Project

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Turning Points in Earth History

English title Turning Points in Earth History
Applicant Mezger Klaus
Number 160034
Funding scheme Project funding (Div. I-III)
Research institution Institut für Geologie Universität Bern
Institution of higher education University of Berne - BE
Main discipline Geochemistry
Start/End 01.07.2015 - 30.11.2019
Approved amount 813'627.00
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All Disciplines (2)

Discipline
Geochemistry
Geochronology

Keywords (4)

oxydation-events; geochemistry; cosmochemistry; mantle-evolution

Lay Summary (German)

Lead
Die Entwicklung der Erde ist gekennzeichnet durch graduelle und kontinuierliche Veränderungen, die von Ereignissen unterbrochen werden die einen neuen Modus im weiteren Prozessverlauf bedingen. In diesem Projekt untersuchen wir drei Schlüsselereignisse die essential waren damit die Erde ein habitabler Planet werden konnte, auf dem höheres Leben sich entwickeln und erhalten konnte. Dazu werden folgende Ereignisse im Detail untersucht: Herkunft der volatilen Elemente in steinigen Planeten, Bildung der ersten grossräumigen Kruste auf der Erde und die Ursachen des zweiten und starken Anstiegs im Sauerstoffgehalt der Atmosphäre im Neoproterozoikum.
Lay summary
 

Die Entwicklung der Erde ist gekennzeichnet durch graduelle und kontinuierliche Veränderungen, die von Ereignissen unterbrochen wurden, die einen neuen Modus im weiteren Prozessverlauf bedingten. In diesem Projekt untersuchen wir drei Schlüsselereignisse, die essential waren für die weitere planetare Entwicklung der Erde und sie massgeblich beeinflussten in der Entwicklung  zu einem geologisch aktiven Planeten mit Plattentektonik, der habitabel wurde und auf dem sich höheres Leben entwickeln und erhalten konnte. Essenziell dafür was Wasser. Deshalb untersuchen wir die Herkunft volatilen Elementen und nehmen dazu das schwerste volatile metallische Element Zinn als Proxy, weil es sehr viele Isotopen besitzt, diese bei unterschiedlichen Prozessen im Laufe der Planetenentstehung fraktioniert werden können und somit Informationen über diese Prozesse liefern können.

Eine Besonderheit der Erde ist ihre grosse Menge an kontinentaler Kruste. Der Beginn der Bildung der ersten sehr grossen Krustensegmente ist nicht genau bekannt, könnte aber mit dem Beginn plattentektonischer Prozesse auf der Erde zusammenhängen. Diese spezielle Phase des frühen Krustenwachstums soll am Beispiel des Singhbhum Kratons (Indien) untersucht werden, weil dort die mit am wenigsten veränderten Gesteine aus diese Zeit erhalten sind.

Die Entwicklung der Erdatmosphäre ist eng an die biologische Evolution gekoppelt. Eine wichtige Frage in diesem Zusammenhang ist die Ursache für den Anstieg des freien Sauerstoffs in der Atmosphäre. In diesem Projekt untersuchen wir den zweiten grossen Schritt im Sauerstoffanstieg im späten Proterozoikum. Insbesondere soll untersucht werden, ob dieser Anstieg eine biologische Ursache hat. Die Variation der stabilen Mo-Isotope in mikrobialen Karbonaten kann dazu Auskunft geben.

Direct link to Lay Summary Last update: 16.07.2015

Lay Summary (English)

Lead
The history of Earth is characterized by gradual and continuous changes that can be interrupted by events that trigger a new mode of operation. This project will study distinct key events in Earth`s history that led to evolution of a habitable planet. We will study the origin of volatiles during planetary accretion, the origin of the first extensive continental crust in the early to mid-Archean and the causes of the second major oxygenation event in the Neoproterozoic.
Lay summary

The history of Earth is characterized by gradual and continuous changes that can be interrupted by events that trigger a new mode of operation. This project will study distinct key events in Earth`s history that were fundamental in influencing subsequent planetary evolution towards a geologically active planet with plate tectonics that became habitable and maintained this habitability. An essential ingredient of any habitable planet is water. We will study the origin of volatiles on Earth by measuring the isotopes of tin, the heaviest among the volatile metallic elements which serves as a surrogate for the source and origin of other volatile elements.

