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Quantification des processus d'infiltration métasomatique au travers de cumulats (intrusion litée de l'île de Rum, Ecosse)

English title Quantifying infiltration metasomatism throughout a mafic crystal mush column (Rum layered intrusion, Scotland)
Applicant Leuthold Julien
Number 145348
Funding scheme Fellowships for advanced researchers
Research institution Institut für Geochemie und Petrologie ETH Zürich
Institution of higher education Institution abroad - IACH
Main discipline Geochemistry
Start/End 01.02.2013 - 30.09.2015
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All Disciplines (2)

Discipline
Geochemistry
Mineralogy

Keywords (7)

crystal mush; layered intrusion; infiltration metasomatism; experimental petrology; fluid inclusion; Rum; Scotland

Lay Summary (French)

Lead
Des processus complexes prennent place dans les chambres magmatiques, à l’aplomb des volcans. Ils peuvent avoir des effets catastrophiques en déclenchant une éruption volcanique, ou être bénéfiques en créant des gisements de minerai. Un travail de précision à différentes échelles et des méthodes analytiques de pointes sont nécessaires afin de déterminer, quantifier et dater chaque événement qui a marqué l’évolution d’une chambre magmatique.
Lay summary

En se refroidissant, les cristaux qui se forment sont idéalement en équilibre avec le liquide contemporain. Mais les chambres magmatiques sont régulièrement réalimentées en magma chaud, provoquant la réaction des cristaux préexistants en déséquilibre avec le nouveau liquide.

Lors d’une première étude financée par le FNS, j’ai eu la possibilité de distinguer différentes étapes de dissolution-recristallisation de cristaux dans la chambre magmatique de l’île de Rum, en Ecosse, refroidie il y a 60 Ma. Mon objectif, avec ce nouveau projet, est de quantifier les modifications des roches et liquides par rapport à une situation plus simple d’un système fermé. Quels sont les volumes de roche affectés, quelles sont les températures nécessaires, quels étaient les cristaux préexistants ? Je vais recréer le même contexte en mélangeant cristaux, liquides et fluides dans de petites capsules placées dans des fourres à 1300-1100°C et 200 bars. Le contrôle de chaque paramètre physico-chimique me permettra de décomposer chacune des étapes du processus de déséquilibre étudié. Les résultats obtenus seront ensuite comparés aux échantillons naturels.

Mon travail permettra de mettre en avant des phénomènes trop souvent négligés dans la plupart des chambres magmatiques. S’il m’est possible de confirmer que les volumes de roches influencées par les phénomènes de dissolution-recristallisation à haute température sont importants, un tel procédé devrait impérativement être considéré lors de l’étude de chambres magmatiques. Les phénomènes étudiés sont certainement responsables de la formation de la plupart des gisements de platine et éléments associés (Ru, Rh, Pd, Os, Ir et Cu, Ni, Au, Ag), mais ils ne sont préservés que sur l’île de Rum. L’étude des processus menant à la concentration de ces métaux dans des proportions économiquement intéressantes permettra d’affiner leur recherche dans le cadre de la prospection minière.

Direct link to Lay Summary Last update: 10.01.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Construction and evolution of igneous bodies: towards an integrated perspective of crustal magmatism
Annen Catherine, Blundy Jonathan, Leuthold Julien, Sparks Steve (2015), Construction and evolution of igneous bodies: towards an integrated perspective of crustal magmatism, in Lithos, 230, 206-221.
Experimental petrology constraints on the recycling of mafic cumulate: a focus on Cr-spinel from the Rum Layered Intrusion, Scotland
Leuthold Julien, Blundy Jonathan, Brooker Richard (2015), Experimental petrology constraints on the recycling of mafic cumulate: a focus on Cr-spinel from the Rum Layered Intrusion, Scotland, in Contributions to Mineralogy and Petrology, 170:12.
Identifying weathering sources and processes in an outlet glacier of the Greenland Ice Sheet using Ca and Sr isotope ratios
Hindshaw Ruth S. Rickli Jörg Leuthold Julien Wadham Jemma Bourdon Bernard (2014), Identifying weathering sources and processes in an outlet glacier of the Greenland Ice Sheet using Ca and Sr isotope ratios, in Geochimica et Cosmochimica Acta, 145, 50-71.
Successive episodes of reactive liquid flow throuh a layered intrusion (Unit 9, Rum Eastern Layered Intrusion, Scotland)
Leuthold Julien Blundy Jon Holness Marian Sides Rachel (2014), Successive episodes of reactive liquid flow throuh a layered intrusion (Unit 9, Rum Eastern Layered Intrusion, Scotland), in Contributions to Mineralogy and Petrology, 167, 1021.

