Open AccessAdjacent releases of mantle helium and soil CO 2 from active faults: Observations from the Marmara region of the North Anatolian Fault zone, Turkey
Author(s) -
Doğan Turhan,
Sumino Hirochika,
Nagao Keisuke,
Notsu Kenji,
Tuncer M. Kemal,
Çelik Cengiz
Publication year - 2009
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2009gc002745
Subject(s) - geology , mantle (geology) , helium , transect , soil gas , geochemistry , soil water , soil science , chemistry , oceanography , organic chemistry
Volatile releases, in terms of CO 2 efflux and noble gas of mantle origin, are investigated in the Marmara region of the seismically active North Anatolian Fault (NAF) zone. A total of 180 CO 2 efflux measurements (1 to 309 g m −2 d −1 ) were carried out along four transects across the NAF. Spatial variability of surface CO 2 effluxes was higher at faulted sites, relative to comparable background areas. The δ 13 C values of soil CO 2 are −24.0 to −15.6‰ without correlation with CO 2 efflux values, which suggest that CO 2 efflux anomaly is caused by fault‐related biogenic gas flow. Furthermore, 36 gas and water samples from spring sites were investigated for 3 He/ 4 He ratios which resulted in a range from 0.26 R / R A to 4.22 R / R A . Large mantle helium contributions were observed from several sources along the NAF. The high CO 2 efflux sector on the Gaziköy‐Saros fault along the NAF coincides with the area of high mantle helium flux. This shows that fault zones play an important role both in transferring mantle helium to the surface and in causing fault‐related biogenic gas flow.