~3,240 Ma, Kangaroo Caves Formation, East Pilbara, Western Australia
Pyritic filaments from within the VHMS deposit were first reported by Rasmussen (2000) and interpreted as microfossils, likely thermophilic, chemotrophic prokaryotes. These filaments are 0.5–2.0 γm in width and up to 300 γm long, can be straight, curved or sinuous and exhibit putative biological behaviour including preferred orientations, clustering and intertwining (Fig. B71). They only occur in early mineral phases that are clearly cross cut by later fractures.
Non-biological fibrous mineral growths are relatively common in hydrothermalore deposits so this is the null hypothesis that needs to be rejected here. Recollection and re-examination of this material by the author shows that these filaments differ from non-biological ones in being unbranched, of constant diameter, and distinctively entangled. There is as yet, however, no evidence for cellular organisation nor for metabolic processing. Even so, this is an intriguing discovery consistent with the hypothesis of a thermophilic habitat for primitive life forms, in the vicinity of sub-marine hydrothermal vents at depths of ~1,000 m, below the light penetration zone.
KeywordsBlack Smoker Massive Sulphide Deposit Volcanogenic Massive Sulphide Geological Context Volcanogenic Massive Sulphide Deposit
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