Multiple Sulphur Isotopic Compositions of Archean Records
Sulphur is closely related to life, environment, and mineral deposits. Multiple sulphur isotopes are a significant tool of recognizing the earliest sulphur-utilizing metabolisms on the Earth, reconstructing the Archean atmospheric oxygen level, and tracing the sulphur sources of mineral deposits.
Although an increasing number of studies on the multiple sulphur isotopes of Archean records have been conducted ever since the discovery of sulphur mass independent fractionation (S-MIF) in the Archean records, many problems still remain.
Two important shortcomings of previous studies are the analytical methods (measuring the sulphur extracted from bulk rock/sulphides) and the lack of sorting pyrite generations (sulphides can be multiple generations and geneses). As a result, the obtained data are essentially the compositions of mixed sulphur.
In this talk, I will present three case studies on the ~3.49 Ga Dresser Formation, ~3.2 Ga-2.72 Ga metasedimentary rocks from the Pilbara Craton, Western Australia, and a typical Neoarchean BIF-hosted gold deposit from the Rio das Velhas Greenstone Belt, Quadrilátero Ferrífero. The quadruple/triple sulphur isotopic compositions of the associated pyrite were obtained by the upgraded SHRIMP-SI based on well-established pyrite generations revealed by a combination of BSE imaging and sodium hypochlorite solution etching.