Study of magmatic rocks and environmental impact of alteration zones in Youzbashi-Chai region (West of Qazvin)

The studied area of Yuzbashi-Chay located in the North West of Qazvin and stratigraphically includes Cenozoic units. Field evidence, petrological studies and geochemical data of magmatic rocks and alteration zone suggest that, this area consist of basalt, basaltic andesite, andesite, trachyandesite, trachyte, rhyodacite, dacite, tuff and dike. Plot of the major and trace elements analysis results in different discrimination diagrams indicate that these rocks formed by subduction-related magmatism in continental margins environment. Based on classification of different alteration unites; the vast parts of studied area affected by intermediate to advanced argillic-type alteration. Besides; due to the effects of alteration zones, the amount of calcium and sulfate have very high anomaly in water. Furthermore; results of water samples analysis indicate that the water hardness is greater than standard limit.The presence of hydrated aluminum potassium sulfate minerals (alunite or alum) is main potential source to produce of acidic waters. Based on drink water standard of Iran, total dissolved solids (TDS) value in alteration areas, especially in Ghazan Daghi mines, is greater than standard limit and waters of Aghche Kand alteration area are classified in toxicant water type.