A realistic mine turned in to an underground city

[Czcibor]

As you probably know every respectable RPG needs an underground complex below a city... Usually it involves high gov spending on spacious severs full of mutated creatures... such constructions are usually hard to justify to taxpayers :D

OK, more seriously, the setting:
1) the city is located on a cool, habitable exoplanet, near a big river, surrounded by semi-desserts (think like Nile but temperature is usually somewhere around 10C-20C)
2) There was general idea to place the city somewhere in lower part of that river. The specific choice was made based on selecting the most reasonable site - some natural resources and suitable place for construction.
3) Technology is not much better than early XXIst century.
4) Restrictions:
-the planet is very poor in fossil fuels, so they are automatically out
-there is no point in mining any luxury stuff at that moment like ex. gold (yes, I know a bit used in electronics, but still don't fit)
-under perfect conditions the mining would start with strip mining and later there would be some shafts
-the rock should be solid enough that such mining would not preclude in any way subsequent construction of low skyscrapers
-the substance should be something essential in huge quantities for survival of industrial civilization, like ex. iron or aluminium
5) Intended history:
-first a mining town with industry processing that ore;
-evolving into big city, where mining would become marginal activity;
-turning empty shafts into an underground district of city, that just in case could be used as nuclear shelter and is connected with outside world with lifts and metro.

Which geological formation and ore would you advice? At best solution would be good at mining, reasonable source of construction material for whole city and simultaneously look as advantageous combination and NOT like a miracle.

 

[snorkack]

1) the city is located on a cool, habitable exoplanet, near a big river, surrounded by semi-desserts (think like Nile but temperature is usually somewhere around 10C-20C)

Anything like Columbia?

 

[Czcibor]

Anything like Columbia?

Much drier, with rainfall around 300 mmEDIT: I play here a bit with single biome planet idea. Theoretically the planet has 85% water cover and over 55% ice cover... so icy water world... just humans settled in a hot, dry region... :D

 

[newjerseyrunner]

Several countries in harms way of a USA / USSR conflict prepared for it with something like you are describing: https://en.wikipedia.org/wiki/National_Redoubt_(Switzerland) The post apocalypse world you are describing sounds a lot like what I would expect humans to do if we had had a nuclear conflict.

 

[Czcibor]

OK, I found that bauxites are on Earth mined almost exclusively by strip mining. So don't fit story.

Maybe hematite? Iron ore is always useful and should be worth some deep mining? Mostly covered with an igneous rock what justifies that relatively shallow deposits are not worth strip mining?

 

[snorkack]

Much drier, with rainfall around 300 mm

That´s wetter. Pasco has 197 mm.

 

[GTOM]

I have also wondered about converting Olympus Mons on Mars to a giant fortress. Should such a dead volcano produce paths of ore worth tunnel mining?

On : real underground cities exists Montreal has quite a large area, or existed, like ancient cappadocia, so supertechnology isn't needed to create one, just good justification.

 

[Czcibor]

I have also wondered about converting Olympus Mons on Mars to a giant fortress. Should such a dead volcano produce paths of ore worth tunnel mining?

I think so, because volcanoes can bring different kind of minerals than surroundings.

https://en.wikipedia.org/wiki/Ore_genesis
(I've found only about ores from submerged volcanoes :( )

On : real underground cities exists Montreal has quite a large area, or existed, like ancient cappadocia, so supertechnology isn't needed to create one, just good justification.

Cappadocia? I've been there. I'd google Montreal.

Here is not a matter of supertech, but more of making it within low price.

 

[GTOM]

What about a salt mine? I read they bury nuclear waste in salt, so it is stabile enough.
Salt and sulphur are necessary for chem industry. Maybe outside climate could be so harsh, that artificial lightning is cheaper than climate systems.

 

[Czcibor]

What about a salt mine? I read they bury nuclear waste in salt, so it is stabile enough.
Salt and sulphur are necessary for chem industry. Maybe outside climate could be so harsh, that artificial lightning is cheaper than climate systems.

Good as material to dig holes in, not specially good material to build an industry around it.