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Heintz et al. 2005

Surface-wave tomography studies: Vs at 100 km depth. High velocities in the Amazon craton. Heintz et al. 2005. Feng et al. 2005. lateral resolution : 700 - 1000km 300 - 500 km T > 40s, long paths T > 15s, shorter paths.

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Heintz et al. 2005

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  1. Surface-wave tomography studies: Vs at 100 km depth High velocities in the Amazon craton Heintz et al. 2005 Feng et al. 2005 lateral resolution : 700 - 1000km 300 - 500 km T > 40s, long paths T > 15s, shorter paths

  2. Note low-velocities beneath the Chaco/Pantanal basins. % S-wave anomalies at 150km (Heintz et al., 2005)

  3. 150km 100km Global tomography (Univ. Colorado) Few stations in South America, very long paths -> low resolution (does not isolate Amazon craton Note low-velocities beneath the Chaco/Pantanal basins. 250km 200km Upper Mantle Shear Velocity Model N.Shapiro Univ.Colorado SDT (diffraction tomography model).

  4. Vs 100 km Separate high-velocity block in Southern S.Francisco craton. Joint inversion results: Generally high velocities In the Amazon craton. No clear separation between the Guyana and Guaporé shields. Possible cratonic block beneath the Paraná basin?

  5. Vs 150 km resolution 300-600km thickest lithosphere in oldest block A TransBrasilian Lineament: generally low velocities or limits high velocity blocks.

  6. Vs 200 km oldest rocks resolution 500-800km 2.9-3.0 Ga granitoids/greenstones Carajás Iron Province

  7. 150 km Guaporé shield NW SE Guyana shield S.Francisco craton

  8. P-wave tomography station craton intrusion 85-60 Ma intrusions 130-120 Ma, Atlantic rift

  9. geochemistry (Gibson et al., 1997) Note striking similarity of lithospheric thicknesses (geochemistry model) with P-wave anomalies along the white line (200km depth) effect of ray paths tomography (BLSP, 2004)

  10. Seismicity Earthquakes tend to occur above low-velocity areas (thinner lithosphere?)

  11. lithosphere/asthenosphere limit? Number of earthquakes along NW-SE profile (+- 100km width) mag>3,5 Iporá S.Mar/plat. SFC APIP

  12. Teresina station Vp/Vs = 1,71 Crustal thickness = 40 km (assuming Vp=6.4km/s)

  13. 33 km 46 km 46 km 33 km 35 km Crustal thicknesses from receiver functions. Note thick crust in the low-topography Paraná basin.

  14. Crustal thickness constrained by 1- Rayleigh waves 2- receiver functions 3- isostasy Feng et al.(2005)

  15. Average crustal Vp/VS ratio 1.74 1.76 Archean is generally more felsic, consistent with low Vp/Vs (<1.73). Mafic rocks, in general, have Vp/Vs >1.75, consistent with Magmatic Arc. 1.71 1.70 1.74 1.73 1.71 Assumpção et al., 2004)

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