Mineralogy of the pollutant products formed in the Masca exploration area (Lower Iara Valley Basin, Cluj County, Romania)

Abstract

In the present study the mineralogy of a tailing dam situated in the Masca mining area is discussed. Our aim was to point out the physicochemical processes, which occur under the action of the exogenous factors. The studied samples were collected from different levels of the dam wall, from the Masca mine and Iara river waters. The applied analytical methods are: transmission polarized microscopy, transmission electron microscopy, X-ray diffractometry, and atomic absorption spectrometry. The physicochemical parameters have been measured in situ and in the laboratory. The minerals present in the tailings are represented by: garnets (andraditegrossular and almandine series), diopside, hedenbergite, actinolite, tremolite, epidote, zoisite, biotite, phlogopite, serpentine minerals, chlorite, tourmaline, quartz, feldspar, anatase, apatite and opaque minerals (pyrrhotite, pyrite, magnetite and hematite). The carbonate minerals belonging to the mining waste are represented mostly by dolomite and subordinately by calcite. The identified neoformation minerals formed as a result of the action of the exogenous factors are the following: illite, illite/smectite, nontronite, palygorskite, chlorite-vermiculite, gypsum, epsomite, hexahydrite, wattevillite, ferrohexahydrite, hallotrichite, bilinite(?), goethite and amorphous iron hydroxide. The chemical analyses undertaken on the water samples show high values of the soluble salts (Na, K, Ca, Mg, and SO4) and heavy metals (Cu, Pb, Fe, Fe, and Zn) contents, exceeding international and national guidelines. Although the pH of the streams originating from the mine area vary between neutral to slightly alkaline, pollution occurs and significantly impacts the mineralized area as well as the neighboring areas.