The Characteristics of Petrography and Fluid inclusions of Vein in Geothermal System of Ilan Plain, Taiwan

Abstract

This study firstly applied fluid inclusions of veins in the core of geothermal area to provide the evolution of thermal fluid in Taiwan. The first one is to analyze the mineral assemblages in veins by microscope. The second aspect to observe the fluid inclusions and minerals relationship. The third is to measure the values of melting temperature and homogenized temperature of fluid inclusions by micro-heating stage, and then calculate the salinity and pressure of fluid inclusion. The results show that the veins are consist of quartz and calcite and formed along cleavage. Quartz and calcite are commonly mosaic deposited that is first stage geothermal fluid, and the deposit of second stage is calcite that cut the quartz grain of first stage. In the first stage, the homogenized temperature and salinity of geothermal fluid are 240°C -260°C and 2~6 wt.% NaCl eq., respectively. However, the secondary stage, the homogenized temperature and salinity of geothermal fluid are 280°C -290°C and 2~6 wt.% NaCl eq., respectively. Finally, this study infers to the veins are produced by meteoric water with anomaly heating, and the temperature value of geothermal fluid is about to 280°C -290°C in the HongTsaiLing of Ilan Plain.