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Final Kloof-South Deep ore body model with incorporated seismically mapped faults, which can be integrated into data mine packages for mine planning and design purposes. Note the crosscutting relationship between faults that is often difficult to see through drilling and/or underground mapping (Courtesy of Gold Fields Ltd).
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We discuss the importance of retrieving, recovering, and reprocessing legacy seismic data for mineral exploration.
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Context 1
... edge detection attribute was applied to enhance detection of horsts and anticlines that might bring the ore body to mineable depths; and grabens, synclines and thrust faults that might have preserved the ore body from erosion. Figure 3 is is the structural framework of the VCR ore body developed from the seismic attributes and structural modelling. These results were integrated with geological information to improve the understanding of the current major South Deep ore body model ( Manzi et al., 2012b). ...
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Citations
... As many petroleum basins have matured, a considerable effort has also been made to collect newer, higher-resolution data from old basins, such as the North Sea (Hayes et al. 2018;Patruno et al. 2020). There have also been procedures put in place to ensure that the legacy of seismic data is not lost through the reprocessing of old data in mature basins (Manzi et al. 2019;Westgate et al. 2020) as well as the general release of large subsurface databases by national geological surveyssuch as those in Denmark, Netherlands, Norway and the UKall of which have been investigated through academic studies. During this time there have been significant improvements in the quality of data that have been collected. ...
Since the last Special Publication on Seismic Geomorphology, the application of seismic data has grown substantially, revolutionising our understanding of basin evolution in the process. The papers presented here provide an insight into the direction of travel for seismic geomorphological analyses and how the science has evolved since 2007. New methods of data collection, new methods of processing and visualisation, and the integration of new types of complementary data, all have played a role in maximising the potential palaeo-environmental insights that can be derived from such studies. The submissions range across different geological settings, consisting of glacial, fluvial, volcanic, deltaic, and slope settings. Many of these studies integrate different methods, showing what can be achieved by combining multiple datasets to understand the subsurface. As more legacy datasets become available, the observed acceleration in seismic data availability and the associated publications will likely continue. Newer methods and the greater understanding of the subsurface are yielding a greater understanding on not just the palaeo-environments, but also what generates seismic reflectivity in the subsurface. The study of seismic geomorphology remains in its infancy, and much exciting research potential is yet to be realised.
... Legacy data have advantages such as: 1) being less contaminated by noise from mining activities (e.g., blasting, drilling, rock crushing, etc.); 2) being less contaminated by electric/electromagnetic noise; 3) have been acquired in places that presently may be unavailable for new surveys; and 4) ultimately coming at a lower cost compared to new acquisition campaigns (i.e., Donoso et al. 2020 and references therein). Reprocessing of reflection seismic legacy data using the latest processing tools can provide valuable new information for both mineral exploration and mine planning purposes Manzi et al. 2019;Donoso et al. 2020). ...
... More than 20 000 line-km of 2D data were acquired in the 1980s and 1990s, covering several important mining regions (Durrheim, 2016;Terracin and Manzi 2017;von Ketelhodt et al. 2019). New insights obtained from legacy data may profit future mine planning operations by finding new ore deposits or constraining discovered ones with greater accuracy, ultimately giving a superior estimation of resources and providing information that may assist with, for example, siting and sinking future shafts (Manzi et al. 2019;Westgate, 2020). In addition, applying modern processing algorithms to legacy seismic data results in improved structural resolution and more accurate delineation of deeper ore deposits (Manzi et al. 2018a, b). ...
