Jacques TOURET | UPMC Sorbonne Universités (original) (raw)

Papers by Jacques TOURET

Lithos, 2019

The complementary roles of granites and rocks of the granulite facies have long been a key issue ... more The complementary roles of granites and rocks of the granulite facies have long been a key issue in models of the evolution of the continental crust. "Dehydration melting", or fluid-absent melting of a lower crust containing H 2 O only in the small amounts present in biotite and amphibole, has raised problems of excessively high temperatures and restricted amounts of granite production, factors seemingly incapable of explaining voluminous bodies of granite like the Archean Closepet Granite of South India. The existence of incipient granulite-facies metamorphism (charnockite formation) and closely associated migmatization (melting) in 2.5 Ga-old gneisses in a quarry exposure in southern India and elsewhere, with structural, chemical and mineral-inclusion evidence of fluid action, has encouraged a wetter approach, in consideration of aqueous fluids for rock melting which maintain sufficiently low H 2 O activity for granulite-facies metamorphism. Existing experimental data at elevated T and P are sufficient to demonstrate that, at mid-crust pressures of 0.5-0.6 GPa and metamorphic temperatures above 700°C, ascending immiscible CO 2-rich and concentrated alkali chloride aqueous fluids in equilibrium with charnockitic (orthopyroxene-bearing) gneiss will inevitably begin to melt granitic rocks. The experimental data show that H 2 O activity is much higher (0.5-0.6) than previously portrayed for beginning granulite facies metamorphism (0.15-0.3). Possibilities for metasomatism of the deep crust are greatly enhanced over the ultra-dry models traditionally espoused. Streaming of ultrasaline fluids through continental crust could be a mechanism for the generation of the discrete mid-crust layer of migmatites suggested to characterize younger tectonometamorphic regions. The action of CO 2-rich and hypersaline fluids in Late Archean metamorphism and magmatism could record the beginning of large-scale subduction of volatilerich surficial materials.

Sedimentology, 1994

Upper Visean limestones in the Campine Basin of northern Belgium are intensively fractured. The l... more Upper Visean limestones in the Campine Basin of northern Belgium are intensively fractured. The largest and most common fractures are cemented by non-ferroan, dull brown-orange luminescent blocky calcite. First melting temperatures of fluid inclusions in these calcites are around-57"C, suggesting that precipitation of the cements occurred from NaCI-CaCl,-MgCl, fluids. The final melting temperatures (T,,,"') are between-5 and-33°C. The broad range in the Tml" data can be explained by the mixing of high salinity fluids with meteoric waters, but other hypotheses may also be valid. Homogenization temperatures from blocky calcite cements in the shelf limestones are interpreted to have formed between 45 and 75°C. In carbonates which were deposited close to and at the shelf margin, precipitation temperatures were possibly in the range 70-85°C and 72-93"C, respectively. On the shelf, the calcites have a 6 l 8 0 around-9.3% PDB and they are interpreted to have grown in a fluid with a 6 1 8 0 between-3.5 and + 1. 0 %~ SMOW. At the shelf margin, blocky calcites (~5~~0 % ~ 13.5%~ PDB) could have precipitated from a fluid with a ~5~~0 between-4.0 and-1.1% SMOW. The highest oxygen isotopic compositions are comparable to those of Late Carboniferous marine fluids (C5"0= ~ 1% SMOW). The lowest values are more positive than a previously reported composition for Carboniferous meteoric waters (d1*0=-7% SMOW). Precipitation is likely to have occurred in marine-derived fluids, which mixed with meteoric waters sourced from near the Brabant Massif. Fluids with a similar negative oxygen isotopic composition and high salinity are actually present in Palaeozoic formations. The higher temperature range in the limestones near the shelf margin is explained by the upward migration of fluids from the 'basinal' area along fractures and faults into the shelf.

