Biosphere, hydrocarbon and ore fluid interactions in the Early Precambrian
This project is collaborative with Adriana Dutkiewicz (Sydney University), Herbert Volk (CSIRO Petroleum), John Ridley (Colorado State University), Roger Buick (University of Washington) and David Mossman (Mount Allison University).
We use oil inclusions as biogeochemical time capsules which retain information for billions of years. Crude oil formed during the Archaean and Proterozoic (>1.0 billion years ago) due to burial and heating of organic matter. In most places this oil has subsequently been lost through leakage, thermal alteration and biodegradation. Sometimes, tiny samples of the oil was trapped in mineral grains as fluid inclusions. We have devised methods of analysing this oil, the chemistry of which (e.g. biomarker distribution) tells us information about the original organic matter in the >1.0 billion year old rocks.
ARC Discovery Project Summary (2005-2010)
Two of the most outstanding problems in Earth Sciences are the genesis of the world's largest early Precambrian hydrothermal ore deposits that are associated with hydrocarbons, and the early evolution of life. This project exploits recently discovered early Precambrian oil inclusions and their geochemical compositions, including biomarkers, to constrain hydrocarbon-ore fluid interactions, the pressure-temperature conditions under which they co-exist, the diversity of the primordial biosphere and the nature of life's earliest habitats. Outcomes of this project will allow mineral and hydrocarbon exploration companies to narrow their search for ancient deposits and will provide a clearer picture of life on early Earth.Outcomes
We have firmly established the extraction of biomarker molecules from Palaeoproterozoic oil-bearing fluid inclusions as a new method that allows us to trace evolution of Earth's early history. This new method avoids the potential contamination problems associated with the shale-hosted hydrocarbons and as oil inclusions are found in a variety of rocks and minerals, they can thus provide new insights into biological evolution and palaeoenvironments during critical stages of Earth's history.
Matinenda Formation Case Study
Our case study of the 2.45 billion-year-old Matinenda Formation demonstrates an earlier evolution of oxygenic photosynthesis and implies that eukaryotes, our strain of life, survived several extreme climatic events, including the Palaeoproterozic "Snowball Earth". A paper documenting these results has been published by Geology:
Dutkiewicz, A., Volk, H., George, S.C., Ridley, J. and Buick, R. (2006) Biomarkers sealed in oil-bearing fluid inclusions trapped before the Great Oxidation Event. Geology 34, 437-440.
George, S.C., Volk, H., Dutkiewicz, A., Ridley, J. and Buick, R. (2008) Preservation of hydrocarbons and biomarkers in oil trapped inside fluid inclusions for >2 billion years. Geochimica Cosmochimica Acta 72, 844-870.
Matinenda Formation charge history
Steranes in Matinenda Formation Sample
Oklo Case Study
We have also shown that the 2.2 billion-year-old Oklo nuclear fission reactors contain hydrocarbon-bearing fluid inclusions that were trapped before, during and after the reactors went critical. In addition, based on molecular geochemistry and a complex suite of biomarkers we are able to show that the hydrocarbons in these fluid inclusions have a biogenic origin. This work has implications not only for the formation of the uranium ores but also for the composition of the biomass at this time. We discussed these results in 2 talks at the 2006 Goldschmidt Conference in Melbourne:
George, S.C., Dutkiewicz, A., Volk, H., Ridley, J. and Mossman, D. (2006) Oil-bearing fluid inclusions: biogeochemical time-capsules for >2.0 billion years . Goldschmidt Conference 2006, Melbourne.
Dutkiewicz, A., Volk, H., George, S.C., Ridley, J., Mossman, D. and Buick, R. (2006) Oil and its biomarkers trapped inside fluid inclusions ca. 2.45-2.0 Ga . Goldschmidt Conference 2006, Melbourne.
This work has also been recently published in full:
Dutkiewicz, A., Mossman, D.J., Ridley, J., George, S.C. and Volk, H. (2007) Oil and its biomarkers associated with the Paleoproterozoic Oklo natural fission reactors, Gabon. Chemical Geology 244, 130-154. doi:10.1016/j.chemgeo.2007.06.010.
Steranes in Oklo Sample