Two legacy reflection seismic profiles were acquired in 1988, north of the Kloof‐Driefontein Complex East (KDC East) Mine in the West Rand goldfield (South Africa), for the purpose of gold exploration and mine planning. These legacy 2D seismic data have been reprocessed using the latest processing tools to improve imaging. Special interest is given to the Black Reef Formation, which hosts a known gold orebody. The original legacy data are of poor quality, especially in areas that are dominated by dolomitic outcrops. To improve the quality of the data, special attention was given to the refraction static correction to enhance the continuity of the reflections below dolomitic rocks. Refraction seismic tomograms from both profiles exhibit three‐layer P‐wave velocity models: 1) topsoil (1 000 ‐ 2 000 m/s), 2) a weathered layer ranging from ca. 100 to 300 m in thickness (2 000 ‐ 5 000 m/s), 3) and bedrock (> 5 000 m/s). Seismic profile OK‐212 shows poor imaging of the Black Reef Formation because of the scattering of seismic energy in the near‐surface due to dolomites from the Transvaal Supergroup, while seismic profile OK‐213 exhibits south‐dipping reflections that are associated with the Black Reef Formation. To improve the structural imaging resolution, we tried pre‐stack time migration (PreSTM), pre‐stack depth migration (PreSDM), and post‐stack time migration (PostSTM) using the Kirchhoff algorithm. Pre‐stack depth migration most improved the imaging of deeper reflections due to its ability to honour complex lateral variations in the velocity field. Both PreSTM and PostSTM enhanced the continuity of the near‐surface reflections below the dolomitic rocks. This article is protected by copyright. All rights reserved
... A series of high-resolution 2D seismic profiles 22 and tens of 3D seismic surveys were first acquired in the late 1990s across the Kaapvaal Craton to search for gold-bearing reefs under the thick cover and to investigate deep crustal-scale structures. 22,42 The results from these early surveys presented pioneering work that demonstrated the effectiveness of reflection seismics for hard rock mineral exploration. In 1996, Anglo Gold Ashanti commissioned a 3D seismic survey ( Fig. 1a and b) for deep mine planning and designs. ...
... The seismic volume extends to about 11 km in depth and was processed using a standard post-stack time-migration workflow. 42,43 The 3D seismic data have been the subject of several studies [42][43][44][45] as part of the ICDP-DSeis project. The detailed information regarding the data acquisition, processing and interpretation is reported by Suzuki. ...
... The seismic volume extends to about 11 km in depth and was processed using a standard post-stack time-migration workflow. 42,43 The 3D seismic data have been the subject of several studies [42][43][44][45] as part of the ICDP-DSeis project. The detailed information regarding the data acquisition, processing and interpretation is reported by Suzuki. ...
Petrophysical properties of cylindrical core specimens from three boreholes from the International Continental Scientific Drilling Program, the DSeis project, measured at ambient pressure and room temperature conditions in various laboratories are presented and compared with downhole petrophysical data (sonic and density). The measured properties are from sixty-six rock specimens constituting metasediments, metabasalts and intrusives. Seismic velocities were measured using 0.5 MHz P- and S-wave transducers. To investigate the source of seismic reflectivity observed on the 2D legacy seismic data, we computed synthetic seismograms for adjacent rock units using downhole petrophysical data and compared them with seismic reflections from the reflection seismic profile. The experimental measurements show that the metasediments exhibit lower bulk densities and seismic velocities than the metabasalts and intrusive specimens. The porosity was found to be less than 2% for all the samples. No clear trends emerge when the Poisson's ratio is plotted against the P-wave velocities and porosities of the samples. A positive relationship is observed between the bulk modulus and P-wave velocities of the rock samples. The highest calculated reflection coefficients (RC) are associated with the metasediment-intrusive interfaces in all three boreholes. The intrusive-metabasalt and the metasediment-metabasalt interfaces exhibit low RC. Synthetic seismograms reveal strong reflections that coincide with high RC calculated using the bulk density and velocity data. The synthetic seismograms also revealed additional strong reflections that were not identified using the reflection coefficients calculated from the rock specimens, due to core loss in some lithological units. Successful correlations are carried out between the synthetic seismic data and the real seismic data, enabling us to correlate the stratigraphic sequence drilled in the boreholes to the seismic reflections observed on the legacy 2D reflection seismic data.
