Geochemical Characteristics of Volcanics from Yangsan, Kyeongnam Province

경남(慶南) 양산지역(梁山地域)에 분포(分布)하는 화산암류(火山岩類)의 지구화학적(地球化學的) 특성연구(特性硏究)

The altered volcanic rocks, ranging from tuffaceous to andesitic rocks are widely distributed around the "caldera" area in the southeastern part of Kyeongsang province. The volcanic activity and tectonic movement are assumed to be followed by the hydrothermal activities in the area. From the mineral assemblage the type of alteration can be divided into two types; propylitic and argillic. The average concentration of gold in hydrothermally altered rocks is somewhat lower (about 20 ppb) than that of fresh rocks (45-25 ppb), but for Ag, vice versa. During the hydrothermal process, the concentration of the trace elements Ag, Hg, Co, As, Hf, Sc, Si, Al increased, and that of Na, Rb, K, Au, Mg, Ca etc. decreased. The high anomalous contents of silver for altered rocks range from 4-7 ppm and 1-3 ppm for relatively fresh rocks.