نقش زهاب اسیدی معدن در تشکیل کانی‌های زیست محیطی در معادن زغالسنگ کارمزد، البرز مرکزی، استان مازندران

Nowadays, acid mine drainage (AMD) is one of the most important problems in coal mine contamination. The Karmozd coal mines in Mazandaran Province are one of the largest and oldest coal extractions in Central Alborze Coal Basin. The samples of coals, host rocks, mine drainages and secondary surface minerals have been collected in summer season of 2005. On the basis of hydrogeochemistry studies of drainages mine in Karmozd, two types of waters including: 1) acid drainage of Mg-SO4 type (pH=4.59) and 2) alkali drainage of Na-HCO3-SO4 type has been recognized. The most important factor in acid drainage formation is non-evacuation of mine drainage in active tunnel nummber13 and a long term contact of mine drainage with sulphidic minerals. As a result, the concentration of SO42- contemporary with oxidation of pyrite is increased. The scatter diagrams indicate that with increasing SO42- which causes the pH and HCO3 to be reduced; while heavy metals, alkali metals, earth alkali metal, (PO4)3-, electrical conductivity (EC) and total dissolved solid (TDS) increase in the water. Hydrogeochemistry modeling indicates that minerals such as jarosite, alunite, iron oxide, oxyhydroxide, Al oxide and oxyhydroxide are mainly in over saturation state, while carbonate minerals like calcite, dolomite and aragonite are undersaturated. X-ray differaction (XRD) proved the existence of natrojarosite, pickeringite, halotrichite, gypsum and iron oxide and oxyhydroxide precipitated due to acid drainage. Gibbs diagram indicates that lithology is the most important factor in increasing the ionic concentration of mine drainage from acidic and neutral to alkali drained.