ABSTRACT The mafic-ultramafic Samapleu deposits of the Yacouba complex, which host nickel, copper sulfides, and platinum-group minerals, are located in the Biankouma-Silipou region, western Ivory Coast. These intrusions originate from the mantle and would have been established during the Proterozoic (2.09 Ga) around 22 km deep within the Archean granulites (3.6–2.7 Ga) which at least partially contaminated them. Platinum-group and sulfide minerals from the Samapleu deposits were studied using optical microscopy, scanning electron microscopy, the electronic microprobe, X-ray fluorescence, fire assay, and a Thermo Fisher Scientific Delta S isotope ratio mass spectrometer system. The sulfide mineralization (mainly pyrrhotite, pentlandite, chalcopyrite ± pyrite) is mainly disseminated with, in places, semi-massive to massive sulfide veins. It is especially abundant in pyroxenite horizons with net or breccia textures. The isotopic ratios of sulfur measured from the sulfides (an average of 0.1‰), the R factor (between 1500 and 10,000), and the Cu/Pd ratios indicate a mantle source. Thus, the sulfides would have formed from sulfide liquids produced by immiscibility from the silicate mantle magma under mafic-ultramafic intrusion emplacement conditions and with possible geochemical modification of the magmas by assimilation of the surrounding continental crust. The platinum-group minerals (michenerite, merenskyite, moncheite, Co-rich gersdorffite, irarsite, and hollingworthite) are mainly associated with the sulfide phases. The nature of the platinum-group minerals is indicative of the probable role of late-magmatic hydrothermal fluids during the mineralizing process.

ABSTRACT The Conakry Igneous Complex is a mafic-ultramafic intrusion emplaced contemporaneously with the opening of the Atlantic, forming a complex, 55 km x 5 km dyke-like body within which three main episodes of injection have been recognized, characterized by a lack of mineral layering. Unit 1 consists of dunite and related facies, Unit 2 of wehrlite and pyroxene peridotite and Unit 3 corresponds to various gabbro facies. Units 1 and 2 constitute the Kaloum Peninsula; Unit 3 is its NW extension, forming the 1010 m high Mount Kakoulima. Unit 3 intrudes the two previous units and corresponds to a tholeiitic liquid that crystallized in an almost closed system, and thus exhibits a strong differentiation trend, in contrast to Units 1 and 2. Mineral compositions suggest the existence of a deeper magma chamber where a first stage of differentiation occurred. Disseminated base-metal sulfides (BMS) are present in all units of the complex and earlier descriptions have mentioned a “massive sulfide layer” with 2 to 4 g/t PGE. Platinum-group minerals (PGM) are almost everywhere included in or attached to composite Ni–Fe–Cu sulfides. Most PGM grains form complex associations resulting either from exsolution or alteration. It is characteristic of the Conakry Igneous Complex PGM, described here for the first time, to be dominated by (Pd,Pt)(Te,Bi) minerals with rare Pd,Sn and Pd,Pb compositions and an absence of Pt,Pd sulfides and Pt,Pd antimonides. The constant association of the PGM with the BMS shows that the magmatic sulfide liquid acts as an efficient collector of PGE. In such a dynamic environment, the process leading to the formation of massive sulfides must be sought in the accumulation of sulfides in the conduit following host-rock assimilation. Accordingly, considering the multiple injection processes that characterize the whole intrusion, the potential for discovering additional Ni–Cu–PGE mineralization in the Conakry Igneous Complex remains high.

Several ophiolite bodies that have been a significant source of chromium ore are located in the Vardar Zone of Macedonia. Three relatively small (maximum 15 × 4 km) bodies have been studied in detail. In the Radusa and Lojane complexes, the mantle series consisting of harzburgite and rare dunite are well preserved, whereas minor pyroxenite and gabbro occurrences belong to a poorly preserved cumulate series. The Rabrovo massif corresponds to the basal part of the cumulate sequence. In all three complexes, chromitite mineralization occurs as pods and irregular layered bodies and exhibits all the characteristics of typical ophiolite mineralization with nodular, orbicular, net, schlieren or massive texture, and an Mg–Cr-rich composition. Platinum-group minerals (PGM) are associated with the chromitite concentrations. Described for the first time in Macedonia, they are typical of ophiolitic chromitite, dominated by the laurite–erlichmanite solid solution, and rare Ru–Os–Ir alloy, cuprorhodsite and cuproiridsite. One of the characteristics of the Macedonian PGM is a relative Cu enrichment, marked by Cu-PGM, but also by the presence of Cu in solid solution in laurite, and the occurrence of a Cu-sulfide rim around the PGM trapped in chromite crystals, suggesting that Cu was present in the PGE–S system.

