This paper is the result of geological survey engineering.

Objective Deep source high-temperature uranium thorium deposits (mineralization) are widely developed in the scientific deep drilling of the Luzong Basin, and the associated electrical stones can effectively indicate the source of ore-forming materials and fluid evolution processes.

Methods The chemical composition and boron isotope characteristics of tourmaline in scientific deep drilling in the Luzong Basin and their implications for the evolution of uranium thorium mineralization fluids were studied in this paper through detailed geological records of drilling, microscopic identification, and the use of electron probe microanalysis (EPMA) and LA–ICP–MS systems to investigate the mechanism and genesis of tourmaline chemical composition displacement, as well as its implications for the evolution of uranium thorium mineralization fluids.

Results Tourmaline is divided into three categories based on its occurrence: N-Tur, Hard gypsum + tourmaline bag; V-Tur, Tourmaline + pyrite + quartz ±gypsum veins; D-Tur, Immersion tourmaline, among which the structure and composition of the second type tourmaline are the most complex, and it coexists with uranium thorium mineralization. Tourmaline has a wide range of Mg/(Fe+Mg) and Na/(Na+Ca) ratios and belongs to magnesium tourmaline and black tourmaline; The U and Th elements in N-Tur are significantly higher, with a depletion of light rare earths and enrichment of heavy rare earths, showing a positive tilt pattern. The other two types of tourmalines are the opposite, showing a negative tilt pattern; The δ¹¹B values of boron isotopes range from −5.8‰ to −1.31‰, showing a decreasing trend in sequence.

Conclusions In the scientific deep drilling of the Luzong Basin, tourmaline belongs to hydrothermal genesis. The hydrothermal fluid is rich in volatile components such as B, F, and H₂O, and has the necessary redox conditions for the activation, migration, enrichment, and precipitation of uranium and thorium elements. U and Th elements were extracted from tourmaline to provide a partial material source for mineralization and precipitation. The structure, composition, and isotopic information of tourmaline effectively record the properties, fluid sources, and evolution of ore-forming hydrothermal fluids, providing important basis for the inversion of mineralization processes.