A further key event on Earth is the formation of extensive felsic continental crust that is concomitant with the depletion of the mantle. The beginning of the major crust formation episode is some time in the Archean; its exact timing is obscure but may be related to the initiation of plate tectonics. This crust formation will be studied using high precision isotope ratio measurements on well preserved paleo-Archean rocks with a simple geologic history that can be found in the Singhbum Craton (India).

The changes in atmospheric composition that have accompanied the evolution of life are among the fundamental issues of science today. The timing and extent of early Earth oxygenation is highly controversial. We study the second major increase in atmospheric oxygen in the Neoproterozoic. The key question is whether it is related to biological evolution. If the ocean was already ventilated at 0.8 Ga -resulting from the diversification of life- Mo stable isotope fractionation should be detectable in coeval sedimentary archives. Microbial carbonates will be used as archives because they are abundant in Proterozoic sediments.

Direct link to Lay Summary Last update: 16.07.2015

Responsible applicant and co-applicants

Employees

Publications

Publication
Initial 87Sr/86Sr as a sensitive tracer of Archaean crust-mantle evolution: Constraints from igneous and sedimentary rocks in the western Dharwar Craton, India
Ravindran Arathy, Mezger Klaus, Balakrishnan S., Kooijman Ellen, Schmitt Melanie, Berndt Jasper (2020), Initial 87Sr/86Sr as a sensitive tracer of Archaean crust-mantle evolution: Constraints from igneous and sedimentary rocks in the western Dharwar Craton, India, in Precambrian Research, 337, 105523-105523.
The Pb isotope evolution of Bulk Silicate Earth: Constraints from its accretion and early differentiation history
Maltese Alessandro, Mezger Klaus (2020), The Pb isotope evolution of Bulk Silicate Earth: Constraints from its accretion and early differentiation history, in Geochimica et Cosmochimica Acta, 271, 179-193.
Genesis of the Singhbhum Craton, eastern India; implications for Archean crust-mantle evolution of the Earth
Pandey Om Prakash, Mezger Klaus, Ranjan Sameer, Upadhyay Dewashish, Villa Igor M., Nägler Thomas F., Vollstaedt Hauke (2019), Genesis of the Singhbhum Craton, eastern India; implications for Archean crust-mantle evolution of the Earth, in Chemical Geology, 512, 85-106.
Formation of Archean continental crust constrained by boron isotopes
Smit M.A., Scherstén A., Næraa T., Emo R.B., Scherer E.E., Sprung P., Bleeker W., Mezger K., Maltese A., Cai Y., Rasbury E.T., Whitehouse M.J. (2019), Formation of Archean continental crust constrained by boron isotopes, in Geochemical Perspectives Letters, 23-26.
Earth’s early O2 cycle suppressed by primitive continents
Smit Matthijs A., Mezger Klaus (2017), Earth’s early O2 cycle suppressed by primitive continents, in Nature Geoscience, 10(10), 788-792.
Ultra-trace element characterization of the central Ottawa River basin using a rapid, lexible, and low-volume ICP-MS method
Babechuk Michael, O’Sullivan Edel, McKenna Cora, Rosca Carolina, Nägler Thomas, Schoenberg Ronny, Kamber Balz, Ultra-trace element characterization of the central Ottawa River basin using a rapid, lexible, and low-volume ICP-MS method, in Aquatic Geochemistry.