The petrology and mineralogy of the Itsindro complex, south-central Madagascar has been investigated using samples obtained from a borehole drilled in the early 1970s on a geophysical and Ni-Cu geochemical anomaly. The host rocks consist of a pyroxenite unit with interbedded gabbro layers and a gabbro unit. A decrease in the Mg-number of cpx, independent of the lithology, is observed from the deepest samples (316 m) up to 163 m, suggesting a regular fractional crystallization process. The evolution of this parameter is more erratic in the upper part of the borehole. The mineralization consists of Fe-Ti-P oxides and Fe-(Cu-Ni) sulfides. The ilmenite-magnetite apatite and pyrrhotite chalcopyrite pentlandite assemblages are always observed in interstitial positions. The contemporaneous character of the oxide and sulfide assemblages strongly suggests a two-stage evolution of the tholeiitic magma: first a separation between immiscible Si-rich and Fe-Ti-P liquids, followed by sulfide contamination of the latter leading to massive Fe-rich over Cu- Ni sulfides.

Stratabound fluorite deposits occur at the unconformity between the Variscan crystalline basement and the Mesozoic sandstone, conglomerate, limestone, and dolomite rocks of the Morvan Massif in central Burgundy. This study describes their petrographic characteristics in an attempt to determine the nature and temperature of mineralizing fluids in order to better understand the fluid migrations that led to massive stratabound fluorite deposition. The general paragenesis encompasses two major mineralizing events causing a succession of fluorite, barite, and quartz in all deposits. The two mineralizing events were preceded by two corrosion (dissolution or karstification) events affecting both the dolomite host rock at Pierre-Perthuis and Marigny-sur-Yonne and the limestone host rock at Courcelles-Frémoy with the creation of 1–10m cavities and microscopic vugs. At Antully, the blocky calcite initially cementing the sandstone was partially dissolved. Microthermometric data on aqueous two-phase inclusions attest to CaCl2-rich fluids giving rise to fluorite deposition in the Pierre-Perthuis, Courcelles-Frémoy, and Antully deposits. Homogenization temperatures range from 80 to 100°C at Pierre-Perthuis and Courcelles-Frémoy, with sporadically higher temperatures. The range of CaCl2 contents is 6.5–15wt.% at Pierre-Perthuis, 1.7–9.4wt.% at Courcelles-Frémoy, and 1.6–16.3wt.% at Antully. The thermal history of the northwestern Morvan, compiled from organic matter, clay minerals and apatite fission track data indicates that the temperatures in fluorite and barite are higher than the maximum temperature recorded in sediments. This implies deep ascendant hydrothermal brine circulation during the Early Cretaceous. The impermeable cap rock retained the ascendant hydrothermal brine and allowed the deposition of massive fluorite stratabound mineralizations.

Zoned clinopyroxenite-dunite Uralian-Alaskan-type complexes of the Uralian Platinum Belt are the source of economic platinum deposits. One of the striking features of Uralian-Alaskan-type complexes is a pronounced Pt anomaly, which clearly distinguishes them from cumulate series of ophiolite massifs elsewhere, but there is still uncertainty regarding the nature of the platinum enrichment and its geodynamic setting. We have studied the platinum-group element (PGE) and Os isotope systematics of platinum-group minerals, chromitites and ultramafic rocks from the Nizhny Tagil zoned clinopyroxenite-dunite massif in the Urals. The whole-rock Os-187/(188) Os ratios of the dunites vary from 0.1160 to 0 . 1332, averaging 0.1247, with more radiogenic values possibly affected by subduction-related fluids during Tagil island arc development (c. 410 Ma). Laurite and Os-Ir alloys have Os-187/(188) Os ratios of 0 +/- 1224560 +/- 00038, which are close to those of chromitites (Os-187/Os-188=0.121560 +/- 0006) and correspond to an Os model age (T-RD) of c. 800 Ma. This model age is c. 400 Myr older than a melt depletion event corresponding to Tagil island arc development, and can be ascribed to a Neoproterozoic mantle melting event under the influence of either a preUralian subduction zone or a superplume, overprinted by younger processes. The Pt/Pd values in the ultramafic rocks show significant variations, increasing towards the chromite-PGE-bearing mineralization zone. The overall primitive mantle normalized PGE patterns are very similar to those reported for sub-arc mantle peridotites, which are characterized by a positive slope and high Pt/Pd ratios, and are distinct from those of typical peridotites and cumulates from Urals ophiolite massifs. Such a similarity may be explained by the melting of metasomatized depleted mantle that had undergone several melt extraction events in a subduction-zone setting. This is also evident from a high oxygen fugacity averaging 2.7 relative to fayalite-magnetite-quartz, which is distinctly more oxidized compared with mid-ocean ridge basalt and ocean island basalt settings. However, the striking similarities (P-T-fO(2) and type of parental magma, high Pt/Pd ratio) to other zoned clinopyroxenite-dunite massifs such as Kondyor, situated within the stable Archean shield, allow us to conclude that this type of massif is not exclusive to subduction-zone settings, but may reflect the presence of a specific depleted, fluid-metasomatized type of relatively shallow mantle in the Paleozoic. The systematic Pt/Pd ratio increase in the Nizhny Tagil rocks towards the chromite mineralized zone suggests that Pt-Pd fractionation may be related to the preferential retention of Pt in chromitites as Pt-Fe alloys.

