The first discovery of the paleo-weathering crust-sedimentary Nb and rare earth deposits at the bottom of Xuanwei Formation in the Muchuan area of southern Sichuan

• WEN Jun, 
• ZHU Helin, 
• ZHANG Jinyuan, 
• Zhang Hangfei, 
• GUO Wenyan, 
• YOU Xuejun, 
• ZHAO Wei, 
• LI Pengcheng, 
• CHEN Dongfang