TY - JOUR
T1 - Spatial variations in 3He/4He ratios along a high strain rate zone, central Japan
AU - Umeda, Koji
AU - Kusano, Tomohiro
AU - Ninomiya, Atusi
AU - Asamori, Koichi
AU - Nakajima, Junichi
N1 - Copyright:
Copyright 2013 Elsevier B.V., All rights reserved.
PY - 2013/9/5
Y1 - 2013/9/5
N2 - A linear zone with high strain rates along the Japan Sea coast, the Niigata-Kobe Tectonic Zone (NKTZ), is considered to be associated with rheological heterogeneities in the lower crust and/or upper mantle. Helium isotope variations along the NKTZ reveal a close association with the geophysical evidence for rheological heterogeneities in the crust and mantle. In the southern NKTZ, the 3He/4He ratios lower than 3.4Ra (Ra denotes the atmospheric 3He/4He ratio of 1.4×10-6) could be interpreted as a two-component mixture of helium stored in aqueous fluids driven off the subducting oceanic crust and radiogenic crustal helium. Higher 3He/4He ratios are observed in the central NKTZ where Quaternary volcanoes and high-temperature hot springs are concentrated, suggesting that the 3He emanation manifest in the central NKTZ results from the effective transfer of mantle helium by intrusion and degassing of mantle-derived magma in the crust. In the northern NKTZ where two large inland earthquakes occurred recently, there appears to be many samples with 3He/4He ratios significantly higher than those observed in the fore-arc side of northeast Japan. A plausible source of mantle helium could be attributed to upward mobilization of aqueous fluids generated by dehydration of the subducting Pacific Plate slab.
AB - A linear zone with high strain rates along the Japan Sea coast, the Niigata-Kobe Tectonic Zone (NKTZ), is considered to be associated with rheological heterogeneities in the lower crust and/or upper mantle. Helium isotope variations along the NKTZ reveal a close association with the geophysical evidence for rheological heterogeneities in the crust and mantle. In the southern NKTZ, the 3He/4He ratios lower than 3.4Ra (Ra denotes the atmospheric 3He/4He ratio of 1.4×10-6) could be interpreted as a two-component mixture of helium stored in aqueous fluids driven off the subducting oceanic crust and radiogenic crustal helium. Higher 3He/4He ratios are observed in the central NKTZ where Quaternary volcanoes and high-temperature hot springs are concentrated, suggesting that the 3He emanation manifest in the central NKTZ results from the effective transfer of mantle helium by intrusion and degassing of mantle-derived magma in the crust. In the northern NKTZ where two large inland earthquakes occurred recently, there appears to be many samples with 3He/4He ratios significantly higher than those observed in the fore-arc side of northeast Japan. A plausible source of mantle helium could be attributed to upward mobilization of aqueous fluids generated by dehydration of the subducting Pacific Plate slab.
KW - Helium isotope
KW - High strain rate zone
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U2 - 10.1016/j.jseaes.2013.04.016
DO - 10.1016/j.jseaes.2013.04.016
M3 - Article
AN - SCOPUS:84878221554
VL - 73
SP - 95
EP - 102
JO - Journal of Asian Earth Sciences
JF - Journal of Asian Earth Sciences
SN - 1367-9120
ER -