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'Gueredonke 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 ore @ 10.52 % TiO2. The lack of typical features of Ural-Alaskan type intrusions and strong differences with classical Gabbro-Anorthosite hosted Fe-Ti-V deposits demonstrate a new type of large low grade high tonnage Fe-Ti-V deposit occurring in Archean craton.

Combined Sr and Caisotopic tracers have beenappliedto stratabound fluorite deposits in the central part ofBurgundy (France). These deposits are spatially related to an unconformity between aPalaeozoic granitic and metamorphic basement and Late Triassic sediments. The aim of this work is to trace the origin of fluid(s)fromwhich stratabound fluorite deposits formed. We suggest thatthe variations of the δ44CaSWin fluorite (-0.1 to +0.2‰ relative to seawater sw) could be explained by1)precipitation from a fluid dominated by a Ca isotopic signature similar to that of seawater (calcite or dolomite dissolution from the host-rock) and a Sr isotopic ratio higher than seawater (granitic basement) and involves no fractionation, the preferred scenarioor 2)cristallization from a fluid with a lowδ44CaSW(carbonate and silicate sources) involving fractionationprocesses.

World-class stratabound fluorite deposits are spatially associated with the basement/sediment unconformity of the intracratonic Paris Basin and the Morvan Massif in Burgundy (France). The reserves are estimated to be about 5.5 Mt of fluorite within six fluorite deposits. In this study, we aim to determine the age of the major fluorite mineralization event of the Pierre-Perthuis deposit (1.4 Mt fluorite) by a combined study of the paragenetic mineral sequence and Sm-Nd dating on fluorite crystals. Fluorite occurs as isolated cubes or filling geodes in a Triassic, silicified, dolomitic formation. Three fluorite stages associated with sphalerite, pyrite, galena, barite, and quartz have been distinguished using optical, cathodoluminescence, and scanning electron microscopes. Seven crystals of the geodic fluorite stage were analyzed for their rare earth element (REE) contents and their 147 Sm/ 144 Nd and 143 Nd/ 144 Nd isotopic compositions. The normalized REE distribution displays homogeneous bell-shaped patterns for all the geodic fluorite samples with a Mid-REE enrichment over the Light-REE and Heavy-REE. The 147 Sm/ 144 Nd varies from 0.3108 to 0.5504 and the 143 Nd/ 144 Nd from 0.512313 to 0.512518. A six-point Sm-Nd isochron defines an age of 130 ± 15 Ma (initial 143 Nd/ 144 Nd = 0.512054, MSWD = 0.21). This Sm-Nd isochron provides the first age for the stratabound fluorite sediment-hosted deposit, related to an unconformity in the Paris Basin, and highlights a major Early Cretaceous fluid circulation event mainly above the basement/sediment unconformity during a flexural deformation of the Paris Basin, which relates to the rifting of the Bay of Biscay and the formation of the Ligurian Sea in the Western Europe domain.

