Protracted Paleozoic–early Triassic thermal events in the Almora nappe, Kumaun Lesser Himalaya, India: Evidence from zircon U–Pb geochronology of Almora paragneiss.

The Almora nappe in the Kumaun Lesser Himalaya (KLH) is mainly composed of Saryu Formation, Gumalikhet Formation and Cambrian felsic intrusives. Zircons from a paragneiss, exposed near Kwarab along Sualbari–Almora transect, of Saryu Formation, are subjected to U–Pb geochronology in order to delineate the timing of tectono-thermal events and its implication on pre-Himalayan orogenic cycle. Zircon rims developed over Neoarchean–Paleoproterozoic zircon cores record U–Pb ages which broadly correspond to three major pre-Himalayan tectono-thermal (metamorphic) events, early Paleozoic, late Paleozoic and early Triassic. These protracted thermal imprints likely represent the metamorphic episodes experienced by the rocks of Almora nappe. The observed early Triassic rim ages of zircons from paragneiss are very well correlatable with the opening-closure of the Palaeo-Tethys Ocean. [ABSTRACT FROM AUTHOR]