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Fusion de gabbro dans la croûte océanique inférieure, le long des rides océaniques, et son effet sur le liquide mantellique qui la percolent

English title Lower crust gabbro partial melting in oceanic spreading ridges and its effect on percolating reactive mantle-derived melt
Applicant Leuthold Julien
Number 161206
Funding scheme Ambizione
Research institution Institut für Geochemie und Petrologie ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Geochemistry
Start/End 01.10.2015 - 28.02.2019
Approved amount 456'996.00
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All Disciplines (2)

Discipline
Geochemistry
Mineralogy

Keywords (6)

gabbro; ophiolite; MORB; crystal-melt reaction; experimental petrology; spreading ridges

Lay Summary (French)

Lead
Grâce à l’étude des chambres magmatiques notre compréhension des phénomènes volcaniques a considérablement augmenté. Une chaîne de volcans actifs longue de 60'000 km sillonne le fond des océans, autours de la Terre. Ces volcans sous-marins ainsi que les chambres magmatiques qui les alimentent sont particulièrement difficiles à étudier. Cependant, ils sont responsables de la formation de 70% des roches à la surface de notre Terre. 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 (fusion, dissolution) des cristaux préexistants. Je fais l’hypothèse que les réactions entre liquides magmatiques et cristaux/roches préexistants ont jusque là été sous-estimées. Si confirmé, mes recherches offriront une bien meilleures compréhension des processus prenant place dans la source profonde des volcans océaniques.
Lay summary

Malheureusement, les réactions entre cristaux et liquides magmatiques ne peuvent être observés in situ. Pour mieux décrire, reproduire et quantifier ces réactions, je vais réaliser une étude pluridisciplinaire incluant des observations à large échelle sur le terrain, des analyses microtexturales et chimiques des roches échantillonnées et de leurs minéraux, combinée à une étude expérimentale. Dans des fours à 1250 à 1100°C et 1 à 4000 bars, je vais reproduire les cristaux naturels et ainsi contraindre les conditions physico-chimiques auxquelles ils se sont formés. Le contrôle des paramètres physico-chimiques me permettra de décomposer chaque étape du processus de déséquilibre étudié et ainsi déterminer quels sont les volumes de roche affectés, quelles sont les températures de cristallisation, quels étaient les cristaux préexistants.

Mon travail va permettre de mettre en avant des phénomènes trop souvent négligés dans la plupart des chambres magmatiques mais ayant une grande importance pour les bilans chimiques et thermiques des volcans et de leur réservoir, le cycle des roches profondes et la formation de gisements métallifères. 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. 

  

 

Deutsch Title: Schmelzen von Unterkrustengabbro in ozeanischen Rücken und dessen Effekt auf durchsickernde, reaktive Mantelschmelzen

English title: Lower crust gabbro partial melting in oceanic spreading ridges and its effect on percolating reactive mantle-derived melt

Direct link to Lay Summary Last update: 14.08.2015

Responsible applicant and co-applicants

Employees

Publications

Publication
Translating Scientific Articles to the Non-scientific Public Using the Wikipedia Encyclopedia
Leuthold Julien, Gilli Adrian (2019), Translating Scientific Articles to the Non-scientific Public Using the Wikipedia Encyclopedia, in Frontiers in Education, 4, 1-10.
The zircon Hf isotope archive of rapidly changing mantle sources in the south Patagonian retro-arc
Ewing Tanya, Müntener Othmar, Leuthold Julien, Ramírez de Arellano Cristóbal, Baumgartner Lukas P, Schaltegger Urs (2018), The zircon Hf isotope archive of rapidly changing mantle sources in the south Patagonian retro-arc, in Geochimica et Cosmochimica Acta, 131(3-4), 587-608.
Incremental growth of mid- to upper-crustal magma bodies during Arabia-Eurasia convergence and collision: A petrological study of the calc-alkaline to shoshonitic Meghri-Ordubad Pluton
Rezeau Hervé, Leuthold Julien, Tayan Rodrik, Hovakimyan Samvel, Kouzmanov Kalin, Moritz Robert (2018), Incremental growth of mid- to upper-crustal magma bodies during Arabia-Eurasia convergence and collision: A petrological study of the calc-alkaline to shoshonitic Meghri-Ordubad Pluton, in Journal of Petrology, 59(5), 931-966.
Partial Melting of Lower Oceanic Crust Gabbro: Constraints From Poikilitic Clinopyroxene Primocrysts
Leuthold Julien, Lissenberg C. Johan, O'Driscoll Brian, Karakas Ozge, Falloon Trevor, Klimentyeva Dina N., Ulmer Peter (2018), Partial Melting of Lower Oceanic Crust Gabbro: Constraints From Poikilitic Clinopyroxene Primocrysts, in Frontiers in Earth Science, 6, 1-20.
Impact of glacial activity on the weathering of Hf isotopes – Observations from Southwest Greenland
Rickli Jörg, Hindshaw Ruth S., Leuthold Julien, Wadham Jemma L., Burton Kevin W., Vance Derek (2017), Impact of glacial activity on the weathering of Hf isotopes – Observations from Southwest Greenland, in Geochimica et Cosmochimica Acta, 215, 295-316.
30 Myr of Cenozoic magmatism along the Tethyan margin during Arabia–Eurasia accretionary orogenesis (Meghri–Ordubad pluton, southernmost Lesser Caucasus)
Rezeau Hervé, Moritz Robert, Leuthold Julien, Hovakimyan Samvel, Tayan Rodrik, Chiaradia Massimo (2017), 30 Myr of Cenozoic magmatism along the Tethyan margin during Arabia–Eurasia accretionary orogenesis (Meghri–Ordubad pluton, southernmost Lesser Caucasus), in Lithos, 288-289, 108-124.
Mineralogical, geochemical, and textural indicators of crystal accumulation in the Adamello Batholith (Northern Italy)
Fiedrich Alina M., Bachmann Olivier, Ulmer Peter, Deearing Chad D., Kunze Karsten, Leuthold Julien (2017), Mineralogical, geochemical, and textural indicators of crystal accumulation in the Adamello Batholith (Northern Italy), in American Mineralogist, 102, 2467-2483.

