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Lower Continental Crust Exhumed: Granulite Grade Terranes and Amphibolite Grade Shear Zones in the Anabar Shield, Polar Siberia

  • O. M. Rosen
Conference paper
  • 79 Downloads
Part of the Proceedings of the International Conferences on Basement Tectonics book series (ICBT, volume 5)

Abstract

The lower continental crust (10–40 km deep), modeled from geophysical data and kimberlite xenoliths studies, is assumed to be composed of mafic granulites with seismic velocities as high as Pv=6.35–7.05 km/s, densities of 2.85–3.08 g/cm3 (Meissner, 1986) and radioactive heat productions of A=0.48–0.53 µW/m3 (Rudnick, 1992, Kremenetsky et al., 1986). In contrast the upper crust is enriched with highly radioactive granite batholiths and granite-migmatite domes (Taylor and McLennan, 1985) and shows Pv=6.06 km/s, an average density of 2.75 g/cm3 and A=1.33–1.75 µW/m3. The lower crust, brought to the surface by upthrusting along decollements, appears to be composed of thinly banded isoclinally folded granulites with intermediate to mafic and ultramafic compositions (Percival et al., 1992, Rutter and Brodie, 1992 and Zingg et al., 1990). Dates from the lower crustal rocks are “very poorly constrained” (Downes, 1993). This paper discusses the isotopically dated two-stages of lower crust formation and the absence of the upper crust in the Anabar shield.

Keywords

Shear Zone Lower Crust Siberian Platform Kimberlite Pipe Mafic Granulite 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

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Copyright information

© Kluwer Academic Publishers 1996

Authors and Affiliations

  • O. M. Rosen
    • 1
  1. 1.Institute of the LithosphereR.A.S.MoscowRussia

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