Application of three-dimensional magnetic anomaly inversion in magnetite exploration
ZHAO Bai-Ru1,2(), LI Hou-Pu3(), ZHANG Heng-Lei1,2
1. School of Geophysics and Geomatics, China University of Geosciences (Wuhan), Wuhan 430074, China 2. Key Laboratory of Geological Survey and Evaluation of Ministry of Education, China University of Geosciences (Wuhan), Wuhan 430074, China 3. School of Electrical Engineering, Naval University of Engineering, Wuhan 430033, China
The Galinge iron deposit in Qinghai is overlain by deposits measuring greater than 150 m in thickness. The great burial depths of ore bodies lead to gentle magnetic anomaly morphology, making it difficult to characterize the spatial distribution of ore bodies. Therefore, this study employed three-dimensional magnetic anomaly inversion to determine the three-dimensional distribution characteristics of subsurface magnetic intensity in the study area. Given the prior information of non-magnetic surrounding rocks, the three-dimensional magnetic intensity model clearly presented the spatial distribution of the ore bodies and reflected the presence of intense magnetic bodies at depths of less than 500 m in existing boreholes. Accordingly, it can be inferred that there exist concealed ore bodies at depths exceeding 500 m in the study area. The results of this study suggest that three-dimensional magnetic anomaly inversion can effectively improve target identification, providing clear information on the horizontal positions, depths, and scales of magnetic ore bodies. The proposed inversion method can offer strong support for drilling design and reserve estimation, warranting promotion in detailed exploration of solid minerals.
Bai-Ru ZHAO,Hou-Pu LI,Heng-Lei ZHANG. Application of three-dimensional magnetic anomaly inversion in magnetite exploration[J]. Geophysical and Geochemical Exploration,
2024, 48(6): 1626-1632.
Cross-section of borehole line 9 (with the location of the section as shown in Figure 3, edited according to Wang et al.[3])
Magnetic anomaly ΔT in the study area
The correlation coefficient diagram between the RTP anomaly and the vertical derivative of the normalized magnetic source intensity
Inverse iteration mean square error curve
Three-dimensional inversion fitting of magnetic anomalies (a) and residual magnetic anomalies (b)
Three-dimensional magnetization intensity horizontal slice at 200 meters depth
Three-dimensional magnetization intensity depth slice (The arrow lines represent the drillhole locations, and the black blocks represent the ore ranges illustrated by the drilling)
Wu X X, Bao G Y, Yi Y C, et al. The study on the genesis and geological characteristics of Galinge high-grade iron deposit of Qinghai Province[J]. Gold Science and Technology, 2007, 15(4):36-40.
He S Y, Qi L Y, Shu S L, et al. Metallogenic environment and potential in the Qimantage porphyry copper deposit,Qinghai[J]. Geology and Prospecting, 2008, 44(2):14-22.
Wang Z L, Wang Y G, Wang Z M, et al. Joint prospecting of ground magnetic survey data inversion and borehole magnetic survey:A case study of Galinge Fe-polymetallic deposit[J]. Geology and Resources, 2020, 29(1):61-67.
Yuan Y, Cui Y A, Chen B, et al. Fast and high accuracy 3D magnetic anomaly forward modeling based on BTTB matrix[J]. Chinese Journal of Geophysics, 2022, 65(3):1107-1124.
Li L L, Zhou J Y, Ma G Q, et al. A study of fast joint physical inversion methods of gravity and magnetic data with undulating observation surface constraints[J]. Progress in Geophysics, 2024, 39(4),1447-1456.
Li Y L, Xing L J, Bai Z H, et al. The application of comprehensive geophysical prospecting method to the exploration of the Yuejinshan iron deposit in Qinghai[J]. Geophysical and Geochemical Exploration, 2018, 42(5):889-895.
Zhang M J, Yan J Y. Application of gravity and magnetic 3D inversion to ore search and reserve increase in the Baoshan iron deposit,Yiwu County,Xinjiang[J]. Geology and Exploration, 2014, 50(1):156-161.
Liu Y, Meng G X, Yan J Y, et al. Application of 3D property inversion for gravity and magnetic data to metal mineral exploration[J]. Geology and Exploration, 2011, 47(3):448-455.
