全谷地域의 알카리火山岩類에 관한 硏究

Abstract

The present study was undertaken to examine the occurrence and the petrochemical properties of Quaternary alkaline volcanics in the Jeongog area. The volcanics occur along the so-called Chugaryeong rift valley which runs into N15°E direction from Seoul to Weonsan. The area studied is considered to be important regarding to study the Quaternary volcanics in Korea and tectonic settings of the Korean peninsula. The area studied is geologically composed of basement of Geonggi metamorphic complex, intrusives of biotite granite of Jurassic, age unknown volcanics and Quaternary Jeongog basalt. The Jeongog basalt consists mainly of olivine, titan-augite, plagioclase and small quantity of magnetite. Under the microscopy, no reaction relations between olivine and pyroxene phenocrysts have been observed. Judging from the paragenesis of rock-forming minerals and petrochemical properties, the basalt is classified into alkaline rock series. The chemical data indicate that the basalt is incipient differentiation stage of magma and belongs to the category of potassic series and continental origin. The basalt is consistent with the Possible straddle-type by means of the Miyashiro's classification of alkaline volcanic association.