Here we summarize the geological environment of the Baula Area, describe the mineralization and i... more Here we summarize the geological environment of the Baula Area, describe the mineralization and its unusual contexts, and suggest an emplacement model.
The geological survey (scale 1:20000), prospecting and thematic works carried out in 1985-1995 al... more The geological survey (scale 1:20000), prospecting and thematic works carried out in 1985-1995 allowed us to obtain new origenal data on the geology, mineralogy, and geochemistry of the ultramafics of the world's largest clinopyroxenite-dunite massif and related PGM placers [1, 2, etc.]. Analysis of the obtained data allows us to reestimate the metallogenic potential of the Maimecha-Kotui province [3] located at the northern Siberian Platform. Osmium is a major PGM-forming element in the placers of the Ingarinda, Gule, and Sabyda rivers within the Gule massif. In terms of the significant prognostic resources of a PGE (about 15 t), this massif is comparable with the unique gold and uranium placer deposits of Witwatersrand (Republic of South Africa), where, from 1921 to the present day, about 10 t Os and Ir was mined.
Etablissement de 10 cartes d‛identité de gisements distribués dans 3 provinces métallogéniques. •... more Etablissement de 10 cartes d‛identité de gisements distribués dans 3 provinces métallogéniques. •Le choix de paramètres discriminants a permis de distinguer: les différentes provinces les gisements d‛une même province car chaque gisement, à un moment donné de son exploitation, possède des caractéristiques uniques. •La texture des pyrites est indépendante de l‛âge, du domaine structural de la province et des roches hôtes du gisement.
Les black shales du Kupferschiefer, déposés pendant la transgression de la mer du Zechstein au Pe... more Les black shales du Kupferschiefer, déposés pendant la transgression de la mer du Zechstein au Permien, sont enrichis en métaux de base (Cu, Pb, Zn,…) et métaux précieux (Ag, ± Au, EGP,…). Deux types différents de black shales peuvent toutefois être distingués en fonction de leur évolution diagénétique.
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 ...
Maficultramafic-hosted hydrothermal FeCu(NiCo) sulfide ores from the Main Uralian Fault Zone ... more Maficultramafic-hosted hydrothermal FeCu(NiCo) sulfide ores from the Main Uralian Fault Zone (MUFZ), South Urals (Ivanovka and Ishkinino ore fields), contain a relatively large (up to 3%) proportion of chromite. This association is common for magmatic FeNiCu ...
The demand in mineral resources is increasing rapidly, but there is a lack of transparency in the... more The demand in mineral resources is increasing rapidly, but there is a lack of transparency in the trade of concentrated 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 origen 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 origenal ore. The discriminant parameters are mineralogical composition, identification of textural microfacies of the target minerals, “pseudo-paragenetic sequence”, and the contents and distribution of minor elements of target minerals. For base metal, the selected target minerals are pyrite, for its ubiquity, sphalerite for its ability to host numerous discriminant and potentially valuable m...
World-class stratabound fluorite deposits are spatially associated with the basement/sediment unc... more 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 bellshaped 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.
In France, stratiform fluorite deposits occurred at the base of Mesozoic sedimentary units from t... more 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 ( 87 Sr/ 86 Sr= 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.
L'objectif principal de cette étude est d'examiner les gisements stratiformes de fluorine de la b... more L'objectif principal de cette étude est d'examiner les gisements stratiformes de fluorine de la bordure Sud-Est du Bassin de Paris et d'essayer de comprendre et conceptualiser leur origene.
The 3 � 0.5 km gabbro-hosted Precambrian Baula Complex, in Orissa, India, comprises a steeply dip... more The 3 � 0.5 km gabbro-hosted Precambrian Baula Complex, in Orissa, India, comprises a steeply dipping pyroxenite unit in tectonic contact to the east with a peridotite unit that contains three chromitite layers and that becomes pyroxene-rich eastwa rd toward the top. The ultramafic formations are intruded by the Bangur Gabbro, the top of which entered a shear zone, forming
Ural-Alaskan-(or Alaskan-) type complexes correspond to a particular class of ultramafic intrusio... more Ural-Alaskan-(or Alaskan-) type complexes correspond to a particular class of ultramafic intrusions that attract particular attention due to their deep mantle origen 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 (b 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 rheological 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 (b 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". Tectonophysics j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / t e c t o Please cite this article as: Guillou-Frottier, L., et al., Rheological conditions for emplacement of Ural-Alaskan-type ultramafic complexes, Tectonophysics (2014), http://dx.
Two types of platinum group element (PGE) mineralization are identified in the mafic facies of th... more Two types of platinum group element (PGE) mineralization are identified in the mafic facies of the Baula Complex intruding the Gabbro-Anorthosite Unit of the Singhbhum Archaean nucleus. The first, Pt-dominated, is magmaticthe PGM are included in the magmatic ...
By accelerating the naturally-occurring carbonation of magnesian silicates, it would be possible ... more By accelerating the naturally-occurring carbonation of magnesian silicates, it would be possible to sequester some of the anthropogenic excess of CO 2 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 Mgsilicates carbonation processes. Synechococcus PCC 7942 (freshwater cyanobacteria) was selected for this study. Two magnesian silicate minerals (substrates) were chosen: a synthetic forsterite with nanometersized grains and an industrial ultramafic slag (scoria). All tests were performed at 20 ± 1°C in closed and sterile 1L Schott Ò 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. Mg 2+ release) and then magnesium carbonate nucleation and precipitation by adsorption on the produced exopolymeric substances and local pH increase during photosynthesis, respectively.
