Microscopic deformation features of low-strained granitoids.

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1. The Kofu granitic rocks were weathered to have formed surfacial weathered layers of several meters or more in thickness during Late Pliocene. The Kofu granitic rocks were hydrothermally altered in two stages: Intermediate/alkalline type alteration under the north-northeast trending stress axis during Early Pliocene, and acidic type alteration under the north-northwest trending stress axis during Late Pliocene. The kofu granitic rocks deformed under north-trending stress axis during the time of weathering and alteration. The representative textures are intragranular cracks of quartz and feldspars, and folds of biotite.2. The Kaikoma granites are less strained in the area apart from the Itoigawa-Shizuoka Line, while are highly strained in the vicinity of the Itoigawa-Shizuoka Line. The former shows the deformation textures similar to those of the Kofu granitic rocks, while the latter shows textures of mylonite and ultramylonite, which are characterized by plastically deformed quartz and fractured feldspars, as well as highly kinked biotite grains.3. The Tsukuba granites are weathered in the same manner with those of the Kofu granitic rocks. The Tsukuba granites have many healed cracks in quartz grains, which have a different general trend from non-healed cracks in quartz grains.Besides these examples, granitoids from Tanzawa, Kitakami, Bathurst, and Ryoke were examined microscopically, which give us some other examples of low-strained granitoids.