Geology：Insights into initial continental rifting of marginal seas from seismic evidence for slab relics in the mid-mantle of the Woodlark rift, southwestern Pacific

Youqiang Yu^1,2,*, Frederik Tilmann^2,3, Stephen S. Gao⁴, Kelly H. Liu⁴, and Jiaji Xi¹

1 State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China

2 GFZ German Research Centre for Geosciences, Telegrafenberg, Potsdam 14473, Germany 

3 Institute for Geological Sciences, Freie Universität Berlin, Berlin 12249, Germany

4 Geology and Geophysics Program, Missouri University of Science and Technology, Rolla, Missouri 65409, USA

Abstract：The initiation and evolution of marginal seas, especially those developing under a convergent setting, is one of the more enigmatic aspects of plate tectonics. Here, we report the presence of slab relics in the mid-mantle of the Woodlark rift in the southwestern Pacific based on a new map of the topography of the mantle discontinuities from a receiver function analysis and evidence from body-wave tomography. The widespread mantle transition-zone thickening rules out active mantle upwelling, and the revealed slab relics in both the upper and middle mantle may hydrate the upper mantle, which can be expected to further weaken the overlying lithosphere. Such a process can then promote initial continental rifting when this lithosphere is exposed to tensional stress like slab-pull stretching originating from the nearby active subduction.

Full Article：https://doi.org/10.1130/G51528.1