ore bodies go?
« Reply #1 on: 02/10/2013 16:49:44 »
Here's a definitive answer: It depends.
Geologists categorize ore deposits on several criteria, one of which is depth of formation.  Epithermal deposits are shallow, many related to the depth of boiling or mixing of hydrothermal (hot waters) with cooler surface waters.  Typically limited to a few hundred meters of depth.  Mesothermal and hypothermal deposits form deeper, typically as veins or sheeted veins.  These may form during metamorphism, or from deeper igneous activity.  These types of deposits can extend downward for thousands of meters.  Most deposits are zoned, including giant porphyry-type deposits- that is the mineralization and alteration change with depth.
IMO, the real question is not depth, but rather economics.  As the price for metals increases, lower grade ores can be profitably mined. The technology of mining and processing can also make lower grade material attractive.  Mining becomes more expensive and hazardous with depth, so lower grade, shallower, cheaper deposits will be developed as the needs of human society dictate.
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