Correlating geophysical anomalies with subsurface lithology: Insights into gold mineralisation

Hydrogeophysical Assessment of Groundwater Potential in the Deccan Basalt.

Groundwater occurrence in the Deccan basalt is highly uncertain. Non-invasive hydro-geophysical techniques, when integrated with a priori geological information, can aid in delineating saturated zones. This study uses electrical resistivity anisotropy with direct current (DC) resistivity and time-domain induced polarization (IP) for delineating groundwater prospects. We utilized the geophysical responses of DC resistivity, induced polarization, anisotropy and available borehole litholog data to locate the potential aquifers. Anisotropic inversion of DC resistivity data enables the identification of fractured basalt. We observed shallow saturation zones where fractured basalt overlies less permeable layers and deeper confined zones below the intertrappeans within fractured amygdaloidal basalts. The most productive shallow aquifers exhibit low to moderate resistivity (1 to 36 Ωm), and moderate to low chargeability (1.1 to 8 mV/V) and anisotropy (1.1 to 1.21). Finally, we conducted aquifer tests in different wells in the study area to quantify the aquifer parameters. This study offers a strong scientific basis for the assessment of groundwater potential zones and their management in the complex basaltic terrains of the Deccan province.

A machine learning-assisted geophysical–geotechnical approach for improved engineering site assessment

Integrating Surface Geological Mapping and Multi-Year Subsurface Data to Identify Lateral Lithological Variations Along the Jatinegara Diversion Tunnel, Central Java, Indonesia

Tunnel design in tropical regions requires careful attention to subsurface variability due to intense weathering and complex lithology. The ongoing design of the Jatinegara Diversion Tunnel, with a diameter of 6 meters and a length of 439 meters, relies solely on the 2024 borehole data without considering the recent 2017 data, revealing a contrast subsurface geological characteristic. This study investigates lateral lithological variations along the tunnel alignment by integrating surface geological mapping with multi-year borehole data from 2017 and 2024. The methodology includes geological mapping of a 2.0 × 2.0 km area, corebox analysis, surface-subsurface stratigraphic correlation, and rock mass quality evaluation using the Rock Mass Rating (RMR) system. Results show the tunnel traverses five zones with distinct rock mass characteristics. Zone 1, Zone 3, and Zone 5 consist of andesitic breccia with RMR values ranging from 20.21 – 39.57, indicating poor quality of rock mass. Zone 2 comprises interbedded carbonate sandstone and siltstone overlain by andesitic breccia, with RMR values ranging from 42.82 – 52.40 (fair). Zone 4 consists of interbedded carbonate sandstone and siltstone overlain by massive sandstone with siltstone intercalation with an RMR of 52.43 (fair). Given these rock mass conditions, the recommended excavation method is a top heading and bench approach with 1.0–1.5 meters advance in the top heading with support system consist of rock bolt, shotcrete, and steel set. These findings highlight the importance of integrating multi-year geotechnical data to support an adaptive and safe tunnel design in complex geological environments.

Integrated geophysical exploration and prospecting model for loess-covered gold deposits: A case study of the southern Yixingzhai Gold Deposit, Shanxi Province

The Yixingzhai Gold Deposit in Shanxi Province is a major gold-polymetallic deposit in northeastern Shanxi, and its southern Sunzhuang area is covered by a thick loess layer, rendering conventional geological prospecting extremely challenging. To achieve a breakthrough in deep prospecting, this study developed a suite of integrated geophysical exploration techniques based on regional geological conditions and the petrophysical properties of local rocks and ores. Time-domain induced polarization (TDIP) surveys with large electrode spacing (AB = 2,000 m), long power supply duration (8 s), and high current intensity (>10 A) were carried out, and combined with high-precision ground magnetic surveys, to interpret the subsurface geological structures, spatial distribution of concealed rock masses, and mineralization information beneath the loess overburden. The results show that integrated geophysical anomalies clearly reveal the distribution characteristics of NW- and SN-trending fault systems and their controlling effects on metallogenesis, and three concealed intermediate-acidic rock masses (diorite, granitic porphyry, quartz porphyry) closely associated with mineralization are accurately delineated. By adopting the multi-information coupling method of “IP anomalies – metal factor – geochemical anomalies”, ore-induced anomalies are effectively distinguished from non-ore interference. Drill verification confirms the exposure of gold-copper ore (mineralized) bodies with a cumulative thickness of over 22 m in the study area, with a maximum gold grade of 1.22 g/t. A comprehensive information prospecting model for loess-covered areas is established in this study, which offers a valuable reference for deep prospecting in similar covered regions.

An Integrated and Hierarchical Geophysical Workflow for Subsurface Cavity Assessment in Legacy Mining Districts

The presence of near-surface cavities poses a significant geohazard due to potential ground subsidence and structural collapse. To mitigate threats to urban stability, this study presents an integrated geophysical framework to locate and characterize abandoned mining galleries and exploitation voids near Linares (Jaén, Spain). The approach combines four complementary techniques: electrical resistivity tomography (ERT), ground-penetrating radar (GPR), frequency-domain electromagnetics (FDEM), and microgravity. The resulting multi-physics responses were cross-referenced with visible surface subsidence features and archival mine plans. Air-filled galleries and shafts generated highly pronounced high-resistivity anomalies. Shallow voids detected at depths of 2–5 m were undocumented in 19th-century mining maps, suggesting older historical origins, whereas deeper ERT profiles and structural disturbance trends (up to 30 m) correlated well with historical records. Within this framework, FDEM provided high-resolution lateral mapping, GPR excelled at resolving ultra-shallow structural boundaries, and ERT characterized deep gallery networks. Crucially, microgravity mitigated inversion non-uniqueness by directly confirming physical mass deficits over the anomalies. This integrated workflow overcomes individual resolution limits, offering a practical tool for land-use planning and early geohazard risk assessment in collapse-susceptible areas.

Integrated DC resistivity and seismic refraction imaging for bedrock discontinuity mapping in New Minia city, Egypt

This study addresses geotechnical challenges in fractured limestone environments by integrating electrical resistivity tomography (ERT), seismic refraction, and direct current (DC) resistivity soundings with borehole data in New Minia city, Upper Egypt. The objective was to delineate shallow subsurface heterogeneity and structural discontinuities and to establish correlations between geophysical and geotechnical parameters. A genetic algorithm (GA) optimization was applied to DC resistivity inversion, reducing non-uniqueness and improving model convergence. Seventeen boreholes (10 m depth) provided constraints for calibration and validation. Results reveal three principal subsurface sequences: (1) sandy–silty soil with clay intercalations, (2) heterogeneous intermediate deposits, and (3) fractured limestone bedrock. Major structural features, including north–south trending faults, were clearly identified. The integrated approach enhances subsurface characterization, reduces interpretational uncertainty, and provides a robust framework for hazard assessment and urban planning in complex carbonate terrains.