Fabrice Gaillard

• Researcher at CNRS Orleans Campus

If primitive arc magmas are primarily oxidized or if they acquire their oxidizing character during crustal evolution remains debated. Mineral-melt V partitioning is extremely redox sensitive and has the potential to resolve this debate, but critical low-temperature, hydrous experimental partitioning data are limited. We present new experimental V p...

Les ressources métalliques jouent un rôle majeur dans la transition énergétique, à la fois pour le développement de nouvelles technologies et dans la production et le stockage d’énergies vertes.Ressources métalliques 1 propose une sélection d’études de provinces métallogéniques ou de gisements européens remarquables qui permettent d’aborder la ques...

A method for analyzing low-salinity fluids (up to ~11 wt% NaCl equivalent) that have been equilibrated with felsic melts in high-pressure, high-temperature experiments is reported. Experiments were performed at a pressure of 200 MPa and 800 °C in internally-heated pressure vessels, wherein magmatic fluids were quenched and recovered in a multi-step...

This study presents new insights into the effects of halogens (F and Cl) and phosphorous (P) on rare earth element (REE) partitioning between carbonatite and alkaline silicate melts. F, Cl and P are elements that are abundant in carbonatites and alkaline magmatic systems and they are considered to play an important role on the REE behaviour. Noneth...

Carbonatites host Earth’s main REE deposits, with bastnaesite (LREE)CO3F being the main economic REE-bearing mineral. However, bastnaesite mineralisation processes are debated between hydrothermal or magmatic origin. This study aims to assess if bastnaesite can be magmatic, and to characterise the REE behaviour during carbonatite crystallisation. C...

The core – mantle differentiation in the magma ocean constitutes a major planetary event that involved two elements that are essential to life: carbon (C) and hydrogen (H). These two elements are conventionally classified as volatiles (i.e. atmophile), but they can also evolve into being siderophile and lithophile at the extreme conditions found in...

The distribution of nitrogen between the different terrestrial reservoirs (core-mantle-atmosphere) and how this may have changed since the earliest planetary stages is uncertain. In particular, the primordial degassing processes of the magma ocean and its role in the formation of the atmosphere remains to be quantified. Since no geological samples...

Cette synthèse inédite dresse un panorama des terres rares en Europe et au Groenland à travers les aspects physico-chimiques, minéralogiques, socio-économiques, gîtologiques, géodynamiques et métallogéniques. This unprecedented synthesis provides an overview of rare earth elements in Europe and in Greenland. All aspects dealing with mineralogy, so...

The C-H-O-N-S elements that constitute the outgassed atmosphere and exosphere have likely been delivered by chondritic materials to the Earth during planetary accretion and subsequently processed over billions of years of planetary differentiation. Although these elements are generally considered to be volatile, a large part of the accreted C-H-O-N...

Previous modeling of carbonate subduction by high‐pressure experimentation has allowed to propose scenarios for bulk carbon return to the mantle, but the detailed transfer mechanisms have seldom been studied. We monitored carbonate–silicate reactions by combining high‐pressure experiments and synchrotron‐based X‐ray diffraction. Carbonates break do...

Exoplanetary science continues to excite and surprise with its rich diversity. We discuss here some key aspects potentially influencing the range of exoplanetary terrestrial-type atmospheres which could exist in nature. We are motivated by newly emerging observations, refined approaches to address data degeneracies, improved theories for key proces...

Nitrogen, carbon, hydrogen and sulfur are essential elements for life and comprise about 1 % of terrestrial planet masses. These elements dominate planetary surfaces due to their volatile nature, but the Earth’s interior also constitutes a major C-H-N-S reservoir. Resolving the origin of the surficial versus deep volatile reservoirs requires the pa...

Decompression melting of the upper mantle produces magmas and volcanism at the Earth's surface. Experimental petrology demonstrates that the presence of CO2 and H2O enhances peridotite melting anywhere within the upper mantle down to approximately 200–300 km depth. The presence of mantle melts with compositions ranging from carbonate-rich to silica...

