Issue |
Bull. Soc. géol. Fr.
Volume 188, Number 1-2, 2017
Insights to the geology and paleontology of Siberia from French-Siberian collaboration in Earth Sciences
|
|
---|---|---|
Article Number | 8 | |
Number of page(s) | 29 | |
Section | Tectonics in the Transbaikal region and Altaï-Sayan area | |
DOI | https://doi.org/10.1051/bsgf/2017009 | |
Published online | 02 June 2017 |
BSGF – Earth Sciences Bulletin
Early to Middle Jurassic history of the southern Siberian continent (Transbaikalia) recorded in sediments of the Siberian Craton: Sm-Nd and U-Pb provenance study
L’histoire Jurassique inférieur-moyen du Sud du continent Sibérien (Transbaikalia) enregistrée dans les sédiments du craton Sibérien : analyse de provenance par Sm-Nd et U-Pb
1
Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia
2
Kazan Federal University, Kazan, Russia
3
A.P. Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia
* Corresponding author: dem@crust.irk.ru
Received:
8
August
2016
Accepted:
19
January
2017
The deposition of Jurassic continental sedimentary rocks in the southern part of the Siberian continent (Transbaikalia) reflects the intensification of tectonomagmatic processes in this region. The most likely cause of this intensification was associated with the formation and development of the Mongol-Okhotsk orogenic belt. The latter was controlled in its turn by the closure of the Mongol-Okhotsk Ocean, for which the timing of its closure, as well as the formation of a collisional orogeny and its subsequent collapse are still under debate. We address this question by studying sediments of the Irkutsk Basin, which were deposited in a short time span in the Middle Jurassic, most likely during the Aalenian. The Sm-Nd data for bulk-rock sandstones demonstrate that the youngest samples of the Irkutsk Basin are characterized by a prominent contribution from a source within the juvenile crust of the Mongol-Okhotsk orogenic belt. U-Pb detrital zircon ages concur with the Sm-Nd data and show that the amount of material derived from local cratonic sources decreased in time whereas material from the remote Transbaikalian sources increased. Our data provide evidence that mountain growth in Transbaikalia intensified rapidly close to the Early and Middle Jurassic boundary.
Résumé
Le dépôt de sédiments continentaux jurassiques dans la partie sud du continent Sibérien (Transbaikalie) reflète l’intensification des processus tectono-magmatiques dans cette région. La cause la plus probable de cette activité est le développement de l’orogène Mongol-Okhotsk qui a suivi, lequel fut contrôlé par la fermeture de l’océan Mongol-Okhotsk, dont l’âge, ainsi que la formation, puis la destruction de l’orogène sont encore discutés. Nous essayons de répondre à ces questions en analysant les dépôts sédimentaires du bassin d’Irkutsk, lesquels ont été déposés dans un temps très court, probablement pendant l’Aalénien. L’analyse Sm-Nd des grès montre que les échantillons les plus jeunes du bassin d’Irkutsk sont caractérisés par une contribution majeure d’une source de type croûte juvénile en lien avec l’orogène Mongol-Okhotsk. Les âges U-Pb sur zircons détritiques confirment les données Sm-Nd et indiquent que le matériel issu d’une source locale cratonique diminue au fil du temps alors que l’apport de matériel en provenance de la zone Transbaikale, plus éloignée, augmente. Nos données démontrent que la surrection des montagnes dans la zone Transbaïkale a été rapide autour de la limite Jurassique inférieur-moyen.
Key words: Mongol-Okhotsk Ocean / Jurassic / Irkutsk Basin / Siberia / Sm-Nd / U-Pb
Mots clés : Océan Mongol-Okhotsk / Jurassique / Bassin d’Irkutsk / Sibérie / Sm-Nd / U-Pb
© SGF, Published by EDP Sciences 2017
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