Youqiang Yu1，2，4*, Frederik Tilmann2，5, Dapeng Zhao3, Stephen S. Gao4, Kelly H. Liu4
1State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China
2GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany
3Department of Geophysics, Graduate School of Science, Tohoku University, Sendai 980-8578,Japan
4Geology and Geophysics Program, Missouri University of Science and Technology, Rolla, Missouri 65409, USA
5Institute for Geological Sciences, Freie Universität Berlin, Berlin, Germany
Abstract: To explore the dynamic mechanism of continental rifting within a convergent setting, we determine the first P wave radial anisotropic tomography beneath the Woodlark rift in southeastern Papua New Guinea, which develops within the obliquely colliding zone between the Australian and SW Pacific plates. The rift zone is depicted as localized low-velocity anomalies with positive radial anisotropy, which rules out a dominant role of active mantle upwelling in promoting the rift development and favors passive rifting with decompression melting as main processes. Downwelling slab relics in the upper mantle bounding the rift zone are revealed based on observed high-velocity anomalies and negative radial anisotropy, which may contribute to the ultra-high pressure rock exhumations and rift initiation. Our observations thus indicate that the Woodlark rift follows a passive model and is mainly driven by slab pull from the northward subduction of the Solomon plate.
Full article：https://doi.org/10.1029/2022GL098086