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A 3-D Image of Iljaq Salt Structure, South of Alborz Belt, Iran


Farhadi, Reza, Geological Survey of Iran, Tehran, Iran


Alborz belt extends for about 1000 kilometers from Aras Fault (west of the South Caspian Depression) to the south of Kopeh Dagh in north of Iran. Miocene sediments and evaporate deposits which called Upper Red Formation in foreland basins in the south of Alborz nappes are simply folded so strata are horizontal to vertical therefore rounded hills upon plains or walls of sandstone and cliffs over hanging valleys with numerous obvious or hidden salt structures are the most common morphs. Iljaq salt structure is formad by gyp­sum, salt and potash plays which are covered by marls sandstone and conglomerates.

Iljaq is a swollen structure which its topography in rims is higher than the center, dip of the strata near the rim is almost 90 degrees and a vertical gypsum layer around the struc­ture in the top of ring shows the border of salt. According to the Bouguer anomalies the cen­ter bowel is lighter than the circular marginal rim.

The origin of pure secondary picromerite and halite in the southern rim of structure is the primary potash beds or lenses, therefore an intersecting radial core drilling plan was designed and done. Under ground data show the conical structure is built by intrusion of salt into the crest of a double plunge inclined anticline as the stratigraphic column is stay with­out any change but similar flow folds are distinguishable in potash zone.