Structure of the Southern Province, Canadian Shield, inferred from scaled 3-D analogue modelling using viscous and granular materials
Zusammenfassung der Projektergebnisse
The Sudbury Basin is a non-cylindrical fold basin occupying the central portion of the Sudbury Impact Structure. To better understand the evolution of structures associated with basin formation, we conducted a series of analogue experiments that were scaled to length, density, viscosity and time. The experimental setup of models consists of a rectangular plexiglass tank filled with layers of com syrup, polydi methyl si loxane (PDMS), PDMS blended with plasticene and various fillers, and granular materials with Mohr-Coulomb rheology. These layers represent respectively the lithospheric mantle, lower crust, middle crust and sedimentary cover rocks. Bulk horizontal shortening ofthe layers was imposed by a piston moving at a constant rate. Meteorite impact removed upper crust in a circular area, about 100 km in diameter, and lead to heating of crust underlying this area. These effects were modeled by omission of granular material in a circular area that is equivalent in size to the mechanical crustal heterogeneity produced by the impact. Model basins mimic many first-order structural characteristics of the Sudbury Basin. Similarities of model and natural prototype include the variable geometry of basin flanks, structures indicating concentric shortening around lateral basin termini and the presence ofa zone of strain concentration at the hinge zones of model basins. Geometrically and kinematically this zone corresponds to the South Range Shear Zone ofthe Sudbury Basin. According to the models, this shear zone is a direct mechanical consequence of basin formation, rather than the result of thrusting following folding. Overall, the models feature the structurally anomalous character of the Sudbury Basin within the Paleoproterozoic Eastem Penokean Orogen. In particular, the Basin formed by pure thickening of crust, whereas transpressive deformation prevailed elsewhere in the orogen. Distict model transpression zones formed due to gradients in the mechanical strength of crust. The models suggest that the Sudbury Basin formed as a consequence of strain localization in the crust that was transiently hotter and mechanically weakened by meteorite impact.
Projektbezogene Publikationen (Auswahl)
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2007. Kinematic evolution of the Sudbury Basin inferred from scaled analogue modelling and structural ground truth. Bridging the Gap ll: Effect of Target Properties on the Impact Cratering Process, p. 105. LPI Contribution 1360, Lunar and Planetary Institute, Houston
Riller, U., Boutelier, D, Cruden, A.R., and Schrank, C.
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2007. Scaled analogue modelling of basement-involved folding with application to the eastern Penokean orogen and the Sudbury impact structure, Ontario, Canada. Annual meeting, Geological Association of Canada/Mineralogical Association of Canada, Abstracts, Vol. 32, p. 69
Riller, U., Boutelier, D., and Cruden, A.R.
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2008. Deformation localization during shortening of heterogeneous crust. North-eastern Section Meeting of the Geological Society of America. Abstract No, 135514. GSA Abstracts with Programs Vol. 40, No. 2
Cruden, A.R., Schrank, C , and Riller, U.
