3D Inversion of Audio Magnetotelluric Data for Sulphide Mineralization over Dhanjori Basin
Authors
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IIT (ISM), Dhanbad
Roshan Kumar Singh -
IIT (ISM), Dhanbad
Ashok K. Gupta
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Observat´orio Nacional, Rua General Jos´e Cristino, 77, Rio de Janeiro, RJ 20.921-400
Ved P. Maurya
-
Geological Survey of India
S. Singh
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IIT (ISM), Dhanbad
Shalivahan
DOI:
https://doi.org/10.1007//s12594-019-1154-4Abstract
Quartz-pebble conglomerate (QPC) in the Dhanjori basin, a rifted greenstone belt, is known for its gold mineralization. Audio-magnetotelluric (AMT) soundings have been acquired for 32 sites spread in grid fashion for frequency 10kHz to 10 Hz along four parallel profiles. Due to noise conditions in the data only 26 sites have been used for further studies. The site spacing between adjacent AMT sites were ~250 m. The grid spreads over QPCD and Mayurbhang Granite (MG) of rocks. The dimensionality and the directionality analysis hinted towards a complex structure which tempted to perform a 3D inversion of AMT data for full impedance data. To obtain the optimum value of initial uniform half space resistivity, 3D inversion of off-diagonal component of inversion data was performed with various values of resistivity. The optimized value of resistivity was then used to perform 3D inversion for full impedance component with different set of error floor for the impedance component. The final 3D model showed the presence of a continuous conducting feature all along the three profile. Whereas, the southernmost profile showed three well developed conductors. The model corroborates well with electrical resistivity tomography (ERT) sections and GSI borehole which lies within the same geological domain. The borehole intercepted sulphide mineralization with varying concentration from the near surface to ~ 100m. The near surface conducting heterogeneity thus is attributed to sulphide mineralization.
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