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
GeoMünster Talk given at a conference Constraints on Earth's Paleoarchean crustal evolution by bulk Lu-Hf isotope analysis of single zircon grains 22.09.2019 Münster, Germany Mezger Klaus; Maltese Alessandro;
Goldschmidt Conference Talk given at a conference Unprecedented High δ98Mo of the Ottawa River: Implications for Marine Palaeoredox Reconstructio 18.08.2019 barcelona, Spain Nägler Thomas; O'Sullivan Edel;
Goldschmidt Conference Poster The Potential Global Contribution of Marine Aerosol to the Mo Cycling in the Critical Zone 18.08.2019 Barcelona, Spain Nägler Thomas; Villa Igor Maria;
Goldschmidt Conference Talk given at a conference Towards a model for the Pb-isotope evolution of bulk silicate Earth 18.08.2019 Barcelona, Spain Mezger Klaus; Maltese Alessandro;
Goldschmidt Conference Talk given at a conference A contribution to the Archean Hf record by bulk Lu-Hf single grain analysis of zircon 18.08.2019 Barcelona, Spain Mezger Klaus; Maltese Alessandro;
Swiss Geoscience Meeting Talk given at a conference A non-traditional stable isotope method to understand Sn isotope fractionation in geochemical and cosmochemical processes 30.11.2018 Bern, Switzerland Pathak Dipankar; Mezger Klaus;
EUG Talk given at a conference Oceanic redox state in the lead-up to Neoproterozoic oxygenation: Insights from REEs and Mo isotopes of microbial carbonates 08.04.2018 Wien, Austria O'Sullivan Edel; Nägler Thomas;
Paneth Kolloquium Poster Stable isotope analysis of Sn: A novel nontraditional isotope application to study planetary materials 11.11.2017 Nördlingen, Germany Pathak Dipankar; Mezger Klaus;
Goldschmidt Conference Individual talk Tin Stable Isotope Analysis: A Comparison between Measurements Corrected Using Different Internal Normalization and External Mass-Bias Method 13.08.2017 Paris, France Pathak Dipankar; Mezger Klaus;
Goldschmidt Conference Talk given at a conference Relics of pristine Paleoarchean continental crust: granitoids from the Bastar craton, India, 13.08.2017 Paris, France Maltese Alessandro; Mezger Klaus;


Associated projects

Number Title Start Funding scheme
188461 Evaluating the contribution of Marine Aerosols to the Mo Surface Water Cycle 01.11.2019 Project funding (Div. I-III)
188592 Turning Points in Earth History Part2 01.11.2019 Project funding (Div. I-III)

Abstract

One major goal of this research project will be to study distinct key events in Earth`s history that were fundamental in influencing subsequent planetary evolution that eventually led to a planet that could be geologically active, support plate tectonics, make it habitable and maintain this habitability. An essential ingredient of any habitable planet is water that exists in its liquid form at part of the time. The origin of water and other volatile components on Earth is still not understood. In this project we will study the origin of volatiles on Earth by measuring the isotopes of tin, the heaviest among the volatile elements that also has a large spread in isotope masses. This element will be studied in different types of meteorites from primitive and differentiated solar system bodies. This element will serve as a surrogate for the source and origin of volatiles in terrestrial planets. A further key event in the evolution of the Earth is the formation of extensive felsic continental crust that is concomitant with the depletion of the mantle in incompatible elements. The beginning of the major crust formation episode is some time in the Archean, but its exact timing is still quite obscure. It can be observed that the mantle derived rocks seem to indicate major mantle heterogeneity at 3.8 Ga followed by a time of a much more homogeneous mantle that becomes heterogeneous again after ca. 3.5 Ga and this degree of heterogeneity continues until today. It is not perfectly clear if this dramatic change reflects a real geologic process (i.e. homogenization of a mantle during the the Hadean and and Early Archean that was differentiated during the magma ocean stage of the Earth) or may be (partially?) due to analytical problems, particularly the back extrapolation in time of isotope ratio measurements on rocks with complex geologic histories. To study this intriguing observation it is planned to obtain high precision isotope ratio measurements on well preserved paleo-Archean rocks with a simple geologic history. Such rocks are exposed in the Singhbum Craton (India) and include mostly igneous and sedimentary rocks that were geologically unaffected since 3.2 Ga and thus belong to the most pristine paleo-Archean rock suites known. These rocks allow a precise determination of initial isotope ratios (Nd, Sr, Hf, Pb) that will yield a firm constraint on mantle heterogeneity for the time of their genesis and thus new insights into the chemical differentiation processes during the early stages of Earth`s history at a time when crustal growth seems to have accelerated significantly. Another key event and turning point in Earth`s history is the second major increase in atmospheric oxygen that appeared in the Neoproterozoic (i.e, Neoproterozoic Oxygenation Event (NOE)). The most significant current question regarding this increase is whether it was an effect or a cause of biological evolution. If ocean oxygenation at 0.8 Ga resulted from the diversification of photosynthetic life-forms, the Mo isotopic composition of microbialites will reveal a shift in the proportion of oxic to reducing Mo sinks. If the NOE represents the Earth's response to a significant modification in the supply of terrestrial weathering products to the ocean due to non-biological (i.e. geologic / tectonic) changes, elevated Mo concentration should be detected in microbialites, without concomitant variations in Mo isotopic compositions.
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