Eric Gloaguen | BRGM - Academia.edu (original) (raw)

Papers by Eric Gloaguen

Ore Geology Reviews, 2019

Lithium, which is an excellent conductor of heat and electricity, became a strategic metal in the... more Lithium, which is an excellent conductor of heat and electricity, became a strategic metal in the past decade due to its widespread use in electromobility and green technologies. The resulting significant increase in demand has revived European interest in lithium mining, leading several countries to assess their own resources/reserves in order to secure their supplies. In this context, we present for the first time a geographically-based and geological compilation of European lithium hard-rock occurrences and deposits with their corresponding features (e.g., deposit types, Li-bearing minerals, Li concentrations), as well as a systematic assessment of metallogenic processes related to lithium mineralization. It appears that lithium is well represented in various deposit types related to several orogenic cycles from Precambrian to Miocene ages. About thirty hard-rock deposits have been identified, mostly resulting from endogenous processes such as lithium-cesium-tantalum (LCT) pegmatites (e.g., Sepeda in Portugal, Aclare in Ireland, Läntta in Finland), rare-metal granites (RMG; Beauvoir in France, Cinovec in the Czech Republic) and greisen (Cligga Head, Tregonning-Godolphin, Meldon in the UK and Montebras in France). Local exogenous processes may result in significant Li- enrichment, such as jadarite precipitation in the Jadar Basin (Serbia), but they are rarely related to economic lithium grades such as in Mn-(Fe) deposits, or in bauxite. We also identified major common parameters leading to Li enrichment: 1) a pre-existing Li-bearing source; 2) the presence of lithospheric thickening, which may be a favorable process for concentrating Li; 3) a regional or local extensional regime; and 4) the existence of fractures acting as channel ways for exogenous processes. Furthermore, we point out the heterogeneity of knowledge for several orogenic settings, such as the Mediterranean orogens, suggesting either a lack of exploration in this geographical area, or significant changes in the orogenic parameters.

The Variscan Armorican belt was the World leading producer of antimony at the beginning of the tw... more The Variscan Armorican belt was the World leading producer of antimony at the beginning of the twentieth century. However, geological controls on the deposits remain unconstrained. Here, we illustrate the field setting of mineralisations and perform a statistical analysis using Geographical Information System software, geophysical and geological data. The analysis shows that Sb deposits are spatially correlated with high-density and magnetic zones. This may reflect the presence of mafic/ultramafic bodies at depth – a suggestion that is further supported by numerous occurrences of doleritic dykes throughout the region. Future antimony prospecting should focus on the high-density and high-magnetic zones which comprise about 18% of the Armorican massif. Links between Sb deposits and mafic intrusions are recognised elsewhere in the West European Variscan belt, emphasising that these may be key for antimony prospecting in deformation belts. Terra Nova, 28: 138–145, 2016

Apatite is a ubiquitous accessory mineral found in most magmatic rocks and is often the only U-be... more Apatite is a ubiquitous accessory mineral found in most magmatic rocks and is often the only U-bearing mineral available to date mafic rocks because primary zircon and/or baddeleyite are not present. In this paper, U-Pb LA-ICP-MS dating of apatite was applied to seven different dike and sill samples of dolerite from the Variscan belt of Brittany (Armorican Massif, western France). These dolerites, which are characterized by a within-plate tholeiite geochemical signature, are organized in several dense swarms across the belt. Their geochemical compositions are homogeneous although they intrude a large geographical area subdivided into several domains each characterized by different tectonic-metamorphic settings. Their emplacement ages were so far poorly constrained due to the difficulty to date these mafic rocks using either the 40Ar/39Ar or the U-Pb methods on classical minerals like mica, plagioclase, or zircon. Although the closure temperature of apatite is lower than the emplacement temperature of the magma, physical models show that the time needed to solidify and cool these mafic dikes and sills below the apatite closure temperature is basically of the order of 100 years or less. Consequently, the U-Pb dates obtained on apatite can be interpreted as the emplacement ages for these mafic intrusions. Our results demonstrate that, in all cases, the apatite grains do carry enough radiogenic Pb to be dated by in situ U-Pb analyses and yield a 207Pb-corrected mean age of 363.4 ± 5.8 Ma. These results reveal the existence of a major and short-lived magmatic event in the Variscan belt of Brittany during the Devonian-Carboniferous transition, a feature further highlighted by field evidence. Beyond the geological implications of these results, U-Pb LA-ICP-MS dating of apatite appears to represent an ideal tool to date small size mafic intrusions.

