飛騨外縁帯ならびに三郡変成帯のヒスイ輝石岩の構造的意義  [in Japanese] Tectonic significance of jadeitite in Hida Marginal Belt and Sangun Metamorphic Belt  [in Japanese]

1. The Omi-Renge Belt occupying the north eastern part of the Hida Marginal Belt is regarded as a serpentinite melange zone as a whole. The belt is composed of four tectonic units from east to west; 1) Mushikawa olistostromal strata and Himekawa Group, 2) Omi limestone and surrounding olistostromal strata, 3) Shiroumadake olistostromal strata, and 4) serpentinite nappe and serpentinite melange including crystalline schists (311-400 Ma). These tectonic units are separated from each other by serpentinite melange (in a narrow sense), and are superposed successively from west to east to form a schuppen structure. 2. The serpentinite melanges are divided into the following three types, according to the lithology and radiometric ages of tectonic inclusions. I-type serpentinite melange includes blocks of jadeite-albitite, albitite, schistose rock, metagabbro, etc. II-type serpentinite melange includes the monomineralic jadeitite, garnet-amphibolite of ophiolitic origin (442 Ma), glaucophanitic crystalline schist, albitite, etc. III-type serpentinite melange includes blocks of acidic volcanics, basic pillow lavas, rodingite, olistostromal sediments and crystalline schist, etc. 3. The geologic ages of protrusion of serpentinite melangeare divided into the following two: the pre-Kuruma and post-Kuruma stages, but the multiple protrusions are presumable from the tectonic features of the serpentinite. 4. According to their inner structure, the monomineralic jadeitites are divisible into three types: Kotaki-type (concentric), Omi-type (stratified) and Tsugaike-type (white coarseve in jadeitite). 5. In the Sangun Metamorphic Belt, the monomineralic jadeitites also occur as tectonic inclusions associated with metagabbros (450 Ma±) within the serpentinite melange protruded in to the Sangun Metamorphic Belt adjacent to the Maizuru Belt. The serpentinite melange belts belong to the Inner ophiolitic belt (KOMATSU et al., 1977), which possibly differs from that of the western extension of the Hide Marginal Belt. However the general tectonic and lithologic features of the former are very similar to that of the latter. 6. The jadeite-bearing serpentinite melange of Southwestern Japan are presumably the products of multiple protrusion, and the high-pressure type crystalline schists associated therewith are the products of multiple stages of subduction.