CHEMICAL AND MINERALOGICAL CHARACTERIZATION OF SEDIMENTS FORMED BY MINE WASTES LEACHATES

Exploitation of mineral ores of skarn type at La Aurora Mine in Xichu Guanajuato generated huge quantities of residues deposited without control in the banks of the river. This residue was oxidized during more than 60 years and has high contents of potentially toxic elements (PTE: arsenic, lead and selenium). Over the channel, great quantities of secondary minerals were formed, main mineralogy are iron oxides and hvdroxi-sulphates as jarosite. These mineral phases can be dissolved with the rains and the runoff. In this work, arsenic distribution in different mineralogical phases, and mobility conditions from tailings deposits were evaluated. For that, samples were collected from residues considering a topographic transect from the upper part of deposit to the base in the hank of the river. Results of X ray fluorescence applied to some samples show that secondary minerals has elevated concentrations with maximum values of 36,559 mg/kg for As, 24,619 ing/kg of Ph, 90 mg/kg of Se. Granulometry is a very important factor for liberation of arsenic species, fine material of residues is composed by soluble secondary minerals, more abundant are.