Ordovician to Triassic episodic growth of the Dananhu arc, Eastern Tianshan (NW China)

ABSTRACT

The evolution and closure timing of the Paleo-Asian Ocean are controversial in the Eastern Tianshan orogen, southern Altaids. The Dananhu arc of the Eastern Tianshan was involved in the long-lived evolution and terminal tectonic events during the formation of the Altaids, and its magmatic rocks are the faithful recorder. To constrain the subduction history of the Paleo-Asian Ocean, we review the tectonic of the Dananhu arc, by summarizing the geochemical and geochronological data of granites and volcanic rocks and mineral deposits, which will shed light on the accretionary history, closure of the Paleo-Asian Ocean, and the continental growth in Altaids. Zircon U-Pb ages of the granitic rocks across the middle of the Dannanhu arc range from 453 Ma to 227 Ma and demonstrate overall southward younging through four main areas: the Kalatage belt (ca. 453–299 Ma), the Keizer belt (ca. 401–268 Ma), the Tuwu belt (360–302 Ma), and the Kanguer subduction complex (ca. 288–227 Ma). These granitic rocks are calc-alkaline arc-related and adakitic granites that are enriched in Si and K. They increase in Th/Yb and decrease in Cr and Ce/Pb southwards over time. The consistent geochemical variations indicate progressive maturity of the arc crust. Their whole-rock ε_Nd(t) and zircon ε_Hf(t) values coordinated with the progressive change in the crustal thickness estimated by the granites indicate a multi-phase switching of subduction. The Ordovician to Permian granitic rocks in the arc have stable high whole-rock ε_Nd(t) values (ca. +5 – +10), and zircon ε_Hf(t) values (ca. +7-+16), which significantly shifted to +2 – +4 and +4 – +12 during ca. 243–227 Ma. These changing relations accompanied a sudden crustal thickening, suggesting that continental crustal material was involved in the petrogenesis of these rocks during the convergence among the Dananhu arc, the Harlik and the Yamansu-central Tianshan continental arc.

Graphical Abstract

KEYWORDS:

• Growing arc
• younging southward
• ordovician to triassic
• subduction switch
• eastern tianshan orogen

Acknowledgments

We are grateful to Editor Robert J. Stern and two anonymous reviewers whose critical comments and constructive evaluation have significantly improved the quality of the paper. This study was financially supported by the Third Xinjiang Scientific Expedition Program (2022xjkk1301), the National Natural Science Foundation of China (41888101, 41822204), One Hundred Talent Program of the Chinese Academy of Sciences (E2250403), Science and Technology Major Project of Xinjiang Uygur Autonomous Region, China (2021A03001 & 4). This is a contribution to IGCP 622, IGCP 629 and IGCP 710.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00206814.2022.2161076

Additional information

Funding

This work was supported by the Third Xinjiang Scientific Expedition Program [2022xjkk1301], Science and Technology Major Project of Xinjiang Uygur Autonomous Region, China [2021A03001-1 & 4, 2022A03010-1-1]; the Third Xinjiang Scientific Expedition Program [2022xjkk1301]; One Hundred Talent Program of the Chinese Academy of Sciences (CAS) [E2250403].