| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 4727129 | Gondwana Research | 2014 | 6 Pages |
•New data reveal multiple sources for carbonaceous material (CM) in the Apex chert.•Some of the CM is 100s my to 1 by younger than the rocks of the Apex chert.•Thus bulk measurements might not be suited to quest for early life in these rocks.
The Pilbara Craton in Western Australia contains the best-preserved and most complete record of Archean rocks in the world. As such, they are some of the most studied rocks in the world; paleontologists, isotopic geochemists, geologists and geobiologists have all investigated these rocks for clues about the early biosphere and atmosphere. Here we show using high-resolution transmission electron microscopy that the carbonaceous material found in the Apex chert, and potentially in other associated units, was formed by multiple processes such as abiotic catalytic synthesis and/or biological synthesis. We use these data as well as the geological history of the craton to demonstrate that when the rocks of the Pilbara Craton experienced a high degree of post-depositional hydrothermal alteration, carbonaceous material could have been remobilized and redeposited. As the carbonaceous material within the Apex chert samples was formed over nearly a billion years, bulk chemistry, even at the micron level, will be unable to unambiguously delineate the presence of life in these ancient rocks, although nanoscale observations may provide a way forward in the search for ancient life.
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