Assessment of the waste rocks acid drainage potential to solve environmental problems

The Ak-Sug Cu-Mo porphyry deposit is located in the northeastern region of the Tuva Republic, Russia. The deposit was explored from 1982 to 1985. Now there are intensions to use it for open pits mining. The purpose of this expertise was to predict the probable formation of acid drainage from the overburden waste rocks piles and the ores to be processed. These rocks were investigated using X-ray fluorescence with synchrotron radiation spectroscopy (XRF-SR), X-ray diffraction analysis (XRD), microscopy, laboratory aqueous leaching and intensive oxidation experiments by peroxide (correspond to short-term and long-term prospects for the development of chemical weathering of rocks). In addition, the sulfide and carbonate contents were determined to calculate the net acid potential (NAP) according to [1]. Fifty representative core samples was obtained in accordance with the 3-D geological model drilling data. The dominant types of rocks include quartz diorite and granodiorite porphyries. The ore associations are quartz-pyrite, with hematite; quartz-molybdenite, with pyrite and chalcopyrite; quartz-chalcopyrite, etc. The high concentrations of the semimetals (As, Sb, Se) are important (50% of the samples contain more than 10 g/t of As, with maximum concentration of 450 g/t). The waste rock materials were generally low potential sources of acid mine drainage: Only 26% of the rock samples produced acidic effluents. These generated acid solutions had contents exceeded the WHO maximum allowable concentrations: Fe-260; Cu-43; Mo-20; As-50; Cd-19; Sb-17 times. For example, arsenic and molybdenum can leach rapidly in neutral and sub-alkaline solutions. Nevertheless, geochemical, mineralogical and thermodynamic studies of the Ak-Sug ores with overburden rocks will provide a threat of acid mine drainage for at least a few decades.