Seismic delineation of the gold‐bearing structures in the South Rand goldfield (South Africa): A comparison of pre‐stack time and depth migration approaches on legacy seismic data

Abstract

To better image complex geological structures and explore for the gold-bearing quartz pebble conglomerate (locally termed Kimberley Reef) near Burnstone mine in the South Rand goldfield (South Africa), we reprocessed legacy 2D reflection seismic data using up-to-date seismic processing algorithms. The mining region is dominated by steeply dipping normal and reverse faults, as well as dolerite intrusions that crosscut the tabular gold mineralization and complicate the extraction of the ore. The legacy seismic data were acquired in 1993 in the South Rand goldfield as part of the gold exploration programme by the Gold Division of Anglo-American Corporation. The pre-stack data quality was improved by cautiously removing noise and applying static corrections to enhance the continuity of the reflection events. Improved structural imaging was then achieved using pre-stack time migration and pre-stack depth migration through careful velocity analysis. In particular, pre-stack depth migration provided better imaging of near-surface stratigraphic units and deep-seated complex structures, relative to older post-stack migrated images produced in 1993. Other reprocessing improvements included accurate imaging of key seismic reflective interfaces that can be used as proxies to 2D map the gold deposit, its dip variations, and geological structures (faults/dykes) crosscutting it. Synthetic shot gathers data computed using a 2D finite-difference algorithm provided some insight into the source of seismic reflectivity observed on the reprocessed seismic data. The new structural information from reprocessing is essential for enhancing ore resource evaluation and guiding future exploration projects in the region.