Ages and Hf isotopes of detrital zircons from the Permian strata in the Bengbatu area (Inner Mongolia) and tectonic implications

Xu, B., Zhao, G., Li, J., Liu, D., Wang, B., Han, Y., Eizenhoefer, P. , Zhang, X., Hou, W. and Liu, Q. (2019) Ages and Hf isotopes of detrital zircons from the Permian strata in the Bengbatu area (Inner Mongolia) and tectonic implications. Geoscience Frontiers, 10(1), pp. 195-212. (doi: 10.1016/J.GSF.2018.08.003)

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Abstract

The Central Asian Orogenic Belt (CAOB) was built up through protracted accretion and collision of a variety of terranes/micro-continents during Neoproterozoic–Mesozoic time. To understand potential links among Paleozoic subduction and accretionary processes that were operative during the development of the southeastern CAOB, we conducted a combined U-Pb and Hf-isotope analysis of detrital zircons from previously defined Devonian, Carboniferous and Early Permian strata in the Bengbatu area, Inner Mongolia. Detrital zircons from (meta-) sandstones in these strata commonly yield major Paleozoic age populations at ca. 300–261 Ma, 351–300 Ma and 517–419 Ma, and also give several Precambrian ages that range from 2687 Ma to 544 Ma. The youngest ages redefine the deposition of all these strata to be in the Middle Permian (Wordian–Capitanian) or later, much younger than previously considered. These ages, coupled with regional magmatic records, support an interpretation of most surrounding areas as possible detritus sources, including the Mongolian arcs to the north, the Northern Accretionary Orogen to the south, and the intervening Erenhot–Hegenshan Ophiolite Belt. Zircons with magmatic ages of ca. 500–350 Ma and ca. 300–261 Ma display a large range of εHf(t) values (−13.97 to +15.31), whereas ca. 350–300 Ma zircons are dominated by positive εHf(t) values (+0.14 to +16.00). These results support the occurrence of two significant shifts of the zircon εHf(t) values, which has tectonic implications for the understanding of the Carboniferous–Permian evolution of the southeastern CAOB. A marked shift from mixed to positive zircon εHf(t) values at 350–330 Ma likely manifests the incipient opening of the Hegenshan Ocean, due to the slab rollback of the subducting Paleo-Asian Oceanic lithosphere. Another shift from positive to mixed zircon εHf(t) values at ca. 300 Ma likely corresponds to a tectonic switch from syn-orogenic subduction-related to post-orogenic extensional setting, genetically related to the tectonic collapse of a formerly overthickened crust.

Item Type:Articles
Additional Information:This research was financially supported by the National Natural Science Foundation of China (Grant Nos. 41730213, 41190075, 41190070), the Hong Kong Research Grants Council General Research Fund (17301915), and the HKU Seed Funding Programme for Basic Research (201611159210). This paper is a contribution to IGCP#648.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:UNSPECIFIED
Authors: Xu, B., Zhao, G., Li, J., Liu, D., Wang, B., Han, Y., Eizenhoefer, P., Zhang, X., Hou, W., and Liu, Q.
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
Journal Name:Geoscience Frontiers
Publisher:Elsevier
ISSN:1674-9871
ISSN (Online):2588-9192
Published Online:30 August 2018
Copyright Holders:Copyright © 2018 China University of Geosciences (Beijing) and Peking University.
First Published:First published in Geoscience Frontiers 10(1):195-212
Publisher Policy:Reproduced under a creative commons licence
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