Mantle roots

Schmidberger S. S. and Francis D. (1999) Nature of the mantle roots beneath the North American craton mantle xenohth evidence from Somerset Island kimberlites. Lithos 48, 195-216. 

The mantle roots of Archean-Proterozoic cratons extend to depths in the range of 200-400 km (e.g., Jordan, 1978 Rudnick et al., 1998), and are sampled as xenoliths empted in kimber-litic lavas. Based on thermobarometric and textural evidence, a twofold classification of cratonic xenoliths has been made that includes (i) shallower, coarse-grained, low-temperature xenoliths (<—1,100°C), and (ii) deeper, sheared, high-temperature xenoliths (>—1,100 °C). 

Albarede F. (1998) The growth of continental cmst. In Continents and their Mantle Roots, Tectonophysics (eds. A. Vauchez and R. O. Meissner). Elsevier, Amsterdam, vol. 296 (1-2), pp. 1-14. 

Klosko E. R., Russo R. M., Okal E. A., and Richardson W. P. (2001) Evidence for a rheologicaUy strong chemical mantle root beneath the Ontong-Java Plateau. Earth Planet. Sci. Lett. 186, 347-361. 

Tomographic results show that high-velocity mantle roots extend locally to depths of at least 250 km beneath undisturbed Archaean craton, with no comparable root structures beneath post-Archaean terranes. Neither body- nor surface-wave analyses have yet produced evidence of a low-velocity zone beneath the cratonic keel (Ritsema van Heijst 2000 Freybourger et al. 2001 ... 

Hoffman, P. F. 1990. Geological constraints on the origin of the mantle root beneath the Canadian Shield. Philosophical Transactions of the Royal Society of London, Series A, 331, 523-532. 

Seismic studies of cratonal lithosphere at both the global and local scale indicate that Archaean cratons are sites of unusually thick, cold lithosphere, which may have mantle roots extending to depths of200-400 km compared with normal continental lithosphere, which is less than 150 km thick (e.g. van der Lee Nolet 1997 Ritsema et al. 1998 Ritsema van Heijst 2000 James Fouch 2002). Heat-flow data place some bounds on lithospheric thickness, but regional comparisons require major assumptions as to the lower-crustal contribution to radioactive heating. 

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