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Exploration of Deep Magnetite Deposit Under Thick and Conductive Overburden with Ex Component of SOTEM: A Case Study in China

  • Dongyang Hou
  • Guoqiang Xue
  • Nannan Zhou
  • Wen Chen
  • Junjie Xue
Article
  • 25 Downloads

Abstract

In northern China, thick loess strata with low resistivity are widely present and can shield the deep induced electromagnetic field signal and influence the accuracy of deep targets while electromagnetic prospecting is being performed. To achieve deep target exploration with high resolution, a new technique known as the short offset transient electromagnetic method (SOTEM) is applied in this research area. This method can be used to perform near-source configuration surveys, but shows no obvious difference between the deep magnetite deposit and low-resistivity layer in this survey area. Therefore, it cannot explore the magnetite deposit directly using the traditional magnetic component (Hz) of SOTEM. The Ex component, which can more effectively distinguish the high-resistivity surrounding rock and overlying low-resistivity layer than the Hz component, is used for exploration. First, 2D forward modeling and sensitivity analysis of the high-resistivity body are carried out to determine the different responses of the Ex and Hz components, respectively. Moreover, to better determine the interface between the surrounding rock and low-resistivity layer, 1D Occam inversion and the generalized inverse matrix inversion method are used. Furthermore, aiming at the static effect of the Ex component in field exploration, joint inversion of the Ex and Hz components is carried out for comprehensive interpretation. Finally, a field test is conducted, and the drilling results are used for verification. The research results can provide an effective geophysical model for the exploration of contact metasomatic magnetite deposits.

Keywords

Low-resistivity layer magnetite deposit SOTEM Ex component joint inversion 

Notes

Acknowledgements

We wish to thank Mr. Yunfei Lu for his help with completing the generalized inverse matrix inversion. This research is supported by the National Key R&D Program of China (grant no. 2017YFC0601204), Natural Science Foundation of China (NSFC) (41474095) and Beijing Natural Science Foundation (8182054).