Contributions to Mineralogy and Petrology, 2000

Chemical Geology, 2002

Melt, fluid and crystal inclusions have been studied in olivine phenocrysts from a suite of picri... more Melt, fluid and crystal inclusions have been studied in olivine phenocrysts from a suite of picritic basalts dredged during the ''Marion Dufresne'' MD 109 cruise (Dredge 6) from a seamount located between the Kerguelen Archipelago and Heard Island (Southern Indian Ocean). A two-stage polybaric crystallisation of the trapped melt is indicated by compositions of the host olivine+spinel assemblage and by the density of coexisting fluid inclusions. The melt trapped in early olivine phenocrysts (Fo 82-85.5) crystallised under pressures from 2 to 4 kbar, whereas the melt trapped in late olivine phenocrysts (Fo 78.7-80) crystallised at shallower depths (<1 kbar). There is a wide range of incompatible elements in the homogenised melt inclusions (P 2 O 5 =0.4-1.6 wt.%, K 2 O=1.4-2.4 wt.%) at a relatively restricted MgO content (7.0-9.6 wt.%). The small amounts of P 2 O 5rich melt trapped in the early olivine phenocrysts are remarkably similar to the contemporaneous basalt suite (Dredge 5) from the same seamount. The chemistry of the host dredge 6 basalts requires a significant contribution (more than 80%) of richer in K 2 O and poorer in P 2 O 5 subalkaline melt (K 2 O > 2.5 wt.%, P 2 O 5 <0.34 wt.%). The contribution of such subalkaline melt with slightly unradiogenic Pb-Nd isotope ratios and major and trace element composition, similar to the low 206 Pb/ 204 Pb-143 Nd/ 144 Nd trachybasaltic suite of the Aphanasey Nikitin Rise, may explain the striking Nb-Ta depletion, Pb enrichment and isotopic compositions of the dredge 6 basalts. The petrogenesis of the picritic basalts from dredge 6 is controlled by two-component mixing between a P 2 O 5-rich Kerguelen plume-derived melt and a subalkaline melt derived from the Kerguelen Plateau lithosphere and provides more evidence for the involvement of low 206 Pb/ 204 Pb-143 Nd/ 144 Nd lithospheric material into young Kerguelen plume-derived basaltic magmas.

Localised low-strain domains in the 3.75 Ga Isua Greenstone Belt, West Greenland, contain a wealt... more Localised low-strain domains in the 3.75 Ga Isua Greenstone Belt, West Greenland, contain a wealth of well-preserved primary structures. These include pillow lavas with dark, fine-grained cooling rims, pillow breccias, debris flows and conglomerates. Here we describe quartz globules from a relatively undeformed pillow breccia, which contains unstrained quartz. Most quartz globules contain only few quartz grains, but some of the larger ones preserve a subidiomorphic rim reminiscent of former geodic lining. The globules are associated with a complex system of quartz veins. Metamorphic conditions recorded in pelites associated with the pillow breccia represent the early stage of a prograde event at 460-480°C and 4 kb. Both globules and quartz veins pre-date the metamorphic fabric, and are interpreted as remnants of a sea-floor type hydrothermal system, operating at the time of lava eruption and pillow formation at 3.75 Ga. The globules, which are interpreted as former gas vesicles filled with quartz (and some carbonate), are embedded in an altered basaltic matrix now comprising biotite, muscovite and quartz 9 tourmaline and carbonate. Silica-filling in the vesicles was contemporaneous with the formation of an intricate hydrothermal vein system. During deformation, the strain was partitioned into the mica-rich rock matrix, when the vesicles behaved as competent objects, eventually cutting or deforming the thinner veins. Amphibolite-facies metamorphic overprint involved a limited flattening of some vesicles and the development of a very faint, sporadic schistosity, preserving most of the pre-metamorphic hydrothermal features. Major metamorphic structures correspond to quartz annealing, yielding curved grain boundaries and triple point junctions. We report rare primary fluid inclusions from quartz in the vesicles. The inclusions contain remnants of two independent fluid/mineral systems comprising pure methane and highly saline aqueous fluids (about 25 wt.% NaCl equivalent), and co-precipitating carbonates (calcite). Especially for the aqueous system, these fluids bear a strong resemblance to present-day sea-floor hydrothermal fluids. They are interpreted as relics of the sea-floor hydrothermal fluid, responsible for the alteration of the pillow fragments and co-precipitation of quartz and carbonate.

