GRANITIC ROCKS OF THE IBARAGI GRANITIC COMPLEX, OSAKA, JAPAN

PETROGRAPHY OF TYPE SPECIMENS

Abstract

The Ibaragi granitic complex is a small scaled calc-alkaline intrusive body, and this complex consists of two plutons, namely, the Nose and Myoken pluton. The complex has been investigated in detail from various geochemical and geophysical points of view by Research Group of the Ibaragi granitic complex. The granitic rocks of the complex can be divided into eight types according to their rock facies and modes of occurrences, namely, Nose pluton; 1. coarsegrained quartz diorite 2. medium-grained quartz diorite 3. coarse-grained granodiorite 4. coarse-grained porphyritic granodiorite 5. fine-grained porphyritic adamellite 6. very fine-grained porphyritic adamellite, Myoken pluton; 7. fine-grained pink adamellite 8. very fine-grained porphyritic pink adamellite. These granitic rocks intruded into Paleozoic formations successively from type 1 to 8 in the late Cretaceous age.
In this paper, the petrographic properties of above eight type specimens which were collected by Research Group of the Ibaragi granitic complex are described in detail. Especially, chemical properties of the constituent minerals are also described. Chemical compositions and modes of the type specimens are shown in Table 1, 2, and optical and chemical properties of constituent minerals are shown in Table 3, 4.