Sulfur is an important element present in natural kimberlites and along with CO2, S can play a role in the kimberlite degassing. We have investigated experimentally the change in S content and CO2 solubility in synthetic kimberlitic melts in response to a range of pressure (0.5 to 2.0 GPa) and temperature (1500 to 1525 °C). Several initial S concen...

Exoplanetary science continues to excite and surprise with its rich diversity. We discuss here some key aspects potentially influencing the range of exoplanetary terrestrial-type atmospheres which could exist in nature. We are motivated by newly emerging observations, refined approaches to address data degeneracies, improved theories for key proces...

The widespread low seismic velocity zone (LVZ) in the shallow oceanic mantle has long been debated in terms of mantle melting. At LVZ depths, volatiles (CO 2 and H 2 O) are present in minute amounts, which implies mantle incipient melting down to below 1000 • C with the production of minute amounts of volatile-rich melt, well below 1 vol.%. However...

Rare earth element (REE) enrichments in carbonatites are often described as resulting from late magmatic-hydrothermal or supergene processes. However, magmatic pre-enrichment linked to the igneous processes at the origin of carbonatites are likely to contribute to the REE fertilisation. Experimental constraints reveals that immiscibility processes...

This paper reviews habitability conditions for a terrestrial planet from the point of view of geosciences. It addresses how interactions between the interior of a planet or a moon and its atmosphere and surface (including hydrosphere and biosphere) can affect habitability of the celestial body. It does not consider in detail the role of the central...

This paper reviews habitability conditions for a terrestrial planet from the point of view of geosciences. It addresses how interactions between the interior of a planet or a moon and its atmosphere and surface (including hydrosphere and biosphere) can affect habitability of the celestial body. It does not consider in detail the role of the central...

Recent investigation showed that the CO 2 solubility in silicate melts is strongly affected by the #Mg (MgO/MgO + CaO). CO 2 solubility is decreasing with increasing #Mg implying that CO 2 molecules dissolves in the vicinity of Ca atoms to form CO 32– molecular groups. We have investigated several CO 2 -bearing (up to 17.2 wt%) silicate glasses usi...

The original PDF version of this Article contained an error in which Fig. 3 and its legend were omitted and Equations 5 and 6 contained errors.This has been corrected in the PDF version of the Article. The HTML version was correct from the time of publication.

Abundant granitic rocks exposed in ancient mountain belts suggest that crustal melting plays a major role in orogenic processes. However, complex field relations and superposition of multiple tectonic events make it difficult to determine the role of melting in orogenesis. In contrast, geophysical measurements image present-day crustal conditions b...

Carbonatite and alkaline magmas are often associated and constitute the principal deposits of REE. Several studies suggested that the economic enrichment of those magmas is related to hydrothermal and supergene processes which remobilized the REE, but little is known about magmatic processes potentially responsible for a pre-enrichment. The princip...

Carbonatite and alkaline magmas are often associated and constitute the principal deposits of REE. Several studies suggested that the economic enrichment of those magmas is related to hydrothermal and supergene processes which remobilized the REE, but little is known about magmatic processes potentially responsible for a pre-enrichment. The princip...

Carbonatites and alkaline magmas to a lesser extent, constitute one of the principal resources of rare metal (REE, Nb, Ti, Zr). No clear cause of enrichment of the carbonatite has so far been isolated. Our statistical analyse reveals the optimum conditions for which carbonatite melts get enriched by >10 with respect to the residual silicate melts....

Alkaline magmatism is formed in intraplate rifting context by partial melting of the mantle. There are two main geological objects resulting from this magmatism: Alkaline Complexes wich correspond to provinces composed by alkaline silica-undersaturated magma (nephelinite or phonolite) and carbonatites which are enriched in carbon dioxide and extrem...

Sulfur is a minor but ubiquitous element in magmas, and is behind major volatile species in magmatic fluids and volcanic gases. It has been shown that sulfur dissolves in silicate melt either as reduced species (sulfide, S 2-) at oxygen fugacity (fO2) values typically below that of the FMQ buffer, or as oxidized species (sulfate, S 6+) at fO2 gener...

