Mid-Paleozoic arc granitoids in SW Japan with Neoproterozoic xenocrysts from South China: New zircon U–Pb ages by LA-ICP-MS

Cambrian plutonism in Northeast Japan and its significance for the earliest arc-trench system of proto-Japan: New U–Pb zircon ages of the oldest granitoids in the Kitakami and Ou Mountains

“…As preliminarily speculated by Isozaki et al (2010) and Suzuki et al (2010), the Paleozoic granitoids in SW Japan (e.g., Fujii et al, 2008;Osanai et al, 2014;Aoki et al, 2015) likely shared a similar fate, i.e. the mature arc plutons were totally removed and disappeared by tectonic erosion.…”

“…500 Ma detrital zircons in younger sedimentary rocks and high-P/T psammitic schists in various areas in Japan (Nakama et al, 2010a,b;Isozaki et al, 2010Tsutsumi et al, 2011;Yoshimoto et al, 2013;Okawa et al, 2013) and of ca. 500 Ma xenocrysts in younger granitoids (Fujii et al, 2008;Osanai et al, 2014;Aoki et al, 2015) suggest the potential development of the coeval granitoid belt throughout early Paleozoic Japan. All of these lines of evidence, although still fragmentary, imply that the 500 Ma granitoid belt formed a major mature arc with a minimum along-arc length of up to 1500 km, at least comparable with the modern Izu-Bonin-Mariana arc (Suyehiro et al, 1996), along the western margin of Panthalassa (=paleo-Pacific).…”

“…The distribution of Early Paleozoic granitoids in Far East Asia (A: compiled from Li et al, 2012;Shu et al, 2014;Khanchuk et al, 1996, andBi et al, 2014), and of the Japanese ca. 500 Ma zircons (detrital and xenocryst) and >400 Ma granitoids (B: compiled from Sakashima et al, 2003;Fujii et al, 2008;Nakama et al, 2010a,b;Isozaki et al, 2010Tsutsumi et al, 2011;Okawa et al, 2013;Yoshimoto et al, 2013;Osanai et al, 2014;Aoki et al, 2015;this study). Although their current distribution is patchy, the Early Paleozoic arc-related granitoids in Japan (B) likely belonged to a much larger arc crust that extended to the northeast to the Khanka block in Primorye, Far East Russia, and possibly further to the eastern Cathaysian margin of South China (A).…”

“…(1) Zircon xenocrysts in mid-Paleozoic granitoids in Japan range in age-range of 3200-500 Ma (Fujii et al, 2008;Osanai et al, 2014;Aoki et al, 2015) that overlap the ages of the Yangtze basement; thus suggest the significant geological connection between the South China crust and the site of granitoid-dominant arc of Paleozoic Japan. (2) Paleozoic sandstones and Paleozoic-Triassic high-P/T metamorphic rocks in Japan often contain abundant Proterozoic detrital zircons (e.g., Nakama et al, 2010a,b;Shimojo et al, 2010;Isozaki et al, 2010Tsutsumi et al, 2011;Yoshimoto et al 2013;Okawa et al, 2013), in particular, Neoproterozoic (1200-600 Ma) zircons have the same ages as the basement of South China (Fig.…”

The first sphinctozoan-bearing reef from an Ordovician back-arc basin

“…Firstly, new geochronological, petrological, structural, and sedimentological data from the South China plate indicate a retroarc thrust belt and foreland basin system in the southeastern Yangtze Block and suggest that the Cathaysian Land may represent a continental arc (Chen et al 2006;Jiang et al 2014;Ran et al 2015). Increasing evidence shows that SW Japan originated from the Cathaysian margin (Aoki et al 2014;Isozaki and Kase 2014) and represented a Late Ordovician (about 445 Ma) arc-trench system that grew along the eastern margin of the South China plate (Aoki et al 2014;Isozaki 2011). Together with the contemporary high-P/T metamorphic rocks in Japan, this confirms oceanic subduction beneath the Cathaysian Land during the entire Ordovician (Isozaki 2011).…”