Journal
GONDWANA RESEARCH
Volume 75, Issue -, Pages 1-15Publisher
ELSEVIER
DOI: 10.1016/j.gr.2019.03.019
Keywords
Western Pacific; South China; Geochronology; Thermochronology; Flat-slab subduction
Categories
Funding
- State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Chengdu University of Technology) [PLC20180501]
- National Natural Science Foundation of China [41703055, 41772118, 41602128]
- Australian Research Council Discovery Project [DP110104799]
- Laureate Fellowship Project [FL150100133]
- Curtin Research Fellowship
- Fundamental Research Funds for the Central Universities [300102278204, 300102279206]
- National Key Research and Development Program of China [2016YFC0601002]
- Natural Science Foundation of Shandong Province [ZR2017LD006]
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The flat-slab subduction model has been proposed to explain the complex Mesozoic-Cenozoic geotectonic record of SE China as part of the Western Pacific margin. Here we investigate the post-250 Mathermal history of the Shaoguan-Longnan region to evaluate the time-temperature evolution of local sedimentary and magmatic rocks in the context of the flat-subduction model. Our multi-chronological approach includes zircon U-Pb geochronology, 40Ar/39Ar dating of K-feldspar and biotite, (U-Th)/He dating of zircon and apatite, and fission-track dating of apatite from basement and/or sedimentary rocks, as well as vitrinite reflectance analysis of coal seams. Zircon U-Pb dating revealed Early Silurian and Late Jurassic crystallization ages for the Fuxi (ca. 438Ma) and Liyuan (ca. 162 Ma) granites, respectively. Syn-/pre-depositional single-grain zircon (U-Th)/He ages from Lower Jurassic sandstones record a Middle Triassic exhumational cooling, interpreted to reflect the Indosinian Orogeny, possibly caused by a flat-slab subduction event. Late Jurassic biotite 40Ar/39Ar age (ca. 156 Ma) obtained from the Late Triassic Mengdong granite, together with maximum vitrinite reflectance values of 1.7%-2.3% measured from a Lower Jurassic coal sample, document a thermal maximum in the Late Jurassic, likely related to the prior regional magmatism arising from delamination of the subducting Paleo-Pacific plate. K-feldspar 40Ar/39Ar plateau age from the Fuxi granite (ca. 125 Ma), and zircon (U-Th)/He mean ages (152-115 Ma) record a protracted cooling through the K-feldspar Ar and the zircon He partial retention zones during the Cretaceous. The Cretaceous cooling is in accord with the prediction of regional uplift and erosion in response to foundering of the flat-slab and consequent lithospheric rebound. The rapid cooling during the Paleocene-Eocene, recorded by apatite fission-track central ages (72-39 Ma) and apatite (U-Th)/Hemean ages (38-33 Ma), is interpreted to reflect Cenozoic rifting in the leadup to the opening of the South China Sea. (c) 2019 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
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