Resource Geology, 2006

Page 1. 1. Introduction Since the publication of the classical example of mag-matic dense saline ... more Page 1. 1. Introduction Since the publication of the classical example of mag-matic dense saline fluid inclusions by Roedder and Coombs (1967), numerous reports of magmatic hydro-saline inclusions characterized by high ...

Bulletin De La Societe Geologique De France, 2001

In direct continuity with the Dead Sea fault, the Syrian rift, which links the rigid Arabian plat... more In direct continuity with the Dead Sea fault, the Syrian rift, which links the rigid Arabian plate to the mobile ophiolite belt of Cyprus-southern Turkey, plays a very important role in the regional geodynamic structure. Its exact position, as well as the related fracture system, has been documented from the analysis of a complete aerial photo coverage of the whole Syrian territory. The rift corresponds to a transform fault, with lateral displacements decreasing from more than 100 km, to the south, to less than 30 km to the north. Several major episodes of volcanic activity have occurred since early Mesozoic times, with eruptive centers located in three major domains, southern (S), center (M) and northern (N), respectively. The recent (Neogene-Quaternary) volcanism is compared to the Cretaceous one (Bhannes-Tayasir episode). Erupted lavas are in general very basic (picrobasalts, basanites), with rather primitive magmas, except for one occurrence at El Kafr (southern Syria) which corresponds to a silica-undersaturated, strongly differentiated phonolite. Major and partial (Rb, Ba, Nb, Sr, Y, Lu) trace-element data show overall similarities between recent and Cretaceous volcanisms, with however a more distinct alkaline trend and stronger variations of LILE-elements for recent lavas. Few volcanoes contain a number of ultrabasic xenoliths, notably lherzolites, harzburgites and pyroxenites. Rare garnet-bearing varieties have also been observed in M and S-domains, including few grenatites. Xenolith texture is protogranular or granular, with a variable (mostly limited) degree of local melting by the enclosing basalt. Olivines are Mg-rich (mg (super *) = 0.93-0.83), as are ortho-and clinopyroxene. This last mineral, which may show spectacular Opx and spinel exsolution lamellae, is relatively abundant, as shown by the frequent occurrence of pyroxenite (Cpx-Opx) and Cpx-rich lherzolite (wehrlite). Because of the possible occurrence of Cretaceous rocks with kimberlitic affinities [Nabi Mata, Sharkov et al., 1993], garnet has been studied in detail. On the garnet triangle, most analyses plot well away from high-pressure mantle rocks, notably kimberlites, but close to infracrustal garnet-bearing rocks (granulites). Very few analytical points (3 out of a total of 20) could correspond to garnet peridotite. All other rocks are equilibrated in the field of spinel peridotite or infracrustal granulites. Pure CO 2 -bearing fluid inclusions have been found in olivine and pyroxenes from xenoliths and in phenocrysts from enclosing basalts. Highest density fluids (up to 1.15 g/cm 3 ), are observed in pyroxenites, especially from M-domain. They occur in primary, tubular inclusions adjacent to or even containing minute spinel grains, oriented along the exsolution lamellae of the clinopyroxene-host. P-T conditions of mineral equilibration in the xenoliths have been estimated from the pyroxene thermometer [Bertrand and Mercier, 1986; Brey and Kohler, 1990] and maximum density of fluid trapped in primary inclusions. They correspond to about 1 100-1 300 degrees C for the temperature, 10-13 kb for the pressure. These P-T conditions do not show any significant variation between different regional occurrences, but well between various petrographical types, the maximum conditions being recorded in pyroxenites. These results suggest that some clinopyroxene at least has been formed by mantle metasomatism caused by ephemeral carbonate magmas, in a mantle plume located under the Arabic plate.

