抄録
Machinoyama ultramafic body is the eastern most part of the Yakuno ophiolite in the Maizuru belt. Outcrops of its southeastern margin show various block-in-matrix structures towards the fault boundary to the Ultra-Tanba belt. The blocks consist of serpentinites and serpentinized peridotites and were fragmented into multiple parts, with the spaces between blocks being infilled by scaly serpentinites (i.e. chrysotile). The blocks decreased their sizes and formed phacoidal-shapes towards the fault boundary, whereas serpentinite matrix becomes dominant with intense foliations. These structural developments in Machinoyama body could be related to the fault activity at the boundary with the Ultra-Tanba belt.
