Helium Isotopic Ratios of Fluid Samples in I-Lan Plain, NE Taiwan and Its Implication of Geothermal Energy Exploration

Abstract

The first comprehensive helium isotope survey of fluid samples in I-Lan Plain is reported here. We have sampled geothermal fluids samples thorough the whole plain. The results from representative sampling sites show that mantle component is significant over all the studied area. The contributions of mantle component of fluid samples can be up to 15% for both plain sites and mountain area. It implies that magmatic fluids might have invaded into I-Lan Plain and provide heat source to elevate the geothermal gradient in this area. If it is the case, the distribution of geothermal energy reservoir will be much larger than previously expected. Meanwhile, it is worthy to note that Ren-Tzer and Ten-Gou-Xi hot springs are characterized by different 3He/4He ratios with different percentages of mantle input, although they are only geographically divided by a river, Ten-Gou-Xi. It implies the existence of some fractures and/or faults as passageways for mantle featured fluids rising through and to the ground in this region.