Collaboration

Group / person Country
Types of collaboration
University of Uppsala Sweden (Europe)
- in-depth/constructive exchanges on approaches, methods or results
University of Lausanne Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
University of St Andrews Great Britain and Northern Ireland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
University of Manchester Great Britain and Northern Ireland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
University of Cambridge Great Britain and Northern Ireland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Geological Survey of Canada Canada (North America)
- in-depth/constructive exchanges on approaches, methods or results
University of Bristol Great Britain and Northern Ireland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
ETHZ Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
EMPG XV Talk given at a conference High temperature crystal-melt reaction in mafic igneous complexes 05.06.2016 Zürich, Switzerland Leuthold Julien;
Forstérite 2015 (Formation en Terre Interne) Talk given at a conference Experimental petrology constraints on the recycling of mafic cumulate 06.10.2015 Toulouse, France Leuthold Julien;
Swiss Journée Métallogénique Talk given at a conference Experimental petrology constraints on the recycling of mafic cumulate 13.03.2015 ETH Zürich, Switzerland Leuthold Julien;
AGU Fall Meeting Poster Cr-Spinel as an Indicator of Cumulates Partial Melting and Liquid Hybridization 19.12.2014 San Francisco, United States of America Leuthold Julien;
Table ronde Individual talk Quantification of successive reactive liquid flow episodes in a layered intrusion 03.12.2014 Lausanne, Switzerland Leuthold Julien;
Swiss Geoscience Meeting Talk given at a conference Cr-spinel as an indicator of cumulate partial melting and liquid hybridization 04.10.2014 Fribourg, Switzerland Leuthold Julien;
ETHZ Isotope Group meeting Individual talk Quantification of successive reactive liquid flow episodes in a layered intrusion 02.10.2014 ETH Zürich, Switzerland Leuthold Julien;
ETHZ Magmatic Group meeting Individual talk Quantification of successive reactive liquid flow episodes in a layered intrusion 24.09.2014 ETH Zürich, Switzerland Leuthold Julien;


Communication with the public

Communication Title Media Place Year
New media (web, blogs, podcasts, news feeds etc.) Updates of various pages Wikipedia International 2015
Talks/events/exhibitions Journée métiers FGSE Western Switzerland 2014
Media relations: print media, online media Les secrets du magma se lisent dans les zircons Le Temps Western Switzerland 2014

Associated projects

Number Title Start Funding scheme
161206 Fusion de gabbro dans la croûte océanique inférieure, le long des rides océaniques, et son effet sur le liquide mantellique qui la percolent 01.10.2015 Ambizione

Abstract

The well studied Rum Isle eastern layered intrusion was built up by emplacement of a series of 15 macro-rhythmic units, composed of feldspathic peridotite, troctolite and gabbro. Crystallizing pressure was estimated by Holness (1999) to 200 bars. Rum picritic magma liquid line of descent is complicated by reactive melt/fluid percolation within crystal mush, either originating from continuous cumulate pile compaction or from younger reactive picritic magma intrusion. During the current SNF Prospective Researcher project, I was able to distinguish successive reactive melt flow episodes, based on detailed field work, a meticulous crystal texture study and high quality mineral geochemistry analyses. With this SNF Advanced Researcher project, I will quantify infiltration metasomatism, using a novel experimental approach. The magma liquid line of descent strongly depends on the volatile composition. Accurate experiments require precisely determined starting compositions, to keep uncertainties minimal. Therefore, I will first determine the magma volatile composition, using microthermometry and Raman techniques on aqueous fluid inclusions. Additionally, to test Bédard et al. (1988) hypothesis of a Ca-rich aqueous fluid metasomatic agent, I will complete the aqueous fluid inclusion study with LA-ICP-MS analyses. Conducting experiments and analysing products will be the main task of this project. I will run accurate experiments at 1300 to 1050°C, 200 bars and QFM conditions, using aphyric picritic dike powder as starting material and the determined volatile composition. SEM, EMPA, FEG-probe, LA-ICP-MS and SIMS analyses will give me precious information about evolving phases’ proportion (i.e. changes in porosity and cumulate composition), changing mineral chemistry and mineral-melt partition coefficients. Results will be used together with my field and mineral geochemistry database to present a precise quantitative model. In a second stage, I will conduct mixing experiments between picritic and Ol+Plg±Cpx assemblages in different proportions to decompose infiltration metasomatism processes throughout the Rum crystal mush. The outputs of this timely SNF Advanced Researcher project will have a strong impact on the layered intrusions, metasomatism and experimental petrology communities. Together with new collaborations and developed hard and soft skills, they will considerably strengthen my research profile.
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