1:250 000 Kana and Rutog Sheets in Xizang

Stratigraphically, the redelineation of the stratigraphic boundaries resulted in the re-establishment of the Duoren and Risum Formations in the Jienu Group, Rigain Punco Group, Ouli and Wufengjian Formations. Petrologically, the lineage units are reconstructed for the intrusive rocks and the tectonic-magmatic belts are determined for the surveyed areas. There occur the Hercynian quartz diorite in southern Qiangtang, and volcanic interbeds and lenses in the Carboniferous-Jurassic strata. Tectonically, the Wufengjian-Larelaxin Late Jurassic-Early Cretaceous continental-margin volcanic-magmatic arc zone is discriminated as a third-order tectonic unit. The Bangong Lake ophiolitic mélange zone is subdivided into the northern and southern subzones. The former was emplaced during the Late Jurassic and the latter during the Late Cretaceous. The Mesozoic Tethyan Ocean in the Bangong Lake area has undergone the following stages of evolution:spreading during the Triassic to Early and Middle Jurassic, bidirectional subduction during the Middle and Late Jurassic, generation of a residual oceanic basin during the Late Jurassic to Early Cretaceous, southward subduction during the latest Early Cretaceous, and continent-arc (continent) collision during the Middle Cretaceous to Middle Eogene.