The Mesozoic Lanping Basin in western Yunnan Province is one of the most important ore-hosting sedimentary basins between the Sanjiang orogenic belt in southeastern Qinghai-Tibet Plateau and the western margin of the Yangtze platform, SW China. The Bijiashan ore concentration area at the southwest part of this basin contains vast stratified fluorite-antimony hydrothermal deposits and occurrences, and always was highly concerned by the academics and industry. The ore-bearing rocks, the underlying and overlying strata were classified into the Upper Triassic strata by local geologists. However, the lack of accurate chronological evidence has seriously affected our understanding of regional stratigraphic framework, tectonic evolution and ore genesis. In this contribution, we have carried out a systematic field geological investigation on the ore-bearing rocks in the Zhujie fluorite-antimony ore field at the north of the Bijiashan ore concentration area. The field geology shows that the main fluorite-antimony ore-bearing horizons of the uppermost member of the Upper Triassic Sanhedong Formation (T₃s^3-2) is mainly composed of crystalline vitreous tuff, siliceous breccias and siliceous rocks, which is a sedimentary-volcaniclastic assemblage, and the orebodies occur in stratiform and/or lenticular shape. The clastic rocks of the overlying Maichujing Formation(T₃m) are also interbedded with multiple layers of lithocrystalline vitreous tuff. The zircon U-Pb dating results show that the weighted average zircon U-Pb age of the ore-hosting crystalline vitreous tuff from the second part of the upper member of the Upper Triassic Sanhedong Formation (T₃s^3-2) is 239.4 Ma, and the weighted average zircon U-Pb age of the lithocrystalline vitreous tuffs from the lower members of the T₃m Formation range from 252.2 Ma to 216.1 Ma, both of which have similar dated age spectra of the inherited zircons. Combined with the analysis data of regional geology, the ore-bearing rocks of the upper member of the Upper Triassic Sanhedong Formation (T₃s³) in the Zhujie ore field deposited at the late Middle Triassic, which represents the proximal volcanic- sedimentary depositions coeval with the arc-volcanism. Whilst the Upper Triassic formations were originated from the filling of uplift and denudation of the arc magmatic rocks, which record multiphase transition of regional basin-range events. Therefore, the known orebodies in the Zhujie fluorite-antimony ore field is a volcanic hydrothermal sedimentary deposit associated with coeval volcanism. The association of siliceous rock and tuff is an important prospecting mark for similar fluorite-antimony deposits in this ore field and adjacent areas with great prospecting potentials.