Journal of African Earth Sciences, 2015

ABSTRACT The Kédougou Kénieba Inlier (KKI) of eastern Senegal forms a typical Paleoproterozoic gr... more ABSTRACT The Kédougou Kénieba Inlier (KKI) of eastern Senegal forms a typical Paleoproterozoic greenstone belt characterised by low-metamorphic sequences of volcanic rocks and volcano-sediments that have been intruded at various stages by gabbroic suites and calc-alkaline granitoids. The main structures of the KKI comprise two anastomosing structures about N-S trending shear belts that are distinguished into the western Main Transcurrent Zone (MTZ) and the eastern Senegalo-Malian Shear zone system (SMSZ). These shear belts are taken to define the limits between the western Mako, the central Diale-Kéniebandi and the eastern Daléma-Kofi domains even though transitions exist between their characteristic deposition sequences.

Mineralogical Magazine, Jul 1, 2013

On a visit to the old Chèdeville underground quarry near Ambazac (Haute Vienne, France) in the ex... more On a visit to the old Chèdeville underground quarry near Ambazac (Haute Vienne, France) in the exceptionally dry spring of 2011, some large crystals up to 30 centimetres long were discovered in a normally flooded zone of the workings in this lithium-rich pegmatite. Like certain specimens from pegmatites in the North of Portugal, these proved on analysis to consist of petalite pseudomorphosed into clay minerals and K-feldspar. This rare lithium silicate had already been reported from the locality by Raimbault (1998) in particular, as small crystals from a restricted precise zone of the pegmatite but this is the first description of crystals several tens of centimetres in dimension. The study also helps to characterise the nature of the Chèdeville pegmatite. Keywords: Chèdeville, Limousin, Ambazac monts, lithic pegmatite, petalite.

Sb-deposits in the Variscan Armorican belt constitute a large part of this resource in France not... more Sb-deposits in the Variscan Armorican belt constitute a large part of this resource in France notably with the La Lucette deposit (42000 tons of Sb). Although these mineralizations are known since the 19 th century, relationships between geological features and antimony deposits remain unclear. Here we perform a spatial statistical analysis using Geographic Information System software (GIS), geophysical and geological data (Ripley's function, spatial distribution analysis of geophysical values, and distance to the nearest neighbour) in order to identify particular geophysical zones where Sb-deposits are potentially clustering and to assess affinity with different geological objects. We show that there are specific ranges of gravity and magnetic values associated to Sb-deposits. These characteristic ranges outline several zones of high density and relatively high magnetic susceptibility that cover only 17.6 % of the surface of the Armorican Massif and contain or are close to more...

A new type of large ultramafic intrusion-hosted Fe-Ti-V deposit has been discovered by BRGM in th... more A new type of large ultramafic intrusion-hosted Fe-Ti-V deposit has been discovered by BRGM in the West-African Archean craton. The N'Guérédonké intrusive complex (7 x 0.9 km) is composed of a dunite core surrounded by rims of wehrlites and pyroxenites. This syntectonic complex is emplaced within a crustal scale shear zone. The disseminated mineralisation made of ilmenite and magnetite is mainly hosted by pyroxenite units along the northern and southern contacts. Surface and drilling exploration work (47 drill holes totalling 10124 m) demonstrate polyphased injection of successive ultramafic melts from core to rims and also crosscutting of dunite core by a network of successive pyroxenite generations. A 3D modeling constrained by drilling and joined inversion of magnetic and gravity data ascribe the thickness of the intrusion up to 1000 m. A first very conservative titanium resource assessment on a small part of the intrusion (1000 x 100 x 250 m) lead to definition of 141.38 Mt ...

ABSTRACT Warning: this map was derived from the October 2011 version of the ProMine Mineral Depos... more ABSTRACT Warning: this map was derived from the October 2011 version of the ProMine Mineral Deposits(MD) database. It therefore does not include subsequent updates of the database. The list of 14 critical commodities is based on the report published by the European Commission, DG Entreprise and Industry: &quot;The raw materials initiative - Critical raw materials for the EU. Report of the Ad-hoc Working Group on defining critical raw materials&quot;

ABSTRACT Warning: this map was derived from the April 2012 version of the ProMine Mineral Deposit... more ABSTRACT Warning: this map was derived from the April 2012 version of the ProMine Mineral Deposits(MD) database. It therefore does not include subsequent updates of the database.

