Metallogenic potential of the Wulong goldfield, Liaodong Peninsula, China revealed by high-resolution ambient noise tomography

Wulong goldfield (WLGF) is situated in the Liaodong Peninsula, northeast of the North China Craton (NCC). During the Mesozoic, the eastern NCC was tectonically reworked, with the stress state to change from compression to extension, accompanied by a large amount of magmatism and extensive gold mineralization. To reveal the relationships among the intermediate to felsic plutons, fault structures, and gold mineralization in the WLGF, we deployed a short-period dense array (WSP array) consisting of 334 portable seismometers. We then processed the ambient noise data to extract a total of 45,531 group velocity dispersion curves with periods of 0.3 to 2.0 s. We adopted a direct inversion method to invert these dispersion curves to construct a 3D ambient noise tomography model of shear-wave velocity structures. The 3D model generated allows us to draw the following conclusions: (1) The model shows prominent NNE-and NW-trending low-velocity anomalies that are interpreted to be caused by the intense hydrothermal alteration related to the gold mineralization along some NNE-and NW trending faults; (2) The distribution of seismic velocity in the Early Cretaceous Sanguliu pluton in the southern WLGF is not homogeneous on account of its lithological variation, whereby compositional zoning is characterized by monzogranite in the centre and granodiorite in the margin; (3) The concealed NW-trending fault has a larger downward extension (>1.4 km) than that of the NNE-trending faults (similar to 1.0 km), indicating the NW trending faults played an ore-conducting role and the NNE-trending ones are likely the structures of ore distributing and/or ore-hosting for the Wulong gold metallogenic system; (4) We suggest three favourable potential areas for future exploration, all of which are located at and around the intersections of the NNE-and NW trending faults and are close to the known (or concealed) Early Cretaceous granite intrusions; (5) Our results demonstrate that ambient noise tomography based on the short-period dense seismic array is effective in determining metallogenic structures at orefield scale and has significant potential application in mineral exploration.