Mesozoic felsic magmatism along the Bangong-Nujiang suture zone, Tibet: Temporospatial variations and tectonic implications

The subduction history and closure of the Meso-Tethys Ocean have not yet been well constrained using data from felsic rocks along the Bangong-Nujiang suture zone. Here we present geochronological, geo-chemical, and isotopic data from Early Jurassic-Late Cretaceous felsic rocks in the Laguo Co area of central Tibet. We combine our results with published data from coeval felsic rocks to explore the temporospatial variations in magmatism and the implications for subduction in and closure of the Meso-Tethys Ocean. The studied rocks include 182-180 Ma granodiorite, 109 Ma granite porphyry, and 68 Ma rhyolite, and zircon grains from each yield different eH eta t) values (+8.9 to +14.0,-5.5 to +0.7, and-4.9 to +1.1, respec-tively). The rocks have low-K tholeiitic to medium-K calc-alkaline compositions, low Y and Yb contents, and positive Sr anomalies. These data suggest an oceanic source for the Early Jurassic granodiorite and a crustal source for the Cretaceous granite porphyry and rhyolite, as well as a tectonic transition from an oceanic arc during the Early Jurassic to continental collision during the Cretaceous. The temporospatial variation in felsic magmatism corresponds to intra-oceanic subduction, bidirectional subduction, oceanic ridge or flat subduction, slab rollback, slab breakoff or sinking, and lithospheric delamination. The timing of closure of the Meso-Tethys Ocean is constrained to the Jurassic-Cretaceous, as evidenced by the major differences of the magma sources and formation processes between the Jurassic and Cretaceous felsic rocks. Finally, we present a model showing that oceanic closure occurred earlier in the east and north and later in the west and south.(c) 2023 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.