... Moreover, a better understanding of the velocity fields from hard rock environment has shown significant improvement in depth imaging of complex geological structures. Several authors (e.g., Manzi et al. 2019;Westgate et al. 2020) have demonstrated through various case studies from hard rock environments how legacy reflection seismic data can be revisited and reprocessed to improve the quality of the data and delineate the complex geological structures that host mineral deposits. The objective of this study is to reprocess the 18 km long, 6 s two-way time (TWT), legacy 2D reflection seismic profile acquired in 1993 near Burnstone mine in the South Rand goldfield of the Witwatersrand Basin (South Africa). ...
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 mineralisation 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 (PreSTM) and pre‐stack depth migration (PreSDM) through careful velocity analysis. In particular, PreSDM provided better imaging of near‐surface stratigraphic units and deep‐seated complex structures, relative to older post‐stack migrated images produced in 1993. Other re‐processing improvements include accurate imaging of key seismic reflective interfaces that can be used as proxies to 2D map gold deposit, its dip variations, and geological structures (faults/dykes) crosscutting it. Synthetic shot gathers data computed using 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. This article is protected by copyright. All rights reserved
... Legacy seismic data have proven their significance in mineral exploration and mine planning, and several studies (e.g., Malehmir et al., 2010;Cheraghi et al., 2011;Manzi et al., 2018;Malehmir et al., 2019;Manzi et al., 2019;Westgate et al., 2020) demonstrate their strength. The main advantages of reappraising legacy seismic data in mineral exploration are cost-efficiency, less noise from mining activities and coverage of areas that might not be accessible for acquisition of new data Manzi et al., 2019). ...
... Legacy seismic data have proven their significance in mineral exploration and mine planning, and several studies (e.g., Malehmir et al., 2010;Cheraghi et al., 2011;Manzi et al., 2018;Malehmir et al., 2019;Manzi et al., 2019;Westgate et al., 2020) demonstrate their strength. The main advantages of reappraising legacy seismic data in mineral exploration are cost-efficiency, less noise from mining activities and coverage of areas that might not be accessible for acquisition of new data Manzi et al., 2019). Furthermore, the geological information obtained from these data can be used for future mine planning and constraining acquisition parameters of new seismic surveys especially in the brownfield environment Malehmir et al., 2019). ...
... South Africa has the largest hard rock seismic database in the world covering the Kaapvaal Craton (Manzi et al., 2019;Westgate et al., 2020). In this study, a subset of these legacy seismic data are reprocessed to image the Platinum-bearing horizons in the Bushveld Complex. ...
... This focus on hard-rock features has meant that comparatively little attention has been devoted to investigating the internal structure of more recent, Phanerozoic, sedimentary basins that cover significant parts of the craton and, thus, its more recent tectonic history. With the significant improvement in processing algorithms and computational power in recent decades, the records of these legacy surveys provide a valuable research resource that can be further interrogated (Malajczuk et al., 2016;Manzi et al., 2018;Malehmir et al., 2019;Manzi et al., 2019). By properly retrieving, recovering and reprocessing legacy seismic data, the potential of the data to reveal second-and third-order subsurface geological features may be significantly enhanced, particularly where more sophisticated processing algorithms and seismic attributes are applied that were not available in past decades. ...
... It thus enhances weak reflections and emphasises subtle changes within a reflection across traces, making it useful to pick up vertical features such as faults (Taner et al., 1979). Westgate (2020) introduced an attribute that is a composite of either of the two above mentioned instantaneous attributes and the novel symmetry attribute (Manzi et al., 2019;Westgate, 2020). The composite attribute is a hue-saturation-intensity (HSI) image that is created by assigning one of the instantaneous attributes to the intensity component of the image and assigning the symmetry attribute to the hue component of the image. ...
