HR: 0830h
AN: T31D-0867    [PDF]
TI: Lithospheric Thermal Structure, Rifting-related Metasomatism, and Subsidence of the East European Platform
AU: * Artemieva, I M
EM: irina@eost.u-strasbg.fr
AF: EOST, Rue Rene Descartes, Strasbourg, 67084 France
AU: * Artemieva, I M
EM: irina@eost.u-strasbg.fr
AF: US Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025 United States
AB: A new mechanism for Paleozoic (Pz) subsidence of the early Proterozoic (ePt) East European Platform (EEP) is suggested, since a model of lithosphere tilting during the Uralian subduction (Mitrovica et al., 1996) does not explain the post-Uralian sedimentation record. The high topography of cratons is commonly attributed to depleted, low-density composition of the cratonic lithospheric mantle. Rifting, however, leads to a density increase of the cratonic lithosphere due to an intrusion of Fe-rich basaltic melts and can be responsible not only for subsidence due to thermal relaxation, but also for compositional subsidence. I propose that the Pt and Pz rifting events modified the cratonic lithosphere and are responsible for the post-Uralian subsidence of the EEP. To support this hypothesis, (a) the thermal regime of the EEP lithosphere is analyzed, and (b) lithospheric density variations of non-thermal origin are calculated from free-board constraints. The results suggest that the EEP subsidence can indeed result from chemical variations in the lithospheric mantle, possibly caused by metasomatism during Pt and Pz rifting. Pt rifting led to a decrease of lithospheric depletion from ca. 1.4% (Kola-Karelia) to 0.6-0.8% (central EEP) and possibly to a formation of a two-layer lithosphere, that can produce a seismic pattern similar to the top of a seismic LVZ at ca. 90-150 km depth. Pz rifting resulted in a compositional modification and/or detachment of the entire lithospheric column and the consequent, on-going, subsidence of the southern EEP.
DE: 7218 Lithosphere and upper mantle
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8124 Earth's interior--composition and state (old 8105)
DE: 8125 Evolution of the Earth
DE: 9335 Europe
SC: Tectonophysics [T]
MN: 2003 Fall Meeting