High-resolution crustal structure and gold mineralization in the southwest Cathaysia block revealed by a dense seismic array

2021 
Abstract This study presents new seismic data and interpretations for the deep structure in the southwest Cathaysia block comprised of Yunkai, Yuegui and Yuezhong blocks. A dense seismic array consisting of 112 short-period, three-component seismic stations was deployed to investigate the geodynamic mechanism of the nappe tectonic zone and gold mineralization with 2.5 km spacing across the Luoding-Yunfu region. Based on this dataset, we are able to image the high-resolution crustal structures of the southwest Cathaysia block using the P-wave receiver function method. Our imaging results reveal distinct structural features beneath the study region, including marked lateral variations of Moho discontinuities. Beneath the Luoding-Yunfu nappe tectonic zone, the Moho uplift indicates that its formation is related to deep melt mantle (e.g., Asthenospheric mantle OIB). Moho features depicted by the Ps image are different from those by the PpPs phase along this tectonic zone, which could be ascribed to the local complex structures as illustrated in the forward analysis for different Moho structures. Such a uplift is also observed from the H-κ stacking results and a low average Vp/Vs ratio (~1.65) is found in this region, which could be attributed to its location within a tectonic strain zone. Based on the analysis and comparisons with previous studies, we infer that the crustal uplift in the Luodin-Yunfu area could be a typical scenario of the ore-controlling structure. This study also suggests that upwelling channels of deep melt mantle in the southwest Cathaysia block could facilitate the progress of migration, enrichment and precipitation of gold mineralization.
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