Velocity models of the shallow subsurface (a few hundred meters) are important in near-surface characterization, improving seismic mapping resolution at depth, and constraining deeper geological models. It is therefore interesting to retrieve them from deep seismic exploration data. We compute the near-surface shear wave velocity model in the vicinity of South Deep Gold Mine, using surface waves present in the small-offset 2D and 3D seismic reflection data acquired between 2022 and 2023 at the mine for research, mine planning, and development purposes. The obtained near-surface model is then used to (1) characterize the near-surface, and (2) better constrain the interpretation of possible water preferential flow-pathways (faults, fracture zones, and dykes) mapped at mining levels, that enable the migration of water from overlying aquifer systems (< 0.5 km depth) to the mining levels (∼ 3 km depth). The analysis is carried-out on reflection seismic data acquired for deep mineral exploration, where the acquisition parameters were not optimized for surface wave techniques and the reciprocity principle is used to improve the data density, coverage, and near-surface mapping resolution. The lithostructural information retrieved from the produced pseudo-2D and 3D shear wave velocity models is consistent with information obtained from available surface borehole data and published records in the study area. To investigate the structural linkage between the deep mining levels and shallow groundwater aquifers, we integrated the near-surface shear wave velocity model produced from the small-offset 2D and 3D reflection seismic data with the large-offset 2003 3D reflection seismic data, and geological structures derived from underground mapping, and exploration drilling. The shear wave velocity models help define the faults, fractures, and dykes that compartmentalize the near-surface groundwater aquifer systems. The large-offset legacy 2003 3D seismic data, underground mapping, and exploration drilling provide a better definition of the orebody and its offsets (e.g., faults) at the mining level. The integrated data show that several geological structures (e.g., faults and dykes), defined by legacy seismic data, underground drilling, and mapping, cross-cut the mining levels at ∼ 3 km depth and intersect the near-surface aquifers, thus making these structures possible preferential flow-pathways for water migration to the deep mining levels. The results of the interpretation illustrate the advantages of integrating shallow and deep subsurface information to constrain the timing of geological events and mitigate the risks associated with water ingress to the mining levels. The final model produced can be used for future mine development, improving safety and production, and for the extension of the Life of Mine (LoM). ... Read more

Surface wave (SW) methods offer promising options for an effective and sustainable development of seismic exploration, but they still remain under-exploited in hard rock sites. We present a successful application of active and passive surface wave tomography for the characterization of the southern continuation of the Siilinjärvi phosphate deposit (Finland). A semi-automatic workflow for the extraction of the path-average dispersion curves (DCs) from ambient seismic noise data is proposed, including identification of time windows with strong coherent SW signal, azimuth analysis and two-station method for DC picking. DCs retrieved from passive data are compared with active SW tomography results recently obtained at the site. Passive data are found to carry information at longer wavelengths, thus extending the investigation depth. Active and passive DCs are consequently inverted together to retrieve a deep pseudo-3D shear-wave velocity model for the site, with improved resolution. The southern continuation of the mineralization, its contacts with the host rocks and different sets of cross-cutting diabase dikes are well imaged in the final velocity model. The seismic results are compared with the latest available geological models to both validate the proposed workflow and improve the interpretation of the geometry and extent of the mineralization. Important large-scale geological boundaries and structural discontinuities are recognized from the results, demonstrating the effectiveness and advantages of the methods for mineral exploration perspectives. ... Read more

The Los Humeros geothermal system is steam dominated and currently under exploration with 65 wells (23 producing). Having temperatures above 380&thinsp;°C, the system is characterized as a super hot geothermal system (SHGS). The development of such systems is still challenging due to the high temperatures and aggressive reservoir fluids which lead to corrosion and scaling problems. The geothermal system in Acoculco (Puebla, Mexico; so far only explored via two exploration wells) is characterized by temperatures of approximately 300&thinsp;°C at a depth of about 2&thinsp;km. In both wells no geothermal fluids were found, even though a well-developed fracture network exists. Therefore, it is planned to develop an enhanced geothermal system (EGS).For better reservoir understanding and prospective modeling, extensive geological, geochemical, geophysical and technical investigations are performed within the scope of the GEMex project. Outcrop analogue studies have been carried out in order to identify the main fracture pattern, geometry and distribution of geological units in the area and to characterize all key units from the basement to the cap rock regarding petro- and thermo-physical rock properties and mineralogy. Ongoing investigations aim to identify geological and structural heterogeneities on different scales to enable a more reliable prediction of reservoir properties. Beside geological investigations, physical properties of the reservoir fluids are determined to improve the understanding of the hydrochemical processes in the reservoir and the fluid-rock interactions, which affect the reservoir rock properties. ... Read more