Bulletin de Minéralogie

... Mots-clés anglais / English Keywords. Fluid inclusions. ; Fluid inclusion. ; Nitrogen. ; Quar... more ... Mots-clés anglais / English Keywords. Fluid inclusions. ; Fluid inclusion. ; Nitrogen. ; Quartz. ; Metasedimentary rocks. ; Devonian. ; Ardennes Department. ; Ardennes. ; Belgium. ; PT conditions. ; Metamorphic rocks. ; Paleozoic. ; Paris Basin. ; France. ; Europe. ; Champagne. ; ...

Granulites constitute a major part of the (lower) continental crust, occurring on a regional scal... more Granulites constitute a major part of the (lower) continental crust, occurring on a regional scale in many metamorphic belts. Their origin is generally discussed in terms of vapour-absent melting and fluid-assisted dehydration. This last model is notably supported by the occurrence of two immiscible free fluids at peak-and retrograde conditions, viz. CO 2 and highly saline brines. Evidence includes fluid remnants preserved in mineral inclusions, but also large scale metasomatic effects. The current paper discusses the presence and action of these fluids in granulites, with special attention to amphibolite to granulite facies transition zones (e.g. the Bamble sector, south Norway). Metasomatic effects induced by fluid percolation at different scales and stages include: (1) Control of state variables (H 2 O activity or O 2 fugacity), regional oxidation and so-called 'granulite facies' islands. (2) Small scale metasomatism at mineral intergrain boundaries (e.g. K-feldspar microveins and/or myrmekites). (3) Large scale metasomatism at the amphibolite to granulite facies transition zone, evidenced by: (a) Incipient charnockites, (b) Metasomatic redistribution of elements traditionally considered as immobile (e.g. Zr, Th, REE), (c) Peak metamorphic to retrograde bulk chemical processes (scapolitization, albitization), (d) Long distance action of granulite fluids. The importance and widespread occurrence of these effects call for large fluid quantities stored in the lower crust at peak metamorphic conditions, later expelled towards shallower crustal levels during retrogradation. Fluid origin, only briefly discussed in this paper, is complicated, not unique. Some fluids are crustal, either far remnants of sedimentary waters (brines) or linked to metamorphic/melt reactions. But, especially for high-temperature granulites, the greatest amount, notably for CO 2 , is issued from the upper mantle, which contain also the same fluid remnants as those found in the lower crust.

Geological Society, London, Special Publications

Abstract Shoksha quartzite is a heritage stone of international importance. This stone, a hematit... more Abstract Shoksha quartzite is a heritage stone of international importance. This stone, a hematitic quartzite composed predominantly of quartz with subordinate amounts of chalcedony and sericite, is Jatulian (2.3–2.0 Ga) in age. The sarcophagus of Napoleon I, Emperor of France, inside the Dôme des Invalides in Paris was cut from Shoksha quartzite quarried by Lake Onega, Russia. The details of the sarcophagus were cut and polished in Paris using steam machinery, an early use of this method. A monument to Russian Emperor, Nicholas I, in St Petersburg is also made in part of this quartzite. This stone also has been utilized in the Grave of the Unknown Soldier and the monument to Heroic Cities near the Kremlin in Moscow, as well as for other uses.

