Etienne Médard

Etienne Médard
Université Clermont Auvergne | Univ BPC · Laboratoire Magmas et Volcans

PhD

About

79
Publications
18,308
Reads
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2,472
Citations
Citations since 2016
37 Research Items
1604 Citations
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
Additional affiliations
January 2016 - July 2017
Universities Space Research Association
Position
  • Researcher
September 2008 - present
Université Clermont Auvergne
Position
  • Professor (Associate)
October 2007 - August 2008
ETH Zurich
Position
  • Posdoctoral Associate

Publications

Publications (79)
Article
Full-text available
We designed and carried out experiments to investigate the effect of H2O on the liquidus temperature of olivine-saturated primitive melts. The effect of H2O was isolated from other influences by experimentally determining the liquidus temperatures of the same melt composition with various amounts of H2O added. Experimental data indicate that the ef...
Article
High-pressure, high-temperature experiments have been performed at ~1.2 GPa and 1360-2100 °C to investigate the partitioning of Pt between a silicate melt and a metallic melt. Our experiments indicate that nanonuggets encountered in previous experiments are experimental artifacts, formed at high temperature by oversaturation caused by high oxygen f...
Article
Magma recharge into a differentiated reservoir is one of the main triggering mechanisms for explosive eruptions. Here we describe the petrology of the eruptive products of the last explosive eruption of Tutupaca volcano (southern Peru) in order to constrain the pre-eruptive physical conditions (P-T-XH2O) of the Tutupaca dacitic reservoir. We demons...
Article
In December 2018, an unusually large intra-and extra-caldera eruption took place at Ambrym volcano (Vanuatu). The eruption drained the volcano's five active lava lakes and terminated, at least momentarily, the surface activity that had been ongoing for decades to hundreds of years, sustaining the largest recorded persistent degassing on the planet....
Article
Full-text available
Deep-sea submarine eruptions are the least known type of volcanic activity, due to the difficulty of detecting, monitoring, and sampling them. Following an intense seismic crisis in May 2018, a large submarine effusive eruption offshore the island of Mayotte (Indian Ocean) has extruded at least 6.5 km3 of magma to date, making it the largest monito...
Article
Large silicic explosive eruptions are one of Nature's most hazardous phenomena. Very few have been witnessed and unravelling the complex conditions that lead to these eruptions remains a difficult task because the characteristics of the feeding magma reservoirs are still insufficiently constrained from geophysical imaging. Here we show that a barom...
Article
Full-text available
Piston-cylinder assemblies exhibit inhomogeneous pressure distributions and biases compared to the theoretical pressure applied to the hydraulic press because of the thermal and mechanical properties of the assembly components. Whereas these effects can partially be corrected by conventional calibration, systematic quantification of friction values...
Article
Full-text available
Formalised elicitation of expert judgements has been used to help tackle several problematic societal issues, including volcanic crises and pandemic threats. We present an expert elicitation exercise for Piton de la Fournaise volcano, La Réunion island, held remotely in April 2021. This involved 28 experts from nine countries who considered a hypot...
Article
Full-text available
Potassium-rich magmatism represents subordinate magma volumes worldwide but has been observed in many geodynamic settings. Most potassic magmas are thought to derive from very-low degrees of melting of metasomatized mantle lithologies. We performed piston-cylinder experiments to determine trace element partition coefficients between incipient potas...
Chapter
Des téphras (ou pyroclastites) couvrant une large gamme de granulométries sont éjectés par tous les types d'éruptions. Ils engendrent de nombreux aléas. Leurs retombées peuvent être étudiés après, mais aussi durant, les éruptions. Les techniques d'étude ont beaucoup évolué et sont devenues plus quantitatives. Ceci donne accès à un nombre croissant...
Article
Full-text available
Since 2018, the submarine east flank of Mayotte Island (Comoros archipelago) is the site of a major eruption located at 3.5 km depth bsl on a WNW-ESE volcanic ridge. Samples brought by oceanographic cruises carried out to monitor this seismo-volcanic crisis indicate that this volcanic ridge is built by a bimodal sodic alkaline magmatic series that...
Preprint
Full-text available
