Temple fell down sinkhole in mining area, toxic gases

My temple was built near a kaolin surface mine, which is itself topping an old deep mine (where they used to mine radioactive metals, rare earths and possibly other miscellaneous, if need be). This temple was so beautiful that one day the gods took it to heaven, i.e. fell down a sinkhole/big mine shaft (it doesn't matter which) that opened/reopened under it. My MC descends through the mine to investigate the temple, which was sealed in kaolin since the day it fell down.

1) What toxic gases can there be besides CO2? There is no coal.

2) Is this setup geologically passable? If not, what should I tweak?

I can tweak the conditions, and I'm not aiming for 100% accuracy. I'm going for passable in case an expert stumbles upon it.

posted over 4 years ago

geneaux‭

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