Collaboration

Group / person Country
Types of collaboration
Université of Toulouse France (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
University of Geneva Switzerland (Europe)
- Publication
- Research Infrastructure
University of Tasmania Australia (Oceania)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
University of Cardiff Great Britain and Northern Ireland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
ETHZ Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Manchester University Great Britain and Northern Ireland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
University of Lausanne Switzerland (Europe)
- 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
Swiss Geoscience Meeting Talk given at a conference High temperature crystal-melt reactions in mafic igneous complexes 30.11.2018 Bern, Switzerland Leuthold Julien;
GeoPetro Seminar Individual talk Recent advances in Magma mixing in mafic sill complexes 25.10.2018 ETH Zürich, Switzerland Leuthold Julien;
International Symposium on Experimental Mineralogy, Petrology and Geochemistry Talk given at a conference The role of oxygen fugacity on clinopyroxene: major, minor and REE elements chemistry 18.06.2018 Clermont-Ferrand, France Leuthold Julien;
International Symposium on Experimental Mineralogy, Petrology and Geochemistry Poster Trace Element Partitioning in Fractionating Mid Ocean Ridge Basalts 18.06.2018 Clermont-Ferrand, France Leuthold Julien;
EGU Talk given at a conference Crystal-melt reaction within the lower oceanic crust: East Pacific Rise (IODP 345 expedition) 09.04.2018 Vienne, Austria Leuthold Julien;
EGU Talk given at a conference High temperature crystal-melt reaction in mafic igneous complexes 09.04.2018 Vienne, Austria Leuthold Julien;
EGU Poster Crystal-Melt Reaction within the Lower Oceanic Crust 09.04.2018 Vienne, Austria Leuthold Julien;
Journée Magmatique Talk given at a conference A basalt/gabbro clinopyroxene-based oxometer 26.01.2018 Zürich, Switzerland Leuthold Julien;
Journée magmatique Talk given at a conference Influence of oxygen fugacity on clinopyroxene-basalt partitioning 13.01.2017 Genève, Switzerland Leuthold Julien;
AGU Poster Partial melting of the mafic lower oceanic crust 12.12.2016 San Francisco, United States of America Leuthold Julien;
AGU Talk given at a conference Identification and quantification of gabbro cumulate partial melting in mafic igneous complexes 12.12.2016 San Francisco, United States of America Leuthold Julien;
Swiss Geoscience Meeting Talk given at a conference Partial melting of the mafic lower oceanic crust 18.11.2016 Geneva, Switzerland Leuthold Julien;
EMPG XV Talk given at a conference High temperature crystal-melt reaction in mafic igneous complexes 05.06.2016 ETH Zürich, Switzerland Leuthold Julien;
Journée magmatique Talk given at a conference Partial melting of the mafic lower oceanic crust 08.01.2016 Bern, Switzerland Leuthold Julien;
Forstérite Talk given at a conference Experimental petrology constraints on the recycling of mafic cumulate 06.10.2015 Toulouse, France Leuthold Julien;


