As an early discovery of independent gold ore in the Xiongcun area of Xietongmen County, Tibet, the study of the metallogenies of the Dongga gold mine is relatively weak. In this paper, petrographic, chronological, geochemical and Hf isotopic characterization studies were carried out on the Tonga gold- bearing tuffs to investigate the petrogenesis and tectonic setting of the Tonga gold- bearing tuffs and to reveal the role of the tuffs in controlling mineralization. The LA- ICP- MS zircon U- Pb dating of tuff shows that the crystallization age of tuff is 185.1 ±1.9 Ma (MSWD = 0.48), and the diagenetic age is Early Jurassic. The geochemical characteristics of the major elements show that the K2O/Na2O ratio (2.91 ~ 12.3) is high and belongs to the calc- alkaline series; the geochemical characteristics of the trace elements show that they are enriched in large ionic lithophile elements (LILEs; such as Sr, Ba) and light rare earth elements (LREEs), and depletion in high- field strength elements (HFSEs; such as Nb, Ta, Ti) and heavy rare earth elements (HREEs). Combined with the trace element tectonic setting discrimination diagrams, it is suggested that the tuffs formed in an oceanic island arc setting are associated with the northward subduction of the Neo- Tethys Ocean crust. In addition, the tuffs are characterized by Nb/Ta ratios of 14.0 ~ 17.8, La/Nb averages < 2.50, and Zr/Ba averages of 0.31, with high positive εHf(t) (+ 8.05 ~ + 14.2), suggesting that the magma source of tuff is a depleted asthenosphere mantle wedge metasomatism of fluids released by Neo- Tethys subduction oceanic crust. During the process of magma ascending and emplacement, it was not contaminated by crustal materials, and mainly underwent the crystalline differentiation of olivine and clinopyroxene. The fractured structure of the ore- bearing tuff not only provides space for the migration of ore- bearing hydrothermal solution but also provides a place for mineral precipitation. At the same time, the tuff also acts as a caprock to protect the deposit from denudation after its formation. Comprehensive analysis suggests that the Dongga gold deposit was formed in the oceanic island arc setting of the northward subduction of the Neo- Tethys Ocean and is a hydrothermal vein- type gold ore body outside of the porphyry copper—gold deposit.