A process for abating hydrogen sulfide during geothermal steam stacking operations is disclosed. The geothermal steam to be stacked is introduced into a geothermal steam stacking line. Ferric chelating solution is injected into the stacking line in an amount effective to convert the hydrogen sulfide in the steam to sulfur. The hydrogen sulfide-abated steam and chelating solution is vented through a rock muffler and the chelating solution is optionally recovered from the muffler, regenerated and recirculated to the injection step.