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The Structure of Potash and Salt on Diapir Pol, Zagros Fold-Thrust Belt, Iran


Farhadi, Reza1, Christopher J. Talbot2 (1) Geological Survey of Iran, Tehran, Iran (2) Uppsala University, Uppsala, Sweden


The Zagros fold-thrust belt extends from East Anatolian left-lateral strike-slip fault in the northwest to Oman line in the southeast. The belt is the result of the structural deformation of a proforeland system and structurally it is a prism of stacked thrust sheets composed of uppermost Neoproterozoic and Phanerozoic strata. Uppermost Neoproterozoic and Lower Cambrian part of these strata (Hurmoz megasequence) have deposited in an extensional pull-apart basin (Prototethys). Diapir Pol is a fountain type extrusion of Hurmoz salt which developed from a pillow of salt before the Eastern Zagros fold-thrust belt began propagat­ing. The structural paterns on Diapir Pol are composed of three generations of tight to iso­clinal similar-type flow folds commonly with sheath like geometry by the intrusion, extru­sion and gravity spreading of salt.

Finally, the flow of salt was ceased moderately then salt was eroded by rivers flowing mainly eastward; maximum amount of potassium in the brines is 70 gr/lit and numerous potash boudins (more competently than salt) on Diapir Pol are the source. The outcrops are two types, iron rich type and white potash (sylvite is 59.64%, and the surface reserve is one million tons).

Sketch maps of the three sets of deformation structures by Prof. C.J. Talbot at the scale of 1/10000 indicated thet the structural levels or horizons of potash boudins are quite close to each other and he showed their stratigraphic extrapolations. Large scale mapping sug­gest strongly thet all potash boudins dispersed along the same stratigraphic level which Talbot introduced and he called it the Zone of Potash Bearing Strata (ZPBS).

The Zagros fold thrust belt with its numerous hydrocarbon fields is the most resource­prolific fold-thrust belt of the world but we must review the topics: 1- The stratigraphy of Hurmoz sequence. 2- The economic aspects of the Prototethys basin.