Piston-cylinder assemblies exhibit inhomogeneous pressure distributions and biases compared to the theoretical pressure applied to the hydraulic press because of the thermal and mechanical properties of the assembly components. Whereas these effects can partially be corrected by conventional calibration, systematic quantification of friction values...
Article
The French Massif Central represents one of the rare occurrences in Europe where lower Pleistocene fossil deposits are associated to a substantial volcanic activity. Thanks to the abundance of volcanic zircons in the differentiated products of the Monts-Dore/Guéry stratovolcano, we were able for the first time to use U/Pb geochronology on zircon to...
Conference Paper
Full-text available
Following an intense seismic crisis in May 2018, a large submarine effusive eruption offshore the island of Mayotte (SW Indian Ocean) has extruded at least 6.4 km 3 of magma, making it the largest witnessed submarine eruption as well as the largest effusive eruption since Iceland's 1783 Laki eruption. We present a detailed petrological and geochemi...
Conference Paper
Full-text available
The Comoros volcanic archipelago is related to a complex E-W zone of immature right-lateral wrenching of the lithosphere in the context of the Lwandle and Somalian plate boundaries. A major volcano-tectonic crisis began in May 2018 offshore Mayotte, the easternmost island of the archipelago, resulting in the construction of a large submarine volcan...
Article
Full-text available
In September 2017, after more than a hundred years of quiescence, Ambae (Aoba), Vanuatu’s largest volcano, entered a new phase of eruptive activity, triggering the evacuation of the island’s 11,000 inhabitants resulting in the largest volcanic disaster in the country’s history. Three subsequent eruptive phases in November 2017, March 2018, and July...
Article
The Tabas Black Land volcanic field (14 Ma) is on the major right lateral Nayband fault, on the Lut Block, Iran. It has a central area of eroded ventd, surrounded by lavas. Lavas are tilted and folded on the east by the Nayband fault. To the west lavas are undeformed and are in inverted relief. We study the evolution of the volcanic field and asses...
Article
It has been demonstrated for several years that the U–Pb zircon system can provide useful dating information for understanding the time-evolution of the volcanic systems. In addition, in situ techniques were successfully used for determining the formation age of young Pliocene and Pleistocene volcanic rocks and to record the spatial and temporal di...
Article
New series of alumino-silicate glasses spanning a wide range of chemical compositions (basanites, tholeiitic basalts, calcalkaline andesites, peraluminous and peralkaline rhyolites) and with water contents from 0.02 to 6.70 wt% were used for improving the method of quantification of dissolved water with a highly confocal Raman micro-spectrometer. A...
Article
Full-text available
Channel-fed lava flow systems lack detailed thermal and textural studies through the boundary between channelized and dispersed flow, and out to the flow front. Here, chemical, textural and morphological analyses were made to define cooling and crystallisation rates down the entire system, especially through the zone of dispersed flow. We compare t...
Article
Martian meteorites are the only samples available from the surface of Mars. Among them, olivine-phyric shergottites are basalts containing large zoned olivine crystals with highly magnesian cores (Fo 70-85) and rims richer in Fe (Fo 45-60). The Northwest Africa 1068 meteorite is one of the most primitive “enriched” shergottites (high initial ⁸⁷Sr/⁸...
Article
Full-text available
A 70-m-thick, 2200-m-long (51 × 10⁶ m³) trachytic lava flow unit underlies the Puy de Cliergue (Mt. Dore, France). Excellent exposure along a 400-m-long and 60- to 85-m-high section allows the flow interior to be accessed on two sides of a glacial valley that cuts through the unit. We completed an integrated morphological, structural, textural, and...
Article
Full-text available
Melting experiments have been performed at 3 GPa, between 1150 and 1450 °C, on a phlogopite-peridotite source in the garnet stability field. We succeeded to extract and determine the melt compositions of both phlogopite-bearing lherzolite and harzburgite from low to high degrees of melting (ϕ = 0.008–0.256). Accounting for the presence of small amo...
Article
Full-text available
The origin and source rocks of alkali-rich and SiO2-undersatured magmas in the Earth’s upper mantle are still under debate. The garnet signature in rare earth element patterns of such magmas suggests a garnet-bearing source rock, which could be garnet lherzolite or garnet pyroxenite. Partial melting experiments were performed at 2.8 GPa and 1345–14...
