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Recent studies evoke dispute whether the Greater Himalayan Crystalline Complex (GHC) was exhumed during more than one phase. This contribution investigates the timing of ductile shear along the South Tibetan Detachment (STD), Main Central Thrust (MCT), and hidden discontinuities within the GHC of the central Himalaya. New data from the Nyalam transect, southern Tibet, suggest that ductile shear along the STD was active from ~ 27–25 Ma to ~ 17–15 Ma, whereas ductile shear along the MCT was active from ~ 19–16 Ma to ~ 10–8 Ma. Pseudosection modeling results and published metamorphic ages indicate a P–T–t path discontinuity within the GHC and the upper GHC reached higher peak metamorphic temperatures (ΔT 100 °C), similar peak pressures and older metamorphic ages (~ 5–10 Myr), in favor of the presence of the Nyalam Discontinuity. Summarized results from literature suggest that timing of ductile shear along the STD was ~ 5–10 Myr earlier than that along the MCT across the Nepal, Sikkim and Bhutan Himalayas. In addition, the GHC in Nepal can be separated into two portions by a regional-scale (> 800 km) in-sequence ductile shear zone — the High Himalayan Discontinuity. This shear zone was active coevally with the STD during 25–16 Ma, but ~ 5–10 Myr earlier than the MCT. The High Himalayan Discontinuity could possibly extend to the Sikkim Himalayas, but ends in Bhutan. The identified new architecture suggests that both in-sequence and out-of-sequence tectonometamorphic discontinuities are important components that formed the duplexing structure of the GHC in the central and eastern Himalaya, thus calling for more sophisticated numerical simulation than the current models such as the channel flow and critical taper. [ABSTRACT FROM AUTHOR]

• UHT metamorphism is reported for the first time in the Himalaya. • The heat source was an over-thickened crust associated with lithospheric thinning. • Cold vs. granulitized eclogites formed during infant vs. mature collisional stages. • 2.0–1.8 Ga eclogites have formed by a Himalaya-type global collisional network. Modern-style plate tectonics, often characterised by subduction, is a fundamental dynamic process for planet Earth. Subduction related eclogites are widely used to indicate initiation of plate tectonics or whether different tectonic regimes dominated Earth history. However, such markers are commonly overprinted in ancient metamorphic terranes and rarely preserved even in most Phanerozoic mountain belts. This study tries to reveal the detailed burial and exhumation processes that formed granulitized eclogites in the Everest east region, central Himalaya, so as to explore the tectonic regimes recorded by similar rocks on early Earth. Robust Pressure-Temperature-time paths were achieved by studying the mineral relicts (Omp, Jd ∼29%), high-temperature mineral textures (Sil-Crd-Qz-Spl-Mesoperthite assemblage, rutile exsolution in biotite), and multiple thermobarometry and petrochronology of eclogites and metapelites. Results show that these eclogites underwent eclogitization at conditions of 730–770 °C and ∼20 kbar (∼11 °C/km) at ∼30 Ma and were overprinted by a heating and decompression path to ultrahigh temperature (UHT) conditions of 6–11 kbar and 900–970 °C (∼40 °C/km) during 25–15 Ma. The resulting exhumation rate (2–3 mm/yr) is slow and prolonged (10–15 Myr) (U)HT favoured re-equilibration of the eclogitic mineral assemblage and textures. The obtained UHT conditions, the first time ever reported for the Himalaya, were induced by combined effects of over-thickened (∼60 km) radioactive felsic crust and thinning of lithosphere to <90 km. This case study provides a critical example to understand the heat sources and timescale of UHT condition during continental collision. By comparing with the western Himalaya eclogites, we suggest that formation of cold vs. granulitized continental eclogites during the Himalayan orogeny is caused by different crustal thickness (normal ∼30 km vs. over-thickened ∼60 km) due to different collisional stages (infant vs. mature). In a wider perspective, ancient eclogites were commonly granulitized by stacking into the over-thickened orogenic crust during mature continental collision. According to similar granulitized eclogites preserved on early Earth, Himalaya-type continental subduction/collision should have become a global pattern during the Paleoproterozoic (2.0–1.8 Ga). [ABSTRACT FROM AUTHOR]