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Carbon and nitrogen on the early and deep Earth: isotope fractionation, carbonatites, carbides and Fe-C redox coupling - experiments from 0.01 to 35 GPa

English title Carbon and nitrogen on the early and deep Earth: isotope fractionation, carbonatites, carbides and Fe-C redox coupling - experiments from 0.01 to 35 GPa
Applicant Schmidt Max Werner
Number 153112
Funding scheme Project funding (Div. I-III)
Research institution Institut für Mineralogie und Petrographie ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Mineralogy
Start/End 01.04.2014 - 31.03.2016
Approved amount 620'825.00
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All Disciplines (2)

Discipline
Mineralogy
Geochemistry

Keywords (6)

Isotope fractionation; Carbon; Early Earth; Diamond/Graphite; Carbonatites; Reduced Mantle

Lay Summary (German)

Lead
Dieses Projekt untersucht zum einen die Verteilung von Kohlenstoff zwischen einer dichten Atmosphaere, dem Magmaozean sowie metallischem Kernmaterial in der sich bildenden Erde, zum anderen den tiefen Kohlenstoffzyklus und wie sich dieser ueber die letzten 4.5 Milliarden Jahre entwickelt hat. Dazu werden experimentell bei Druecken und Temperaturen bis 350 kbar und 2200 C die Stabilitaet und physikalischen Eigenschaften der stabilen Reservoire (Kohlenstoff-haltige Mineralien) und der Materialien die Kohlenstoff transportieren (Schmelzen, Fluide und Gase) untersucht. Gleichzeitig wird die Verteilung von Kohlenstoff und seiner Isotope zwischen diesen Phasen bestimmt und anhand dieser Daten die Verteilung des Kohlenstoffes zu Beginn der Erde bestimmt und der sich dann entwickelnde Kohlenstoffkreislauf modelliert.
Lay summary

Inhalt und Ziel

Um obigem Ziel gerecht zu werden, wird in einem Projekt die Verteilung und Isotopenfraktionierung von Kohlenstoff zwischen einer dichten Atmosphaere (10-500 bar) einer Silikat- und einer Metallschmelze gemessen. Damit laesst sich die Ausgangssituation der Erde vor 4.5 Milliarden Jahren bestimmen sowie der bis jetzt unbekannte Kohlenstoffgehalt des Erdkerns modellieren. Um die weitere Entwicklung des Kohlenstoffkreislaufes zu verstehen, wird in einem zweiten Projekt die Kohlenstoffverteilung und Isotopenfraktionierung zwischen Mineralien (Diamant, Graphit, Karbide, Karbonate) und Schmelzen und Fluids untersucht. Dabei spielt der Oxidationszustand des Kohlenstoffs, der sich ueber die Erdgeschichte von oberflaechennah stark reduziert zu stark oxidiert veraendert hat,  eine wesentliche Rolle (von Methan bis CO2 im Fluid). In einem dritten teilprojekt werden dann die physikalischen Eigenschaften von Karbonatschmelzen und damit ihr Transportverhalten sowie die Schmelzbedingungen von Eisenkarbiden im Erdmantel bestimmt.

Gesellschaftlicher Kontext

Um den Kohlenstoffkreislauf ueber geologisch lange Zeitraeume zu verstehen und die CO2-Entwicklung in der Atmosphaere ueber diese Zeitraeume richtig einordnen zu koennen, muss auch der Austausch mit der tiefen Erde, welcher ueber Millionen von Jahre erfolgt, verstanden werden.

Die Entwicklung der anfaenglich extrem reduzierten Sauerstoff-freien Atmosphaere von den Anfaengen bis zum fruehen Leben wird massgeblich durch Austausch mit der tiefen Erde beeinflusst. Die Experimente dieses Projektes werden einen wesentlichen Baustein zum Verstaendniss dieser Dynamik liefern.

