HR: 1340h
AN: T13A-0438    [Abstracts]
TI: The Preservation of Crustal Roots in Cratons: Constraints on Lithospheric Strength
AU: * Jaupart, C
EM: cj@ccr.jussieu.fr
AF: Institut de Physique du Globe, 4 Pl Jussieu, Paris, 75252 France
AU: Perry, C
EM: perry@ipgp.jussieu.fr
AF: Institut de Physique du Globe, 4 Pl Jussieu, Paris, 75252 France
AU: Perry, C
EM: perry@ipgp.jussieu.fr
AF: GEOTOP-UQAM-McGill, University Of Quebec at Montreal, P.O.B. 8888, sta. "downtown", MONTREAL, QC H3C3P8 Canada
AU: Mareschal, J
EM: jcm@olympus.geotop.uqam.ca
AF: GEOTOP-UQAM-McGill, University Of Quebec at Montreal, P.O.B. 8888, sta. "downtown", MONTREAL, QC H3C3P8 Canada
AB: Tectonic events and emplacement of large mafic intrusions induce lateral variations in crustal thickness and density which induce deviatoric stresses ~10-30MPa. In the Canadian Shield and the Kaapvaal craton, seismic reflection and refraction studies show that the Moho is flat in regions that have experienced compression. One explanation is that with past crustal heat production higher than present, the lower crust was hot and weak and could not sustain the stress induced by a crustal root. Within the Canadian Shield a few crustal roots have been preserved: (1) the 1.9Ga Kapuskasing structural zone in the Archean Superior Province, (2) the LynnLake region in the 1.8Ga Trans Hudson Orogen, (3) the eastern part of the 1.1Ga Grenville Front, (4) the 1.1Ga Keweenawan rift system beneath Lake Superior. The average of all the heat flow values available in the southern Canadian Shield is 41mW~m^-2. In all the regions where a crustal root has been maintained, we noted that the heat flow is low: 33mW~m^-2 at Kapuskasing, 28mW~m^-2 at Lynn Lake, 28mW~m^-2 at the Grenville Front east, 30-35mW~m^-2 beneath Lake Superior. For all these regions, we have back-calculated crustal heat production and heat flow and determined lithospheric temperatures after the time of formation of the crustal root. We show that temperatures in the lower crust remained sufficiently low and that the rheology was sufficiently strong for the crust to sustain the stress due to crustal thickening without flow.
DE: 8103 Continental cratons
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8159 Rheology: crust and lithosphere (8031)
DE: 8164 Stresses: crust and lithosphere
SC: Tectonophysics [T]
MN: Fall Meeting 2005