Anomalous fractionation of mercury isotopes in the Late Archean atmosphere

Mass-independent fractionation of sulfur isotopes in Archean sediments: strong evidence for an anoxic Archean atmosphere.

Mass-independent fractionation (MIF) of sulfur isotopes has been reported in sediments of Archean and Early Proterozoic Age (> 2.3 Ga) but not in younger rocks. The only fractionation mechanism that is consistent with the data on all four sulfur isotopes involves atmospheric photochemical reactions such as SO2 photolysis. We have used a one-dimensional photochemical model to investigate how the...

Mass-independent fractionation of mercury isotopes in the environment

[1] The toxicity of mercury’s methylated species and its biomagnification in aquatic food chains and global dispersion by the atmosphere are the cause of worldwide health problems. Recent reports have observed natural mass-dependent fractionation in mercury isotopes, and recent theoretical work has demonstrated that isotopic separation in mercury is due primarily to nuclear field shifts (nuclea...

Iron isotopes in an Archean ocean analogue

Iron isotopes have been extensively used to trace the history of microbial metabolisms and the redox evolution of the oceans. Archean sedimentary rocks display greater variability in iron isotope ratios and more markedly negative values than those deposited in the Proterozoic and Phanerozoic. This increased variability has been linked to changes in either water column iron cycling or the extent...

The Late Archean Biospheric Explosion

biogenic platform carbonates [4]. By c.2.45 Ga oxygen levels had begun to rise in the Earth’s atmosphere setting the stage for the evolution of the modern biosphere. Here we focus on concretionary structures, which can act as sensitive barometers of biological activity, to provide us with potential insights into the expansion of this early biosphere prior to the first appearance of oxygen in th...

Theoretical investigation of the anomalous equilibrium fractionation of multiple sulfur isotopes during adsorption