Petrology and structure of the Renbu gneiss dome, southeast Tibet

The Renbu granitic gneiss dome is the most northerly and one of the easternmost domes in the chain of North Himalayan gneiss domes. The Renbu dome comprises upper amphibolite-facies metasedimentary rocks of the lower Tethyan Himalaya Sequence intruded by a large, relatively undeformed leucogranite body. Paragneisses and schists have the assemblage Qtz + Kfs + Pl + Bt ± Ms ± Grt ± St ± Hbl ± Gr ± Chl and lack migmatite; leucogranite dikes locally intrude the country rock along a sharp contact between country rock and the leucogranite body. Structural data were collected from the northeastern exposure of the dome: the mean pole to foliation trends 203° and plunges 57°; stretching lineations define a great circle and are folded about an axis trending 292° and plunging 47°. The Renbu gneiss dome is likely an upwelling of a ductile mid-crustal channel that conveys partial melts of Indian crust beneath the Tibetan plateau to the topographic/erosional front of the Himalaya further south, in the Greater Himalayan Sequence. U-Pb SHRIMP dating of zircon from the Renbu leucogranite yields the youngest ages reported for Himalayan granites at ~7 Ma; this young granite age may constrain the timing for the end of active channel flow in the latest Miocene or suggest channel flow is modern, ongoing process.