瀬戸内海地域の岩脈群の分布様式
スポンサーリンク
概要
- 論文の詳細を見る
Dyke swarms in the Late Mesozoic granites of the Setonaikai (Seto inland sea) region are divided into several groups with respect to intrusion phase. At the Shodoshima area placed in the eastern part of the Setonaikai region have been found dyke swarms of four phases (Yokoyama, 1978). The dyke swarms examined in this paperare of the intrusion phase correlated with those of the 3rd phase in the Shodoshima area. Those appear to have intruded during the later phase of cooling of granitic rocks in the Setonaikai region. The dykes in question are divided into three rock types, basic, intermediate and acid, in chemical composition. Those do not uniformly distribute in the region but concentrate in many small restricted domains. Each of the domains which consists of anyone of three rock types is designated as dyke-province. In the region have been found 50 dyke-provinces. At the Shodoshima area the acid dyke-provinces superpose partly the basic dyke-provinces. The basic dykes appear to be older than the acid dykes. Number of dykes in individual dyke-provinces varies from 10 to 220, but many of them have 20-50 dykes. Among 50 dyke-provinces, 28 dyke-provinces consisit of basic dykes, 5 dyke-provinces of intermediate dykes, and 17 dyke-provinces of acid dykes. Number of dykes is more in basic dyke-province than in acid dyke-province. Dykes are preferably oriented in individual dyke-provinces. Generally, dyke-provinces show elongate form whose long axis is parallel to the orientation direction of dykes. Many dyke-provinces are elongated approximately parallel to N-S direction and some others to E-W direction. Most of basic dykes are smaller than 1 m in width, while many acid dykes are 50 cm to 10 m. Namely, the basic dykes are generally smaller than the acid dykes in width. It is also noticeable that there is adistinct tendency that dykes with phenocrysts are greater than those without phenocrysts in average width.
- 日本地質学会の論文
- 1979-09-20