Petrogenesis of the ca. 820–810 Ma felsic volcanic rocks in the Bikou Group: Implications for the tectonic setting of the western margin of the Yangtze Block

Age, genesis, and geological significance of Permian–Triassic boundary volcanic tuffs in the northeastern margin of South China

“…In the Zuoshan section in this study, the Permian tuff contains a high proportion (52%) of zircons with positive ε Hf ( t ) values. If zircons with positive ε Hf ( t ) values are interpreted as the recycling of Neoproterozoic crustal materials, the age of the early Neoproterozoic crustal accretion activities (1220–705 Ma, especially 970–720 Ma) in the north to the western margin of the SCB (Cai et al, 2021; Liu, Yang, et al, 2015; Wang, Xu, & Santosh, 2019; Wang et al, 2021; Wu et al, 2019), which are rare in the NCB, is equivalent to the T DM2 age of zircons with positive ε Hf( t ) values, indicating that the Neoproterozoic materials on the northern SCB have involved the source magma of the Permian tuff in the Zuoshan section. Referring to middle and late Triassic magmatic records related to subduction and collision of the Mianlue Ocean in western Qinling Orogenic Belt (Gou et al, 2019; Zhang, Qiu, et al, 2021), the zircons with positive ε Hf ( t ) values, interpreted as the addition of juvenile mantle‐derived materials, occur in the syn‐collisional to post‐collisional (210–220 Ma) granites (Figure 11; Ping et al, 2013; Qin et al, 2013; Yang, Liu, et al, 2012), also supporting that the zircons with positive ε Hf ( t ) value from the Permian tuff can be used as an indicator of the beginning of the continental subduction and continent‐continent collision.…”

Neoproterozoic active margin in the northwestern Yangtze Block, South China: new clues from detrital zircon U–Pb geochronology and geochemistry of sedimentary rocks from the Hengdan Group

“…and the overlying c. 750-720 Ma siliciclastic Liantuo Formation (XM J Wang et al 2013;Pi & Jiang, 2016). The SE margin is predominantly characterized by a large proportion of meta-sedimentary rocks and parts of c. 830-820 Ma granitic plutons XL Wang et al 2004, 2014bZheng et al 2008;Xue et al 2010;Yao et al 2014;Wu et al 2019;Hui et al 2020b). All these units are unconformably overlain by Cryogenian-Ediacaran strata, which are mainly composed of glacial to epicontinental marine deposits (e.g.…”

“…Zhou et al 2002Zhou et al , 2006aDong et al 2011Dong et al , 2012Zhao et al 2018) have been proposed. As a consequence, many scholars have disparate interpretations of the Neoproterozoic tectonics of the Bikou Terrane (Pei, 1989;Xu et al 2002;Yan et al 2004;Lai et al 2007;Xiao et al 2007;XC Wang et al 2008;Ye et al 2009;W Wang et al, 2012;Xia et al 2012;Wu et al 2019).…”

“…The main reason for these contradictory interpretations is identification of different types of volcanic rocks in the Bikou Group. For instance, some studies report the occurrence of some oceanicisland and mid-ocean-ridge-featured basalts as well as several bimodal volcanics, and thus suggest that they were formed in a continental rifting setting related to a c. 820-810 Ma mantle plume (Xu et al 2002;Lai et al 2007;Wang et al 2008;Xia et al 2012;Wu et al 2019). Alternatively, Pei (1989) and Yan et al (2004) suggest that a large amount of c. 845-770 Ma volcanic rocks developed in a subduction-related arc setting, based on their typical arc chemical characteristics.…”

“…Therefore, the Bikou Terrane in the NW margin of the Yangtze Block was mainly controlled by a subduction process during the early Neoproterozoic period. These multi-genetic volcanic rocks, along with corresponding sedimentary sequences in the Bikou Group, may represent the products formed under different tectonic settings that subsequently collaged together in late processes (Pei, 1989;Xu et al 2002;Yan et al 2004;Lai et al 2007;Xiao et al 2007;XC Wang et al 2008;Ye et al 2009;W Wang et al 2012; Xia et al 2012;Wu et al 2019). Nevertheless, further detailed studies remain necessary to test this hypothesis.…”