The highly fractionated high-silica rhyolite is a potential host of the rare earth elements (REE) deposits. The Tarim large igneous province (T-LIP) is characterized by a high proportion of felsic rocks; nevertheless, the potential capacity of the REE mineralization remains unclear. In this study, ignimbrite from well S42 in Northern Tarim Uplift was studied, and several Fe-P-REE enriched mineral assemblages were recognized: ① the lithoclast consisting of quartz rim and magnetite+monazite+alkali feldspar core; ② the magnetite+monazite+rutile+apatite in the groundmass; ③ the monazite+pyrite in the quartz phenocryst. Further analysis of quartz SIMS oxygen isotopes in situ showed that the δ18OV-SMOW values of lithic quartz range from 11.15‰ to 14.60‰, while those of the quartz phenocrysts are from 7.23‰ to 7.84‰, consistent with the bulk-rock oxygenic composition (5.00‰~7.21‰). A titanium thermometer of quartz shows that the formation temperature of quartz phenocryst was 756~815℃, and that of lithic quartz was 566~645℃. In addition, trace elemental compositions of magnetite associated with quartz in the lithoclast also show consistency with those of the hydrothermal origin. The above evidence indicates that the Fe-P-REE mineral assemblage in the lithoclast was derived from the late hydrothermal fluids. On the other hand, the occurrence of Fe-P-REE mineral aggregates in the groundmass of the ignimbrite and quartz phenocryst indicates that REE were sufficiently concentrated in magma and then REE minerals were crystallized in the late stage of evolution. Therefore, the Fe-P-REE enriched mineral aggregates in the ignimbrite were mainly related to the magmatic fractional crystallization and the late hydrothermal fluids. Their recognition provides an important implication for the REE mineralization of felsic rocks in the T-LIP.