Time domain spectral IP and FCM-constrained CSAMT inversions: An integrated approach to gold exploration

To address the challenges of strong electromagnetic interference and thick layers in the exploration of gold mines in Zhangjiakou, this study proposes a joint exploration strategy based on induced polarization (IP) and controlled-source audio-frequency magnetotellurics (CSAMT). Time-domain IP data are subjected to time–frequency conversion and spectral parameter inversion using the Cole–Cole model. For 1D inversion of CSAMT, the physical-property-based FCM clustering constraints are incorporated with the total variation regularization factor to improve inversion resolution and sharpen anomalous boundaries. Field application in the Yaoziwan area adjacent to the Dongping gold mine demonstrates that (1) spectral IP inversion can effectively suppress interference and clearly delineate the polarization anomalies, (2) the improved CSAMT inversion algorithm can significantly improve the resolution of the resistivity model and the definition of anomalous boundaries, and (3) the joint exploration scheme combining an IP intermediate-gradient array survey with CSAMT depth measurement can successfully delineate high-resistivity and polarization anomalies (m1). This has been verified by drilling as gold-bearing quartz veins and altered rocks, confirming the vertical extension of the ore body. The integration of IP and CSAMT techniques facilitates gold exploration in areas affected by severe electromagnetic interference, while the proposed prior-physical-property-constrained inversion strategy improves the recognition and interpretation accuracy of deep concealed ore bodies. The results provide a reliable technical pathway and practical reference for deep concealed gold exploration under complex geological and electromagnetic conditions.