Carbonatite and alkaline magma are key pieces of the deep carbon cycle and constitute one of the principal resources of rare metal (REE, Nb, Ti, Zr). Little is known on the processes responsible for rare metal enrichments since magmatic, metamorphic and hydrothermal events are often tangled. The aim of this study is to simulate, by experiments at p...

Partitioning of chalcophile and siderophile elements between sulfide and silicate melts (D sul/sil) has been largely investigated, mainly through experiments at mantle conditions and under low oxygen fugacities (fO2 < FMQ-1). However, the formation of magmatic sulfide ore deposits occurs at crustal conditions and most likely at higher oxygen fugaci...

Carbon dioxide is a ubiquitous component of low-silica melts such as kimberlites or melilitites. It is currently assumed that CO2 molecules dissolving in low-silica melts as carbonate groups (CO3²⁻) induce a strong polymerization of the silicate network; however, the exact molecular configuration of this dissolution mechanism is still debated. Usin...

Mantle-derived volcanic rocks on Mars display physical and chemical commonalities with mafic-ultramafic ferropicrite and komatiite volcanism on the Earth. Terrestrial komatiites are common hosts of massive sulfide mineralization enriched in siderophile-chalcophile precious metals (i.e., Ni, Cu, and the platinum-group elements). These deposits corre...

Most of the intrusions in the Noril’sk-Talnakh region (Siberia) are hosted in thick sedimentary sequences including abundant evaporitic and terrigenous sedimentary rocks. Three mafic-ultramafic intrusions in this region contain unusually thick massive sulfide deposits, which represent one of the world’s largest economic concentrations of Ni, Cu and...

Deep mantle melts contain massive amounts of CO2 but three critical issues related to the effect of CO2 on molecular structure and physical properties of magmatic melts remain poorly constrained: 1) there is no exact picture of CO2 dissolution mechanism in silicate melt, 2) the silicate melt polymerization upon CO2 dissolution has not been reliably...

Following an experimental approach conducted between 0.5 and 1.5 GPa, we investigated the change in CO2 solubility as a function of the XMg (MgO/(MgO+CaO)) for a range of silicate glasses. The synthesised CO2-bearing glasses have XMg up to 0.72, stoichiometric NBO/T (degree of polymerization) up to 2.6 corresponding to highly depolymerized composit...

Geophysically detectible mid-lithospheric discontinuities (MLD) and lithosphere-asthenosphere boundaries (LAB) beneath cratons have received much attention over recent years, but a consensus on their origin has not yet emerged. Cratonic lithosphere composition and origin is peculiar due to its ultra-depletion during plume or accretionary tectonics,...

• Les gisements de terres rares sont divisés en deux grandes catégories: d’une part les gisements primaires ou endogènes associés aux processus magmatiques et hydrothermaux (carbonatites, complexes alcalins, placers etc...) , et d’autre part les gisements secondaires ou exogènes dont les enrichissements sont liés à des processus sédimentaires et/ou...

Magnetotelluric surveys image conductive anomalies at depth in the crust. To interpret the conductive layers underneath the Himalaya-Tibet Collision Zone, we carried out experimental measurements of the electrical conductivity of hydrated leucogranite melts under high temperture and high pressure. The bulk rock was collected from Burang county in T...

On Earth, high temperature mafic to ultramafic lava flows, such as komatiites and ferropicrites of the Archean and Proterozic eons, can be hosts to Ni-Cu-PGE sulphide mineralisation. Mechanical/thermo-mechanical erosion and assimilation of sulphur-rich crustal rocks is ascribed as the principal mechanism that leads to sulphide supersaturation, batc...

One Sentence Summary: Geophysical, laboratory conductivity and petrological experiments reveal that deep electrical conductivity anomalies beneath the Central Andes, Cascades and Taupo Volcanic Zone image the ponding of super-hydrous andesitic melts which contributes to the growth of continental crust. The formation of the continental crust at sub...

Transitional melts, intermediate in composition between silicate and carbonate melts, form by low degree partial melting of mantle peridotite and might be the most abundant type of melt in the asthenosphere. Their role in the transport of volatile elements and in metasomatic processes at the planetary scale might be significant yet they have remain...

