Contraints On Lithospheric Extension From Break-Up Of The Proterozoic Siberia-Laurentia Connection
Abstract
A robust Proterozoic plate reconstruction that joins the NE Siberian and SW North American cratons provides constraints on tectonic, sedimentary, and thermal evolution of lithospheric extension leading to continental break-up. The reconstruction blends clues from Siberia and North America to show that the lithospheric extension occurred in temporally isolated episodes spanning more than one billion years. The first episode culminated in opening of the intracratonic Mesoproterozoic Belt basin at about 1.5 Ga, with widespread anorogenic magmatism, dike swarms, and rifting. It may have responded to drift stagnation of the parent supercontinent with attendant entrapment of heat and thermal expansion of the sub-lithospheric mantle. The rifting and magmatism followed a continent-wide icosahedral pattern but did not open into sea-floor spreading. The second episode took place at about 780 Ma, much along the lines of the first rifts, culminating in the Gunbarrel magmatic event and Windermere rift sedimentation, as drift stagnation and thermal expansion re-opened the older icosahedral lithospheric fractures. The third episode began in latest Proterozoic to earliest Cambrian, and proceeded to sea-floor spreading and thermal subsidence of conjugate margins, with transform movement along some earlier rift lines. Transform segments of the rift system evolved into steep continental margins, as along the Rocky Mountain trench of Canada, whereas linking segments formed low-angle detachment surfaces with broad continental shelves on upper and lower plates, as in the Verkhoyansk Mountains of Siberia and and conjugate Great Basin of North America. The relative pole of rotation between the cratons appears to have shifted in Late Devonian leading to renewed extension and mafic magmatism in some areas and convergence in other areas of the developing conjugate margins. The overall history implies that initial rifting of sluggish supercontinents may be driven by thermal expansion of insulated asthenosphere, but that an advance to seafloor spreading awaits permissive plate-tectonic circuits that exploit previously opened lithospheric fractures.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.T31C1833S
- Keywords:
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- 8110 TECTONOPHYSICS / Continental tectonics: general