Sulphate concentrations in the ocean prior to 2.4 Gyr ago were lower than today. The sulphur isotope systematics of 2.7-Gyr-old sulphide deposits suggests that these low concentrations were maintained by a balance between hydrothermal sources and microbial sulphate reduction.
- J. W. Jamieson
- B. A. Wing
- M. D. Hannington