Hu B, Jia Z Y, Zhang G B, et al. Three-dimensional inversion of gravity and magnetic data and its application in the study on the characteristics of magmatic rocks in the Gangdise belt and adjacent areas,Tibetan Plateau[J]. Chinese Journal of Geophysics, 2019, 62(4):1362-1376.
Zhao L F, Li X Y, Li C L, et al. Recognition of concealed porphyry body and deep prospecting practice in Duobaoshan ore concentration area based on gravity,magnetic and electromagnetic surveys[J]. Mineral Deposits, 2022, 41(6):1217-1231.
Suo K, Zhang G B, Mei Y H, et al. Density and magnetic susceptibility distribution of central Yili Basin by three-dimensional inversion of gravity and magnetic data[J]. Chinese Journal of Geophysics, 2018, 61(8):3410-3419.
Yan J Y, Lyu Q T, Chen X B, et al. 3D lithologic mapping test based on 3D inversion of gravity and magnetic data:A case study in Lu-Zong ore concentration district,Anhui Province[J]. Acta Petrologica Sinica, 2014, 30(4):1041-1053.
Rao C F, Yu P, Hu S F, et al. The 3D inversion of the normalized source strength data based on weighted model parameters[J]. Geophysical Prospecting for Petroleum, 2017, 56(4):599-606.
Wang J, Yao C L, Li Z L. Deep structure in the Emeishan large igneous province revealed by inversion of magnetic anomalies[J]. Chinese Journal of Geophysics, 2019, 62(4):1394-1404.
Zhang Z H, Lu R Q, Liao X L, et al. Inversion of magnetic anomaly and magnetic gradient anomaly based on fully convolution network[J]. Progress in Geophysics, 2021, 36(1):325-337.
Zhang H L, Geng M X, Hu X Y. Three-dimensional inversion of gravity/magnetic anomalies based on curvelet compression and its applications[J]. Oil Geophysical Prospecting, 2023, 58(4):993-1001.
[18]
Li Y G, Oldenburg D W. Fast inversion of large-scale magnetic data using wavelet transforms and a logarithmic barrier method[J]. Geophysical Journal International, 2003, 152(2):251-265.
Zhu C J, Zhou Z W, Liu T Y, et al. Application of high-precision magnetic survey to prospecting:A case study in the Galinge ore district of Qinghai Province[J]. Geology and Exploration, 2011, 47(2):277-283.
[20]
Zhang H L, Ravat D, Marangoni Y R, et al. NAV-Edge:Edge detection of potential-field sources using normalized anisotropy variance[J]. Geophysics, 2014, 79(3):43-53.
[21]
Zhang H L, Ravat D, Hu X Y. An improved and stable downward continuation of potential field data:The truncated Taylor series iterative downward continuation method[J]. Geophysics, 2013, 78(5):75-86.
Liu S, Liu T Y, Zeng Q Q. On inversion methods of estimating top buried depth of magnetic body based on magnetic anomalies:A case study of magnetic datainterpretation in Galinge mining area[J]. Chinese Journal of Engineering Geophysics, 2012, 9(4):413-418.
[23]
Huang L, Zhang H L, Sekelani S, et al. An improved Tilt-Euler deconvolution and its application on a Fe-polymetallic deposit[J]. Ore Geology Reviews, 2019, 114:103114.
[24]
Zhang H L, Li H P, Hu X Y. Fine interpretation of magnetic data for a concealed mineral deposit:A case study of the Fe-polymetallic deposit from Western China[J]. Journal of Applied Geophysics, 2024, 228:105468.
[25]
Zhang H L, Ravat D, Marangoni Y R, et al. Improved total magnetization direction determination by correlation of the normalized source strength derivative and the reduced-to-pole fields[J]. Geophysics, 2018, 83(6):75-85.
Zhang H L, Liu T Y, Zhu C J, et al. The effects of applying high-precision magnetic survey:A case study of the Galinge ore district in Qinghai province[J]. Geophysical and Geochemical Exploration, 2011, 35(1):12-16.
Song S, Zhang H L. The application of downward continuation to deep mineral exploration:A case study of an ore district in Qinghai Province[J]. Geophysical and Geochemical Exploration, 2014, 38(6):1195-1199.
Zhang H L, Y R Marangoni, Zuo R G, et al. The improved anisotropy normalized variance for detecting non-vertical magnetization anomalies[J]. Chinese Journal of Geophysics, 2014, 57(8):2724-2731.