During shallow subsurface (< 200 m depth) weathering processes, temperatures may reach several tens of °C as a result of exothermic chemical reactions, such as hydration of olivine in ultramafic rocks or chloritization of biotite in granitic rocks. These mineralogical transformations enhance mineral fracturing, and the growth of fracture networks leads to further reactions and increases the permeability. The subsequent deepening of the weathering front creates new reactions, thus self-maintaining the weathering process over several million years (Myr). For more than 20 Myr, the peridotite massifs of New Caledonia have undergone intense weathering that has produced thick lateritic weathering mantles. The observable undulations of the weathering front and the protrusions of unweathered peridotite, from several meters to several tens of meters high, attest to a corrugated bedrock topography, which may result from inhomogeneous fluid circulation patterns within the coarse, permeable and porous (30-50%) saprolite layer. Combined together, the excess heat (up to ≈ 100°C) and high permeability (10-14 to 2  10-13 m²) within lateritic weathering mantles could potentially trigger hydrothermal convection (buoyancy-driven flow). This was numerically modeled by accounting for temperature-dependent fluid density and viscosity, and for time-dependent and spatially varying parameters simulating the deepening of the weathering front. Modeling the transient evolution of the thermal and flow velocity fields over 10 Myr reveals that hydrothermal convection can be triggered in the weathering lateritic mantles of New Caledonia, even on sloped surfaces where topography-driven flow prevails. Convective cells develop above the weathering front, and the amplitudes of thermal undulations are enhanced when feedback mechanisms between permeability and temperature are accounted for. The models also allow definition of the most probable zones of mineralization and reveal two-dimensional corrugations below which weathering is no longer efficient.

Mineralization processes in ultramafic laterites are partly controlled by fluid flow regimes in these porous and permeable systems. During weathering of ultramafic rocks, exothermic chemical reactions, such as hydration of olivine, may generate shallow subsurface (< 200 m) temperatures of several tens of °C. The reaction-induced fracturing leads to further reactions and increases the permeability. For more than 20 Myr, the peridotite massifs of New Caledonia have undergone intense weathering, and the observable undulations along the weathering front, attest to a corrugated bedrock topography. Combined together, the excess heat (up to 70-90°C) and high permeability (10^-14 to 9 10^-13 m²) might have potentially triggered hydrothermal convection, as confirmed by Rayleigh number estimates. This was numerically modeled by accounting for temperature-dependent fluid properties, and for time-dependent and spatially varying parameters simulating the deepening of the weathering front. Modeling the transient evolution of the thermal and flow velocity fields over 10 Myr reveals that hydrothermal convection can develop in the New Caledonian laterites, even on sloped surfaces where topography-driven flow prevails. Convective cells develop above the weathering front, and the models reveal two-dimensional corrugations below which weathering is no longer efficient.

This article presents the main outputs from the multidisciplinary Carmex project (2009-2012), which was concerned with the possibility of applying ex situ mineral carbonation concepts to mafic/ultramafic mining wastes. Focus points of the project included (i) matching significant and accessible mining wastes to large CO2 emitters through a dedicated geographical information system (GIS), (ii) analysis of aqueous carbonation mechanisms of mining waste and process development and (iii) environmental assessment of ex situ mining waste carbonation through life cycle assessment (LCA) methodology. With a number of materials associated with the mining sector, the project took a close look at the aqueous carbonation mechanisms for these materials and obtained unexpected carbonation levels (up to 80%) by coupling mechanical exfoliation and reactive carbonation. Results from this work support the possibility of processing serpentine-rich peridotites without applying the classical first step of heat activation. Perspectives are also given for the carbonation of Ni-pyrometallurgical slag available closed to ultramafic mining residues. LCA of the mining waste carbonation system as a whole made it clear that the viability of this CO2 storage option lies with the carbonation process itself and optimisation of its operating conditions. By combining the body of knowledge acquired by this project, it is concluded that New Caledonia, with its insularity and local abundance of 'carbonable' rocks and industrial wastes coupled with significant greenhouse gas (GHG) emissions from world-class nickel pyro and hydrometallurgical industries stands out as a strong potential candidate for application of ex situ mineral carbonation. (C) 2014 Elsevier Ltd. All rights reserved.

By accelerating the naturally-occurring carbonation of magnesian silicates, it would be possible to sequester some of the anthropogenic excess of CO2 in more geologically-stable solid magnesium carbonates. Reaction rates can be accelerated by decreasing the particle size, raising the reaction temperature, increasing the pressure, using a catalyst, and hypothetically, by bacterial addition. We aimed here at assessing quantitatively the added value of photosynthetic microbial activity on the efficiency of Mg-silicates carbonation processes. Synechococcus PCC 7942 (freshwater cyanobacteria) was selected for this study. Two magnesian silicate minerals (substrates) were chosen: a synthetic forsterite with nanometer-sized grains and an industrial ultramafic slag (scoria). All tests were performed at 20 +/- 1 degrees C in closed and sterile 1L Schott (R) glass bottle reactors. With the aim to elucidate the interaction between mineral phases and bacteria, we used pH and concentration measurements, scanning and transmission electron microscopy along with Raman spectroscopy. The results show that, at ambient temperature, cyanobacteria Synechococcus can accelerate silicate dissolution (i.e. Mg2+ release) and then magnesium carbonate nucleation and precipitation by adsorption on the produced exopolymeric substances and local pH increase during photosynthesis, respectively. (C) 2014 Elsevier Ltd. All rights reserved.

