| 概要 |
The Nomo peninsula is mainly composed of a group of crystalline schist, and partly of serpentinite, metagabbro and granite. This area is divided by faults and a thrust into. three blocks, the eastern,... central and western. The crystalline schist is mainly green and pelitic schists, accompanied by psammitic schist. Siliceous schist is rare in this area, and some small bodies of crystalline limestone are found in the western block. These crystalline schists are nearly flat, or dip at a low angle to N or NW, in general, with folding axes of the E-W or NE-SW direction. The stratigraphic sequence of the schists in the eastern and western blocks is grouped into B and A subgroups respectively as shown in Fig. 2, and that in the central block corresponds probably to the lower part of the B subgroup of the eastern one. The stratigraphic relation between the two subgroups cannot be known due to the presence of a thrust between them and the absence of reliable evidences, but the geologic structure of this area suggests that the A subgroup might have possibly been underneath the B subgroup. Comparing with the succession of the schists in the Chikushi Mountains (MATSUMOTO, 1958), the B subgroup may correspond to B_4, and the A to B_2 and the lower part of B_3. The crystalline schists are produced by progressive regional metamorphism, and are divided by mineral assemblages and textures into two zones, the E-zone and W-zone, both of which belong to green schists facies. The E-zone belongs to a so-called "spotted schist" zone in texture, and occupies the eastern and central blocks. The W-zone is a "nonspotted schist" zone, and is distributed in the western. It is interesting that all of the pelitic schists in both the zones belong to quatz-albite-muscovite subfacies (chlorite zone) of F. J. TURNER and others (1958), but some of the green schists in the E-zone have an assemblage of quartzalbite-epidote-biotite subfacies (biotite zone). Aureole of contact metamorphism by granite is restricted to a small portion of the western block.続きを見る
|
Mendeley出力
