丹波帯中央部の火成岩岩脈群の産状と岩石記載

Abstract

Many dikes of various rock types are observed in the central area of the Tamba belt, They intruded into the Tamba Group of age from late Carboniferous to late Jurassic. Whereas basic to intermediate dikes are uniformly distributed in a relative sense, acidic dikes are unevenly spread. Many dikes are distributed around the Shuzan syncline, however, no dikes are found in sandstone area. These observations are suggestive that the dikes were formed under the structural control of the Tamba belt. The rocks from the dikes are classified into seven groups with two subgroups as follows: (1), Granite-porphyry; (2), Felsite; (3), Diorite-porphyry; (4), A, Hornblende-porphyrite with plagioclase phenocryst; B, Hornblende-porphyrite with no plagioclase phenocryst; (5), Clinopyroxene-brown hornblende-porphyrite; (6), Diabase; (7), Diabase-porphyrite. The groups, (1) to (4) A, are acid to intermediate rocks, and the others are intermediate to basic rocks. Petrographic descriptions for these rocks have been carried out.