Intraoceanic Subduction System Within the Neo‐Tethys: Evidence From Late Cretaceous Arc Magmatic Rocks of the Eastern Himalaya

The tectonic evolution of the Neo‐Tethys Ocean remains highly controversial, with several models existing in the community that conflict with each other. Here, we present new geochronologic and geochemical data for orthogneisses and amphibolites from the Greater Himalayan Sequence, eastern Himalayan orogen, which indicate that these rocks have Cenozoic metamorphic ages (∼52–3 Ma), but were derived from Late Cretaceous (∼89 Ma) magmas with arc‐like and depleted mantle geochemical signatures. Considering that northern India was a passive continental margin during the Mesozoic, and the previously reported Late Cretaceous magmatic rocks in the eastern Himalaya formed in a continental rifting setting, we suggest that the studied Late Cretaceous arc‐type magmatic rocks formed in an intraoceanic arc setting within the Neo‐Tethys, and accreted onto the passive margin of the Indian continent prior to the terminal continental collision. When combined with the existence of Late Mesozoic and intraoceanic arc‐type magmatic rocks in the western Himalaya, we suggest that a huge Late Cretaceous subduction system operated within the eastern Neo‐Tethys Ocean. This study supports two subduction zones having been responsible for the consumption and closure of the Neo‐Tethys basin, and a two‐stage collision history between India, Asia, and the intermediate island arc system. Our data therefore provide important constraints on the evolution of the Neo‐Tethys Ocean and India‐Asia collisional orogeny in southern Tibet. Plain Language Summary We have conducted petrological, geochronologic and geochemical studies of high‐grade metamorphic rocks from the Greater Himalayan Sequence, eastern Himalayan orogen. Our results show that the rocks have Cenozoic metamorphic ages, but were derived from Late Cretaceous arc‐type magmatic rocks. We suggest that the magmatic rocks formed in an intraoceanic arc setting within the Neo‐Tethys, and accreted onto the passive margin of the Indian continent prior to the terminal continental collision, and that a huge intraoceanic subduction system operated within the eastern Neo‐Tethys Ocean during the Late Cretaceous. Key Points Late Cretaceous subduction‐related magmatic rocks with Cenozoic metamorphic ages occur in the eastern Himalaya The rocks formed in an intraoceanic arc setting, and accreted onto the India passive margin prior to the continental collision A huge and Late Cretaceous northward subduction system operated within the entire Neo‐Tethys