References

  1. Chen, M. S. (2014). Analysis of generalized inverse matrix inversion. Coal Geology and Exploration, 42(6), 87–92.Google Scholar
  2. Chen, W., Xue, G., Khan, M. Y., et al. (2017a). Using SOTEM method to detect BIF bodies buried under very thick and conductive quaternary sediments, Huoqiu Deposit, China. Pure and Applied Geophysics, 174(3), 1013–1023.CrossRefGoogle Scholar
  3. Chen, W. Y., Xue, G. Q., Muhammad, Y. K., Gelius, L. J., Zhou, N. N., Li, H., et al. (2015). Application of short-offset TEM (SOTEM) technique in mapping water-enriched zones of coal stratum, an example from East China. Pure and Applied Geophysics, 172(6), 1643–1651.CrossRefGoogle Scholar
  4. Chen, W., Xue, G., Olatayo, A. L., et al. (2017b). A comparison of loop time-domain electromagnetic and short-offset transient electromagnetic methods for mapping water-enriched zones—a case history in Shaanxi, ChinaTEM mapping water-enriched zones[J]. Geophysics, 82(6), B201–B208.CrossRefGoogle Scholar
  5. Constable, S. C., Parker, R. L., & Constable, C. G. (1987). Occam’s inversion: A practical algorithm for generating smooth models from electromagnetic sounding data[J]. Geophysics, 52(3), 289–300.CrossRefGoogle Scholar
  6. Danielsen, J. E., Auken, E., Jørgensen, F., et al. (2003). The application of the transient electromagnetic method in hydrogeophysical surveys[J]. Journal of Applied Geophysics, 53(4), 181–198.CrossRefGoogle Scholar
  7. DeGroot-Hedlin, C., & Constable, S. (1990). Occam’s inversion to generate smooth, two-dimensional models from magnetotelluric data[J]. Geophysics, 55(12), 1613–1624.CrossRefGoogle Scholar
  8. Fitterman, D. V., & Stewart, M. T. (1986). Transient electromagnetic sounding for groundwater[J]. Geophysics, 51(4), 995–1005.CrossRefGoogle Scholar
  9. Hai, L., Guoqiang, X., Nan, N. Z., & Weiying, C. (2015). Appraisal of an Array TEM Method in Detecting a Mined-out Area Beneath a Conductive Layer. Pure and Applied Geophysics, 172(10), 2917–2929.CrossRefGoogle Scholar
  10. Hansen, P. C. (1990). Truncated singular value decomposition solutions to discrete ill-posed problems with ill-determined numerical rank[J]. SIAM Journal on Scientific and Statistical Computing, 11(3), 503–518.CrossRefGoogle Scholar
  11. He, L., Chen, L., Dorji, D., et al. (2018). Mapping chromite deposits with audio magnetotellurics in the Luobusa ophiolite of southern Tibet[J]. Geophysics, 83(2), 1–44.CrossRefGoogle Scholar
  12. Hu, X., Peng, R., Wu, G., et al. (2013). Mineral exploration using CSAMT data: Application to Longmen region metallogenic belt, Guangdong Province, China[J]. Geophysics, 78(3), B111–B119.CrossRefGoogle Scholar
  13. Key, K. (2009). 1D inversion of multicomponent, multifrequency marine CSEM data: Methodology and synthetic studies for resolving thin resistive layers. Geophysics, 74(2), F9–F20.CrossRefGoogle Scholar
  14. Melo, A. T., Sun, J., & Li, Y. (2017). Geophysical inversions applied to 3D geology characterization of an iron oxide copper-gold deposit in Brazil[J]. Geophysics, 82(5), K1–K13.CrossRefGoogle Scholar
  15. Metwaly, M., Elawadi, E., Moustafa, S. S. R., et al. (2014). Groundwater contamination assessment in Al-Quwy’yia area of central Saudi Arabia using transient electromagnetic and 2D electrical resistivity tomography[J]. Environmental Earth Sciences, 71(2), 827–835.CrossRefGoogle Scholar
  16. Oristaglio, M. L., & Hohmann, G. W. (1984). Diffusion of electromagnetic fields into a two dimensional earth: A finite difference approach. Geophysics, 49(7), 870–894.  https://doi.org/10.1190/1.1441733.CrossRefGoogle Scholar
  17. Parker, R. L. (1994). Geophysical inverse theory[M]. Princeton: Princeton University Press.Google Scholar
  18. Spies, B. R. (1989). Depth of investigation in electromagnetic sounding methods [J]. Geophysics, 54(7), 872–888.CrossRefGoogle Scholar
  19. Sui, W., Christensen, D. A., & Durney, C. H. (1992). Extending the two-dimensional FDTD method to hybrid electromagnetic systems with active and passive lumped elements[J]. IEEE Transactions on Microwave Theory and Techniques, 40(4), 724–730.CrossRefGoogle Scholar
  20. Sullivan, D. M. (2013). Electromagnetic simulation using the FDTD method[M]. Oxford: Wiley.CrossRefGoogle Scholar
  21. Wang, J. Y. (2002). Inverse Theory in Geophysics. 2nd ed (in Chinese) (2nd ed.). Beijing: Higher Education Press.Google Scholar
  22. Wang, T., & Hohmann, G. W. (1993). A finite-difference, time-domain solution for three-dimensional electromagnetic modeling[J]. Geophysics, 58(6), 797–809.CrossRefGoogle Scholar
  23. Ward, S. H., & Hohmann, G. W. (1991). Electromagnetic theory for geophysical exploration. In N. Nabighian (Ed.), Electromagnetic methods in applied geophysics (pp. 121–223). Tusla: Society of Exploration Geophysics.Google Scholar
  24. Xue, G., Bai, C., Yan, S., et al. (2012a). Deep sounding TEM investigation method based on a modified fixed central-loop system[J]. Journal of Applied Geophysics, 76, 23–32.CrossRefGoogle Scholar
  25. Xue, G. Q., Chen, W. Y., Zhou, N. N., et al. (2013a). Short-offset TEM technique with a grounded wire source for deep sounding[J]. Chinese Journal of Geophysics, 56(1), 255–261. (in Chinese).Google Scholar
  26. Xue, G. Q., Cheng, J. L., Zhou, N. N., et al. (2013b). Detection and monitoring of water-filled voids using transient electromagnetic method: A case study in Shanxi, China[J]. Environmental Earth Sciences, 70(5), 2263–2270.CrossRefGoogle Scholar
  27. Xue, G. Q., Gelius, L. J., Sakyi, P. A., et al. (2014). Discovery of a hidden BIF deposit in Anhui province, China by integrated geological and geophysical investigations[J]. Ore Geology Reviews, 63, 470–477.CrossRefGoogle Scholar
  28. Xue, G. Q., Li, X., Quan, H. J., et al. (2012b). Physical simulation and application of a new TEM configuration[J]. Environmental Earth Sciences, 67(5), 1291–1298.CrossRefGoogle Scholar
  29. Zhao, A. P. (2002). Analysis of the numerical dispersion of the 2D alternating-direction implicit FDTD method[J]. IEEE Transactions on Microwave Theory and Techniques, 50(4), 1156–1164.CrossRefGoogle Scholar
  30. Zhou, N. N., Xue, G. Q., Chen, W., et al. (2015). Large-depth hydrogeological detection in the North China-type coalfield through short-offset grounded-wire TEM[J]. Environmental Earth Sciences, 74, 1–12.CrossRefGoogle Scholar

Copyright information

© Springer Nature Switzerland AG 2018

Authors and Affiliations

  1. 1.Key Laboratory of Mineral ResourcesInstitute of Geology and Geophysics, Chinese Academy of SciencesBeijingChina
  2. 2.Institutions of Earth ScienceChinese Academy of SciencesBeijingChina
  3. 3.University of Chinese Academy of SciencesBeijingChina
  4. 4.College of ScienceLiaoning University of TechnologyJinzhouChina

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