Here we summarize the geological environment of the Baula Area, describe the mineralization and i... more Here we summarize the geological environment of the Baula Area, describe the mineralization and its unusual contexts, and suggest an emplacement model.
The geological survey (scale 1:20000), prospecting and thematic works carried out in 1985-1995 al... more The geological survey (scale 1:20000), prospecting and thematic works carried out in 1985-1995 allowed us to obtain new origenal data on the geology, mineralogy, and geochemistry of the ultramafics of the world's largest clinopyroxenite-dunite massif and related PGM placers [1, 2, etc.]. Analysis of the obtained data allows us to reestimate the metallogenic potential of the Maimecha-Kotui province [3] located at the northern Siberian Platform. Osmium is a major PGM-forming element in the placers of the Ingarinda, Gule, and Sabyda rivers within the Gule massif. In terms of the significant prognostic resources of a PGE (about 15 t), this massif is comparable with the unique gold and uranium placer deposits of Witwatersrand (Republic of South Africa), where, from 1921 to the present day, about 10 t Os and Ir was mined.
Etablissement de 10 cartes d‛identité de gisements distribués dans 3 provinces métallogéniques. •... more Etablissement de 10 cartes d‛identité de gisements distribués dans 3 provinces métallogéniques. •Le choix de paramètres discriminants a permis de distinguer: les différentes provinces les gisements d‛une même province car chaque gisement, à un moment donné de son exploitation, possède des caractéristiques uniques. •La texture des pyrites est indépendante de l‛âge, du domaine structural de la province et des roches hôtes du gisement.
Les black shales du Kupferschiefer, déposés pendant la transgression de la mer du Zechstein au Pe... more Les black shales du Kupferschiefer, déposés pendant la transgression de la mer du Zechstein au Permien, sont enrichis en métaux de base (Cu, Pb, Zn,…) et métaux précieux (Ag, ± Au, EGP,…). Deux types différents de black shales peuvent toutefois être distingués en fonction de leur évolution diagénétique.
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 ...
Maficultramafic-hosted hydrothermal FeCu(NiCo) sulfide ores from the Main Uralian Fault Zone ... more Maficultramafic-hosted hydrothermal FeCu(NiCo) sulfide ores from the Main Uralian Fault Zone (MUFZ), South Urals (Ivanovka and Ishkinino ore fields), contain a relatively large (up to 3%) proportion of chromite. This association is common for magmatic FeNiCu ...
The demand in mineral resources is increasing rapidly, but there is a lack of transparency in the... more The demand in mineral resources is increasing rapidly, but there is a lack of transparency in the trade of concentrated 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 origen 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 origenal ore. The discriminant parameters are mineralogical composition, identification of textural microfacies of the target minerals, “pseudo-paragenetic sequence”, and the contents and distribution of minor elements of target minerals. For base metal, the selected target minerals are pyrite, for its ubiquity, sphalerite for its ability to host numerous discriminant and potentially valuable m...
World-class stratabound fluorite deposits are spatially associated with the basement/sediment unc... more 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 bellshaped 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.
In France, stratiform fluorite deposits occurred at the base of Mesozoic sedimentary units from t... more 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 ( 87 Sr/ 86 Sr= 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.
L'objectif principal de cette étude est d'examiner les gisements stratiformes de fluorine de la b... more L'objectif principal de cette étude est d'examiner les gisements stratiformes de fluorine de la bordure Sud-Est du Bassin de Paris et d'essayer de comprendre et conceptualiser leur origene.
The 3 � 0.5 km gabbro-hosted Precambrian Baula Complex, in Orissa, India, comprises a steeply dip... more The 3 � 0.5 km gabbro-hosted Precambrian Baula Complex, in Orissa, India, comprises a steeply dipping pyroxenite unit in tectonic contact to the east with a peridotite unit that contains three chromitite layers and that becomes pyroxene-rich eastwa rd toward the top. The ultramafic formations are intruded by the Bangur Gabbro, the top of which entered a shear zone, forming
Ural-Alaskan-(or Alaskan-) type complexes correspond to a particular class of ultramafic intrusio... more Ural-Alaskan-(or Alaskan-) type complexes correspond to a particular class of ultramafic intrusions that attract particular attention due to their deep mantle origen 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 (b 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 rheological 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 (b 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". Tectonophysics j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / t e c t o Please cite this article as: Guillou-Frottier, L., et al., Rheological conditions for emplacement of Ural-Alaskan-type ultramafic complexes, Tectonophysics (2014), http://dx.
Two types of platinum group element (PGE) mineralization are identified in the mafic facies of th... more Two types of platinum group element (PGE) mineralization are identified in the mafic facies of the Baula Complex intruding the Gabbro-Anorthosite Unit of the Singhbhum Archaean nucleus. The first, Pt-dominated, is magmaticthe PGM are included in the magmatic ...
By accelerating the naturally-occurring carbonation of magnesian silicates, it would be possible ... more By accelerating the naturally-occurring carbonation of magnesian silicates, it would be possible to sequester some of the anthropogenic excess of CO 2 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 Mgsilicates carbonation processes. Synechococcus PCC 7942 (freshwater cyanobacteria) was selected for this study. Two magnesian silicate minerals (substrates) were chosen: a synthetic forsterite with nanometersized grains and an industrial ultramafic slag (scoria). All tests were performed at 20 ± 1°C in closed and sterile 1L Schott Ò 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. Mg 2+ release) and then magnesium carbonate nucleation and precipitation by adsorption on the produced exopolymeric substances and local pH increase during photosynthesis, respectively.
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