Provenance of a Permian accretionary complex (Nishiki Group) of the Akiyoshi Belt in Southwest Japan and Paleogeographic implications

Tectonic Switching of Southeast China in the Late Paleozoic

“…Recently, an oceanic island arc (proto-Japan arc) outboard of eastern south China has been delineated by some geologists to interpret the geological history of SW Japan in the Paleozoic (Figure 11a; e.g., Cocks & Torsvik, 2013;Domeier & Torsvik, 2014;Isozaki et al, 2010). The subduction of the Paleo-Pacific plate beneath the proto-Japan arc may have started in the Early Paleozoic (Aoki et al, 2015;Hara et al, 2018;Zhang et al, 2018), consistent with its counterpart along the Paleo-Pacific east Gondwana margin (Cawood & Buchan, 2007). According to this model, eastern south China was in a distal continental back-arc setting related to the subduction of the Paleo-Pacific Ocean plate beneath the proto-Japan arc (Figure 11a).…”

“…However, Permian arc magmatism has not been discovered along the coastal provinces of southeast China so far. Instead, it occurs in SW Japan (Hara et al, 2018;Zhang et al, 2018, and references therein). Thus, Japan could have acted as a source for these Permian-Jurassic sedimentary rocks (L. Hu et al, 2015), which was once a part of the southeast China margin until Middle Jurassic time (Figure 11b; e.g., Hara et al, 2018;Jahn, 2010;Zhang et al, 2018).…”

Tracing the origin of Southwest Japan using the Hf isotopic composition of detrital zircons from the Akiyoshi Belt

“…scholasticus Assemblage and fusulina Lepidolina multiseptata, have been reported from the Nishiki Group and suggest it was deposited in the Middle to Late Permian (Naka & Ishiga, ; Nishimura, ; Nishimura, Itaya, Isozaki, & Kameya, ). The Nishiki Group is divided into four units based on their contact relationship (Zhang et al., ) (Figure c). Unit I mainly consists of chert, siliceous shale, felsic tuff and mudstone with a total thickness of greater than 100 m. Unit II rests on top of the Unit I by a thrust‐faulted contact and is an assemblage of coarse‐grained siliciclastic rocks with chert, siliceous shale, felsic tuff, mudstone and conglomerate with a thickness of about 1 km.…”

“…Numerous studies have used detrital zircon U–Pb dating to discuss the provenance and tectonic evolution of various accretionary belts in Japan (e.g. Aoki et al., ; Hara, Hirano, Kurihara, Takahashi, & Ueda, ; Isozaki et al., ; Tsutsumi, Yokoyama, Terada, & Sano, ; Zhang, Takeuchi, Ohkawa, & Matsuzawa, ); however, Hf isotopic studies are still rare. New Hf data from accretionary belts in Japan could be compared with the existing Hf data of late Palaeozoic rocks in the eastern margin of the Asian continent to offer new insight into the tectonic evolution of the Japanese Islands.…”

“…On top of the sequence is a unit of arc‐derived siliciclastic sedimentary rocks, deposition of which in the Late Permian corresponds to the early stage of a Pacific‐type orogen along the eastern margin of the South China block (Isozaki, ; Isozaki et al., ; Maruyama et al., , ). U–Pb dating of detrital zircons from the Late Permian sandstones yielded predominantly Carboniferous to Permian ages, suggesting magmatic activity along the southern and eastern rim of the South China block lasted from at least the Late Carboniferous to the Late Permian (Zhang et al., ). Herein, we present the Hf isotopic data for U–Pb dated detrital zircons from the Late Permian sandstones in SW Japan for the first time in order to understand its origin and tectonics in the late Palaeozoic.…”