Dating of detrital zircon grains and fossils from Late Palaeozoic sediments of the Baruo area, Tibet: constraints on the Late Palaeozoic evolution of the Lhasa terrane

ABSTRACT

To determine the Late Palaeozoic evolution of the Lhasa terrane, we report the results of field mapping, petrological and fossil investigations, and U–Pb dating of detrital zircon grains (n = 474) from lower-greenschist-facies clastic rocks of the Lagar Formation in the Baruo area, Tibet. Our results indicate that the Lagar Formation was deposited during the Late Carboniferous to Early Permian in a shallow-marine environment on the northern margin of Gondwana. Glacial marine diamictites are common within the Lagar Formation and record glaciation of Gondwana during the Late Palaeozoic. Moreover, the detrital materials of the Lagar formation originated mostly from the collision orogenic belt. The ages of detrital zircon grains from the Lagar Formation make up five main groups with ages of 410–540 Ma, 550–650 Ma, 800–1100 Ma, 1600–1800 Ma, and 2300–2500 Ma, which display three characteristic age peaks at ~1150, 2390 and 2648 Ma. We tentatively suggest that the Lhasa terrane was a shallow-marine basin under the influence of the Gondwanan glaciation during the Late Carboniferous–Early Permian.

Graphic abstract

KEYWORDS:

• Tibet
• Lhasa terrane
• detrital zircons
• fossil
• Late Palaeozoic

Highlights

• The Lagar Formation was deposited in a shallow-marine environment and contains abundant glacial marine diamictite deposits.

• The Lagar Formation records the glaciation of Gondwana during the late Palaeozoic.

• The Lagar Formation records the late Palaeozoic sedimentary record of the Lhasa Plate, on the northern margin of Gondwana.

• The early Palaeozoic geological record of the Lhasa Plate is similar to that of other plates in Tibet.

• The Lhasa terrane was a shallow-marine basin during the Late Carboniferous–Early Permian.

Acknowledgments

We thank the journal editor for useful comments and effective editorial handling. We are grateful to two anonymous reviewers for constructive comments that have improved the quality of this paper. This research was funded by the National Science Foundation of China [grant numbers 41602230 and 41702227] and China Geological Survey [grant numbers DD20160026]. We thank the staff of the Geological Laboratory Center of China, University of Geosciences (Beijing, China), for help with the LA–ICP–MS zircon U–Pb dating, and the staff of the Institute of Physics, Beijing University, for help with CL imaging. We also thank Dr Zhang Tianyu, and Dr Liu Yiming for their assistance in the field.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

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Additional information

Funding

This work was supported by the National Natural Science Foundation of China [41602230 and 41702227].