Precambrian Research, 2014

Evidence is accumulating from experimental petrology and thermodynamic calculations based on deta... more Evidence is accumulating from experimental petrology and thermodynamic calculations based on detailed descriptions of key natural occurrences that H2O activity at the regional amphibolite facies- granulite boundaries in high-grade Precambrian gneiss terranes (coincident with the orthopyroxene isograd) is considerably higher (0.3–0.6) than previously thought (0.15–0.3). This revision provides insight into the significance of fluid inclusions in minerals of the incipient charnockites characteristic of the granulite facies transitions in several Precambrian gneiss terranes. Observations on NaCl-dominated brine inclusions in minerals, including some new data in this paper, in rocks from such places as the Kabbal–Satnur–Halagur area of the Archean Shield of South India have salt concentrations conso- nant with the stabilization of orthopyroxene relative to calcic amphibole and biotite; closely associated CO2-dominated fluid inclusions can have substantial H2O contents at typical incipient granulite facies conditions (700–750 ◦ C and 0.5–0.7 GPa) and can thus have been in equilibrium with the associated brines as immiscible metamorphic fluids. Observed densities of the best-preserved CO2-rich fluid inclusions in quartz are consistent with those expected from the equation of state of CO2 at incipient granulite facies pressure-temperature conditions.
It seems likely that the role of fluids in granulite facies metamorphism of the deep crust has been considerably underemphasized in discussions, still prevalent, which concentrate on the role of fluid- deficient partial melting as the primary agent, to the exclusion of a possible role of metamorphic fluids and metasomatism.

Pendant la plus grande partie du XIXe siecle, la geologie francaise a ete dominee par la personna... more Pendant la plus grande partie du XIXe siecle, la geologie francaise a ete dominee par la personnalite ecrasante de Leonce Elie de Beaumont, inventeur du " reseau pentagonal ". On detaille les principes et l'illustration de ce modele, premier essai de tectonique globale, dont l'oubli actuel parait aussi immerite que la confiance aveugle que lui ont accordee bon nombre de ses contemporains.

Hydrothermal graphite vein deposits hosted in granulite facies metamorphic rocks in Sri Lanka are... more Hydrothermal graphite vein deposits hosted in granulite facies metamorphic rocks in Sri Lanka are unique because of their large size and high crystallinity. In this paper, we present a review of the structural-meta-morphic setting of the graphite veins and of the graphite stable carbon isotope data, and we present fluid inclusion data from quartz in the graphite veins and in the host rocks from several graphite deposits in Sri Lanka. The studied host rocks show decompression rims of plagioclase and orthopyroxene after garnet. The quartz in these decompression rim textures comprise, in order of abundance, high-salinity brine, H 2 O-CO 2 , and low-salinity aqueous fluid inclusions. The brine fluid is responsible for metasomatic features observed in garnet decompression rims, including feldspar leaching and re-precipitation. Quartz cogenetic with vein graphite comprises, in order of abundance, low-salinity aqueous, CO 2 , high-salinity brine, and H 2 O-CO 2 fluid inclusions. Published ...

Bulletin de Minéralogie

Remarques historiques sur le developpement de l'etude des inclusions fluides et vitreuses. Ac... more Remarques historiques sur le developpement de l'etude des inclusions fluides et vitreuses. Actualite de l'œuvre de Sorby (1858).

Vestnik of Saint Petersburg University. Arts

The crypt and sarcophagus of Napoleon in the Dôme des Invalids in Paris which were constructed by... more The crypt and sarcophagus of Napoleon in the Dôme des Invalids in Paris which were constructed by an Italian-born French architect and designer Louis Tullius Joachim Visconti evince an extraordinarily expressive and harmonic colour combination in French and Italian marbles with those of so called porphyries in Napoleon's tombstone (they are really green andesite from France and purple quartzite from Russia). Works continued over a twenty year period (1840-1861) which saw in France three Kings, one Republic and one Emperor, and in Russia two emperors. Every political change in France exerted critical influence on the continuation of these works. The events surrounding the constructing the crypt and tombstone, applying steam machinery to cut and polish the sarcophagus, the budgets of the work is described from archival documents in detail. J.-F. Bujatti (an Italian from St Petersburg) played an important role in the quarrying of the Russian ornamental stone and in its transport to Paris. Refs 16. Figs 3.