The Yacouba layered complex intrudes the Archean (3.5–2.7 Ga) Kenema-Man craton in the Samapleu-Yorodougou area, western Ivory Coast. In Samapleu area, the complex was recognized in drill holes at three locations: Samapleu Main (SM); Samapleu Extension 1 (E1) and Yorodougou (Yo). It comprises websterites, peridotites and gabbro-norites arranged symmetrically with mafic layers at the center and ultramafic layers at both margins. The complex is inclined at 70–80° to the SE. The thickness of individual layers varies from 2 to 60 m and the total thickness is 120 to 200 m. At the E1 site, the complex extends to depths > 500 m. Contacts with the country rock gneiss are characterized by a hybrid zone that is a few meters thick and composed of plagioclase-orthopyroxene bearing metabasites, and locally (E1 site) a metamorphic assemblage of sapphirine-cordierite-sillimanite-spinel ± rutile. This assemblage is attributed to contact metamorphism during intrusion of the complex in the lower crust at a depth of about 25 km. Zircons in country rock gneisses and granulites, as well as in the hybrid facies, yield Archean ages of ~ 2.78 Ga, similar to ages reported in the Man craton. Rutiles in the hybrid zone give a U-Pb age of 2.09 Ga, which is interpreted as the age of contact metamorphism and emplacement of the intrusion. The Samapleu Main and Samapleu Extension 1 sites contain Ni and Cu sulfide deposit with reserves estimated as more than 40 million tons grading 0.25% Ni and 0.22% Cu (Sama Nickel-CI, August 2013). The Ni-Cu mineralization is composed of pentlandite, chalcopyrite, pyrrhotite and rare pyrite, which is disseminated mainly in pyroxenite or occurs as subvertical and semi-massive to massive sulfide veins. The sulfide textures range from matrix ore, net-textured, droplets or breccia textures. Zones enriched in PGM, particularly Pd, are associated with the sulfides and several chromite bands are also present. These observations suggest that an immiscible sulfide liquid formed from a parental silicate liquid and percolated through the crystal pile. The parental melt composition, determined using the Chai and Naldrett [1992] method, has a SiO2-rich mafic composition with 53% SiO2 and 10% MgO. This result, the presence of the hybrid zone, and the trace-element signature determined using the Bedard [1994] method, suggest a mantle-derived basaltic parental magma that had assimilated abundant continental crust. These observations indicate that Samapleu intrusion corresponds to a magmatic conduit of the Yacouba complex as at Jinchuan (China), Voisey’s bay (Canada), Kabanga (Tanzania) or Nkomati (South Africa).

The demand in mineral resources is increasing rapidly, but there is a lack of transparency in the trade of concentrates raw mineral materials because of speculation and involvement in the finance of armed conflicts. Because of the distance between primary extraction and the final production sites it is difficult to check the origin of these products. An identity card is required for mineral commodities, so that trading in the industry can be verified and the traceability of concentrates ensured. This problem may be considered as an inversion process: studying the products sold to identify the original ore. The discriminant parameters are mineralogical composition, identification of textural microfacies of the target minerals (pyrite, sphalerite and chalcopyrite), " pseudo-paragenetic sequence " , and the contents and distributions of minor elements of target minerals. Statistical tests are used to compare the chemical composition of three target minerals. The application to Volcanic Massive Sulphide ore deposits shows that it is possible to distinguish target minerals between ore deposits in the Iberian Pyrite Belt province and from the Urals province using the selected characteristics. Ore deposits from different provinces may be discriminated using the identity cards, as well as different deposits in the same province.

