The Characteristics of Andesite Under Weathering and Alteration in Tatun Volcano Group, Taiwan

Abstract

The weathering and hydrothermal alteration affect rock, and rock would record two processes. The Tatun Vaocano Group (TVG) is located in monsoon zone and active volcano phenomenon area, it belongs two pyroxenes basaltic andesite. This study major aim is to find what is kind of factor would affect the two pyroxenes basaltic andesite, and provides the information of corrosion process for geothermal power plant. This study analyzed the petrography, mineral assemblages, geochemistry of andesite by microscope, x-ray diffraction, and energy dispersive x-ray fluorescence spectrometer. This study presents that the predominant mineral assemblages are augite, hypersthene, and bytownite, and the alteration mineral assemblages are cristobalite, halloysite and limonite. The two pyroxenes basaltic andesite is distinguished four stages by degrees of rock mass weathering based on the petrography, mineral assemblages, and geochemistry data in TVG. The two pyroxenes basaltic andesite has higher sulfur concentration near the active fumarole area, and that indicates the hydrothermal alteration influence two pyroxenes basaltic andesite more than weathering in Tatun Volcano Group of Taiwan.