Communication with the public

Communication Title Media Place Year
Talks/events/exhibitions ArtSci 2019 – Hémisphères (ETHZ) German-speaking Switzerland 2019
New media (web, blogs, podcasts, news feeds etc.) Crystal mush Wikipedia Encyclopedia International 2019
New media (web, blogs, podcasts, news feeds etc.) Deep crustal hot zone Wikipedia Encyclopedia International 2018
Talks/events/exhibitions ETH Dozierende-Lunchseminar German-speaking Switzerland 2018
Talks/events/exhibitions ETH Innovedum learning and teaching Fair German-speaking Switzerland 2018
New media (web, blogs, podcasts, news feeds etc.) Lower oceanic crust Wikipedia Encyclopedia International 2018
Talks/events/exhibitions Science in tomorrow's classroom (poster at EGU) International 2018
Talks/events/exhibitions Eye on Science German-speaking Switzerland 2017
Other activities SNSF Scientific Image Competition Western Switzerland German-speaking Switzerland 2017

Associated projects

Number Title Start Funding scheme
145348 Quantification des processus d'infiltration métasomatique au travers de cumulats (intrusion litée de l'île de Rum, Ecosse) 01.02.2013 Fellowships for advanced researchers

Abstract

MORB (i.e. Mid Ocean Ridge Basalt, erupted along spreading ridges) covers 70% of the Earth surface. Its composition is used to estimate the mantle source partial melting conditions and composition. However, closely associated lavas and melt inclusions may cover a very wide geochemical range. Expensive 1D drilling projects in active spreading ridges and studies on ophiolites (i.e. obducted [i.e. lifted in a mountain chain] fossil oceanic crust and mantle) provide important constrains on spreading ridges processes. The original complexity in structures and lithologies is additionally complicated by cumulate-liquid reactions, resulting in significant mineralogical, textural and chemical variations of cumulate rocks and percolating liquid. Although this has important implications, it is frequently neglected. Along spreading ridges, successive mantle-derived melt batches intrude, percolate and react with the oceanic lithosphere. Current models state that mantle rocks react with ascending, percolating mantle-derived pyroxene-undersaturated melt that are responsible for the formation of the dunitic transition zone (i.e. a hundreds of meter thick olivine-rich rocks layer below the Moho [i.e. the mantle - crust interface]). Trapped mantle-derived melt crystallizes as gabbro (i.e. olivine + plagioclase + clinopyroxene-rich rocks) lenses similar to the lower crustal layered gabbro, and clinopyroxene and Cr-spinel saturated melts (pyroxenite, wehrlite, chromitite) intrudes the lower crust. Dunite and troctolite also occur within the lower oceanic crust. Their petrogenesis is strongly debated. In the analogue successively replenished Rum shallow layered intrusion, Leuthold et al. (2014a) have recently demonstrated and quantified gabbro partial melting and mixing with intruded reactive picrite (i.e. hot mafic basalt). The products are clinopyroxene-poor gabbro, troctolite and dunite restites and clinopyroxene- and Cr-enriched liquids. The latter crystallized abundant chemically distinct clinopyroxene rims around partly resorbed clinopyroxene relics in melt channels, veins of pyroxenite and spinel, as illustrated by the following reaction: initial rock (Olivine1 +Plagioclase1 +Clinopyroxene1) + hot reactive melt (picrite) = restite (Olivine1 ±Plagioclase1 relics) + modified melt (Clinopyroxene-rich basalt) = modified rock (Olivine2 +Plagioclase2 +Clinopyroxene2 +Spinel)Applying our model to (fast-)spreading ridges, I suggest: 1) Some lower oceanic crust and dunitic transition zone dunites and troctolites formed by olivine ± plagioclase fractionation from hot picrite, from gabbroic crystal mush re-heating and from gabbro cumulate partial melting; 2) Late stage clinopyroxenite, gabbronorite and wehrlite (i.e. olivine + pyroxene ± plagioclase-rich rocks) crystallized from pyroxene-saturated gabbro partial melts mixed with invading mantle-derived hot melt. MORB liquid represents fractionated mantle-derived melt, hybridized during percolation through the oceanic crust filter. For the first time, I will use experimental petrology, combined with field observations, mineral micro-textures, bulk rock and mineral geochemistry and numerical modelling, to quantify melt-rock interactions in the lower oceanic crust. I will start with field campaigns to the world´s best studied Oman ophiolite, and the distinctly fresh Leka ophiolite (Norway). I will acquire micro-textural and micro-analytical data on collected and lent samples to testify melt-rock interactions evidenced by reactions and distinct mineral generations. The preliminary results are very promising. I will run and analyse three sets of experiments at ETHZ, in collaboration with Prof. Peter Ulmer: (1) phase equilibria experiments of mantle-derived melt at lower crust pressure, (2) experiments of mantle-derived melt equilibrated with gabbro and (3) kinetic experiments of mantle-derived melt percolation into gabbro. Thanks to a multi-disciplinary approach, I will produce a robust quantitative numerical model about reactive liquid flow in the oceanic lower crust and its effect on the MORB liquid line of descent and the percolated lower oceanic crust. The outcomes will offer a new vision on the evolution of mantle-derived melt, with important consequences for spreading ridges processes and mantle geochemistry.
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