Three-component wide-angle seismic data acquired in southern Tibet during Project INDEPTH show strong P-to-S converted reflections from reflectors that area aligned at a depth of similar to 15 kilometers beneath the northern Yadong-Gulu rift, These converted reflections are locally higher in amplitude than the corresponding P-wave reflections; Modeling of reflection mode conversion as-a function of incidence angle indicates that this condition obtains for a reflector that is a solid over fluid interface; it is not typical of a solid-solid interface, The likely candidates for a fluid trapped within the crystalline crust of southern Tibet are granitic magma and water (brine).