Alteration and structural controllers of gold and copper ores in Ahar region, Arasbaran zone, northwest of Iran

Ahar area is a part of the Arasbaran metallogenic zone in northwestern Iran, where numerous hydrothermal Cu-Au deposits have been formed. In this regard, Safikhanlu, Niaz, Mazraeh, Anjerd and Kujanagh deposits, as representative deposits, have been observed and structural measurements were performed in the field. In this area, Cretaceous limestones along with volcanic rocks are exposed as the oldest rocks in the region along with Eocene latite-andesites. These volcanic rocks have been intruded by Oligocene plutons such as Safi Khanlu with the combination of granite-quartz monzonite and Khan Kandi with the combination of Monzonite-Gabbro, causing phyllite, argillic and siliceous alterations in Safi Khanlu, extensive argillic alteration in Kujanagh and potassic in the Niaz  area. With a time interval, magmatic activity in the Late Miocene-Pliocene resumed and caused phyllic and propylitic alteration in the Mazraeh and argillic, phyllic, propylitic and potassic in Anjerd area. These alterations were studied using ASTER satellite images and PCA and SAM methods. Then, with field studies, the trend of major fractures in each of the mentioned deposits was determined and compared with the results obtained from remote sensing. The structural analysis showed that the predominant trend of mineralization and alteration zones in the studied deposits is northeast-southwest and is consistent with the predominant trend of the fault lines extracted from satellite images. Based on these results, it can be concluded that fault and fracture have played a major role in controlling and forming gold and copper reserves in the Ahar region.