T140 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

CAUSE AND CONSEQUENCES OF FLAT-SLAB SUBDUCTION AND FOUNDERING: A SOUTH CHINA EXAMPLE

Paper number: T140-12
Program: Technical Sessions
Time: 4:15 PM – 4:30 PM

Authors

Abstract

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).

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-335001

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