The Study on the Spherulitic Rhyolites

The Study on the Spherulitic Rhyolites in the northern part of Juwang Mt., Cheongsong.

Chang Whan Oh1, Sung Won Kim2, Sang Koo Hwang3, Chang Whan Son1, Chang Suk Kim1 and Hyung Shik Kim41Department of Earth and Environmental Sciences, Chonbuk National Universlty, Jeonju 561-756, Korea2Basic Science Research Institute, Chonbuk National University, jeonju 561-756,
Korea 3Department of Earth and Environmental Sciences, Andong National University, Andong 760-749, Korea4Department of Earth and Environmental Sciences, Korea University, Selul 136-701, Korea*Corresponding author: Tel. 82-63-270-3397, E-mail, ocwhan@chonbuk.co.krAbstract:

In Cheongsong area, very rare spherulitic rhyolites both in Korea and foreign countries occur as dykes showing various types. The spherulites in them represent an undercooling caused by very fast cooling of the dykes in a shallow depth near to the surface and the variety of types were resulted from the difference of relative cooling rate. Cheongsong spherulitic rhyolites can be classified into five types based on the cooling rate; radiated simple spherulite, layered simple spherulite, layered multiple spherulite, radiated-layered multiple spherulite, radiating layered multiple spherulite. Radiated simple and radiating layered multiple spherulites formed by diffusion current caused by undercooling related to very fast cooling. On the other hand, layered multiple spherulites formed by relatively slow diffusion as a Liesegang ring during relatively slow cooling. If the cooling rate is between the two cases, layered simple spherulites formed. This interpretation indicates that Chrysanthemum, Dahlia and Sunflower types which are included in radiated simple or radiating layered multiple spherulite formed in the dykes with the fastest cooling rate in Cheongsong area while Peony, Rose and Innominate types classified as layered multiple spherulite formed in the dykes with the relatively slowest cooling rate. At the cooling rate between them, Apricot type spherulites formed. The K-Ar age-dating for Cheongsong spherulitic rhyolites indicate then to be formed between 48 and 50 Ma. The Cheongsong rhyolites are very valuable for research and preservation because of their rarity, beauty and diversity.

http://www.flowerstone.co.kr/index.php?status=eng&path=eng1