The 150 km long, 6 s TWT, 2D seismic profile KBF03A, which was acquired in 1994 and lies near the western edge of the Kaapvaal craton in South Africa, has been reprocessed using standard reflection seismic processing methods. The results exhibit a significant improvement in the imaging quality of the subsurface features and an evident boost in the signal-to-noise ratio. The improved seismic data, combined with application of seismic attributes, integration with surficial geological and geophysical maps, and computation of velocity tomograms, has revealed previously undetected structural features within the supracrustal sequences underlying the profile. In particular, the Phanerozoic sediments found along the profile, comprising exclusively Kalahari Group and Dwyka Group deposits, are disrupted by multiple folds of varying wavelengths (~1–10 km) and variably oriented normal and thrust faults. Additionally, the effect of the Moshaweng fault, previously characterised as a listric fault extending to depths of >10 km, on the Phanerozoic sediments has been further constrained to suggest repeated extensional reactivations and a more recent (<1 Ma) inversion. Considerations of the eastern end of the profile have suggested links between some of the observed structural features and the nearby ~146 Ma Morokweng impact structure, the lateral expanse of which is poorly constrained in the literature. The collection of these newly imaged features is interpreted as evidence for multiple Late Mesozoic to Cenozoic tectonic events, including polyphasic reactivation of basement structures, under both extensional and compressional stress regimes. By analysing these newly detected features, our study not only provides new insight into the neotectonic evolution of the Phanerozoic sediments along the western margin of the Kaapvaal craton, but also demonstrates the utility in reprocessing legacy data and reveals its untapped potential.
... In parallel, the hydrocarbon industry also added value using legacy seismic reflection data (Nicholls et al., 2015) by applying new processing approaches and techniques. Furthermore, reprocessed high-resolution (HR) seismic reflection data have also been used in exploration for mineral resources (Manzi et al., 2019;Donoso et al., 2020) and civil engineering (Martí et al., 2008) and are also successful for the characterization of seismogenic zones and hazard assessment (Ercoli et al., 2020). Therefore, legacy data are extremely valuable for basic and applied Earth sciences, and their preservation and availability constitute an effort that should contribute to move science forward. ...
Seismic reflection data (normal incidence and wide angle)
are unique assets for solid Earth sciences as they provide critical
information about the physical properties and structure of the lithosphere
as well as about the shallow subsurface for exploration purposes. The
resolution of these seismic data is highly appreciated; however they are
logistically complex and expensive to acquire, and their geographical
coverage is limited. Therefore, it is essential to make the most of the data
that have already been acquired. The collation and dissemination of seismic
open-access data are then key to promote accurate and innovative research and
to enhance new interpretations of legacy data. This work presents the
Seismic DAta REpository (SeisDARE),
which is, to our knowledge, one of the first comprehensive open-access
online databases that stores seismic data registered with a permanent
identifier (DOI). The datasets included here are openly accessible online
and guarantee the FAIR (findable, accessible, interoperable, reusable)
principles of data management, granting the inclusion of each dataset in a
statistics referencing database so its impact can be measured. SeisDARE
includes seismic data acquired in the last 4 decades in the Iberian
Peninsula and Morocco. These areas have attracted the attention of
international researchers in the fields of geology and geophysics due to the
exceptional outcrops of the Variscan and Alpine orogens and wide foreland
basins, the crustal structure of the offshore margins that resulted from a
complex plate kinematic evolution, and the vast quantities of natural
resources contained within. This database has been built thanks to a network
of national and international institutions, promoting a multidisciplinary
research and is open for international data exchange and collaborations. As
part of this international collaboration, and as a model for inclusion of
other global seismic datasets, SeisDARE also hosts seismic data acquired in
Hardeman County, Texas (USA), within the COCORP project (Consortium for
Continental Reflection Profiling). SeisDARE aims to make easily accessible
old and recently acquired seismic data and to establish a framework for
future seismic data management plans. SeisDARE is freely available at
https://digital.csic.es/handle/10261/101879 (a detailed list of the datasets can be found in Table 1), bringing endless
research and teaching opportunities to the scientific, industrial, and
educational communities.
... Indeed, reappraisal of legacy data has shown to provide valuable insights into the data (e.g. Malehmir et al., 2019;Manzi et al., 2019c). ...
... The findings of the seismic profiles on the western margin, where our study area is located, showed no evidence of the Wiwatersrand gold-bearing reefs to extend to such extremities (Tinker et al., 2002;Pretorius et al., 2003). These data have been donated to the Seismic Research Centre at the University of the Witwatersrand, which now hosts one of the world's largest hard rock seismic data sets that is providing further insight into the deep crustal structure of the Kaapvaal Craton and the mineralization contained therein (Manzi et al., 2019c). Supporting magnetotelluric data are also available, with four particular stations, KIM001-KIM004, crosscutting the seismic line at the point of interest (Fig. 1a,b). ...
