A potential field geophysical study to image a Potash resource through Depth from Extreme Points, Ghareh-Aghaj deposit in NW of Iran

Document Type : Research Paper


School of Mining Engineering, University of Tehran, Tehran, Iran.



Based on magnetic susceptibility and density contrast models, the final purpose of analyzing potential field data is to estimate the parameters of the sought source, such as depth, structural index, horizontal location, and physical characteristics. Meanwhile, when conducting geophysical explorations, it is critical to ascertain the exact depth of the underground source as accurately as possible. In this study, the potential field is interpreted using the depth from extreme points “DEXP” automatic transformation technique, founded on the accurate processing of the local wavenumber at various scales and the extreme points of the DEXP field to extract the depth, horizontal position and structural index of the source. This highly stable method demonstrates low sensitivity to noise-contaminated data since it employs an upward continuation filter and a potential field derivative operator. In addition, the findings are more dependable than those of alternative techniques. Furthermore, the procedure is entirely automatic and does not require any basic information from the data collection area. In other words, DEXP can be considered a fast imaging method. Since multiscale methods are less reliant on the magnetic induction field, nowadays, they are utilized more frequently in magnetic field computations. At the beginning of this research, synthetic scenarios are simulated, and then the depth extension of the postulated models was demonstrated by implementing the DEXP technique to the synthetic gravity and magnetic data. Subsequently, this method has been implemented on data from the Ghareh-Aghaj potash exploratory area in Zanjan Province, North of Iran. By summarizing this method's results, it can be seen that the potash mass exhibits a minimal transverse expansion and has extended more in the depth dimension. Compared to the findings obtained via exploratory boreholes, these findings demonstrate a level of agreement that can be considered satisfactory.


Main Subjects

  1. Nabighian M.N, Grauch V.J.S, Hansen R.O, Lafehr T.R, Li Y, Peirce J.W, Phillips J.D, Ruder M.E (2005) Historical development of the magnetic method in exploration. Geophysics 70: 33ND-61ND.
  2. Nabighian M.N (1972) The analytic signal of two-dimensional magnetic bodies with polygonal cross-section: its properties and use for automated anomaly interpretation. Geophysics 37: 507-517.
  3. Thurston J.B, Smith R.S (1997) Automatic conversion of magnetic data to depth, dip, susceptibility contrast using the SPI method. Geophysics 62: 807-813.
  4. Fedi M, Rapolla A, Russo G (1999) Upward continuation of scattered potential field data. Geophysics 64: 443-451.
  5. Thompson D.T (1982) EULDPH: A new technique for making computer assisted depth estimates from magnetic data. Geophysics 47: 31-37.
  6. Reid A.B, Allsop M, Granser H, Millet A.J, Somerton W (1990) Magnetic interpretation in three dimensions using Euler deconvolution. Geophysics 55: 80-91.
  7. Stavrev P, Reid A.B (2007) Degrees of homogeneity of potential fields and structural indices of Euler deconvolution. Geophysics 72: L1-L12.
  8. Salem A, Ravat D (2003) A combined analytic signal and Euler method AN-EUL for automatic interpretation of magnetic data. Geophysics 68: 1952-1961.
  9. Salem A, Ravat D, Smith R, Ushijima K (2005) Interpretation of magnetic data using an enhanced local wavenumber (ELW) method. Geophysics 70: 141-151.
  10. Smith R.S, Thurston J.B, Dai T.F, MacLeod I.N (1998) ISPITM—the improved source parameter imaging method. Geophys. Prospect. 46 (2): 141–151.
  11. Fedi M (2007) DEXP: a fast method to determine the depth and the structural index of Potential field sources. Geophysics 77(1): G13-G24.
  12. Fedi M, Florio G, Quarta T (2009) Multiridge analysis of potential fields: Geometric method and reduced Euler deconvolution. Geophysics 74(4): L53-L65.
  13. Fedi M, Pilkington M (2012) Understanding imaging methods for potential field data. Geophysics 77(1): G13-G24.
  14. Abbas M.A, Fedi M, Florio G (2014) Improving the local wavenumber method by automatic DEXP transformation. Journal of Applied Geophysics 111: 250-255.
  15. Bracewell R (1965) The Fourier transform and its applications. McGraw-Hill Book Co.
  16. Phillips J.D, Hansen R.O, Blakely R.J (2007) The use of curvature in potential-field interpretation. Exploration Geophysics 38(2): 111–119.
  17. Telford W.M, Geldart L.P, Sheriff, R.E (1990) Applied Geophysics. Cambridge University Press.
  18. Mushayandebvu M.F, van Driel P, Reid A.B, Fairhead J.D (2001) Magnetic source parameters of two-dimensional structures using extended Euler deconvolution. Geophysics, 66, 814-823.
  19. Blakely RJ (1995) Potential Theory in Gravity and Magnetic Applications. Cambridge Univ. Press.
  20. Razavi S.A, Jafari F (2008) Report of potash explorations employing magnetometric and gravimetric techniques in Aji-Chai and Ghareh-Aghaj areas. Geological Survey and Mineral Exploration of Iran.
  21. Abedi M (2018) An integrated approach to evaluate the Aji-Chai potash resources in Iran using potential field data. Journal of Applied Geophysics, 139, 379-391.
  22. Abedi M., Oskooi B (2015) A combined magnetometry and gravity study across Zagros orogeny in Iran. Tectonophysics, 664, 164-175.