SPATIAL AND TEMPORAL VARIATIONS IN THE GEOCHEMISTRY OF CRETACEOUS HIGH-Sr/Y ROCKS IN CENTRAL TIBET

Recent studies based on low-temperature chronology and sedimentology have proposed the existence of a proto-Tibetan Plateau (p-TP); however, the timing and mechanisms of its formation and evolution remain ambiguous. High-Sr/Y rocks are an important petrological indicator of thickening. Here, we compile geochemical data of Cretaceous rocks to interpret their petrogenesis and to constrain dee p geodynamic processes. Geochemical characteristics, in combination with zircon Hf isotopic compositions, indicate that the high-Sr/Y rocks were derived from the partial melting of thickened juvenile lower crust, with or without contamination by mantle peridotite. Comparing geochronological and geochemical data, we observe a correlation between magma migration and the composition of high-Sr/Y rocks. Based on these observations, we propose a revised tectonomagmatic evolution model for central Tibet, involving crustal thickening, retreating delamination, and breakoff. Our research suggests that the rapid uplift of the p-TP was a consequence of the removal of isostatic load during the Mesozoic.