Smart Exploration: from legacy data to state-of-the-art data acquisition and imaging

Malehmir, Alireza; Donoso, George A.; Markovic, Magdalena; Maries, Georgiana; Brodic, Bojan; Pecheco, N.; Marsden, P.; Bäckström, Emma; Penney, M.; Araújo, Vítor

doi:10.3997/1365-2397.n0049

Cited by 11 publications

(6 citation statements)

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“…To evaluate the electromagnetic vibrator (E‐Vib) in a hardrock setting, a field campaign took place in September 2019. One of the advantages of the E‐Vib is its design and dimensions enabling versatility (Malehmir et al ., 2019; Brodic et al ., 2021a, 2021b) and allowing it to be attached to locally available vehicles such as skid‐steers or telehandlers, and the latter was used in this test (Fig. 3a).…”

Section: Data Acquisitionmentioning

confidence: 99%

Broadband seismic source data acquisition and processing to delineate iron oxide deposits in the Blötberget mine‐central Sweden

Pertuz

Malehmir

Bos³

et al. 2021

Geophysical Prospecting

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A prototype electromagnetic vibrator, referred to here as E‐Vib, was upgraded and developed for broadband hardrock and mineral exploration seismic surveys. We selected the iron oxide mine in Blötberget, central Sweden, for a test site in 2019 for the newly developed E‐Vib because of the availability of earlier seismic datasets (from 2015 to 2016) for verification of its performance for hardrock imaging purposes. The two‐dimensional data acquisition consisted of a fixed geometry with 550 receiver locations spaced at every 5 m, employing both cabled and wireless seismic recorders, along an approximately 2.7 km long profile. The E‐Vib operated at every second receiver station (i.e. 10 m spacing) with a linear sweep of 2–180 Hz and with a peak force of 7 kN. The processing workflow took advantage of the broadband signal generated by the E‐Vib in this challenging hardrock environment with varying ground conditions. The processed seismic section shows a set of reflections associated with the known iron oxide mineralization and a major crosscutting reflection interpreted to be from a fault system likely to be crosscutting the mineralization. The broadband source data acquisition and subsequent processing helped to improve signal quality and resolution in comparison with the earlier workflows and data where a drophammer seismic source was used as the seismic source. These results suggest new possibilities for the E‐Vib source for improved targeting in hardrock geological settings.

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Section: Data Acquisitionmentioning

confidence: 99%

Broadband seismic source data acquisition and processing to delineate iron oxide deposits in the Blötberget mine‐central Sweden

Pertuz

Malehmir

Bos³

et al. 2021

Geophysical Prospecting

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“…As part of a large research-innovation project (Malehmir et al, 2019), a 3D seismic dataset (approximately 3 by 2 km) was acquired during April-May 2019 using a fixed geometry comprising 1266 receivers (9 receiver lines, P1-P9) and 1056 shots (10 shot lines, no shots on P2), and the 32t vibrator of TU Bergakademie Freiberg generating three shot records per location with a 20 s long sweep ranging from 10-160 Hz (Figs. 1 and 3).…”

Section: Sparse 3d Survey (2019)mentioning

confidence: 99%

Sparse 3D reflection seismic survey for deep-targeting iron-oxide deposits and their host rocks, Ludvika Mines-Sweden

Malehmir¹,

Markovic²,

Marsden³

et al. 2020

Preprint

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Abstract. Many metallic mineral deposits have sufficient contrasts, particularly density, to be detectable using seismic methods. These deposits are sometimes significant for our society, economic growth and can help to accelerate the energy transition towards decarbonization. However, their exploration at depth requires high-resolution and sensitive methods. Following a series of 2D seismic trials, a sparse, narrow source-receiver azimuth, 3D seismic survey was conducted in the Blötberget mine, in central Sweden, covering an area of approximately 6 km2 for deep targeting iron-oxide deposits and their host rock structures. The survey benefited from a collaborative work by putting together 1266 seismic recorders and a 32t vibrator generating 1056 shot points in a fixed geometry setup. A linear sweep ranging from 10–160 Hz and 20 s long was generated three times per shot point. Shots were fired at every 10 m where possible and receivers placed at every 10–20 m. Notable quality data were acquired although the area is dominated by swampy places as well as by built-up roads and historical tailings. The data processing had to overcome these challenges in particular for the static corrections and strong surface-waves. A tailored for hardrock-setting-processing workflow was developed for handling such a dataset, where the use of mixed 2D and 3D refraction static corrections were relevant. The resulting seismic volume is rich in terms of reflectivity with clear southeast dipping reflections originated from iron-oxide deposits extending vertically and laterally at least 300 m beyond what was known from boreholes. We estimate potential additional resources from the 3D reflection seismic experiment on the order of 10 Mt worth drilling for detailed assessments. The mineralization is crosscut by at least two major sets of northwest dipping reflections interpreted to be dominantly normal faults and responsible for much of the lowland in the Blötberget area. Moreover, these post-mineralization faults likely control the current 3D geometry of the deposits. Curved and submerged reflections interpreted from folds or later intrusions are also observed showing the geological complexity of the study area. The seismic survey also delineates the near-surface expression of a historical tailing as a by-product of refraction static corrections demonstrating why 3D seismic data. The sparse 3D survey illustrates that performing cost-effective reflection surveys for mineral exploration is achievable if they are conducted and planned carefully, systematically and based on earlier experiences.

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“…); (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 with 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 (Donoso et al., 2020; Malehmir et al., 2019; Manzi et al., 2019). South African hard rock reflection seismic data, in particular, is worthy of reappraisal.…”

Section: Introductionmentioning

confidence: 99%

Seismic imaging of the gold deposit and geological structures through reprocessing of legacy seismic profiles near Kloof–Driefontein Complex East Mine, South Africa

Mutshafa¹,

Manzi²,

Westgate³

et al. 2022

Geophysical Prospecting

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Two legacy reflection seismic profiles were acquired in 1988, north of the Kloof–Driefontein Complex 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 (1000–2000 m/s), (2) a weathered layer ranging from ca. 100 to 300 m in thickness (2000–5000 m/s) and (3) bedrock (> 5000 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, pre‐stack depth migration and post‐stack time migration using the Kirchhoff algorithm. PreSDM most improved the imaging of deeper reflections due to its ability to honour complex lateral variations in the velocity field. Both pre‐stack time migration and post‐stack time migration enhanced the continuity of the near‐surface reflections below the dolomitic rocks.

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Smart Exploration: from legacy data to state-of-the-art data acquisition and imaging

Cited by 11 publications

References 0 publications

Broadband seismic source data acquisition and processing to delineate iron oxide deposits in the Blötberget mine‐central Sweden

Broadband seismic source data acquisition and processing to delineate iron oxide deposits in the Blötberget mine‐central Sweden

Sparse 3D reflection seismic survey for deep-targeting iron-oxide deposits and their host rocks, Ludvika Mines-Sweden

Seismic imaging of the gold deposit and geological structures through reprocessing of legacy seismic profiles near Kloof–Driefontein Complex East Mine, South Africa

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