Research ArticleGEOLOGY

Seismological evidence for the earliest global subduction network at 2 Ga ago

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Science Advances  05 Aug 2020:
Vol. 6, no. 32, eabc5491
DOI: 10.1126/sciadv.abc5491
  • Fig. 1 North China craton and high-density seismic array.

    (A) Tectonic map of the North China craton and location of the high-density seismic array (green dashed line) with the Khondalite belt (yellow) and exhumed Paleoproterozoic high-pressure rocks (stars). Phanerozoic magmatism, metamorphism, and faults are from Ren et al. (19). Paleo-Asian domain is the Neoproterozoic–Early Mesozoic accretionary orogenic system that reworked the northern margin of North China. Tethyan domain is the Mesozoic to Cenozoic collisional orogenic system that affected the southwest margin of North China. Pacific domain is the Mesozoic to Cenozoic subduction system along the eastern margin of Eurasia. Globe inset depicts positions of teleseismic events in this study, with red and blue representing earthquakes from the west and east, respectively. (B) Positions of 609 short-period seismic stations (yellow) that form a north-south transect from the stable interior of the craton to its reworked margin. Piercing points for receiver functions (RFs) at a depth of 40 km produced by 16 earthquakes from west and east BAZ (red and blue, respectively).

  • Fig. 2 Seismic transect across the Khondalite belt.

    (A) RF section for a teleseismic event from southwest that shows the dipping Moho. (B) RF section for a teleseismic event from southeast with unclear Moho. The average RF is shown on the right, where the direct P and the averaged Moho arrival are shown at 0 and ~6 s. (C) CCP section image of the crustal structure along transect (Fig. 1). The position of the first seismic station is at 0 km. The segment between a distance of −14 and 156 km was stacked using the three teleseismic events coming from the southwest, and the segment between 156 and 280 km was stacked using all 16 teleseismic events. T-K, Triassic through Cretaceous; Q, Quaternary.

  • Fig. 3 Synthetic tests for the dipping Moho.

    (A) Left: Seismic stations and teleseismic event distribution, with events coming from the southwest (red) and the southeast (blue). Model used in forward-modeled synthetic RFs is shown in the middle. Right: BAZ variation in the radial RFs resulting from the dipping Moho interface. Direct P arrival at 0 s and Ps conversions from the dipping interface near 5 s. The Ps conversions with azimuths between 50° and 190° (gray shading) have a smaller amplitude. (B) Synthetic RFs (left) computed from two BAZ (128° and 233°) and their corresponding RFs computed from real data (right). RFs from 128° BAZ along a north-south trend (same direction as our profile) shows weak Moho conversions, but RFs from 233° show a coherent dipping Moho.

  • Fig. 4 Modern Himalayan orogen and Orosirian Khondalite orogen.

    Comparison of surface tectonics (left) and deep seismic structures (right) between modern (top) and Paleoproterozoic (bottom) continent collision zones. Light blue lines on the tectonic maps represent the locations of the RF profiles. Modern Himalayan range and its RF image across the main central thrust from 50 to 105 km along the profile of Nábelek et al. (10). Tectonic map of western North China (5) and the deep RF image shown from a distance of 5 to 60 km along our array (Fig. 2C). Comparison of entire profiles is shown in fig. S7.

  • Fig. 5 Global subduction and supercontinent Nuna.

    Reconstruction of supercontinent Nuna ~1.8 Ga ago (33), including the position of North China (7, 35). Convergence directions (black arrows) inferred from subduction polarity (black triangles) indicated at seismic profiles (blue). Speculated continuation of seismically confirmed sutures (red). Details of Orosirian orogens are in the Supplementary Materials. A 2.15-Ga-old blueschist immediately preceding the Orosirian period is shown (6). Green region marks configuration of core continents assembled through two to three major sutures. Putative positions in the larger supercontinent Nuna are suggested for other less studied continents (slightly transparent). Seismic evidence is consistent with previous paleomagnetic and geological configurations in the green region under the paradigm of a modern, global subduction-driven plate tectonic network.

Supplementary Materials

  • Supplementary Materials

    Seismological evidence for the earliest global subduction network at 2 Ga ago

    Bo Wan, Xusong Yang, Xiaobo Tian, Huaiyu Yuan, Uwe Kirscher, Ross N. Mitchell

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    This PDF file includes:

    • Sections S1 and S2
    • Figs. S1 to S7
    • Table S1
    • References

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