3D seismic attributes for structural mapping and enhancement of deep gold mining: a case study from the West Wits Line goldfields, South Africa
Nomqhele Z. Nkosi 1 Musa S. D. Manzi 1 3 Oleg Brovko 2 Raymond J. Durrheim 1
+ Author Affiliations
- Author Affiliations
1 University of the Witwatersrand, School of Geosciences, 1 Jan Smuts Avenue, Braamfontein 2000, Johannesburg, South Africa.
2 De Beers Group Services RSA Pty Ltd, Technical Services Johannesburg, Johannesburg 2193, South Africa.
3 Corresponding author. Email: musa.manzi@wits.ac.za
Exploration Geophysics 49(3) 345-362 https://doi.org/10.1071/EG16058
Submitted: 26 May 2016 Accepted: 2 April 2017 Published: 24 May 2017
Abstract
Volumetric and horizon-based seismic attributes were carried out on the 3D reflection seismic data acquired on the deep crystalline rock environments of the Witwatersrand Basin (South Africa). This study aimed at improving the delineation of minor faults that cross-cut the gold-bearing quartz pebble conglomerate horizons (termed reefs) in the complex geology of the West Wits Line (WWL) goldfield using different seismic attributes. The 3D seismic data show delineation of faults that cross-cut and displace the target horizons by tens to hundreds of metres, leading to the delineation of the ore resources in faulted areas of the mines. In particular, the ant-tracking technique has provided better stratigraphic and structural imaging in complex faulted areas, relative to conventional interpretation methods. Other improvements include more accurate mapping of the depths, dip and strike of the key seismic horizon (Roodepoort shale) using the edge detection attributes, yielding a better understanding of the interrelationship between fault activity, reef distribution and the relative chronology of tectonic events. The integration of the 3D reflection seismic data, seismic attributes and information from borehole logs and underground mapping has provided better imaging and modelling of important fault systems that might have a direct effect on mining. This information could be used for future mining planning and designs to: (1) assess and mitigate the risks posed by mining activities, and (2) improve the resource evaluation of the gold-bearing reefs in the WWL goldfield.
Key words: azimuth, dip, faults, imaging, interpretation, mineral exploration, mining, mining geophysics, seismic reflection.
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