Yeh,^Gau-Hua

Abstract

Mud volcanoes (MVs) are commonly found in southern Taiwan. They are believed to be the products related to the accretionary prism due to the ongoing arc-continent collision between Eurasian plate and Luzon arc. For better understanding their fluid compositions, samples of representative MV fluids were collected for geochemical analyses. Compared to the hot spring waters in Taiwan, all the MV fluids show much higher content of chlorine concentration. This indicates that marine pore waters play an important role for the sources of the MV fluids. Interestingly MV fluids from eastern Taiwan show unique geochemical characteristics of sodium-deficit and calcium-excess, which may be explained by the process of albitization during water-rock interaction.The H–O isotopic data of the MV fluids samples from eastern Taiwan, in contrast to those from western Taiwan, fall along the local meteoric water line. It implies that meteoric water is an important component for the source of MV fluids from eastern Taiwan but not for those from western Taiwan. Meanwhile, samples collected from the region near deep structures in western Taiwan usually exhibit higher δ18O value, which suggests that these fluids may contain dehydrated waters of clay minerals at deep source.