Lithos, 2019

The complementary roles of granites and rocks of the granulite facies have long been a key issue ... more The complementary roles of granites and rocks of the granulite facies have long been a key issue in models of the evolution of the continental crust. "Dehydration melting", or fluid-absent melting of a lower crust containing H 2 O only in the small amounts present in biotite and amphibole, has raised problems of excessively high temperatures and restricted amounts of granite production, factors seemingly incapable of explaining voluminous bodies of granite like the Archean Closepet Granite of South India. The existence of incipient granulite-facies metamorphism (charnockite formation) and closely associated migmatization (melting) in 2.5 Ga-old gneisses in a quarry exposure in southern India and elsewhere, with structural, chemical and mineral-inclusion evidence of fluid action, has encouraged a wetter approach, in consideration of aqueous fluids for rock melting which maintain sufficiently low H 2 O activity for granulite-facies metamorphism. Existing experimental data at elevated T and P are sufficient to demonstrate that, at mid-crust pressures of 0.5-0.6 GPa and metamorphic temperatures above 700°C, ascending immiscible CO 2-rich and concentrated alkali chloride aqueous fluids in equilibrium with charnockitic (orthopyroxene-bearing) gneiss will inevitably begin to melt granitic rocks. The experimental data show that H 2 O activity is much higher (0.5-0.6) than previously portrayed for beginning granulite facies metamorphism (0.15-0.3). Possibilities for metasomatism of the deep crust are greatly enhanced over the ultra-dry models traditionally espoused. Streaming of ultrasaline fluids through continental crust could be a mechanism for the generation of the discrete mid-crust layer of migmatites suggested to characterize younger tectonometamorphic regions. The action of CO 2-rich and hypersaline fluids in Late Archean metamorphism and magmatism could record the beginning of large-scale subduction of volatilerich surficial materials.

Sedimentology, 1994

Upper Visean limestones in the Campine Basin of northern Belgium are intensively fractured. The l... more Upper Visean limestones in the Campine Basin of northern Belgium are intensively fractured. The largest and most common fractures are cemented by non-ferroan, dull brown-orange luminescent blocky calcite. First melting temperatures of fluid inclusions in these calcites are around-57"C, suggesting that precipitation of the cements occurred from NaCI-CaCl,-MgCl, fluids. The final melting temperatures (T,,,"') are between-5 and-33°C. The broad range in the Tml" data can be explained by the mixing of high salinity fluids with meteoric waters, but other hypotheses may also be valid. Homogenization temperatures from blocky calcite cements in the shelf limestones are interpreted to have formed between 45 and 75°C. In carbonates which were deposited close to and at the shelf margin, precipitation temperatures were possibly in the range 70-85°C and 72-93"C, respectively. On the shelf, the calcites have a 6 l 8 0 around-9.3% PDB and they are interpreted to have grown in a fluid with a 6 1 8 0 between-3.5 and + 1. 0 %~ SMOW. At the shelf margin, blocky calcites (~5~~0 % ~ 13.5%~ PDB) could have precipitated from a fluid with a ~5~~0 between-4.0 and-1.1% SMOW. The highest oxygen isotopic compositions are comparable to those of Late Carboniferous marine fluids (C5"0= ~ 1% SMOW). The lowest values are more positive than a previously reported composition for Carboniferous meteoric waters (d1*0=-7% SMOW). Precipitation is likely to have occurred in marine-derived fluids, which mixed with meteoric waters sourced from near the Brabant Massif. Fluids with a similar negative oxygen isotopic composition and high salinity are actually present in Palaeozoic formations. The higher temperature range in the limestones near the shelf margin is explained by the upward migration of fluids from the 'basinal' area along fractures and faults into the shelf.

