GMS has been given a 2.0 mining bonus for gold. This will last at least as long as the gold buff, and perhaps longer. We will see what kind of drama/activity this generates before making any permanent decisions.
It doesn't seem to be in effect yet.
I tried the two northern fields in Dublin. Got ~2 units per shot while using the best mining ship available (Tournez with 6 mining lasers).
The results are consistent either with disabled fields or no mining bonus.
Right after that I tried the Niobium field in Leeds and that one was working properly.