Mineral prospection in the northwest of Orumiyeh
Based on a contract between Industries and Mines Organization of Azarbaijan-e Gharbi province and Kavoshgaran Consulting Engineers, an area, 600 Km2 was selected for geochemical assessment at northwest of the Orumiyeh County. The study area is located between 44 45' to 45 degrees E and 37 45' to 38 N. this area is accessible by the Orumiyeh-Salmas road. The area has cold winters and temperate short summers. The geomorphology of the area is under influence of local geology that includes Oligo-Miocene cliff-forming limestone, Permian crystalline limestone, Precambrian Kahar slates and shales, and Eocene-Oligocene detritus rocks. This area is situated in the intersection of Central Iran, Alborz and Sanandaj-Sirjan zones.
The lithology of the area consists of Precambrian gneiss, mica schist, amphibolite, marble (Green schist-Amphibolite facieses), Kahar slate and shale exposed in the center and north of the area. Solvana complex at southwest is composed on marble slate and phyllite. It only exposes in the Shekoftic village. Volcanic rocks and quartz porphyry to microgranites have intruded in the Kahar formation. Bayandor and Soltaniyeh formations have shale, micaceous sandstone, dolomite and dark crystalline limestone with chert nodules exposed in the Chaharshanbeh Mountain. Lower Paleozoic rocks including shale, sandstone, dolomite of Barut, laminated sandstones of Zaigun, sandstone and conglomerate of Lalun, chert-bearing dolomite of Mila, and Ordovician Lashgarak formation are widespread in the Chaharshanbeh and Bayazid mountains and also Khaneqah-Meskin road. Fossiliferous Permian limestones exist in the Sharifabad village that covers the Lower Paleozoic unconformably.
After Permian rocks, there is just a small outcrop of Cretaceous limestone in the area that thrust over the Permian. Toward south of the area, polygenetic conglomerate of Paleocene-Eocene covers the older rocks unconformably. This unit itself is situated beneath the Oligocene conglomerate unconformably. Limited exposures of Qom formation exist in the area that composed of marl and massive limestone, showing gentle folding. The youngest rocks include alluvial terraces in various parts of the area.
In addition to intrusive rocks cut the Kahar formation, there are quartz diorite, diorite and gabbro bodies in this zone. The largest gabbro-diorite body is located in the Meskin and Chir villages with some pegmatites. Amphibole gabbro of Tershen mountain is located at south of Mamakan village. It is full of ferromagnesian minerals. Other intrusive rocks in the area include granodiorite rocks in the Lower Golanik village, ultrabasic rocks (wehrlite) of the Qara Aghaj that have considerable amount of titanium and phosphate as ilmenite, magnetite and apatite. The Qara Aghaj intrusion should be differentiated from an oceanic alkaline ultrabasic magma that is comparable with Bushveld and Stillwater ultrabasic bodies. Based on the thermal metamorphism of Mila dolomite and Permian limestones and dolomites due to intrusion of gabbros, and the similarities between these bodies with the Triassic diorite-gabbros of Central Iran, these bodies may be formed in the Early Cimmerian orogeny.
From tectonic viewpoint and with consideration of lithological diversity, the area has various macroscopic and microscopic structures. Macroscopic structures include faults having two major strikes, NW and N. The Sheikh Bazid thrust and the Qara Aghaj fault are two important examples of the first trend, Hashtian thrust and Meskin fault are two examples of the second trend. There are minor faults with different attitude in the area.