Metamorphic evolution of the Tethyan Himalayan flysch in SE Tibet

Abstract

The metamorphic conditions and the age of thermal overprint were determined in meta-pelites, metaarenites and metabasites of the Tethyan Himalayan Sequence (THS) in SE Tibet using Kübler Index and vitrinite reflectance data and applying thermobarometrical (Thermocalc and PERPLEX) and geochronological methods (illite/muscovite K-Ar and zircon and apatite (U-Th)/He chronology). The multiple folded thrust pile experienced a thermal overprint reaching locally peak conditions between the diagenetic stage (c. 170 °C) and the amphibolite facies (c. 600 °C at 10 kbar). Burial diagenesis and heating due to Early Cretaceous dyke emplacement triggered the growth of illite in the metapelites. Eocene collision-related peak metamorphic conditions have been reached at c. 44 Ma. During collision the different tectonic blocks of the THS were tectonically buried to different structural levels so that they experienced maximum green-schist to amphibolite facies metamorphism. Later, during Oligocene to Miocene times the entire THS underwent anchi- to epizonal metamorphic conditions, probably associated to continuous deformation in the flysch fold-thrust-system. This period terminated at c. 24-22 Ma. Adjacent to the north Himalayan metamorphic domes, the base of the THS was metamorphosed during Miocene times (c. 13 Ma). Post-metamorphic cooling below c. 180 °C lasted until Late Miocene and took place at different times

Pressure–temperature–time–deformation path of kyanite-bearing migmatitic paragneiss in the Kali Gandaki valley (Central Nepal): Investigation of Late Eocene–Early Oligocene melting processes

“…The GHS is tectonically overlaid by the Tethyan Sedimentary Sequence (TSS) via a large scale ductile to brittle system of normal faults, named South Tibetan Detachment System (Burchfiel et al, 1992;Burg et al, 1984;Caby et al, 1983;Carosi et al, 1998Carosi et al, , 2002Searle, 2010). 4) The TSS consists of early Palaeozoic to late Mesozoic polydeformed unmetamorphosed to low grade metamorphic sediments Dunkl et al, 2011;Godin et al, 1999a,b) originally deposited on the northern passive margin of the Indian Plate. Towards the N, the TSS is bounded by flysches and ophiolites (often with a blueschist metamorphic imprint, Hodges, 2000) of the Indus-Tsangpo suture zone ( Fig.…”

Eocene partial melting recorded in peritectic garnets from kyanite-gneiss, Greater Himalayan Sequence, central Nepal

“…northern passive margin of the Indian plate (Gaetani & Garzanti 1991). The sequence was generally deformed under very low-grade metamorphic conditions, with the highest metamorphic grade corresponding to the greenschist facies, at the base of the sequence in the Cambro-Ordovician rocks affected by the activity of STDS (Crouzet et al 2007;Antolín et al 2011;Dunkl et al 2011).…”

Provenance of the Upper Cretaceous to Lower Tertiary Sedimentary Relicts in the Renbu Mélange Zone, within the Indus-Yarlung Suture Zone

“…These ophiolitic rocks are associated with late Jurassic-early Cretaceous island-arc volcanic rocks (McDermid et al 2002;Aitchison et al 2007) and the controversial Liuqu Conglomerate Fang et al 2006;Wei et al 2011). The ophiolitic rocks are locally in thrust contact with a 10-to 50-km-wide mud-matrix turbidite mélange exposed in the hanging-wall Zhongba-Gyantse or Lhunze thrusts (Ding et al 2005;Yin 2006;Li et al 2010Li et al , 2011Dunkl. et al 2011;Cai et al 2012;figs.…”