Ural-Alaskan- (or Alaskan-) type complexes correspond to a particular class of ultramafic intrusions that attract particular attention due to their deep mantle origin and their platinum-group element (PGE) mineralization. When defined as massifs of dunite-clinopyroxenite, only forty-six complexes are reported in the literature. These large-scale dunite pipe-like structures are rarely isolated and they even can appear in clusters. To better understand genesis of these relatively young (<460 Ma) complexes, a worldwide compilation has been built, and three categories have been defined: single circular or elliptical bodies, twin bodies with similar shapes, and dismembered dunite bodies. PGE enrichment in Alaskan-type complexes is highest for the second category, where twin bodies are interpreted as horizontal sections of Y-shaped dunite pipes. To constrain mechanical properties of the lithosphere allowing emplacement of the Alaskan-type complexes, the forceful diapiric ascent hypothesis is investigated through numerical thermo-mechanical models. One hundred high resolution experiments accounting for realistic phase changes and softening mechanisms have been performed. The experiments show that with no theological softening of the host rock and in case of a relatively weak ductile lower crust, the uprising magma tends to spread laterally without reaching the surface. To account for the forceful ascent of deep magmas, it is hence necessary to assume a strong lower crust rheology and strong local softening mechanisms. Besides reproducing the clustered distribution of the weakness zones representing magma pathways, these latter experiments reproduce large-scale pipe-like (cylindrical) structures, Y-shaped and funnel-shaped bodies, and laterally-shifted structures. Interestingly, zones of highest strain rates are located at the bottom parts of the inclined edges of Y-shaped and funnel-shaped bodies. The restricted age range of Alaskan-type complexes (<460 Ma) would mean that prior to this time, the lower crust was less resistant due to the hotter geotherm, prohibiting the possibility of "Alaskan-type magmatism". (C) 2014 Elsevier B.V. All rights reserved.

Certain basaltic flows of the Permian volcanism in the Esterel (France) are enriched at their top and bottom in amygdules containing various minerals. Some of these amygdules appear to be particularly enriched in synchysite-(Ce), developed as fibrous aggregates together with chlorite and calcite. The rare earth element (REE) distribution pattern in individual amygdules appears very similar to that of the host basalt, suggesting that during the basalt's late hydrothermal evolution the REE were coherently remobilized and reprecipitated in the amygdules in the form of REE minerals. In such an environment, enriched in carbonate and F, the most stable REE mineral to crystallize from the hydrothermal solution was synchysite-(Ce), whose REE pattern has strong similarities to the host basalt.

Traceability of concentrates is required to introduce transparency in the trade of raw minerals. In this context traceability may be considered as a kind of inversion process: studying the product sold (i.e. the concentrate) in order to identify the original ore, in terms of ore deposit-type and if possible, location. The difficulty of making this inversion from concentrate toward bulk ore corresponds to the "memory loss" of the crude ore which occurs during mineral processing. Based on textural characterization and the chemical composition of the material at different steps of processing, as well as the minimum residence corresponding to each step, an estimation of this "memory loss" is proposed and the relations between memory loss and global kinetic rate of flotation are established."Memory loss" calculations are applied to the Neves Corvo plant. Throughout the process, the parameter of memory loss increases respectively from 0 to 195.06 for Cu; 0 to 46.15 for Zn and 0 to 0.43 for Fe. The "global memory loss", namely as the "experimental memory loss". For the Neves Corvo plant at the moment of the study this "experimental memory loss" was 14,146 min for Cu, 3408 min for Zn and 36 min for Fe. The results show that "memory loss" is greater for Cu than for Zn, thus emphasizing the importance of secondary elements for traceability purposes. (C) 2013 Elsevier Ltd; All rights reserved.

In France, stratiform fluorite deposits occurred at the base of Mesozoic sedimentary units from the Paris Basin around the Morvan massif, and reserves are estimated to about 5Mt. Detailed paragenetic sequence, fluid nature and the timing of the mineralization are still poorly constrained. In this study we examine the petrographical properties, trace elements composition and isotopic signatures of the fluorite deposits. These investigations provide insights into the parameters controlling the mineralization stages. The petrographical observations revealed a distinct growth zonation of fluorite crystals and a mineral paragenesis composed of multiple fluorite stages associated with various minerals (barite, sphalerite, galena and others). Significant variations of U, Th, Sr, Ba, and especially U/Th ratios are recorded from all fluorite stages. Concerning Rare Earth Element (REE), a bell-shaped pattern is recognized for all fluorite stages. Sr isotopic data of fluorite (Sr-87/Sr-86=0.7119 to 0.7134) are incompatible with a seawater signature. Available microthermometric data and the thermal history of the basin indicate hydrothermal fluid flow. A preliminary isochron data suggest a Lower Cretaceous age for the fluorite mineralization at the Pierre-Perthuis deposits.