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Using Archean sedimentary rocks to understand how the first continents were formed

Applicant Garçon Marion
Number 161218
Funding scheme Ambizione
Research institution Institut für Geochemie und Petrologie ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Geochemistry
Start/End 01.09.2016 - 31.05.2019
Approved amount 468'276.00
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All Disciplines (2)

Discipline
Geochemistry
Geochronology

Keywords (6)

Sedimentary rock; Archean; Continental crust; Superior Province; Sm-Nd isotopic compositions; Lu-Hf isotopic compositions

Lay Summary (French)

Lead
Il y a plusieurs milliards d’années, l’apparition des premiers continents emmergés a certainement eu un impact profond sur l’évolution de notre planète, le développement de la vie non-aquatique et les cycles géochimiques de l’eau, du carbone et de l’oxygène. Cependant nos connaissances sur le timing, la composition et les mécanismes de formation de la croute continentale dans la première partie de l’histoire de la Terre (époque Archéenne, de 4.5 à 2.5 milliards d’années) sont peu connus et très débattus dans la communauté scientifique. Les roches temoins de cette époque sont rares et souvent très mal préservées par le temps, ce qui rend leur étude d’autant plus difficile et controversée. De plus, la plupart des études précédentes se sont focalisées sur l’analyse d'un type de roche, les roches magmatiques, ce qui ne permet pas d’apprécier la composition et la morphologie de la croute Archéenne dans sa globalité.
Lay summary

Contenu et objectifs du travail de recherche

Dans ce projet, nous proposons d’étudier les compositions chimiques et isotopiques (Sm-Nd, Lu-Hf, U-Th-Pb, Rb-Sr) de roches sédimentaires Archéennes bien préservées et échantillonnées dans le plus grand craton au monde: le craton Canadien. Ces roches contiennent les produits d’érosion des continents emmergés à la surface de la Terre il y a ~3.8 et 2.7 milliards d’années. Leur analyse apportera des informations détaillées sur la taille et morphologie des anciens continents, sur la nature des roches qui les constitutaient et sur l’environnement qui les entouraient.

 

Contexte scientifique et social du projet de recherché

Notre projet repose l’analyse géochimique de haute précision d’échantillons extremement rares, certains faisant même parties des roches les plus vieilles jamais découvertes sur Terre. Les résultats de ce projet fournira des informations inédites et peut-etre de nouvelles perspectives sur l’evolution précoce de notre planète.   

Direct link to Lay Summary Last update: 18.05.2016

Responsible applicant and co-applicants

Employees

Publications

Publication
High-precision strontium isotope analysis of geological samples by thermal ionisation mass spectrometry
Henshall Tom, Cook David L., Garҫon Marion, Schönbächler Maria (2018), High-precision strontium isotope analysis of geological samples by thermal ionisation mass spectrometry, in Chemical Geology, 482, 113-120.
Factors influencing the precision and accuracy of Nd isotope measurements by thermal ionization mass spectrometry
Garçon Marion, Boyet Maud, Carlson Richard W., Horan Mary F., Auclair Delphine, Mock Timothy D. (2018), Factors influencing the precision and accuracy of Nd isotope measurements by thermal ionization mass spectrometry, in Chemical Geology, 476, 493-514.

Collaboration

Group / person Country
Types of collaboration
N. T. Arndt, ISTerre, Université Grenoble Alpes France (Europe)
- in-depth/constructive exchanges on approaches, methods or results
E. Van Hees, MNDM, Timmins Canada (North America)
- in-depth/constructive exchanges on approaches, methods or results
M. Boyet, Laboratoire Magmas et Volcans, UCA, Clermont-Ferrand France (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
D. Murphy, Queensland University of Technology, Australia Australia (Oceania)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
J. O'Neil, University of Ottawa Canada (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
H. Rizo, University of Montréal Canada (North America)
- in-depth/constructive exchanges on approaches, methods or results
J. Goutier, MERN Canada (North America)
- in-depth/constructive exchanges on approaches, methods or results
R. W. Carlson, Carnegie Institution of Washington United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Goldschmidt conference - Invited keynote Talk given at a conference Creating Earth’s most ancient crust 13.08.2018 Boston, United States of America Garçon Marion;
Goldschmidt conference - Invited oral presentation Talk given at a conference A new look at the Nd isotopic record of sedimentary rocks through Earth’s history 13.08.2018 Boston, United States of America Garçon Marion;
EGU general meeting Poster Using Archean sedimentary rocks from the Superior Province to decipher the crustal history and composition of the Canadian Shield 09.04.2018 Vienna, Austria Garçon Marion;
Invited seminar at Brown University Individual talk Erosion of Archean continents and recycling into the Earth’s mantle 08.03.2018 Providence, United States of America Garçon Marion;
Goldschmidt conference Talk given at a conference 142Nd Anomalies in Mid- to Late- Archean Sedimentary Rocks: Large-scale Recycling of Hadean Crust? 14.08.2017 Paris, France Garçon Marion;


Abstract

Knowing how and when the first continents were formed is an important, first order question in Earth Sciences. The appearance of the first continents has had a profound effect on the geodynamics of our planet, including the morphology and topography of the early Earth’s surface. These key processes also drive the global geochemical cycles, including that of water, carbon or oxygen, that eventually contributed to the development of a habitable environment for primitive life. Yet, our knowledge of the timing, composition and formation mechanisms of the continental crust in the first two billion years of Earth history is far from complete, and is limited by the sparse outcrops of Archean rocks exposed at the Earth’s Surface today. Most recent studies have focused on the igneous Archean record to investigate the mechanisms by which the early continents were formed and have evolved through time. Limited research has concentrated on the chemical and isotopic signatures of Archean sedimentary rocks. This is precisely what the proposed project aims to do. Sedimentary rocks amalgamate the erosion products of large continental areas, reflecting the full spectrum of lithologies that were exposed at the surface of the early Earth. Therefore, they offer a more comprehensive view of the composition and morphology of the Archean continents that is not available from the igneous rock record. The proposed project focuses on chemical and detrital sedimentary rocks from the Superior Province (3.0-2.7 Ga) and the Saglek-Hebron area (3.8 Ga) in the Canadian Shield. These samples are unique witnesses of Early and Late Archean sedimentation. They have trapped the vestiges of ancient continent-formation processes that can be explored using petrological and geochemical analyses at ETH Zurich. The samples will be analyzed for petrography, trace and major element concentrations, in-situ U-Pb and Hf isotopes on zircons and high-precision whole-rock Nd-Hf-Pb-Sr isotopic compositions. These combined data will provide new insights into the origin and compositional evolution of the continental crust eroded in different settings, as well as the paleo-climatic conditions, sediment depositional environment and continent topography in the Early and Late Archean. This information is needed to constrain the geodynamic processes involved in the formation and evolution of the Archean continents, and to clarify the role and importance of mantle plumes, subduction and collision processes at the Archean time. Samples from the Saglek-Hebron area, dated at ~3.8 Ga, are amongst the most ancient remnants of sedimentary rocks discovered on Earth so far. They have never been subjected to high-precision isotopic analysis, and will therefore bring new perspectives and ideas concerning the early evolution of our planet. Samples from the Superior Province are associated with some of the largest ore deposits in the world, and their geochemical characterization will allow a better understanding of the relationship between metallogenesis and Archean geodynamic processes. The proposed project promotes the application of cutting-edge analytical methods in geochemistry, with an emphasis on further methodological development to measure in-situ isotopic compositions in detrital minerals. The research plan also includes strong international collaborations.
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