Integrated mineral chemistry and monazite–zircon U–Pb geochronology of Wangtu metasediments and granite-gneisses, NW Himalaya, and their implications in Columbia assembly

The Wangtu Gneissic Complex (WGC) is a Paleoproterozoic granite-gneiss complex located in the Wangtu-Karcham-Akpa section of the Sutlej Valley in the Himachal Himalaya, India. The basement of the WGC remains mostly in its original state. This article presents the geochronology of the granite gneisses, as well as a study of the thermal effects these rocks had on the neighbouring Wangtu metasediments. Dating of zircons by the ID-TIMS method in two granite-gneisses yields ages of 1872.1 ± 2.5 Ma and 1861 ± 13 Ma. The granite-gneisses exhibit similarities to porphyry-type granite, characterised by the presence of feldspar and quartz clasts, which are wrapped around by biotite and muscovite minerals. Monazite in two metasedimentary rocks of the WGC define U-Th-Pbtotal chemical ages of ~ 1800 Ma but with partly more reset values down to 1400 Ma. Partial discordance of both zircon and monazite reflects the Cenozoic tectonics affecting the region. The results obtained from this study reveal the north Indian continental margin was an active subduction zone during the Paleoproterozoic Columbia supercontinent assembly that extends across the Himalaya.