Trachyrhyodacite and trachyrhyolite dikes and small sheets with specific structural features (melting-through bodies) and composition were found in the dike complex of the Khangilai ore field in eastern Transbaikalia. They are restricted to the area of the Orlovka Li-F granite massif. They have anomalously high potassium contents (7.5-10.35 wt% K₂O) at SiO₂ = 67.3 wt% and show strong enrichment in trace elements of two groups. One of them includes lithophile elements, such as Rb (up to 2400 ppm), Li (up to 950 ppm), Cs (up to 85 ppm), and F (up to 1800 ppm), which are typical of Li-F granites of the Orlovka Massif. The other group consists of melting-resistant elements, incompatible with silicic magmas, i.e., Ba (up to 1200 ppm), Zr (90 ppm), Y (44 ppm), and REEs (total REEs up to 250 ppm), which are also high in subalkali basaltoid dikes of the ore field. Close ages of trachyrhyodacites (139 ± 4 Ma) and granites (142 ± 1.7 Ma) and their geochemical affinity (including similar REE patterns) could indicate similar compositions of their source rocks. However, their Sr and Nd isotopic compositions suggest larger contribution of crustal component in the initial trachyrhyodacite melt, which could be related to magma contamination by K-rich (pelitic?) crustal material. The isotopic and geochemical data obtained allow suggestion of a hybrid origin of trachyrhyodacite melt by interaction of crustal granite magma with mantle-derived basic melts.