In the easternmost Himalaya and southeastern Tibet, the Namche Barwa–Gyala Peri massif and adjacent Lhasa block host some of the Earth’s most active geologic processes and extreme topography. Synthesis of U-Th/He and Ar-Ar thermochronology, anatectic history, seismicity, and structural geology shows the important role that surface processes have played in this region in both local and orogen-scale crustal dynamics. Basement rocks of the massif underwent an episode of metamorphism, partial melting, and focused deformation that began ca. 10 Ma and likely remains active due to thermally mediated feedbacks between these processes and erosion. Strong differential rock uplift at Namche Barwa established the immense Namche Barwa knickzone on the Yarlung Tsangpo River, which has been stabilized through coupling between erosion driven by high stream power and localized deformation. This knickzone has maintained a high secondary base level of ~3000 m for the upper Yarlung Tsangpo watershed and so has shielded a large region of southeastern Tibet from excavation by the river, which in turn could alter the morphology and so the dynamics of the eastern Himalayan orogenic wedge. The landscape evolution of the southeast Lhasa block involved slow regional unroofing or incision in the Neogene, a significant pulse of ~5 km of rapid exhumation from ca. 10 to 5 Ma, and since then a great reduction in exhumation started once the Namche Barwa knickzone on the Yarlung Tsangpo was established. The low-relief high-elevation surface in the area is a relatively young feature, developed after the rapid 10–5 Ma exhumation pulse.

There are three sutures in the Qinling-Dabie-Sulu orogen in the Tongbai–Xinxian (northern Hong'an)–northern Dabie area: the Silurian Sino-Korean craton–Erlangping intra-oceanic arc suture, the Silurian Erlangping arc–Qinling unit (microcontinent) suture, and the Early Triassic Qinling unit–Yangtze craton suture. We resolve the controversy regarding the age of the Sino-Korean craton–Yangtze craton collision by recognizing that there was Paleozoic collision between the Qinling unit and the Sino-Korean craton and Mesozoic collision between the Qinling unit and the Yangtze craton. The Qinling unit constitutes a long and narrow microcontinent that extends through the Qinling-Dabie area and probably into the Sulu area. Its common characteristics are the Mesoproterozoic (ca. 1.0 Ga) Jinningian orogeny, ca. 0.8–0.7 Ga arc formation and rifting, and Late Silurian–Early Devonian (ca. 400 Ma) arc magmatism with concomitant regional contact metamorphism up to granulite-facies conditions (peak: 680–740 °C at 0.9–1.1 GPa). A common Proterozoic history links the Qinling microcontinent to the Yangtze craton. Its 400 Ma arc, forearc basin, and its separation from the Yangtze craton by the partly oceanic Huwan mélange make the Qinling microcontinent distinct. The forearc basin sits on the southern part of the 400 Ma arc and underlying Proterozoic continental basement, and detrital geochronology ties it to the Qinling microcontinent basement and its arc. The Huwan mélange is a subduction-accretion complex containing elements of the Qinling micro-continent and its arc, the Paleotethyan ocean floor, and possibly the Yangtze craton. Quartz eclogites (540–590 °C, 2.1 GPa) signify ca. 315 Ma subduction. Devonian to Permian eclogite zircon ages, 40 Ar/ 39 Ar and Rb/Sr mineral ages in the forearc and its basement, and static, Permian blueschist metamorphism in the upper-plate basement testify to subduction throughout the late Paleozoic. The ∼10-km-wide Huwan detachment bounds the high- and ultrahigh-pressure rocks of the Xinxian–Hong'an block (pressure peak at older than 240 Ma) along their northern margin. It is partly responsible for exhumation of the high- and ultrahigh-pressure rocks, but the entire basement core of Hong'an–Dabie orogen is also strongly deformed. The Huwan shear-zone high-strain deformation indicates passage of rocks through the lithosphere by subhorizontal N-S extension and vertical contraction, showcased by condensed Triassic isograds (420 °C and ∼0.4 GPa in the hanging wall and ∼530 °C and 2.2 GPa in the footwall). The Huwan detachment produced Triassic crustal exhumation rates of 1.9–1.4 mm/yr; synkinematic phengite grew as early as ca. 235 Ma, and the main retrograde deformation occurred at 224–195 Ma. The Tongbai-Xinxian area shows a massive 130–115 Ma cluster of cooling ages, reflecting regional cooling after granitoid injection and regional Cretaceous heating. Apatite fission-track ages cluster at 80–55 Ma and signify cooling related to transtension that coincided with rifting marked by Late Cretaceous–Eocene red bed deposition throughout eastern China. Exhumation rates of for the last 70 m.y. have been slow: ∼0.06 mm/yr. The India-Asia collision reactivated the orogen in the Eocene, particularly along the Tanlu fault zone and locally along fault zones in Tongbai-Xinxian.