... When compared with the legacy data, as shown in Fig. 9, the reprocessed data provide a clearer image of the target horizons as well as the underlying strata, providing a strong indication that legacy data may contain untapped potential that can be fully realized by reprocessing the data, a topic that is rapidly growing in the seismic literature (e.g. Górszczyk et al., 2015;Malajczuk et al., 2016;Ketelhodt et al., 2019;Malehmir et al., 2019;Manzi et al., 2019c). By carefully reprocessing legacy data, modern and more sophisticated algorithms improve upon the potential of the data and yield results that may enhance features not evident in the original data. ...
Two overlapping legacy seismic profiles, 130 km long end to end, were shot in the 1990s over the Kuruman Hills on the western margin of the Kaapvaal Craton in southern Africa. The 6 s profiles were aimed at investigating the crustal structure of the western Kaapvaal Craton as well as to locate potential continuation of the Witwatersrand gold‐bearing horizons beneath the cover rocks, the latter of which was unsuccessful. In this study, the legacy seismic data are reprocessed and used to image the iron‐oxide (mainly haematite) mineralisation found in the Kuruman Formation of the Griqualand‐West Supergroup, which outcrops along the two seismic profiles. The seismic profiles are located close to the Sishen open pit iron mine, where one of the world's largest iron ore concentrations (986 Mt) is mined. The reprocessed and merged seismic data are combined with magnetic, magnetotelluric, borehole and outcrop data to constrain the interpretation, and all indicate the mineralisation host rocks to have ∼500 m thickness and 950 m depth, respectively. The seismic data further reveal seismic reflections associated with multiple iron ore horizons, which are affected by a first‐order scale syncline and numerous near‐vertically dipping (∼65–80o) normal and reverse faults of various orientations and throws, thus providing insight into the structurally‐controlled iron ore mineralisation in the area. Seismic tomography and magnetotellurics characterise the sediments to have a velocity ranging between 5000 and 6000 m/s and a resistivity of < 10 Ωm. The seismic imaging of the syncline and associated structural disruptions are important for future mining purposes and plans in the area as these structures might have preserved iron‐oxide mineralisation from erosion. The reprocessed data thus provide information that could be incorporated in potential future underground mine planning in the area, thus improving the resource evaluation of the iron‐oxide deposit. Legacy seismic data are thus shown to hold intrinsic quality and possible untapped potential that can be realised via data reprocessing.
This article is protected by copyright. All rights reserved
As the global need for aluminum constantly rises, bauxite is considered to be a critical mineral, and the mining industry is in search of new and effective exploration solutions. In this context, we designed and implemented a purely earthquake-based passive seismic survey at the Gerolekas bauxite mining site, in Greece. It is a very difficult exploration setting, characterized by rough topography, limited accessibility, and a very complex geotectonic regime. We gather a passive seismic dataset consisting of 4 months of continuous recordings (May-August 2018) from 129 stand-alone three-component seismological stations. We then analyze this dataset and extract 848 microearthquakes that will serve as sources for the application of local earthquake tomography (LET) and transient-source seismic interferometry (TSI) by autocorrelation. We apply LET to estimate 3D P- and S-wave velocity models of the subsurface below the study area and TSI by autocorrelation to retrieve the zero-offset virtual reflection responses below each of the recording stations. The velocity models provide a relatively coarse image of a previously completely unexplored part of the mining concession, while the higher-resolution virtual reflection imaging illuminates in detail the different interfaces. We also reprocess three lines of legacy active seismic data that were shot in 2003, using the LET P-wave velocity model for depth migration, and confirm the improvement of seismic imaging. Finally, we evaluate the obtained results using well data and jointly interpret them, extracting useful information on the expected target depths and showing that earthquake-based passive seismic techniques can be an innovative and environmentally friendly option for mineral exploration.
