Petrogenesis and dynamic significance of Miocene-Holocene alkali basalts in the southeastern Tibetan Plateau

• Published in: Lithos 2023-07, Vol.448-449, p.107165, Article 107165
• Main Authors: Wu, Jingkai, Lei, Hangshan, Ma, Qian, Zhao, Zhidan, Teng, Fang-Zhen, Zhang, Shuangquan, Cousens, Brian, Miao, Zhuang, Yang, Yiyun, Liu, Dong, Wang, Qing, Zhu, Di-Cheng, Hou, Zengqian, Mo, Xuanxue
• Format: Article
• Language: English
• Subjects: Alkali basalts; Mantle metasomatism; Mantle-derived magma; Petrogenesis; Post-collisional; Southeastern Tibetan Plateau
• ISSN: 0024-4937; 1872-6143
• DOI: 10.1016/j.lithos.2023.107165

A series of Cenozoic post-collisional mantle-derived magmas developed in the Southeastern Tibetan Plateau (the SE Plateau), which can be utilized to trace source components and mantle metasomatism, and further constrain the mantle evolution. In this paper, we present a systematic study on petrography, whole-rock major and trace element, Sr-Nd-Pb-Mg isotopes of Miocene-Holocene alkali basalts at the southeastern margin of the SE Plateau. These Miocene-Holocene alkali basalts were the products of the northward extension of the Cenozoic mantle-derived magmatism in Southeast Asia (SE Asia), since they are comparable in terms of geographical distributions, petrographic characteristics, geochronology patterns, and geochemical compositions. The alkali basalts in this study are mainly basanite and trachybasalt, characterized by enriched LILEs, depleted Sr-Nd-Pb isotopes, positive anomaly in HFSEs, and significantly lighter Mg isotopes (−0.51‰ to −0.32‰) relative to primitive mantle. Integrated Sr-Nd-Mg isotopes and seismic tomography suggest a source regions from the mantle transition zone that has been enriched by significant carbonate sediments. The decoupling of high Sr contents and depleted SrNd isotopes in the alkali basalts indicate that the mantle carbonation is subjected to recent subduction events and is possibly related to the subduction of the Neo-Tethyan seafloor. The calculated melting temperature of these basalts are generally high (1487–1583 °C), which is consistent with that of Cenozoic basalts in SE Asia (1470–1480 °C) and Hainan island (1480–1530 °C), showing a high-temperature gradient similar to that of mantle plume-related magmatism. Consequently, the generation of Miocene-Holocene alkali basalts is plausibly associated with the Hainan plume. •Sanjiang alkaline basalts are the northward extension of basalts in Southeast Asia.•Sanjiang alkali basalts are originated from the mantle transition zone.•Alkali basalts in the southeastern Plateau originated from the carbonated mantle.•Alkali basalts are related to the Hainan mantle plume.