Journal of Mining Engineering

Journal of Mining Engineering

Study of Chromite Ore in the West of Sabzevar Ophiolite (Foroomad) Using ERT and VLF-EM Geophysical Methods

Document Type : research - paper

Authors
Alireza Shirzadi 1
Reza Ghanati 2
1 Graduate student of MSc, Institute of Geophysics, University of Tehran, Iran
2 Associate professor, Institute of Geophysics, University of Tehran, Iran
10.22034/ijme.2024.2015585.1992
Abstract
Research and experiences have shown that the geophysical exploration of chromite, compared to many other mineral ores, has been less confident and less successful. In Iran, many promising areas of chromite deposits have been left unplanned due to the lack of a definitive method for exploration and exploitation, which could cause economic prosperity for the area. In the present research, two geophysical methods, namely “electric resistivity tomography” and “very low frequency electromagnetic”, using 9 electromagnetic and 4 resistivity profiles, are used to identify chromite ore's geoelectric and electromagnetic properties. Laboratory studies, including electrical resistivity measurements on the rock cores and mineralography studies, have been conducted to evaluate the field results better. The resistivity was measured between 2800-3600 for one chromite ore, between 5500-8600 for the other, and between 2000-2300 Ω.m for a serpentinite, which is the chromite ore host rock. VLF-EM parameters (real magnetic field component) were obtained using different radio signals, including 29.6 and 18.1 kHz. The map of the real component of the vertical magnetic field of VLF-EM and the use of the Karous and Hjelt filter (1983) showed acceptable results in revealing fault zones and joints in serpentinized ultramafic rocks. The resulting maps showed that the lower resistances are along the faults and discontinuities in the rock, which are sometimes accompanied by chromite ore in their planes. I applied electrical resistivity tomography with the Wenner alpha array in areas with known chromite deposits, revealing, to some extent, that the zones with higher resistivity were related to chromite-bearing areas. The results of the interpretation of geophysical data were, in some cases, confirmed by the excavations and exploratory boreholes in the study areas. It can be concluded that if the required conditions are met, the methods employed can potentially reveal hidden chromite deposits..
Keywords
Sabzevar ophiolite
Chromite
Exploration
Electrical resistivity tomography (ERT)
very low frequency electromagnetic (VLF-EM)
Subjects
Papp, J. F., and Lipin, B. R., 2001; Chromium: U.S. Geological Survey Open-File Report 01–381, 161 p.## Ali, M.; and Jahangir Khan, M.; 2013; Geophysical Hunt for Chromite in Ophiolite; Int. j. econ. environ. geol. Vol: 4(2) 22-28. ## Mohanty W. K.; Mandal, A.; Sharma, S. P.; Gupta, S.; and Misra, S.; 2011; Integrated geological and geophysical studies for delineation of chromite deposits: A case study from Tangarparha, Orissa, India; Geophysics. Vol. 76, No. 5; P. B173–B185. ## Bayrak, M.; 2002; Exploration of chrome ore in Southwestern Turkey by VLF-EM; Journal of the Balkan Geophysical Society, Vol. 5, No 2, p. 35-46. ## Yaghubpur, A.; Hassannejad, A. A.; 2006; The Spatial Distribution of Some Chromite Deposits in Iran, Using Fry Analysis; Journal of Sciences, Islamic Republic of Iran, v. 17(2), p. 147-152. ## Lench, G.; Mihm, A.; and Alavi-Tehrani, N.; 1977; Petrography and geology of the ophiolite belt north of Sabzrvar/Khorasan (Iran); Neues Jahrbuch fur Geology un Palaontologie Monatshefte v. 131, p. 156-178. ## Dilek, Y.; 2003; Ophiolite concept and its evolution; Geological Society of America; Special Paper 373. ## Fruh-Green, G.; Plas, A.; and Lecuyer, C., 1996; Petrologic and stable isotope constraints on hydrothermal alteration and serpentinization of the EPR shallow mantle at hess deep site 895, Proc. Ocean Drill. Program Sci. Results, 747, 255. ## Nogol-e Sadat, M, A, A; and Almasian, M; 1993; Tectonic map of Iran, Scale 1:1000,000; Geological Survey of Iran. ## Klein, C.; Hurlbut, C. S.; 1985; Manual of Mineralogy (after James D. Dana), 20th Edition, Publisher: Wiley; p 596. ## Roberts, S.; 1988; Ophiolitic Chromitite Formation: A Marginal Basin Phenomenon? Economic Geology, Vol. 83, pp. 1034-1036. ## Paterson, N. R.; and Ronka, V.; 1971; Five years of surveying with the very low frequency electro magnetics method. Geoexploration, 9, l- 26. ## Kearey, P.; Brooks, M.; and Hill, l.; 2002; An Introduction to Geophysical Exploration, 3rd Edition; Wiley-Blackwell; 288 Pages. ## Vella, L.; and Emerson, D.; 2012; Electrical Properties of Magnetite and Hematite-Rich Rocks and Ores, ASEG Extended Abstracts, 1, 1-4, DOI: 10.1071/ASEG2012ab232. ## Stesky, R. M. and W. F. Brace; 1973; Electrical conductivity of serpentinized rocks to 6 kilobars, J. Geophys. Res., 78, 7614–7621. ## Karous, M.; and Hjelt, S. E.; 1983; Linear Filtering of VLF Dip-Angle Measurements; Geophysical Prospecting 31,782-794. ## Fallahsafari, M.; Ghanati, R.; 2022; DC Electrical Resistance Tomography Inversion; Journal of the Earth and Space Physics, 47(4). ## Ghanati, R.; Azadi, Y.; Fakhimi, R.; 2020; RESIP2DMODE: A MATLAB-Based 2D Resistivity and Induced Polarization Forward Modeling Software; Iranian Journal of Geophysics 13 (4), 60-78. ## Xi, X.; Yang, H.; He, L.; and Chen, R.; 2013; Chromite mapping using induced polarization method based on spread spectrum technology. Symposium on the Application of Geophysics to Engineering and Environmental Problems Proceedings, 13–19. ## Kospiri, A.; Kosho, P.; And Vukzaj, N.; 1999; Case Histories of the Application of Geophysical Methods to Chromite Exploration in the Balkans, Second Balkan Geophysical Congress and Exhibition. ## Wynn, J. C.; and Hasbrouck, W. P.; 1980; Geophysical studies of chromite deposits in the Josephine ultramafic complex of Northwest California and Southwest Oregon; U.S. Geological Survey, Open-File Report 80-936. ##
Journal of Mining Engineering
Volume 19, Issue 63
Spring 2024
Pages 47-65

  • Receive Date 12 November 2023
  • Revise Date 25 May 2024
  • Accept Date 26 June 2024