The “Domaine Schisteux de Galice Centrale“ (DSGC) is located within the NW Spain (Galicia), withi... more The “Domaine Schisteux de Galice Centrale“ (DSGC) is located within the NW Spain (Galicia), within internal part of the Hercynian domain. The late-orogenic evolution is characterized by the emplacement of four granites called G1 (335 Ma), G2 (322 Ma), G3 (318 Ma) and G4 (303 Ma). Pegmatite and granite dykes and sills associated with gold and Sn-W lodes are found around the intrusions. Gold-bearing lodes are linked to the G3 and Sn-W ones to G2. Structural data demonstrated that deformation is continuous since granite emplacement until mineralization. The mineralogical and textural characteristics are similar for Au and Sn-W systems. Fluid inclusion study reveals that aquo-carbonic fluids are dominant although high-salinity fluids are found. The Ar/Ar dating of granites and orebearing veins (ca. 300 Ma) were interpreted to traduce the effects of Ar resetting or, alternatively, to record cooling through temperatures of 300-400°C. The age of mineralization remains unknown but certainly...

Mineralogy and Petrology, 2015

Mineralogy and Petrology (in press), 2015

Ore Geology Reviews, 2019

Journal of African Earth Sciences, 2015

Mineralogical Magazine, Jul 1, 2013

Mineralogy and Petrology, 2015

Mineralogy and Petrology (in press), 2015

Relations between Au / Sn-W mineralizations and late hercynian ... E. Gloaguen, A. Chauvet, Y. Br... more Relations between Au / Sn-W mineralizations and late hercynian ... E. Gloaguen, A. Chauvet, Y. Branquet, O. Gerbeaud & C. Ramboz Institut des Sciences de la Terre d'Orléans UMR CNRS 6113, Université d'Orléans, BP 6759, 45067 Orléans Cedex2, France

ABSTRACT The Bouillante geothermal field, located on the west coast of Guadeloupe (Lesser Antille... more ABSTRACT The Bouillante geothermal field, located on the west coast of Guadeloupe (Lesser Antilles), was explored in the 1970s, developed in the 1980s, brought into production in 1986, and expanded in 2005 to currently produce up to 15 MWe. In addition to its electricity-producing role, the Bouillante field is an outstanding research laboratory for improving our knowledge of a reference high temperature (260°C) geothermal system in island-arc environment. A great deal of scientific research and exploration investigation have been carried out on the Bouillante geothermal field for 10 years, including geological investigation (volcanism), structural analysis of the fluid conduits, geophysical investigations both offshore (magnetics and high-resolution shallow seismics, see Calcagno et al.) and onshore (gravimetry, electrical resistivity tomography profile and passive seismic, see Gailler et al.), characterization of the surface and deep hydrothermal manifestations, numeric geological modelling of the developed field, fluid geochemistry and tracer tests (Sanjuan et al.) and hydrogeological modelling. This large range of multidisciplinary data has made it possible to develop an innovative conceptual model of this type of high-temperature geothermal system. The model highlights the major influence of structural control on the development of the geothermal activity at different scales and especially on the geometry of the reservoir. It also explores new ideas concerning the geothermal system in terms of heat source, fluid circulation and spatio-temporal scenario. This scenario takes into account all events from the early magmatic activity of the Bouillante volcanic Chain (~500,000 y) up to the beginning of the geothermal field some 250,000 years later, having probably started with a phreatic explosion in the bay of Bouillante (see Patrier-Mas et al., Verati et al.). This 2D geothermal resource conceptual model will be used as an exploration tool to reduce geological risks for the next exploration drilling campaign. This work is supported by the French Agency for Energy and Environment (ADEME).

