Ambient-noise tomography links crustal faults and magma chambers beneath the Youjiang Basin: a metallogenic framework for Carlin-type gold

The Youjiang Basin at the junction of Yunnan–Guizhou–Guangxi in South China hosts a major Carlin-type gold province, yet the deep crustal architecture and magmatic system that control fluid pathways remain debated. We analyze continuous ambient seismic noise recorded by 114 broadband stations of a dense temporary array from May 2011 to January 2012 (~260 effective days). Interstation Green’s functions are retrieved, Rayleigh-wave dispersion is measured, and a three-dimensional shear-wave velocity model from 0 to ~50 km depth is obtained via direct inversion of surface-wave dispersion. The model shows strong lateral heterogeneity: a high-velocity domain in the northwest aligns with carbonate-platform facies, whereas a broad low-velocity domain in the southeast matches clastic basin facies. Between 104° and 105°E, a gently dipping low-velocity band corresponds to slope-facies strata and likely represents a mechanically weak, fluid-favorable unit. Several SW–NE and NW–SE trending, steeply dipping low-velocity corridors delineate major boundary and intra-basin fault systems, consistent with deep-reaching conduits for magma and hydrothermal fluids. At depth, a Moho-adjacent high-velocity anomaly at ~35–40 km suggests mafic underplating, while lens-shaped high-velocity bodies at ~15–20 km beneath the main ore field indicate solidified felsic intrusions and magma chambers. Together these features define a two-tier magmatic system linked by faults, providing a physically consistent deep-to-shallow metallogenic framework in which deep heat and magmatic inputs drive fluid generation, faults focus upward transport, and favorable stratigraphic units promote fluid–rock interaction and gold precipitation. This crustal image links basin segmentation, fault-controlled connectivity, and multi-level magmatism, offering new geophysical constraints on tectono-magmatic processes and associated mineralization in the Youjiang Basin.