Abstract The Kitomyo Schist from Kurosegawa Belt, Shikoku, has been long considered as the oldest records of subduction metamorphism in Japan, based on an early 1970s K Ar dating of white mica. The schist consists of mafic and pelitic layers and occurs as a tectonic block within serpentinite. Reappraisal of the schist confirmed the schist is characterized by an epidote-amphibolite peak metamorphic facies. The mafic portion is characterized by zoned amphibole + epidote + chlorite + titanite ± phengite ± rutile. The presences of relict rutile surrounded by titanite and the barroisitic cores of zoned amphibole suggest a high-pressure intermediate type metamorphism at the metamorphic peak (P = ~0.8–1.5 GPa and T = ~500–570 °C). The presence of Mn-rich garnet and the lack of biotite, oligoclase and paragonite also support high-pressure intermediate type metamorphism that eliminate the possibility of a typical blueschist-facies metamorphism. New SHRIMP and LA-ICPMS zircon U Pb geochronology on a pelitic sample show detrital grains of Mesoproterozoic and Early Paleozoic ages, suggesting a maximum deposition age for the trench-fill sediment of ~440 Ma. Also the U Pb data confirmed ~360 Ma overgrown rims that might have formed during the subduction zone epidote-amphibolite facies metamorphism. Reappraisal revealed that the Kitomyo Schist is not the oldest high-pressure type schist in Japan and rather comparable to the Late Paleozoic Renge Metamorphic Rocks and their equivalents in the Kurosegawa Belt. The Devono–Carboniferous high-pressure metamorphic rocks in Japan might have been paired with their coeval batholiths along the ‘Greater South China’ margin that was extensively eroded during later tectonic processes.

中文翻译：

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日本最古老高压型片岩重估：黑濑川带北东片岩新锆石U Pb年龄

摘要 来自四国黑濑川带的 Kitomyo 片岩一直被认为是日本最古老的俯冲变质记录，基于 1970 年代初期对白云母的 K Ar 定年。片岩由镁铁质和泥质岩层组成，作为蛇纹岩内的构造块出现。片岩的重新鉴定证实片岩的特征是绿帘石-角闪石峰变质相。镁铁质部分的特征是分区闪石 + 绿帘石 + 绿泥石 + 钛铁矿 ± 菱镁矿 ± 金红石。被钛铁矿包围的残余金红石和分带角闪石的重晶石核的存在表明变质峰处存在高压中间型变质作用（P = ~0.8-1.5 GPa 和 T = ~500-570 °C）。富锰石榴石的存在和黑云母的缺乏，寡长石和平行长石也支持高压中间型变质作用，消除了典型蓝片岩相变质作用的可能性。泥质岩样品上的新 SHRIMP 和 LA-ICPMS 锆石 U Pb 年代学显示中元古代和早古生代的碎屑颗粒，表明沟渠填充沉积物的最大沉积年龄约为 440 Ma。U Pb 数据也证实了可能在俯冲带绿帘石-角闪岩相变质过程中形成的~360 Ma 过度生长的边缘。重新评估表明，北大片岩并不是日本最古老的高压型片岩，而是可与黑濑川带中晚古生代 Renge 变质岩及其等效物相媲美。