The isotropic and anisotropic passive seismic tomography for mineral exploration: a case study of Dongchuan copper deposit, China

Abstract Conventional metallic mineral exploration has primarily relied on potential field and electromagnetic methods, while reflection-based seismic methods have seen limited application in this field. However, currently tomography-based seismic methods have demonstrated significant potential in resolving shallow subsurface across multiple fields. This study introduces a passive seismic tomography method into deep structural exploration of metallic mineral deposits. The Dongchuan copper deposit ranks among China’s most economically significant copper resources. Although decades of geological and geochemical studies have established fundamental stratigraphic frameworks, the absence of high-resolution geophysical constraints at the deposit scale has hindered the understanding of deep structural controls on metallogenic processes. In this study, we conducted a passive seismic tomography focusing on shear wave velocity structures and radial anisotropy characteristics in the Dongchuan deposit. We deployed a dense seismic array, consisting of 90 seismic stations, achieving optimal spatial sampling through a 5 km interstation grid. Continuous seismic recordings ~ 30 days enabled extraction of both Rayleigh and Love wave dispersion curves from seismic noise cross-correlations. Then three-dimensional isotropic and anisotropic velocity models were reconstructed from surface to 4.5 km depth. We found that copper deposits preferentially locate at seismic velocity transition zones between high-velocity and low-velocity anomalies. The negative radial anisotropy (Vsh < Vsv) observed beneath the ore deposits may reveal the upward migration process of magmatic-hydrothermal fluids along fault zone structures. This study demonstrates the great potential of the isotropic and anisotropic passive seismic tomography to resolve critical metallogenic systems, providing methodological references for deep mineral exploration. Highlights High-resolution isotropic and anisotropic velocity models was obtained below the Dongchuan copper system. All the copper deposits were formed in the transition areas between high- and low-velocity anomalies. Negative radial anisotropy (Vsh < Vsv) could indicate the magmatic-hydrothermal fluids along fault zone structures.