Crustal-scale structure of the Nasr-Abad buried salt diapir in northwest Central Iran from a profile magnetotelluric dataset

Abstract

Great Kavir, located in the northern part of the Central Iran depression, is the largest salt desert in Iran with groups of clustered salt diapirs in its northwestern part. The Nasr-Abad salt diapir in the Shurab diapiric group is the largest buried salt diapir in this region, whose geometry at depth and surrounding structure are rarely known. In this study, we investigate a broadband magnetotelluric (MT) dataset recorded at 37 stations distributed along a 14 km, SW-NE profile to characterize the geometry, substratum, and overburden of the Nasr-Abad salt diapir. The spatially distributed MT responses obtained in this study are associated with geological structures at depths of less than 25 km. The measurements were used to generate a crustal-scale resistivity model of the study area, which correlates well with the known lithostratigraphy of the region. The resistivity model reveals a dipping resistive body that has been uplifted from a deep resistive layer to shallower depths. The geometry of this body indicates a well-defined base and a northeastward dip, suggesting that it corresponds to the Nasr-Abad buried salt diapir. We applied various numerical tests to verify geologically important model features and constrain their properties. The results identify a basement fault with significant vertical throw in the southwestern part of the profile and demonstrate an approximately symmetric shape for the Nasr-Abad buried salt diapir.