[O-02] Poster presentations by senior high school students

[O02-P70] what is equigranular texture

*Harumu Sasaki¹, *Hiroki Kato¹, Madoka Seo¹ (1.Chiba Prefectural Kashiwa high school)

Keywords:equigranular texture, phaneritic, aphanitic

Toryujo soshiki(≒equigranular texture), which means ‘plutonic rock's texture’, is a well-known word in junior and senior high school textbooks in Japan. Toryu means ‘grains of the same size’, but the structure of ‘plutonic rock's texture’ is not always made of grains of the same size. We researched why it is called Toryujo soshiki in Japanese and reconsidered the fitness of the word for ‘plutonic rock's texture’. As a result, we found the following things. In foreign countries, there are three categories of igneous rock texture: phaneritic, porphyritic and aphanitic. Those are divided by observing structures with naked eyes. In the structure of fine grained basalt, mineral particles can not be seen with naked eyes, so aphanitic rock's texture. But in Japan, the texture of basalt is determined as porphyritic. In foreign countries, porphyritic texture is regarded as both plutonic and effusive rocks.