Study Of The Velocity Structure Of The Baiyun Gold Mine Area In Liaoning Province China From Ambient Noise Tomography

The Baiyun Gold Mine is a large gold mine in the Qingchengzi polymetallic ore eastern Liaoning Province,China.In order to investigate the metallogenic background of the Baiyun gold mine area and to explore the deeping minerals,we use ambient noise tomography to construct a three-dimensional S-wave velocity structure model of Baiyun gold deposit and its surrounding.At the same time,it also tests the feasibility of using dense array ambient noise tomography to explore metal minerals.From August to November in 2016,We deployed 21 broadband seismic stations in an area of 15 km x 14 km centered on the Baiyun gold deposit,and recorded the data continuously for about three months.The vertical component of seismic waveform is pre-processed by band-pass filtering,normalization and spectrum whitening.And we extracted the empirical Green's function of Rayleigh wave between 210 station pairs by using cross-correlation of interstation ambient noise and phase-weighted stack;then we measured the group velocity dispersion in the period band of 0.8-3 s by frequency analysis technology.Finally,we obtained fine 3D S-wave velocity structure from the surface to the depth of 1.8 km beneath the Baiyun gold mining area from an direct inversion method of surface wave dispersion based on ray tracing.The results show that:(1)the distribution of S-wave velocity in the study area is in good agreement with the geological characteristics of the surface.Beneath the Baiyun gold deposit and the ore-controlling fault,Jianshanzi fault,there are obviously low velocity structure with S-wave velocity of about 1.6 km/s,while the areas exposed in the remaining Gaixian Formation and Dashiqiao Formation show relatively high velocity of more than 2.4 km/s.(2)Significantly low S-wave velocity extends to a depth of 1.8 km below the Baiyun gold deposit and the Jianshanzi fault,which may be an indicator of the blind ore bodies within the depth range.In the two areas,a lot of magmatic dikes have been found,thus we could infer that both of them should sufferlarge-scale magmatic movement.These results also support that the Baiyun gold deposit is a "magmatic hydrothermal" type deposit andthe metallogenic time should be roughly Indosinian-Yanshanian.(3)Demarcating the ore vein using the S-wave velocity value of 1.6 km/s is combined with the characteristics and metallogenic conditions of the "magmatic hydrothermal" type deposit,we can delineate the Jianshanzi fault and its adjacent area as the most possible metallogenic prospecting area.In conclusion,this study reveals the deep metallogenic background of the Baiyun gold deposit,which provides a direction for deep prospecting in the later stage,and this study also shows that the ambient noise tomography has the potential for the exploration of metal deposits.