Transtensional deformation in the central Himalaya and its role in accommodating growth of the Himalayan orogen

摘要: [1] Field mapping, structural analysis, and geochronologic data from northwestern Nepal reveal major normal right-slip motion along a previously unrecognized west-northwest striking system of shear zones that we term the Gurla Mandhata–Humla fault (GMH). The GMH obliquely cuts across Greater Himalayan Crystalline sequence into Lesser imbricate thrust belt via two right-step-over structures. average slip direction on parallels strike orogen. Motion this has resulted in an apparent left separation South Tibet Detachment, Main Central zone, north segment system. We estimate minimum 21 km net southern branch by restoring trace zone parallel to fault. Taking account estimates northern yields 24.4 32.4 for GMH. 232Th/208Pb ion microprobe monazite ages leucogranite bodies indicate occurred after 15 Ma. Its initiation immediately followed crustal thickening between Indus-Yalu suture zone. is contemporaneous with arc-normal contraction southernmost These observations can be explained model involves foreland propagating systems facilitating arc-parallel extension hinterland work together maintain arcuate shape