This study by Ling Chen and colleagues pertains to the vertical structural heterogeneities of cratonic lithosphere and their roles in the dynamic evolution of continents. They identified from dense seismic data a negative velocity discontinuity at ~100-km depth within the more than 160-km thick lithosphere beneath the central and western North China Craton (NCC). This together with similar observations in many other cratonic regions indicates that vertical structural heterogeneities are common in the lithosphere of cratons. The intra-lithospheric discontinuity may represent a long-existing mechanically weak layer within the overall strong cratonic lithosphere, and probably also existed beneath the eastern NCC before the Mesozoic. The presence of the horizontal weak layer may have facilitated simultaneous lithospheric modification both within and at the base of the lithosphere, eventually leading to the destruction of the eastern NCC in the Mesozoic. It, however unlikely, strongly affected the stability and evolution of the central and western NCC. This difference could be associated with the strong/weak influences of plate boundary processes, particularly the subduction of the Pacific plate under East Asia, on these regions. The different roles of the intra-lithospheric weak layer in the evolution of the NCC appear also applicable to the other stable and destabilized cratons in the world.
Order of magnitude increase in subducted H2O due to hydrated normal faults within the Wadati-Benioff zone
Tom Garth and Andreas Rietbrock, Department of Earth, Ocean, and Ecological Sciences, University of Liverpool, Liverpool, Merseyside L69 3GP, UK; firstname.lastname@example.org. Pos
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Geological Society of America