根田茂帯礫岩から得られた含ザクロ石泥質片岩礫の白雲母^<40>Ar/^<39>Ar年代

概要

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Conglomerate containing garnet-bearing pelitic schist pebble was obtained from the Nedamo Terrane, an Early Carboniferous accretionary prism of northeast Japan. Phengite in the schist pebble is dated to be 347-317 Ma based on the ^<40>Ar/^<39>Ar spot-heating method. The schist in the pebble can be correlated with the Renge Metamorphic Rocks of southwest Japan, and the Yamagami Metamorphic Rocks in the Kitakami-Abukuma massif. The age data suggest that high-P/T metamorphism which produced the garnet-bearing pelitic schist may have been in progress within Early Carboniferous (359-318 Ma) and the schists were rapidly exhumed to provide pebbles, or that the conglomerate containing the pebbles may belong to a post-Early Carboniferous accretionary unit which is not identified yet. In case that the age has been all rejuvenated by secondary effects, the schist pebble may have been derived from pre-Late Devonian high-P/T metamorphics as the Matsugadaira Metamorphic Rocks, probably 380 Ma.
日本地質学会の論文
2008-06-15