Aqueous fluids and melts (silicate, carbonate/carbonatites or metallic melts) are major vectors of massand heat transfer in planetary interiors and play an important role in a variety of geochemical andgeodynamical processes that shape the internal and surficial evolution of planetary systems. Theseprocesses occur over a broad range of pressure and...

Dai and Karato (2014a) reported new electrical conductivity measurements on oriented single crystals of hydrous olivine showing a higher increase in conductivity and conductivity anisotropy at high temperature than previously reported. After recalling that the highest conductivities of the upper mantle (e.g. >0.1 S/m) cannot reasonably be explained...

The Earth's mantle redox state regulates the fate and transfer of metals by magmatism, buffers the igneous inputs of volcanic gases in the atmosphere and controls the depth of mantle melting. It therefore strongly affects ore forming processes, biogeochemical cycles and deep geodynamic processes. This paper reviews the current knowledge on the redo...

Carbon dioxide and water, being present in the Earth's mantle at concentration levels of tens to hundreds of ppm, greatly lower the peridotite solidus temperature and drastically modify the composition of produced melts. The presence of CO2 produces silica-poor, carbonate-rich liquids at the onset of melting, and these liquids shift toward silica r...

Emissions of sulphur and metals from magmas in Earth’s shallow crust can have global impacts on human society. Sulphur-bearing gases emitted into the atmosphere during volcanic eruptions affect climate, and metals and sulphur can accumulate in the crust above a magma reservoir to form giant copper and gold ore deposits, as well as massive sulphur a...

Emissions of sulphur and metals from magmas in Earth's shallow crust can have global impacts on human society. Sulphur-bearing gases emitted into the atmosphere during volcanic eruptions affect climate, and metals and sulphur can accumulate in the crust above a magma reservoir to form giant copper and gold ore deposits, as well as massive sulphur a...

T he demand for metals continues to grow, but the capital available for prospecting is limited. Scientific innovations and improved understanding of how economically viable mineral deposits form are therefore critical to aid the search for new deposits at moderate cost 1,2. The Witwatersrand gold deposit in South Africa is the source of 40% of the...

Résumé du contenu du manuscrit: Ce manuscrit est organisé en sept parties suivies de deux annexes. Le premier bloc est un curriculum vitae étendu résumant de façon succincte mon vécu scientifique et quelques points charnières de ma carrière, puis de façon classique, sont déclinées mes activités et productions scientifiques. Les parties deux et troi...

To better constrain the rheology of the mantle, experimental studies on olivine grain growth have been conducted (Faul and Scott, 2006; Karato, 1989; Nichols and Mackwell, 1991) since the grain size is an important parameter under dynamic regimes (e.g. diffusion creep and grain boundary sliding). In order to better define the melt effect on the rhe...

To better constrain the rheology of the mantle, experimental studies on olivine grain growth have been conducted (Faul and Scott, 2006; Karato, 1989; Nichols and Mackwell, 1991) since the grain size is an important parameter under dynamic regimes (e.g. diffusion creep and grain boundary sliding). In order to better define the melt effect on the rhe...

It has long been proposed that water incorporation in olivine has dramatic effects on the upper mantle properties, affecting large scale geodynamics and triggering high electrical conductivity. But the laboratory-based laws of olivine electrical conductivity predict contrasting effects of water, precluding the interpretation of geophysical data in...

Despite CO2 is the second most abundant volatile species implied in magmatic systems, its impact on the molecular structure of aluminosilicate glasses in complex systems is currently not well-constrained. Inasmuch, whether CO2 induces an increase in glass polymerization or not is yet not clear for complex glass compositions. Using the set of nephel...

Carbonated melts constitute a key medium in the global deep carbon cycle: their impact on the geochemical signature of deep rocks is well studied because of their role as metasomatic agents in the deep mantle. However, their physical properties and in particular their electrical conductivity at high temperature and high pressure remain poorly const...

Magmatic degassing is ubiquitous and enduring, yet its impact on both planetary surficial chemistry and how it may have varied among planetary systems remains imprecise. A large number of factors are likely to be involved in the control of magmatic gas compositions, leading roles being given to the redox state and volatile abundances in planetary i...