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Petrogenesis of Triassic granitoids in the East Kunlun Orogenic Belt, northern Tibetan Plateau and their tectonic implications

: Shao, F.L.; Niu, Yaoling; Chen, S.; Kong, J.J.; Meng, Duan

Petrogenesis of Triassic granitoids in the East Kunlun Orogenic Belt, northern Tibetan Plateau and their tectonic implications Thumbnail


Authors

F.L. : Shao

Yaoling Niu

S. Chen

J.J. Kong

Duan Meng



Abstract

The East Kunlun Orogenic Belt (EKOB), an important part of the Greater Tibetan Plateau, is an ideal region for understanding the tectonic evolution of the Anyemaqen Ocean. Here, we present zircon U–Pb ages, bulk-rock major and trace element analyses and Sr-Nd-Hf isotope compositions on representative samples of the syn-collisional Dulan batholith at the eastern end of the EKOB. The zircon U–Pb age data indicate that the bulk of the Dulan batholith was emplaced at 240–235 Ma. The granitoids have high- to medium-K and metaluminous characteristics. They are enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs) and depleted in some high field strength elements (HFSEs, e.g., Nb and Ta), while having a flat heavy REE (HREEs) pattern. The mafic magmatic enclaves (MMEs) share the same age, mineralogy and indistinguishable Sr-Nd-Hf isotopes with their granitoid hosts except for the higher HREE abundances. We show that the MMEs represent cumulate formed at earlier stages of the same magmatic system. The trace element data (e.g., Nb/Th, Ta/U) and inherited mantle isotopic characteristics of the Dulan batholith are also consistent with an origin via partial melting of the last fragments of underthrusting ocean crust. Simple mass balance calculations using the Sr-Nd-Hf isotopic data show that ~ 85% Paleo-Tethys MORB and ~ 15% mature crustal material (the Proterozoic gneiss of the study area) contribute to the source of the granitoids. The Dulan batholith shows compositional similarities to the bulk continental curst with inherited mantle isotopic signatures. The syn-collisional felsic magmatism must have contributed to the net continental crust growth in the EKOB. We infer that the Kunlun and Qinling orogens may actually be one single orogen offset later by the Wenquan fault system

Citation

: Shao, F., Niu, Y., Chen, S., Kong, J., & Meng, D. (2017). Petrogenesis of Triassic granitoids in the East Kunlun Orogenic Belt, northern Tibetan Plateau and their tectonic implications. Lithos, 282-283, 33-44. https://doi.org/10.1016/j.lithos.2017.03.002

Journal Article Type Article
Acceptance Date Mar 2, 2017
Online Publication Date Mar 9, 2017
Publication Date Jun 1, 2017
Deposit Date Mar 13, 2017
Publicly Available Date Mar 28, 2024
Journal Lithos
Print ISSN 0024-4937
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 282-283
Pages 33-44
DOI https://doi.org/10.1016/j.lithos.2017.03.002

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