In addition to fluids, the concept of sediment‐derived melts infiltrating the fore‐arc mantle during subduction initiation has been proposed based on studies of modern subduction zones and ophiolite mélange. However, outcrops that contain the products of such melts are rare, especially in conjunction with boninite. New U‐Pb zircon dating reveals that the Darutso volcanic rocks (DVRs) within ophiolitic mélange in the Beila area, central Tibet, crystallized at ∼164–162 Ma. This is the first recognition of Jurassic volcanic rocks in the middle section of the Bangong‐Nujiang Suture Zone. Geochemically, the DVRs are high‐Mg andesites with moderate SiO₂ (59.03–63.62 wt %) and high MgO (3.74–6.53 wt %), Cr (up to 395 ppm), and Mg^# (50.3–67.9). They also have high Th contents, (La/Sm)_N ratios, and (⁸⁷Sr/⁸⁶Sr)_i values (0.7085–0.7147); low Ba/Th, U/Th, and Sr/Y ratios; and negative values of ε_Nd(t) (−8.7 to −9.8) and zircon ε_Hf(t) (−7.4 to −9.9). The ε_Nd(t) values of the DVRs overlap those of regional sediments. Detailed analyses of these geochemical characteristics indicate that the DVRs were derived from partial melting of subducted sediments and subsequent interaction with overlying mantle peridotite in a shallow and hot setting. In combination with the regional geology, in particular adjacent ophiolites that contain MORB‐like and boninite mafic lavas, these rocks collectively recorded the evolution of a fore‐arc setting during the initiation of the northward subduction of the south branch of the Bangong‐Nujiang Ocean. Therefore, the results provide direct evidence for sediment melting during subduction initiation and constrain the Jurassic tectonic evolution of the Lhasa terrane.

The Permian tectonic setting of the Lhasa Terrane in southern Tibet remains controversial (i.e., continental rift vs. subduction‐collision) and is crucial to palinspastic reconstructions of the eastern Tethys during the breakup of Gondwana. In this study, we present new geochronological, geochemical, and mineralogical data for the Permian (~262 Ma) Yawa intrusions in the southern Lhasa Terrane. These rocks are silica‐undersaturated and alkaline, with high TiO₂ and moderate MgO, and exhibit enrichments in Th, light rare earth elements, and Nb‐Ta, and depletions in K. These chemical compositions, combined with uniform whole‐rock (⁸⁷Sr/⁸⁶Sr)_i (0.7039–0.7044), ε_Nd(t) (1.85–2.81), and ε_Hf(t) (4.21–6.90) values, and zircon ε_Hf(t) (4.53–9.97) and δ¹⁸O (5.04‰–5.76‰) values, indicate the magmas were derived by partial melting of amphibole‐rich lithospheric mantle. The magmas subsequently underwent fractionation of clinopyroxene, amphibole, and Fe‐Ti oxides. The amphibole in the lithospheric mantle likely formed as cumulates from low‐degree asthenospheric melts during incipient extension. Given that the amphibole‐rich metasomatic veins have a lower melting temperature than the surrounding peridotite, they were susceptible to melting during the early stages of thermal perturbation of the mantle. Because there is no evidence of Permian continental subsidence in the Lhasa Terrane, we suggest the Yawa intrusions were formed at the onset of lithospheric extension associated with initial rifting of the Lhasa Terrane from the Indian Plate during Gondwana breakup, which was a precursor to the opening of the Neo‐Tethys Ocean.