U-Pb and Sm-Nd Isotopic Study of the Upper Riphean to Paleozoic Sandstones from the Taimyr Fold-and-Thrust Belt: Implication for Late Paleozoic and Mesozoic Tectonic Evolution
Andrei K. Khudoley1, Vasily F. Proskurnin2, and Sergey A. Sergeev2
1St. Petersburg State University, St. Petersburg, Russia.
2VSEGEL, St. Petersburg, Russia.
An upper Riphean - Paleozoic sedimentary succession exposed in the central and southern zones of the Taimyr fold and thrust belt contains several thick clastic units. We collected five samples from the upper Riphean - Lower Cambrian unit and one sample from the Lower Permian unit for U-Pb detrital zircon and Sm-Nd whole-rock isotopic analysis. Both U-Pb and Sm-Nd studies were done at VSEGEI, St. Petersburg.
All samples collected from the upper Riphean - Lower Cambrian unit have similar isotopic characteristics. Two samples from the upper Riphean redbeds show predominance of detrital zircon grains with ages varying from 800 Ma to 950 Ma. Approximately 40% of grains are Paleoproterozoic and Archean. Vendian sandstone samples also have many zircons of 780-950 Ma, but samples from southern Taimyr show significant amount of 1930 Ma - 2020 Ma grains, whereas sample from central Taimyr contains several detrital grains of 640-605 Ma. Source of 640-605 Ma grains is not clear, whereas all other grains have local granite intrusion or Siberian craton basement source. A mixture of local and Siberian craton sources is assumed from Sm-Nd isotopic data as well.
In the Permian sandstone sample, detrital zircon grains with age varying from 440 Ma to 540 Ma predominate, although some peaks at 300 Ma and 780 Ma occur as well. The only possible sources for most grains are granite and metamorphic rocks from northern zone of the Taimyr fold and thrust belt and Kara plate. No evidence for erosion of the Siberian craton is documented. Absence of Paleoproterozoic and Archean grains widespread in the upper Riphean - Lower Cambrian clastic units also points to no erosion of the central zone of the Taimyr fold and thrust belt. Whole-rock Sm-Nd isotopic study show evidence of erosion of oceanic-type rocks which also supports location of source area in the Taimyr fold and thrust belt.
Combined results of U-Pb detrital zircon and Sm-Nd whole-rock studies of Permian sandstone with reference to those of upper Riphean - Lower Cambrian sandstones imply that during Permian both southern and central zones of the Taimyr fold and thrust belt were lowlands and no divide separated eroded northern Taimyr from sedimentary basin in its southernmost part. It demonstrate that no Hercynian tectonic event affected southern zone of the Taimyr fold and thrust belt and numerous thrusts which cut Vendian - Paleozoic succession of the southern zone were formed during a Mesozoic tectonic event.
AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia