Advanced SOTEM survey for the exploration of low-sulphidation epithermal gold: Insights from Lvyuan, eastern Junggar, China

This graphical abstract illustrates the application of the Short-Offset Transient Electromagnetic (SOTEM) method for exploring concealed low-sulphidation epithermal gold deposits. It depicts the process from field data acquisition over the Gobi Desert, through simultaneous inversion of resistivity and chargeability, to the identification of a diagnostic ‘low-resistivity & high-chargeability’ signature. Validated by drilling, this signature successfully delineates alteration zones and fault structures, culminating in the precise prediction of four high-priority exploration targets, providing a direct roadmap for future discovery. • Simultaneous inversion of resistivity and chargeability using SOTEM allowing the mapping of alteration zones and structural features. • Key electrical signature with low to moderate resistivity and high chargeability linked to pyritization and limonitization. • Four prospective targets identified, controlled by faults and guiding deep ore exploration. The investigation of low-sulfidation epithermal gold deposits presents significant challenges due to their intricate geological frameworks and frequently obscured mineralization. This research details the implementation of the short-offset transient electromagnetic method (SOTEM) to concurrently invert resistivity and chargeability parameters within the Lvyuan Gold Deposit located in Eastern Junggar, China. Utilizing a grounded-wire source alongside dual-base-frequency transmission, high-fidelity electromagnetic data were collected across ten survey lines encompassing the No. 7 alteration zone. One-dimensional inversion of the transient electromagnetic responses elucidated detailed subsurface electrical structures to depths of approximately one kilometer, facilitating the identification of fault systems and alteration zones linked to gold mineralization. Measurements of rock physical properties substantiated that elevated chargeability values (>20%) combined with moderate to low resistivity (<300 Ω·m) are strongly indicative of hydrothermally altered lithologies, particularly those exhibiting pyritization and limonitization. Integration of these geophysical results with drilling data confirmed that mineralized bodies predominantly occur within shallow zones characterized by low resistivity and high chargeability proximal to fault structures. Consequently, four prospective target areas were delineated, underscoring the effectiveness of SOTEM in delineating alteration zones and informing subsequent exploration efforts for epithermal gold deposits.