Scientific Quarterly Journal of Geosciences

Scientific Quarterly Journal of Geosciences

Structural Modelling of Qom-Aran Depression

Document Type : Original Research Paper

Authors
Soheyla Bouzari 1
Mohammad Hashem Emami 2
1 Department of Geology, Islamic Azad University of North Tehran Branch, Tehran, Iran
2 Geological Survey of Iran , Tehran, Iran
Abstract
The intracontinental Qom- Aran depression basin is located in the central Iran zone and correlated with its tectonic environment. Some of the depression basins such as Qom- Aran, Aredstan- Yazd and Rafsanjan- Zarand basins show NW- SE trend and are located between two subordinate uplifted subzones of the central Iran zone (mid triangle subzone in the north and Urumiyeh-Dokhtar volcanic belt in the south). From Urumiyeh- Dokhtar magmatic subzone toward middle parts of the central Iran zone, there are various subordinate trends and morphostructures, probably due to the affected stress and the reflection of brittle behaviour of the central Iranian crystalline basement, that have produced faulted and rotated blocks with different forms and dimensions as well as the complexity of the morphostructures. Therefore, In the Qom-Aran depression basin, there are three structural trends, NW-SE, SW (Davazdah Emam-Narreh khar kuh fault), NNW- SSE (Qom-Ravand­-Zefreh - fault) and NE-SW (Maranjab fault).
During the Neogene, spreading of the Red Sea and movement of Arabian Plate to the north produced compressional stress in the Iranian platform. Strike- slip movements of Central Iranian blocks caused some local extensional movements, such as a long the bended part of Qom- Zefreh fault, and as a result the Qom- Aran pull - a part basin was formed. In the later phases a huge amount of continental facies sediments of the Upper Red Formation and related Ml, M2 and M3 members deposited in this basin. The above mentioned deposits are originated by erosion of surrounding uplifted areas. The latter form reliefs which bounded mainly with reverse fault are located in the margin of the Qom-Aran depression basin. In the late Neogene the continuation of the Red Sea spreading and related compressional stress to the north, caused an anticlock rotational movement of the Qom-Aran block. According to this structural evolution some NE-SW trends (Maran.jab Fault) are activated so that, the trend of Maranjab Fault shows 75 degree divergence to the Qom-Ravand - Zefreh faults trend. All structural evidences indicate an extentional movement along the bended parts of the Qom-Ravand - Zefreh strike - slip fault and consequently the formation of the Qom-Aran pull- apart basin. On the other hand, the folding of Upper Red Formation deposits with axial NW-SE (Alborz and Sarajeh anticline) and E-W trends (Qaleh Sardar Anticline) in the border of Qom- Aran depression indicate the limitation of basin dimension due to the oblique convergence of southern sub- block in eastern part of the depression which has produced a narrow-folded area in the Qaleh Sardar area. The above-mentioned rotational movements are in agreement with geophysical and microseismic data, and resulted the structural subdivisions of the area into active (Maranjab), Passive (Yakhab), captured (Daryacheh- ye - Namak) and isolated (daryacheh-ye - Hozsoltan) blocks.

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Scientific Quarterly Journal of Geosciences
Volume 13, 49-50
Autumn & Winter 2004, Vol. 13, No. 49-50
Winter 2004
Pages 62-77