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HPP-01 General contributions to Precambrian geology
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Meso- and Neoproterozoic evolution of southern Siberia: A billion year gap in magmatism and sedimentation
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Dmitry Gladkochub, Institute of the Earth?s Crust, Siberian Branch of Russian Academy of Sciences (Russian Federation)
Eugene Sklyarov, Institute of the Earth?s Crust, Siberian Branch of Russian Academy of Sciences (Russian Federation)
Tatiana Donskaya, Institute of the Earth?s Crust, Siberian Branch of Russian Academy of Sciences (Russian Federation)
Sergei Pisarevsky, The University of Edinburgh (United Kingdom)
Anatoliy Mazukabzov, Institute of the Earth?s Crust, Siberian Branch of Russian Academy of Sciences (Russian Federation)
Michael Wingate, Geological Survey of Western Australia (Australia)
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The Siberian craton is generally assumed to have been a part of the Paleo-Mesoproterozoic supercontinent Nuna (Columbia) as well as the Meso-Neoproterozoic supercontinent Rodinia. Recent geochronological data indicate that a c. 1.9 Ga peak of magmatic activity and metamorphism in the southern Siberian craton was probably related to its incorporation into Nuna. A younger (c. 0.7 Ga) peak of igneous activity in southern Siberia probably reflects the breakup of Rodinia. Paleomagnetic reconstructions suggest that in both Precambrian supercontinents, the southern margin of Siberia was located opposite northern Laurentia.
Until recently, a number of igneous complexes in southern Siberia were considered to be of Mesoproterozoic age. However, our new geochronological data discount Mesoproterozoic ages for these rocks and reveal a c. 1 billion year gap in igneous activity and the absence of sedimentary sequences with ages between c. 1.7 and 0.7 Ga. The absence of igneous activity (in 'Grenville' time in particular) in the area studied can be explained by its location within the interior of a Proterozoic mega-continent - a large fragment of Nuna (Columbia) composed of Laurentia, Siberia, and possibly some minor continental blocks. Recent paleomagnetic data support its existence at least since c. 1.5 Ga. Later this mega-continent became part of the core of Rodinia. It broke apart around 0.7 Ga simultaneously with dispersion of Rodinia.
The absence of Mesoproterozoic sediments in southern Siberia could be explained by their erosion, transportation from marginal uplands (orogenic belts), and accumulation in adjacent basins. According to some paleomagnetic reconstructions, these basins could have been located between southern Siberia and northern Laurentia, and moved away from Siberia following Neoproterozoic breakup.
Ediacaran shallow-water sediments cover the entire Siberian craton, suggesting its subsidence following Rodinia breakup. We assume that the dense lithospheric keel of the Siberian craton could cause this subsidence after detachment of more buoyant crustal blocks south of the craton. Solidification of magma chambers that fed Neoproterozoic mafic dyke swarms and glacial loading caused by late Neoproterozoic ice sheets may also have contributed to the subsidence. A similar style of late Neoproterozoic evolution (dyke intrusion - glaciation - subsidence) is suggested in other Archean cratons with lithospheric keels. Probably the combination of factors mentioned above provides a significant influence on global tectonics controlling surface uplifts and subsidence of ancient cratons.
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