ELEMIN · How the earliest life on Earth became mineralized

How the earliest life on Earth became mineralized

- What is the problem/issue being addressed? Project ELEMIN targets geochemical and petrographic investigations of Proterozoic and Archean stromatolites, i.e. lithified microbial mats, to (I) determine the genesis of mineral phases preserved within the stromatolites and (II) reconstruct physico-chemical environmental conditions prevailing in microbial habitats. The timing and conditions of formation of individual mineral phases in stromatolites is under debate and, thus, their reliability as geochemical archives is uncertain. One controversy is whether different mineral phases record the elemental composition derived from continental weathering or from submarine hydrothermal sources. - Why is it important for society? The evolution and environmental conditions favoring life on Earth are of interest for mankind. Stromatolites are considered exemplary for potential microbial life on other planets and provide unique archives to better understand environmental conditions favoring the evolution of life on Earth. A detailed understanding of favorable environmental conditions for early life on Early Earth opens new horizons for society and researchers to better understand environmental conditions of putative life in the search of life on other planets. - What are the overall objectives? The objectives of project ELEMIN are to determine the mineralization history of mineral phases in stromatolites, to compare the source(s) of elements in Proterozoic and Archean seawater and to reconstruct environments in which early life on Earth developed. - Conclusions 1. Carbonates of the 1 billion year old Paranoá Group stromatolites (Brazil) and the 3.34 billion years old Strelley Pool Formation stromatolites (Australia) are prime geochemical archives of ancient waters from which chemical sediments precipitated. Rare earth elements, radiogenic Sm-Nd and stable Cd isotopes show pristine geochemical compositions. In contrast, silica phases in the Strelley Pool stromatolites were formed during the post-depositional processes. 2. Stromatolites from the Strelley Pool Formation were formed in seawater that received variable elemental fluxes from high-temperature, hydrothermal fluids and from terrestrial weathering and erosion processes. Stromatolites from the Paranoá Group were deposited under more oxidized atmospheric-hydrospheric conditions in an epicontinental lagoon and on the open shelf. Their elemental budget is exclusively derived from continental weathering. 3. A novel geochemical toolbox applied to stromatolites from the Mesoproterozoic Paranoá Group stromatolites unravels different environmental conditions within individual layers of stromatolitic carbonates on centimeter-scale resolution, i.e. can be used to distinguish carbonate that formed at the seawater-mat interface from carbonate that was formed within the microbial mat. This unique geochemical combination may serve in future studies as prime tool to reconstruct biogeochemical conditions in ancient microbial mats of the earliest microbial communities on Earth.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз