Occurrence of Dolomite in Yangsan Fault, Yeongdeok, Gyeongbuk, Korea, and Implications for Possible Fault Activity Related to Seawater = Occurrence of Dolomite in Yangsan Fault, Yeongdeok, Gyeongbuk, Korea, and Implications for Possible Fault Activity Related to Seawater

다국어 초록 (Multilingual Abstract)

This study focused on characterization of dolomite occurring in Yangsan Fault, Namsan-ri, Yeongdeok, Korea and provided implications for possible fault activity related to seawater. Dolomite was commonly identified as veinlets or irregular lenticular pocket in volcanic rocks, suggesting specific origin so called hydrothermal dolomite (HTD). The fault is characterized by a fault core with 1.2 m thickness and the fault planes have N40~50E/74~80SE. Brecciated fragments and veinlets develop in the fault zone where fault gouge with 10 cm thickness is observed, though negligible in some places. We analyzed fractured materials collected from the fault core using photomicroscope on thin sections, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Main mineralogy of fractured materials consists of quartz, illite, dolomite, pyrite, and iron oxides. Quartz as residual grains in gouge indicates that it experienced size reduction with grain rotation during faulting. It was assumed from field and textural observations that dolomite formed right after main fault event, possibly due to seismic pump effect or injection of seawater associated with highly brine deep water. HTD has implications for fault activity related to seawater in northern part of the Yangsan Fault, quite different from that found in other sites of the fault.
The research was supported by Earthquake disaster prevention specialist training funded by Administration safety, Korean government.