Was Late Triassic Tanggula granitoid (central Tibet, western China) a product of melting of underthrust Songpan-Ganzi flysch sediments?

Geochronological (laser ablation-inductively coupled plasma–mass spectrometry, LA-ICP-MS), mineral chemistry, major and trace element, and Sr-Nd-Hf isotopic data are presented for the Tanggula granitoid, the largest granitic pluton in the northern Tibetan Plateau. The Tanggula pluton yields a Late Triassic emplacement age (228–223 Ma) and is magnesian (Mg# = 29.10–49.81), high-K calc-alkaline (K2O/Na2O = 0.76–3.51, mostly >1), and strongly peraluminous (molar Al2O3/(CaO + Na2O + K2O), A/CNK = 1.06–1.42, mostly >1.1). High initial 87Sr/86Sr ratios (0.716849 to 0.730577) and low ƐNd(t) (−10.95 to −9.60) and ƐHf(t) values (−16 to −5.1), along with an abundance of aluminosilicate minerals (e.g., biotite), enrichments in light rare earth and large ion lithophile elements, negative Eu anomalies, and depletion in high field strength elements suggest that the Tanggula granitoid is an S-type granite derived mainly from the anatexis of metasedimentary source rocks. Geochemical fingerprinting using Sr-Nd-Hf isotopes and detrital zircon U-Pb age spectra shows that Triassic flysch sediments from the Songpan-Ganzi Paleo-Tethyan Ocean to the north of the pluton are the most likely source of the Tanggula granitic magmas. The Tanggula granitoid could thus have been formed by the partial melting of the flysch sediments from the Songpan-Ganzi complex as they were underthrust beneath the Qiangtang terrane along the Jinsha subduction zone during the Late Triassic.