Thermochronological perspectives on the deep-time evolution of the deep biosphere

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Importance

The Earth’s deep biosphere is one of the least explored and understood environments. It hosts interesting microbial lines to understand the origin and evolution of life on our planet. Understanding the history of these microbial communities requires evaluating the complex evolution of habitable conditions. This study presents the first thermochronological perspective on the habitability of Earth’s Precambrian cratons through time and suggests that the longest continuous habitability record to date does not extend well beyond a billion d ‘years. This thermochronological approach provides a context for prospecting and interpreting the unexplored geological record of the deep biosphere of Earth’s cratons and points to candidate areas for the oldest records of subterranean microorganisms.

Abstract

The Earth’s deep biosphere is home to some of its oldest chemilithotrophic lineages. The history of habitat in this environment is therefore interesting for understanding the origin and evolution of life. The oldest rocks on Earth, formed around 4 billion years ago, are found in continental cratons that have known complex histories due to burial and exhumation. The isolated fluids harbored by fractures in these cratons may have residence times of over a billion years, but understanding the history of their microbial communities requires evaluating changing habitable conditions. Here, we present a thermochronological perspective on the habitability of Precambrian cratons over time. We show that rocks now in the upper few kilometers of the cratons have been uninhabitable (> ∼122 ° C) for most of their lives or have experienced high temperature episodes, so that the longest record of habitability does not exist. does not extend well beyond a billion years. . In several cratons, the conditions of habitability go back only 50 to 300 million years, in agreement with dated biosignatures. The thermochronological approach described here provides a context for prospecting and interpreting the little explored geological records of the deep biosphere of Earth’s cratons, when and where microbial communities may have thrived, and candidate areas for the oldest traces. of chemilithotrophic microbes.


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