Natural attenuation processes applying to antimony: a study in the abandoned antimony mine in Goesdorf, Luxembourg.

The processes leading to the attenuation of the antimony concentration in the water draining from the abandoned antimony mine in Goesdorf, Luxembourg, have been studied. Antimony has been mined in Goesdorf since Roman times from a stibnite-rich mesothermal vein system hosted in metasedimentary schist. The draining waters have pH values between 7 and 8 because the mineralization itself contains calcite and dolomite. This study combines the identification of minerals in the supergene zone with the application of bulk techniques (e.g., measurement of antimony in the waters of the adit and the creek draining the mine, sediment sequential extractions) over a period of five years. Antimony concentrations in the water that leaves the supergene zone are controlled by the dissolution of stibnite and the subsequent formation of Sb(III) oxides and sulphates. The relative proportions of the main secondary minerals can be qualitatively estimated as follows: 70% valentinite, 15% senarmontite and 12% sulphates (coquandite, klebelsbergite and peretaite). Further antimony attenuation along the adit and the creek that drain the mine waters is due partly to dilution, through mixing with waters that have not been in contact with the ore, and partly to sorption onto amorphous iron and manganese oxides present in the colluvial sediments.