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Identifying deep recycled carbonates through Miocene basalts in the Maguan area, SE Tibetan Plateau

Lei, Hangshan and Zhao, Zhidan and Niu, Yaoling and Zhang, Shuangquan and Cousens, Brian and Ma, Qian and Teng, Fang-Zhen and Liu, Dong and Miao, Zhuang and Yang, Yiyun and Wu, Jingkai and Wang, Qing and Zhu, Di-Cheng (2021) 'Identifying deep recycled carbonates through Miocene basalts in the Maguan area, SE Tibetan Plateau.', Lithos, 400-401 .

Abstract

Cenozoic mantle-derived magmas are widespread on the Tibetan Plateau, and provide evidence for the evolution of deep mantle and its influence on the Plateau development. Miocene basalts in the Maguan area on the southeastern Plateau have high MgO (9.13–13.10 wt%) and Mg# (0.60–0.70) with high Ce/Pb (10.6–32.5) and Nb/U (43.7–52.9) ratios, similar to those of oceanic basalts. Distinct from Eocene-Oligocene mantle-derived potassic magmas in Western Yunnan and Cenozoic basic volcanic rocks in Tengchong, these Maguan basalts are characterized by high large ion lithophile elements (LILEs) concentrations, positive anomaly in high field strength elements (HFSEs) and depleted Srsingle bondNd isotopes, consistent with the melt of an asthenospheric mantle origin. The high Ce/Pb and Nb/Y (1.80–2.68) ratios together with low Ba/Y and Ba/Th ratios indicate a significant input of slab-derived melt into the asthenospheric source. Besides, Hf/Hf* and Ti/Ti* ratios are significantly lower than those of ocean island basalt (OIB), which are proportional to the lighter δ26Mg (-0.6‰ to -0.4‰) values. Based on the results of experimental petrology, the Srsingle bondMg isotope mixing model suggests that the asthenospheric mantle beneath the Maguan area had undergone the significant metasomatism of recycled carbonates prior to the late Miocene. The above petrological and geochemical understanding, together with the geophysical data, allows us to propose that the mantle metasomatism is most probably associated with the Neo-Tethys seafloor subduction, which is further testified by the decoupling between depleted Srsingle bondNd isotopes and elevated LILE concentrations.

Item Type:Article
Full text:Publisher-imposed embargo until 08 July 2022.
(AM) Accepted Manuscript
Available under License - Creative Commons Attribution Non-commercial No Derivatives 4.0.
File format - PDF
(16499Kb)
Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1016/j.lithos.2021.106356
Publisher statement:© 2021 This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Date accepted:08 July 2021
Date deposited:01 December 2021
Date of first online publication:14 July 2021
Date first made open access:08 July 2022

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