Sedimentary response to the non-synchronous closure of Paleo-Asian Ocean: evidence from U-Pb ages and Hf isotopic compositions of detrital zircons from the Linxi Formation, NE China

ABSTRACT

The Linxi Formation is widely deposited in eastern Inner Mongolia (NE China), especially along northern parts of the Solonker-Xar Moron Suture (SXMS) in the eastern Central Asian Orogenic Belt, yet its depositional age and provenance remain ambiguous. We studied the petrography, geochronology, and Hf isotopes of two sandstone samples from this formation, and estimated the depositional age and the provenance of the Linxi Formation, and further constrained the evolution of the Paleo-Asian Ocean (PAO). Based on detailed field observations and measurements, we. Zircons from rocks of the Linxi Formation are mainly composed of detrital zircons of magmatic origin. The determined ages of detrital zircons range from 233 ± 2 Ma to 1365 ± 14 Ma, and indicate that the provenance of the Linxi Formation experienced at least four tectonic-thermal events between 1365 and 233 Ma: Neoproterozoic (ca. 1365–543 Ma), Early Palaeozoic (ca. 512–426 Ma), Late Palaeozoic (ca. 418–251 Ma), and Early Mesozoic (ca. 249–233 Ma). The youngest detrital zircon, with a U-Pb age of 233 ± 2 Ma, defines the maximum depositional age of the Linxi Formation. The ε_Hf (t) values of dated zircons from the sandstone samples have a large range (−7.8–15.0). The four dominant age groups and the range in ε_Hf (t) values are widely found in the Xing’an Block and Songnen-Zhangguangcai Range, which imply that the source of the Linxi Formation had an affinity with northeastern China. These data together with previous geochronological data (from west to east along the SXMS) on the crystallization and depositional ages of detrital zircon suggest that the Linxi Formation was deposited in different tectonic settings: convergent, collisional, and extensional. This study provides further evidence and constraints for the non-synchronous closure of the PAO.

Graphical abstract

KEYWORDS:

• Zhalute area
• Linxi Formation
• Paleo-Asian Ocean
• Detrital zircons
• Hf isotopes
• NE China

Highlights

• The Linxi Formation was mainly deposited during the Late Permian and extended to the Late Triassic.

• The provenances of the Linxi Formation mainly derived from the XMOB, thus implying that the PAO closed at ~233 Ma in the Zhalute area.

• Non-synchronous closure of the PAO (from the west to the east) occurred in the eastern CAOB.

Acknowledgments

We thank Prof. Robert Stern, Editor in Chief, and two anonymous reviewers for their constructive suggestions that helped us to improve the manuscript. We also thank the staff of Tianjin Geological Mineral Testing Center, Tianjin, China, for their advice and assistance during zircon U-Pb dating by LA-MC-ICP-MS and in situ zircon Hf isotopic analysis. We gratefully acknowledge the research funding from the National Key R&D Program of China (No. 2017YFC0601304) and the China Geological Survey Program (No. DD20160048 and No. 12120115031701).

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the China Geological Survey Program [DD20160048; 12120115031701];National Key R&D Program of China [2017YFC0601304].