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GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 140-11
Presentation Time: 4:15 PM

CAUSE AND CONSEQUENCES OF FLAT-SLAB SUBDUCTION AND FOUNDERING: A SOUTH CHINA EXAMPLE (Invited Presentation)


LI, Zheng-Xiang, Earth Dynamics Research Group, School of Earth and Planetary Sciences, Curtin University, Bentley, Perth, WA GPO Box U1987, Australia, LI, Xian-Hua, State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China, ZHU, Kongyang, School of Earth Sciences, Zhejiang University, 38 Zheda Road, Hangzhou, Zhejiang 310027, China, MENG, Lifeng, School of Geoscience and Technology, Southwest Petroleum University, Chengdu, Sichuan 610503, China, PANG, Chongjin, College of Earth Sciences, Guilin University of Technology, Guilin, 541004, China and TAO, Ni, School of Earth Science and Resources, Chang'an University, Xi'an, 710054, China

Flat-slab subduction likely occurred throughout Earth history after the initiation of plate tectonics, and would have impacted on the orogenic, basin, and magmatic histories of all continents. Yet, documented pre-Cretaceous records are extremely rare, mostly due to our lack of understanding of the related processes and diagnostic features, and an underappreciation of the significance of flat-slab subduction in Earth history. Here we review the cause and consequences of a Permo-Triassic flat-slab subduction and subsequent foundering in South China, featuring (1) a ca. 1300 km land-ward migration of an orogenic front and foreland basin between ca. 250 Ma and ca. 200 Ma, (2) a ca. 1000 km-wide magmatic gap during the phase of land-ward orogenic propagation (the flat-slab subduction stage, 250–200 Ma), (3) repeated kilometers-scale vertical topographic movements above the subducted flat-slab: first the formation of a broad orogenic belt over a previously continental shallow marine due to orogenic compression and isostatic uplift caused by the underplating of the buoyant flat-slab (250–200 Ma), followed by continental-scale (~1000 km diameter) sagging of the young orogen to below sea-level caused by gradual eclogitization of the underplated oceanic plateau (reached maximum subsidence at ca. 185 Ma), and finally continental-scale rebound after the delamination and foundering of the now dense flat-slab (after 185 Ma); (4) a radiating anorogenic magmatic flair-up accompanied by crustal extension (after 200 Ma till the Cretaceous), and (5) re-initiation of the coastal normal subduction soon after the cessation of the land-ward propagation of the flat-slab subduction (after 200 Ma).

Session No. 140

T53. Present-Day and Ancient Flat-Slab Subduction in Rock Records, Geophysical Images, and Geodynamic Models
Monday, 23 September 2019: 1:30 PM-5:30 PM
Room 132ABC, North Building (Phoenix Convention Center)
Geological Society of America Abstracts with Programs. Vol. 51, No. 5
doi: 10.1130/abs/2019AM-335001
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