# Subduction Evolution Controlled Himalayan Orogenesis: Implications from 3-D Subduction Modeling
## 3 Results  
Considering the influence of crustal deformation, developed folds, and arc magmatism, the regions adjacent to the Yarlung-Zangpo suture zone are conjectured to have undergone rapid crustal thickening accompanied by structural shortening after the initial collision, which is evidenced by the formation of adakitic rocks (e.g., [22; 23]). The Himalayan orogen is inferred to have featured a north-south compressional setting according to magmatic rock exhumation. The effect of crustal thickening was predominant in determining the uplift rate in the Paleocene and Eocene during the early evolution of the Himalayas (Figures 5a and 6a). The velocity field of the Himalaya orogen flows from south (>0.3 mm/year) to north (<0.1 mm/year), indicating strong shortening between India and Eurasia (Figure 4). In the second stage, the Himalayan uplift was linked to the detachment of the subducted Indian Plate. The mean compressive stress increased within the Indian  
Figure 4: The vertical surface deformation field in and around the Himalayan orogen. (**a**,**b**) indicate the variation in vertical flow velocity (mm/year) in the Oligocene (42\(-\)23 Ma) and Miocene (23\(-\)11 Ma), respectively. plate and decreased the slab pull (e.g., [24]). Associated rebound occurred, facilitating uplift and increasing the elevation of the Himalayas by approximately 1.5 km prior to 23 Ma (Figures 5b and 6b). After slab break-off, the upwelling asthenospheric mantle flow also affected the acceleration of the uplift rate after 23 Ma in stage 3 (Figures 5c and 6c). [PERSON] and [PERSON] [25], using Sr-Nd-Pb isotope data, indicated a change in the distribution of magmatism in Tibet, implying that asthenospheric mantle flow triggered further melting. Subducted Indian slab rollback could also have resulted in east-west-trending slab break-off ([26], shown in Figure 2). A large number of small tears within the underthrusting Indian plate are due to the upwelling of asthenospheric flow [27]. To explore the uplift rate of the Himalayas and its relationship to stress variation, we calculated the stress state in the underthrusting and overlying plates. [PERSON] et al. [28] showed that the Himalayan uplift is caused by increased fault slip rates in response to stresses. Our results imply that the vertical flow velocity indicating the Himalayan uplift in the Miocene (23\(-\)11 Ma) was significantly higher than that in the Oligocene, which is a result of the bending of the Indian lithosphere due to lithospheric flow beneath the Himalayas (Figure 4). From the results, we found that the vertical flow velocity (uplift) was much greater than the average erosion rate (Figures 4 and 6). Although the strong monsoon climate results in a high erosion rate (e.g., [29]), erosion has not kept pace with the uplift of the Himalayas. The vertical velocity field reveals a phase of rapid uplift of the Himalayas in the Miocene (Figure 4b), and the range is still rising at a maximum rate of \(\sim\)2 mm/year (e.g., [30]). Figure 5: Schematic illustration of the 2-D tectonic evolution of the Himalayan orogen corresponding to the four evolutionary stages of the Himalayas. The insets indicating variation of the height along the distance are specified in Figure 6. (**a**) Plate-convergence-induced thickening (60\(-\)42 Ma). (**b**) Progressive uplift of the Himalayas caused by slab detachment and rebound (42\(-\)23 Ma). (**c**) Upward asthenospheric flow causes rapid uplift of the Himalayas (23\(-\)11 Ma). (**d**) Slowed uplift of the Himalayas affected by surface erosion (11\(-\)0 Ma). The onset of slab detachment to reproduce surface morphometry results in significant surface uplift in southern Tibet (Figures 3d, 5d and 6d). The modeled uplift rates exhibit gradual along-subduction gradients (Figures 4 and 6), with faster uplift occurring predominantly in the regions adjacent to the Himalayas, where the plate interface is shallower and descends rapidly.