Sedimentary petrological comparison of Jurassic clastic rocks between the Mino terrane and the Chichibu terrane

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The main results of this study are as follows:1. EPMA analyses of detrital garnets in Jurassic sandstones of the Mino terrane have revealed that the garnets are generally of Mg-rich almandine with small amounts of Mn and Ca. These garnets were probably derived from granulite facies pelitic gneisses.2. Unlike detrital garnets in the Mino terrane, garnets in Jurassic sandstones of the Chichibu terrane are more enriched in Mn and Ca. From the chemical composition of detrital garnets, there was a significant difference in provenance rocks between the Mino and Chichibu terranes.3. Sandstones of Jurassic Tetori Group in the Hida terrane contain a number of Mg-rich garnets, compositionally similar to those in the Mino terrane. Re-examinations of the Kamihirose conglomerate in the circum-Hida tectonic zone have revealed the occurrence of a garnet-bearing gneiss cobble.4. Chert clasts containing Permian radiolarians have been found from the Yokoo conglomerate in the circum-Hida tectonic zone.5. Petrological and geochemical investigations of "Mn-nodules" in Jurassic siliceous shales in the Mino terrane have shown that barite and length-slow chalcedony occur within the nodules. Chemically the Jurassic "Mn-nodules" are quite different from those on the Pacific ocean floor.