Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
4677308 | Earth and Planetary Science Letters | 2012 | 10 Pages |
Surrounded by seismicity and other manifestations of active deformation, the Ordos plateau, or the western portion of the North China craton (NCC), is a uniquely stable terrane in Asia. Results from virtual deep-seismic sounding and crustal receiver functions suggests that the crust under the eastern Ordos is thicker (at least 60 km) than expected from previous studies and from its modest elevation (∼1500 m above sea-level). Receiver functions also reveal a pronounced elastic impedance contrast within the crust (at ∼40 km depth), which we interpret as the Conrad discontinuity. The presence of a 20 km thick layer of mafic lower crust between the Conrad and Moho discontinuities would maintain crustal isostasy. The ∼1000 km long seismic profile from the Ordos plateau in the west to the North China basin in the east reveals that crustal thickness changes by almost a factor of two across the active Shanxi rift in central NCC (over a distance of only about 100 km). Insofar the current configuration of the lithosphere under the Ordos plateau might serve as a proxy for the initial condition prior to reactivation of the eastern part of NCC—where a cratonic keel no longer seems to exist—our results support the hypothesis that lower crust foundering was due to transformation of a thick mafic lower-crust to a garnet-rich assemblage (possibly caused by hydration associated with subduction during and/or before mid-Mesozoic times).
Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (519 K)Download as PowerPoint slideHighlights► Intriguing variations in crustal properties across the NCC are revealed by combining VDSS and RF methods. ► Significant crustal thickness variation occurs over a distance of only 100 km near the eastern margin of the Ordos plateau. ► Thick crust under the Ordos is characterized by a distinct layer of lower crust. ► Structure under the Ordos provides constraints prior to the reactivation of the ENCC.