Direct link to Lay Summary Last update: 28.03.2014

Responsible applicant and co-applicants

Employees

Publications

Publication
An experimental investigation of the stability of majoritic garnet in the Earth’s mantle and an improved majorite geobarometer.
Wijbrans CH Rohrbach A Klemme S. (2016), An experimental investigation of the stability of majoritic garnet in the Earth’s mantle and an improved majorite geobarometer., in Contributions Mineralogy Petrology, 171, 50.
Ultra-reducing conditions in the mantle: a thermo-dynamic model for SiC formation.
Golubkova A Schmidt MW Connolly JAD (2016), Ultra-reducing conditions in the mantle: a thermo-dynamic model for SiC formation., in Contributions Mineralogy Petrology, 171, 41.
Crystal structure and high pressure – high temperature behavior of carbonates on the K2Mg(CO3)2 – Na2Mg(CO3)2 join.
Golubkova A Merlini M Schmidt MW (2015), Crystal structure and high pressure – high temperature behavior of carbonates on the K2Mg(CO3)2 – Na2Mg(CO3)2 join., in American Mineralogist, 100, 2458-2467.
Experimental determination of trace element partition coefficients between spinel and silicate melt: The influence of chemical composition and oxygen fugacity.
Wijbrans CH Klemme S Berndt J Vollmer C. (2015), Experimental determination of trace element partition coefficients between spinel and silicate melt: The influence of chemical composition and oxygen fugacity., in Contributions Mineralogy Petrology, 69, 45.
Melting of FeCO3 to 20 GPa and thermodynamic properties of siderite melt.
Kang N Schmidt MW Poli S Franzolin E Connolly JAD (2015), Melting of FeCO3 to 20 GPa and thermodynamic properties of siderite melt., in Chemical Geology, 400, 34-43.
Melting of phase D in the lower mantle and implications for recycling and storage of H2O in the deep mantle
Ghosh S Schmidt MW (2014), Melting of phase D in the lower mantle and implications for recycling and storage of H2O in the deep mantle, in Geochimica Cosmochimica Acta, 145, 72-88.
Natural moissanite – a low temperature mineral formed from highly fractionated ultra-reduced COH-fluids.
Schmidt MW Gao C Golubkova A Rohrbach A Connolly JAD (2014), Natural moissanite – a low temperature mineral formed from highly fractionated ultra-reduced COH-fluids., in Progress Earth Planetary Sciences, 1, 27.
The stability of Fe-Ni carbides in the Earth's mantle: evidence for a low Fe-Ni-C melt fraction in the deep mantle.
Rohrbach A, Ghosh S, Schmidt MW, Wijbrans CH, Klemme S (2014), The stability of Fe-Ni carbides in the Earth's mantle: evidence for a low Fe-Ni-C melt fraction in the deep mantle., in Earth Planet Sci Lett, 388, 211-221.
Melting relations in the system FeCO3-MgCO3 and thermodynamic modeling of Fe-Mg carbonate melts.
Kang N Schmidt MW Poli S Franzolin E Connolly JAD, Melting relations in the system FeCO3-MgCO3 and thermodynamic modeling of Fe-Mg carbonate melts., in Contributions Mineralogy Petrology.
Tracing the depositional history of Kalimantan diamonds by zircon provenance and diamond morphology studies.
Kueter N Soesilo J Fedortchouk Y Nestola F Belluco L Troch J Wälle M Guillong M Von Quadt A, Tracing the depositional history of Kalimantan diamonds by zircon provenance and diamond morphology studies., in Lithos.

Associated projects

Number Title Start Funding scheme
166153 Carbon and nitrogen transfer on the early and in the deep Earth 01.04.2016 Project funding (Div. I-III)
140541 Subduction derived carbonatites, related mantle metasomatism, and redox coupling of Fe and C - experiments from 2 to 35 GPa 01.04.2012 Project funding (Div. I-III)
140541 Subduction derived carbonatites, related mantle metasomatism, and redox coupling of Fe and C - experiments from 2 to 35 GPa 01.04.2012 Project funding (Div. I-III)

Abstract

The redistribution of carbon within the early Earth and the deep carbon cycle since Earth accretion is one of the most fascinating topics in modern petrology and geochemistry. This project is about how carbon moves and redistributes in the deep Earth. The tools to understand these transfers between different reservoirs are experiments (i) defining stabilities and compositions of minerals, melts and fluids involved, (ii) quantifying physical properties of carbonatites, and (iii) determining carbon (and nitrogen) isotope fractionation factors between minerals and liquids. In subproject A this project addresses Fe-carbide and Fe-C-melt involving redox equilibria that occur when subduction derived carbonatites reduce to elemental carbon in a metal bearing mantle. Furthermore we investigate the high pressure density and wetting angles of carbonatite melts which are key physical and thermodynamic properties of such melts. Their knowledge is necessary to understand melt percolation and to calculate phase relations of carbonatite melts. Subproject B investigates element and isotope fractionation of N and C between a reducing gas phase, representing the early reduced atmosphere, and a silicate or metal melt representing the magma ocean and suspended metal droplets therein. The experimental results will allow modeling C and N degassing from the magma ocean and establish C and N contents of primordial mantle and core material and to understand the related isotope fractionation. This project addresses the accretion stage of the Earth and its volatile budget. Finally, project C deals with recycling of carbon during subduction, its mobilizing in a fluid or melt and a possible re-precipitation in the mantle. We will investigate carbon isotope fractionation between the main carrier minerals of C (carbonates, graphite, diamond, carbides) and fluids, carbonatites or C-rich silicate melts. This project will constrain changes in the C-isotope composition during recycling into the mantle, the transport ways of carbon in the deep Earth (through the related isotope fractionation) and quantify e.g. the effects of Rayleigh fractionation on the C-isotope composition of diamonds.
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