In search of early life: Carbonate veins in Archean metamorphic rocks as potential hosts of biomarkers
Field | Value | Language |
dc.contributor.author | Peters, Carl A. | |
dc.contributor.author | Piazolo, Sandra | |
dc.contributor.author | Webb, Gregory E. | |
dc.contributor.author | Dutkiewicz, Adriana | |
dc.contributor.author | George, Simon C. | |
dc.date.accessioned | 2019-08-16 | |
dc.date.available | 2019-08-16 | |
dc.date.issued | 2016-11-01 | |
dc.identifier.citation | Peters, C. A., Piazolo, S., Webb, G. E., Dutkiewicz, A., & George, S. C. (2016). In search of early life: Carbonate veins in Archean metamorphic rocks as potential hosts of biomarkers. Earth and Planetary Science Letters, 453, 44–55. https://doi.org/10.1016/j.epsl.2016.08.003 | en_AU |
dc.identifier.issn | 0012821X | |
dc.identifier.uri | http://hdl.handle.net/2123/20930 | |
dc.description.abstract | The detection of early life signatures using hydrocarbon biomarkers in Precambrian rocks struggles with contamination issues, unspecific biomarkers and the lack of suitable sedimentary rocks due to extensive thermal overprints. Importantly, host rocks must not have been exposed to temperatures above 250 °C as at these temperatures biomarkers are destroyed. Here we show that Archean sedimentary rocks from the Jeerinah Formation (2.63 billion yrs) and Carawine Dolomite (2.55 billion yrs) of the Pilbara Craton (Western Australia) drilled by the Agouron Institute in 2012, which previously were suggested to be suitable for biomarker studies, were metamorphosed to the greenschist facies. This is higher than previously reported. Both the mineral assemblages (carbonate, quartz, Fe-chlorite, muscovite, microcline, rutile, and pyrite with absence of illite) and chlorite geothermometry suggest that the rocks were exposed to temperatures higher than 300 °C and probably ∼400 °C, consistent with greenschist-facies metamorphism. This facies leads to the destruction of any biomarkers and explains why the extraction of hydrocarbon biomarkers from pristine drill cores has not been successful. However, we show that the rocks are cut by younger formation-specific carbonate veins containing primary oil-bearing fluid inclusions and solid bitumens. Type 1 veins in the Carawine Dolomite consist of dolomite, quartz and solid bitumen, whereas type 2 veins in the Jeerinah Formation consist of calcite. Within the veins fluid inclusion homogenisation temperatures and calcite twinning geothermometry indicate maximum temperatures of ∼200 °C for type 1 veins and ∼180 °C for type 2 veins. Type 1 veins have typical isotopic values for reprecipitated Archean sea-water carbonates, with δ13CVPDB ranging from −3‰ to 0‰ and δ18OVPDB ranging from −13‰ to −7‰, while type 2 veins have isotopic values that are similar to hydrothermal carbonates, with δ13CVPDB ranging from −18‰ to −4‰ and δ18OVPDB ranging from −18‰ to −12‰. Evidently, the migration and entrapment of hydrocarbons occurred after peak metamorphism under temperatures congruous with late catagenesis and from fluids of different compositions. The relatively high temperatures of vein formation and the known geotectonic history of the rocks analysed suggest a probable minimum age of 1.8 billion yrs (Paleoproterozoic). Our results demonstrate that post peak-metamorphic veins provide an exciting opportunity in the search for evidence of early life. The integration of petrological and organic geochemical techniques is crucial for any future studies that use biomarkers to reconstruct the early biosphere. | en_AU |
dc.description.sponsorship | We thank D. Birch and N. Vella from the Microscopy Unit, Faculty of Science and Engineering, Macquarie University, for help and technical assistance with microscopy. M. Bebbington is thanked for preparing the polished sections and S. Craven is thanked for help with the SelFrag. We thank D. Adams and W. Powell for help and technical assistance with major, minor, and trace element analysis. J. Cali from RSES at the Australian National University is thanked for the help and assistance with the isotopic data, and The Society for Organic Petrology (TSOP) is thanked for its funding with a Spackman Award awarded to C.A.P. We acknowledge J. Schmatz (University of Aachen, Germany) for discussion regarding the vein microstructures. We thank three anonymous reviewers for valuable comments that improved this work. Macquarie University is thanked for a PhD scholarship awarded to C.A.P. We gratefully thank the Agouron Institute for funding the AIDP drilling and sample analyses, and the Australian Research Council ( DP130102547 ) for funding. | en_AU |
dc.language.iso | en_AU | en_AU |
dc.publisher | Elsevier | en_AU |
dc.relation | ARC DP130102547 | en_AU |
dc.rights | © 2016 . This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ | en_AU |
dc.subject | Archean | en_AU |
dc.subject | biomarkers | en_AU |
dc.subject | carbonate veins | en_AU |
dc.subject | early life | en_AU |
dc.subject | organic matter | en_AU |
dc.subject | Pilbara Craton | en_AU |
dc.title | In search of early life: Carbonate veins in Archean metamorphic rocks as potential hosts of biomarkers | en_AU |
dc.type | Article | en_AU |
dc.subject.asrc | 040300 | en_AU |
dc.subject.asrc | 040200 | en_AU |
dc.identifier.doi | 10.1016/j.epsl.2016.08.003 | |
dc.type.pubtype | Post-print | en_AU |
Associated file/s
Associated collections