Archean kerogen as a new tracer of atmospheric evolution: implications for dating the widespread nature of early life
D.V. Bekaert, M. W. Broadley, F. Delarue, G. Avice, F. Robert, B. Marty
Feb. 2018. Science Advances, 4(2), eaar2091.
doi: 10.1126/sciadv.aar2091
Xe isotopes provide a time stamp for dating Archean kerogens and therefore narrowing the time window for the diversification of early life.
The Pilbara Craton (Australia) – Credit: Bernard Marty.
This study presents new evidence that atmospheric Xe was progressively enriched in heavy isotopes and depleted in light isotopes during the Archean eon. The large amounts of ancient atmospheric Xe preserved in Archean kerogens, when compared to fluids trapped in minerals, unlock a previously untapped reservoir and allow for the evolution of atmospheric Xe to be determined with unprecedented resolution.
Noble gases can be used as powerful tools to provide information about the depositional environment of organic materials at the time of life blossoming. The degree of mass fractionation of Xe isotopes relative to modern atmosphere provides a model age for dating the last chemical equilibration between the organic matter and the atmosphere. Comparing this model age with the age of the host rock provides a new method to test the syngenetic origin of ancient organic materials.