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Chemical characteristics of hydrothermal fluids from the TAG Mound of the Mid‐Atlantic Ridge in August 1994: Implications for spatial and temporal variability of hydrothermal activity
Author(s) -
Gamo Toshitaka,
Chiba Hitoshi,
Masuda Harue,
Edmonds Henrietta N.,
Fujioka Kantaro,
Kodama Yukio,
Nanba Hiromi,
Sano Yuji
Publication year - 1996
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/96gl02521
Subject(s) - hydrothermal circulation , alkalinity , mid atlantic ridge , geology , mineralogy , geochemistry , ridge , precipitation , chemical composition , chemistry , paleontology , physics , organic chemistry , seismology , meteorology
The TAG hydrothermal mound on the Mid‐Atlantic Ridge (26°08′N, 44°50′W) was revisited in August 1994 with the submersible Shinkai 6500 in order to characterize time‐series fluid chemistry prior to the ODP drilling. Fluid samples were taken from both black smokers and white smokers. Si, pH, alkalinity, H 2 S, major cations (Na + , K + , Ca 2+ , Mg 2+ ), major anions (Cl − , SO 4 2− ), and minor elements (Li, Sr, B, Fe, Mn, Cu, Zn, Br) as well as Sr isotope ratios were measured. We report the first Br/Cl ratios for the TAG hydrothermal fluids, showing no fractionation between Br and Cl during the fluid‐rock interaction. This study shows small changes in composition of the black smoker fluids from the 1990 data (Edmond et al., 1995). Changes of pH, alkalinity, Fe, K, and 87 Sr/ 86 Sr values are suggestive of subsurface FeS precipitation and a decrease of water/rock ratio at a deeper reaction zone. Differences in chemical characteristics between the black and white smoker fluids were similarly observed as in 1990.