Géosciences Montpellier
Université de Montpellier
Campus triolet cc060
Place eugène bataillon
34095 montpellier cedex05
FRANCE
Where to find us
How did the evolution of the Earth’s dynamics and the emersion of continental surfaces influence the appearance and evolution of life? How did the irreversible oxidation of the Earth’s surface generate biological and mineralogical diversity, including minerals of economic interest? We address the history of plate tectonics and outer envelopes using field observations on five continents, sedimentological, mineralogical, geochemical and structural analyses, magnetic property measurements, dating and thermo-mechanical modeling.
The theme is organized around 3 main questions
What are the mechanisms involved in the formation, destruction and recycling of continental crust over time? Implications for the onset of plate tectonics?
What are the mechanisms and timing of oxygenation of the atmosphere-hydrosphere-biosphere system, and its influence on the evolution of living organisms and mineralizations of economic interest (Fe, Mn, Au)?
What is the redox balance on a planetary scale, and what are the consequences in terms of habitability?
Our Tools
Les outils utilisés inclus :
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Our studies
The studies are based on an extensive collection of key interval samples spanning the Precambrian era:
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more than 1500 m of drill core from Australia, South Africa and Brazil
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large collection of samples and zircons from 5 continents
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access to a number of core libraries in mining companies in Australia, Brazil, Gabon and South Africa.
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Core shacks in mining companies in Brazil
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Core shacks in mining companies in South Africa
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Core shacks in mining companies in Australia
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Core shacks in mining companies in Gabon
Our strengths
The structuring element of the Primitive Earth theme is that it brings together people interested in internal geodynamics or surface processes, and using complementary methodologies. This duality enables us to study the relationships between the evolution of the Earth’s internal geodynamics, notably the onset of subduction processes and the formation of continental crust, and the evolution of the external envelopes (atmosphere, hydrosphere and biosphere), notably the appearance of photosynthesis and oxygenation of the atmosphere and oceans.
Highlights
[08/30/2024 – Nature Geoscience]
Neoarchaean oxygen-based nitrogen cycle en route to the Great Oxidation Event
Alice Pellerin, Christophe Thomazo, Magali Ader, Camille Rossignol, Eric Siciliano Rego, Vincent Busigny & Pascal Philippot.
The nitrogen isotopic composition of sedimentary rocks (δ15N) can trace redox-dependent biological pathways and early Earth oxygenation. However, there is no substantial change in the sedimentary δ15N record across the Great Oxidation Event about 2.45 billion years ago (Ga), a prominent redox change. This argues for a temporal decoupling between the emergence of the first oxygen-based oxidative pathways of the nitrogen cycle and the accumulation of atmospheric oxygen after 2.45 Ga. Here we report strongly positive δ15N values (>30‰) in the 2.68-Gyr-old shallow to deep marine sedimentary deposit of the Serra Sul Formation, Amazonian Craton, Brazil. Our findings are best explained by regionally variable extents of ammonium oxidation to N2 or N2O tied to a cryptic oxygen cycle, implying that oxygenic photosynthesis was operating at 2.7 Ga. Molecular oxygen production probably shifted the redox potential so that an intermediate N cycle based on ammonium oxidation developed before nitrate accumulation in surface waters. We propose to name this period, when strongly positive nitrogen isotopic compositions are superimposed on the usual range of Precambrian δ15N values, the Nitrogen Isotope Event. We suggest that it marks the earliest steps of the biogeochemical reorganizations that led to the Great Oxidation Event.
https://www.nature.com/articles/s41586-024-07842-x
[Nature Geoscience]
Sub-arc mantle fugacity shifted by sediment recycling across the Great Oxidation Event
Hugo Moreira and colleagues show how the GreatOxidation Event (GOE) between 2.5 and 2.2 billion years ago modified the oxygen fugacity of the mantle and the type of subduction zone magmatism.
[PNAS NEXUS]
Low-phosphorus concentrations and important ferric hydroxide scavenging in Archean seawater
Eric Siciliano Rego and colleagues report a correlation between P and Fe contents measured in 2.74 billion-year-old iron formations showing the same characteristics as those recorded in modern sediments. These results argue for low-phosphorus conditions throughout the first half of Earth’s history, likely as the result of limited continental emergence.
Involved Persons
THEME ANIMATOR : Pascal Philippot
THEME MEMBERS :
Diane Arcay
Nicolas Arnaud
Michael Bonno
Delphine Bosch
Olivier Bruguier
Pierre Camps
Alain Chauvet
Bruno Dhuime
Fanny Garel
Flavia Girard
Arnauld Heuret
Michel Lopez
Manuel Muñoz
Mélodie Philippon
Catherine Thoraval