ABSTRACT L'influence des circulations fluides sur la cristallisation est connue depuis de... more ABSTRACT L'influence des circulations fluides sur la cristallisation est connue depuis de nombreuses années, cependant il existe peu d'approches quantitatives décrivant ce phénomène dans les milieux naturels. Cette étude propose une méthode d'estimation des paléo-vitesses de circulation à partir d'observations texturales et de modèles de croissance cristalline liés à l'hydrodynamique du milieu. L'étude de la texture des calcites précipitées dans les canalisations de la source thermale de Chaudes-Aigues (Cantal, France) met en évidence un allongement des sections dans le plan isomorphe (0001). Cet allongement a une distribution bi-modale avec deux orientations préférentielles symétriques par rapport à l'axe de la canalisation et faisant chacune un léger angle par rapport cet axe. Pour comprendre comment une telle texture s'est formée, un modèle analytique de croissance cristalline a été élaboré en utilisant les équations décrivant la diffusion des éléments dans le cadre de l'approximation de la couche limite. Cette approximation permet de reconstruire cette texture à partir d'une expression quasi-analytique de la croissance cristalline dans un fluide en écoulement. Malheureusement ce modèle est limité aux écoulements ayant une valeur élevée du nombre de Reynolds local. Pour s'affranchir de cette limite, une deuxième approche est proposée. Elle se base sur la résolution des équations de Navier-Stockes et de la conservation de la masse par éléments finis. Les calculs montrent que lors de la croissance cristalline, les flux chimiques absorbés sur les faces amonts sont supérieurs à ceux des faces avales. Une série de simulations pour des vitesses de circulations variant de 10-6 à 10-2 m/s montre que le rapport du flux de la face amont sur celui de la face avale varie avec la vitesse du fluide. Les flux étant proportionnels aux épaisseurs des bandes de croissance, ces simulations sont utilisées pour déterminer les vitesses de circulation des fluides à partir des rapports des épaisseurs de bande de croissance. Cette nouvelle méthode est appliquée aux tourmalines formées par métasomatoses lors de la mise en place des leucogranites de la Chaîne Hercynienne (Galice, Espagne). Les vitesses de circulations estimées sont relativement rapides avec une moyenne de l'ordre de 10-3 m/s.

ABSTRACT The magmatic-hydrothermal transition is subject to debate in numerous cases where minera... more ABSTRACT The magmatic-hydrothermal transition is subject to debate in numerous cases where mineral deposits are spatially related to granite intrusions. In most of cases, intrusion only appears as a rheological trap for mineralizations (e.g. Pb-Zn deposits). Some rare examples suggest a magmatic origin for mesothermal gold deposit emphasis by magmatic to hydrothermal transition textures (Mustard, 2003). We studied two neighbouring deposits (Brués As-Au deposit and Mina Soriana Sn-W deposit), both emplaced on top of two different granite cupola (respectively Boborás granite and Beariz granite). For both granites, during emplacement, granitic melts injected hosting micaschists forming regular sills and dykes network. In both cases: i) Granitic dykes, sills and feldspar-quartz veins developed hydrothermal alteration within host micaschists (mainly tourmalinitisation at Mina Soriana and greisenification at Brués). Internal textures of the quartz-feldspar veins show gradual evolution from quartz-feldspar (border) to early single quartz (center). ii) this early quartz-feldspar veins are reopened and filled by a second quartz generation, followed by arsenopyrite deposition. iii) A third generation of quartz filled arsenopyrite cavities. Further fracturation of these composite veins allow trap of polymetallic sulphides, followed by bismuthinite stage. Differences are: Sn-W deposition during early quartz stage in Mina Soriana and Au-Bi-Te deposition with associated phengite during ultimate stage at Brués. Exceptional exposures and similarities of textural/mineralogical evolutions between these two deposits allow us to trace a continuous transition from magmatic to hydrothermal processes during ore deposits genesis. In spite of aquo-carbonaceous and low salinity fluid inclusions in Brués gold deposit, like other intrusion-related gold deposits (Lang and Baker, 2001), this continuous transition suggests the persistence of a magmatic input into fluid responsible for the mineralising stages. Lang J.R. and Baker T. (2001). Mineralium Deposita, 36:477-489. Mustard R. (2003).Proceedings of the 7th SGA Meeting, Athens, Greece, 24-28 Aug. 2003, 1:355-358.

Lithium Process Chemistry, Jun 22, 2015

This chapter provides data and information on the factors underpinning the current lithium demand... more This chapter provides data and information on the factors underpinning the current lithium demand/supply balance and its long-term evolution from a sustainable development perspective. Many issues outlined in this chapter are also applicable to other rare metals of strategic importance to advanced economies, including for the transition toward a “green,” low-carbon economy. After a warning about the issues related to data availability and reliability, it starts with an analysis of the current lithium demand through a presentation of the main lithium uses and an estimation of the future demand that could result from these uses. It then presents the supply side, by providing information on lithium minerals and carriers (brines), lithium deposit types, and their respective importance, with an estimate of the currently known resources, reserves, and production processes. Indications of capital expenditure and of operating costs related to the main production processes are given. Further on, issues related to Li recycling are discussed. In the concluding part, several factors that will determine the long-term demand/supply balance (2025–2030 and beyond) are discussed, highlighting the need for a mix of policy decisions, governance, and scientific innovations if the objective of a long-term balance is to be met.