TY - JOUR
T1 - Mantle degassing along strike-slip faults in the Southeastern Korean Peninsula
AU - Lee, Hyunwoo
AU - Kim, Heejun
AU - Kagoshima, Takanori
AU - Park, Jin Oh
AU - Takahata, Naoto
AU - Sano, Yuji
N1 - Publisher Copyright:
© 2019, The Author(s).
PY - 2019/12/1
Y1 - 2019/12/1
N2 - On September 12, 2016, a ML 5.8 earthquake hit Gyeongju in the southeastern part of the Korean Peninsula (SeKP), although the area is known to be far from the boundary of the active plate. A number of strike-slip faults are observed in heavily populated city areas (e.g., Busan, Ulsan, Pohang, and Gyeongju). However, dissolved gases related to the active faults have rarely been studied despite many groundwater wells and hot springs in the area. Here we report new results of gas compositions and isotope values of helium and carbon dioxide (CO2) in fault-related fluids in the region. Based on gas geochemistry, the majority of gas samples are abundant in CO2 (up to 99.91 vol.%). Measured 3He/4He ratios range from 0.07 to 5.66 Ra, showing that the mantle contribution is up to 71%. The range of carbon isotope compositions (δ13C) of CO2 is from −8.25 to −24.92‰, showing mantle-derived CO2 is observed coherently where high 3He/4He ratios appear. The weakening of faults seems to be related to enhanced pressures of fluids containing mantle-derived helium and CO2 despite the ductile lower crust underneath the region. Thus, we suggest that the SeKP strike-slip faults penetrate into the mantle through ductile shearing.
AB - On September 12, 2016, a ML 5.8 earthquake hit Gyeongju in the southeastern part of the Korean Peninsula (SeKP), although the area is known to be far from the boundary of the active plate. A number of strike-slip faults are observed in heavily populated city areas (e.g., Busan, Ulsan, Pohang, and Gyeongju). However, dissolved gases related to the active faults have rarely been studied despite many groundwater wells and hot springs in the area. Here we report new results of gas compositions and isotope values of helium and carbon dioxide (CO2) in fault-related fluids in the region. Based on gas geochemistry, the majority of gas samples are abundant in CO2 (up to 99.91 vol.%). Measured 3He/4He ratios range from 0.07 to 5.66 Ra, showing that the mantle contribution is up to 71%. The range of carbon isotope compositions (δ13C) of CO2 is from −8.25 to −24.92‰, showing mantle-derived CO2 is observed coherently where high 3He/4He ratios appear. The weakening of faults seems to be related to enhanced pressures of fluids containing mantle-derived helium and CO2 despite the ductile lower crust underneath the region. Thus, we suggest that the SeKP strike-slip faults penetrate into the mantle through ductile shearing.
UR - http://www.scopus.com/inward/record.url?scp=85074132665&partnerID=8YFLogxK
U2 - 10.1038/s41598-019-51719-3
DO - 10.1038/s41598-019-51719-3
M3 - 学術論文
C2 - 31653922
AN - SCOPUS:85074132665
SN - 2045-2322
VL - 9
JO - Scientific Reports
JF - Scientific Reports
IS - 1
M1 - 15334
ER -