Super-large-scale critical metal mineralization triggered by Emeishan Large Igneous Province waning stage eruptions: Evidence from ore beds spatial distribution and geochemical characteristics

• Super-large Xuanwei Nb–Zr–REE–Ga deposit formed during waning stage of Emeishan LIP. • Integrated lithological and gamma ray data for 56 boreholes and one outcrop section. • Primary magmatic source derived from Nb–Ta mineralized syenites in Panxi region. • Critical metals deposits cover 11 × 10 4 km 2 with maximum cumulative thickness of 10 m. • Estimated resources of 3.55 × 10 8 t Nb, 2.32 × 10 9 t Zr, 1.18 × 10 9 t REY, 5.90 × 10 7 t Ga. Basal upper Permian strata of SW China host extensive Nb-Zr-rare earth elements and yttrium (REY)-Ga ore beds in non-coal sequences characterized by significant natural gamma-ray logging (GR) positive anomalies and are named the Xuanwei Nb-Zr-REE-Ga deposit. Since past work has largely focused on single section or borehole records, the spatial distribution of ore beds within the Western Yangtze Cratonic Basin (WYCB) remains incompletely understood. This study integrates lithological and GR data from 56 boreholes and one outcrop section across the WYCB coal measures, supplemented by geochemical analyses of samples from the Xia’aimao village section and Borehole ZX1302. We integrated this dataset to investigate the spatial distribution, geochemical characteristics, petrology, and mineralogy of critical metals ore beds across the basin. The depositional center is located in the Yanjin-Yiliang-Zhenxiong areas of northeastern Yunnan, from where the single-layer thickness, cumulative bed count and thickness, and grain size of the ore beds gradually decrease from west to east and from south to north. Geochemical data reveal that the primary magmatic source of volcanic ash was predominantly derived from Nb-Ta mineralized syenites in the Panxi region. Widespread air-fall volcanic ash sequences bearing typical pyroclastic minerals, coupled with the occurrence of ore beds on paleo-uplifts, suggest an air-fall transport mechanism rather than a fluvial one. The distribution and preservation of ore beds were significantly influenced by sedimentary environments and tectonics. The ore beds underwent intense low-temperature hydrothermal alteration. Plants may also play an important role in volcanic ash preservation and critical metals enrichment. The deposit covers an area of over 11 × 10 4 km 2 , with estimated total resources amounting to 3.55 × 10 8 t of Nb, 2.32 × 10 9 t of Zr, 1.18 × 10 9 t of REY, and 5.90 × 10 7 t of Ga, constituting a globally important super-large-scale critical metal deposit.