Contributions to Mineralogy and Petrology, 2000

Chemical Geology, 2002

Melt, fluid and crystal inclusions have been studied in olivine phenocrysts from a suite of picri... more Melt, fluid and crystal inclusions have been studied in olivine phenocrysts from a suite of picritic basalts dredged during the ''Marion Dufresne'' MD 109 cruise (Dredge 6) from a seamount located between the Kerguelen Archipelago and Heard Island (Southern Indian Ocean). A two-stage polybaric crystallisation of the trapped melt is indicated by compositions of the host olivine+spinel assemblage and by the density of coexisting fluid inclusions. The melt trapped in early olivine phenocrysts (Fo 82-85.5) crystallised under pressures from 2 to 4 kbar, whereas the melt trapped in late olivine phenocrysts (Fo 78.7-80) crystallised at shallower depths (<1 kbar). There is a wide range of incompatible elements in the homogenised melt inclusions (P 2 O 5 =0.4-1.6 wt.%, K 2 O=1.4-2.4 wt.%) at a relatively restricted MgO content (7.0-9.6 wt.%). The small amounts of P 2 O 5rich melt trapped in the early olivine phenocrysts are remarkably similar to the contemporaneous basalt suite (Dredge 5) from the same seamount. The chemistry of the host dredge 6 basalts requires a significant contribution (more than 80%) of richer in K 2 O and poorer in P 2 O 5 subalkaline melt (K 2 O > 2.5 wt.%, P 2 O 5 <0.34 wt.%). The contribution of such subalkaline melt with slightly unradiogenic Pb-Nd isotope ratios and major and trace element composition, similar to the low 206 Pb/ 204 Pb-143 Nd/ 144 Nd trachybasaltic suite of the Aphanasey Nikitin Rise, may explain the striking Nb-Ta depletion, Pb enrichment and isotopic compositions of the dredge 6 basalts. The petrogenesis of the picritic basalts from dredge 6 is controlled by two-component mixing between a P 2 O 5-rich Kerguelen plume-derived melt and a subalkaline melt derived from the Kerguelen Plateau lithosphere and provides more evidence for the involvement of low 206 Pb/ 204 Pb-143 Nd/ 144 Nd lithospheric material into young Kerguelen plume-derived basaltic magmas.

Localised low-strain domains in the 3.75 Ga Isua Greenstone Belt, West Greenland, contain a wealt... more Localised low-strain domains in the 3.75 Ga Isua Greenstone Belt, West Greenland, contain a wealth of well-preserved primary structures. These include pillow lavas with dark, fine-grained cooling rims, pillow breccias, debris flows and conglomerates. Here we describe quartz globules from a relatively undeformed pillow breccia, which contains unstrained quartz. Most quartz globules contain only few quartz grains, but some of the larger ones preserve a subidiomorphic rim reminiscent of former geodic lining. The globules are associated with a complex system of quartz veins. Metamorphic conditions recorded in pelites associated with the pillow breccia represent the early stage of a prograde event at 460-480°C and 4 kb. Both globules and quartz veins pre-date the metamorphic fabric, and are interpreted as remnants of a sea-floor type hydrothermal system, operating at the time of lava eruption and pillow formation at 3.75 Ga. The globules, which are interpreted as former gas vesicles filled with quartz (and some carbonate), are embedded in an altered basaltic matrix now comprising biotite, muscovite and quartz 9 tourmaline and carbonate. Silica-filling in the vesicles was contemporaneous with the formation of an intricate hydrothermal vein system. During deformation, the strain was partitioned into the mica-rich rock matrix, when the vesicles behaved as competent objects, eventually cutting or deforming the thinner veins. Amphibolite-facies metamorphic overprint involved a limited flattening of some vesicles and the development of a very faint, sporadic schistosity, preserving most of the pre-metamorphic hydrothermal features. Major metamorphic structures correspond to quartz annealing, yielding curved grain boundaries and triple point junctions. We report rare primary fluid inclusions from quartz in the vesicles. The inclusions contain remnants of two independent fluid/mineral systems comprising pure methane and highly saline aqueous fluids (about 25 wt.% NaCl equivalent), and co-precipitating carbonates (calcite). Especially for the aqueous system, these fluids bear a strong resemblance to present-day sea-floor hydrothermal fluids. They are interpreted as relics of the sea-floor hydrothermal fluid, responsible for the alteration of the pillow fragments and co-precipitation of quartz and carbonate.

