Core,
If you put gold into solution The mercury and lead will be in the waste you have now, no these cannot be put back into the mine, by leaching the ore you have put them into a different more dangerous state than the were when in the rock or mine originally, putting this back into the mine it could end up in someones drinking water. this toxic waste needs to be dealt with properly and responsibly, so that you are not poisoning people with the waste you generate, to do this you need to educate yourself, preferably before trying to leach any ore, so that you will have an understanding of the chemistry and the danger of what you are doing, and how to properly handle these dangers.
Gold in solution as a chloride, (silver, lead and mercury are insoluble as chlorides).