Journal
AMERICAN JOURNAL OF SCIENCE
Volume 319, Issue 2, Pages 105-121Publisher
AMER JOURNAL SCIENCE
DOI: 10.2475/02.2019.02
Keywords
Proto-Tibetan Plateau; high-Sr/Y rocks; crustal thickening; retreating delamination; breakoff; rapid surface uplift
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Funding
- China Postdoctoral Science Foundation [2016M600353, 2017T100321]
- Natural Science Foundation of Jiangsu Province [BK20170877]
- State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences [SKLabIG-KF-16-11]
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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.
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