Conference Paper
Full-text available
Several Martian meteorites show evidence that volatiles (H, C, S, O, Cl, F) were present during the crust formation [1] [2] [3] [4]. These volatiles influenced magmatic processes (e.g., melt extraction, fractional crystallization, degassing, assimilation, magma mixing), and are, therefore, recorded in minerals that are chemically zoned. In particul...
Article
Santorini caldera has had a long history of plinian eruptions and caldera collapses, separated by 20–40 kyr interplinian periods. We have carried out a study to constrain magma storage/extraction depths beneath the caldera. We analysed H2O in 138 olivine-, pyroxene- and plagioclase-hosted melt inclusions from plinian and interplinian products from...
Article
Full-text available
This study investigates the oxidation of fayalite Fe22+SiO4 that is present in lithophysae from a rhyolite flow (Obsidian Cliffs, Oregon). Textural, chemical, and structural analyses of the successive oxidation zones are used to constrain: (1) the oxidation processes of olivine, and (2) the role of temperature, chemical diffusion, and meteoric infi...
Conference Paper
Full-text available
The partitioning of Fe 3+ between silicate melts and minerals is a key parameter to understand magmatic processes, as it is directly linked to oxygen fugacity (fO2). fO2 is, a priori, not a constant during magmatic processes, and its evolution depends on the compatibility of Fe 3+. We have experimentally determined the partition coefficients of Fe...
Article
Full-text available
asaltic lavas collected at the Muliwai a Pele lava channel, built during 1974 as part of Mauna Ulu’s eruption on Kilauea’s east rift zone, have been studied to investigate the effect of cooling and crystallization on the rheological prop- erties of the lava. We have quantified the viscosity-strain-rate dependence of lava during cooling and crystall...
Article
Full-text available
The Muliwai a Pele lava channel was emplaced during the final stage of Mauna Ulu’s 1969–1974 eruption (Kilauea, Hawaii). The event was fountain-fed, lasted around 50 h, during which a channelized flow system developed, where a 6-km channel fed a zone of dispersed flow that extended a further 2.6 km. The channel was surrounded by initial rubble leve...
Conference Paper
The Cappadocia area of Central Turkey superbly exposes a succession of Neogene dacitic to rhyolitic ignimbrites and fallout deposits, recording 10 Ma of magmatic activity. This provides an excellent example of long-lived, relatively low frequency magmatic system, with a low average magma production rate (about 10-3 km3/a), but short-lived large eru...
Conference Paper
Full-text available
Element map analysis provides accurate bulk rock compositions of LAR 06319 and NWA 1068 that allow the investigation of parental melt compositions. This method shows that olivine-melt disequilibrium cannot be explained by simple olivine accumulation.
Article
Full-text available
Columnar jointing is a common feature of solidified lavas, sills and dikes, but the factors controlling the characteristic stoutness of columns remain debated, and quantitative field observations are few in number. In this paper, we provide quantitative measurements on sizing of columnar joint sets and our assessment of the principal factors contro...
Article
Full-text available
The sound velocities and elastic properties of a series of hydrous rhyolite, andesite, and basalt glasses have been determined by Brillouin scattering spectroscopy at ambient conditions to elucidate the effect of glass composition on the compressibility of dissolved water. Both the adiabatic bulk (KS) and shear modulus (μ) of the dry glasses decrea...
Conference Paper
Full-text available
We report experimental results on the stability of pure Fe3+ fayalite end-member and on fayalite oxidation processes, using microscopic and nanoscopic analyses.
Article
The Auvergne region, in France’s Massif Central, was an important source of gems from the Middle Ages to the end of the 19th century (F. H. Forestier, “Histoire de l’un des gisements de gemmes le plus anciennement connu d’Europe occidentale: Saphirs, grenats et hyacinthes du Puy-en-Velay [History of one the oldest known gem deposits in western Euro...
Article
Full-text available
The processes that give rise to arc magmas at convergent plate margins have long been a subject of scientific research and debate. A consensus has developed that the mantle wedge overlying the subducting slab and fluids and/or melts from the subducting slab itself are involved in the melting process. However, the role of kinematic variables such as...