Resource Geology, 2006

Page 1. 1. Introduction Since the publication of the classical example of mag-matic dense saline ... more Page 1. 1. Introduction Since the publication of the classical example of mag-matic dense saline fluid inclusions by Roedder and Coombs (1967), numerous reports of magmatic hydro-saline inclusions characterized by high ...

Bulletin De La Societe Geologique De France, 2001

In direct continuity with the Dead Sea fault, the Syrian rift, which links the rigid Arabian plat... more In direct continuity with the Dead Sea fault, the Syrian rift, which links the rigid Arabian plate to the mobile ophiolite belt of Cyprus-southern Turkey, plays a very important role in the regional geodynamic structure. Its exact position, as well as the related fracture system, has been documented from the analysis of a complete aerial photo coverage of the whole Syrian territory. The rift corresponds to a transform fault, with lateral displacements decreasing from more than 100 km, to the south, to less than 30 km to the north. Several major episodes of volcanic activity have occurred since early Mesozoic times, with eruptive centers located in three major domains, southern (S), center (M) and northern (N), respectively. The recent (Neogene-Quaternary) volcanism is compared to the Cretaceous one (Bhannes-Tayasir episode). Erupted lavas are in general very basic (picrobasalts, basanites), with rather primitive magmas, except for one occurrence at El Kafr (southern Syria) which corresponds to a silica-undersaturated, strongly differentiated phonolite. Major and partial (Rb, Ba, Nb, Sr, Y, Lu) trace-element data show overall similarities between recent and Cretaceous volcanisms, with however a more distinct alkaline trend and stronger variations of LILE-elements for recent lavas. Few volcanoes contain a number of ultrabasic xenoliths, notably lherzolites, harzburgites and pyroxenites. Rare garnet-bearing varieties have also been observed in M and S-domains, including few grenatites. Xenolith texture is protogranular or granular, with a variable (mostly limited) degree of local melting by the enclosing basalt. Olivines are Mg-rich (mg (super *) = 0.93-0.83), as are ortho-and clinopyroxene. This last mineral, which may show spectacular Opx and spinel exsolution lamellae, is relatively abundant, as shown by the frequent occurrence of pyroxenite (Cpx-Opx) and Cpx-rich lherzolite (wehrlite). Because of the possible occurrence of Cretaceous rocks with kimberlitic affinities [Nabi Mata, Sharkov et al., 1993], garnet has been studied in detail. On the garnet triangle, most analyses plot well away from high-pressure mantle rocks, notably kimberlites, but close to infracrustal garnet-bearing rocks (granulites). Very few analytical points (3 out of a total of 20) could correspond to garnet peridotite. All other rocks are equilibrated in the field of spinel peridotite or infracrustal granulites. Pure CO 2 -bearing fluid inclusions have been found in olivine and pyroxenes from xenoliths and in phenocrysts from enclosing basalts. Highest density fluids (up to 1.15 g/cm 3 ), are observed in pyroxenites, especially from M-domain. They occur in primary, tubular inclusions adjacent to or even containing minute spinel grains, oriented along the exsolution lamellae of the clinopyroxene-host. P-T conditions of mineral equilibration in the xenoliths have been estimated from the pyroxene thermometer [Bertrand and Mercier, 1986; Brey and Kohler, 1990] and maximum density of fluid trapped in primary inclusions. They correspond to about 1 100-1 300 degrees C for the temperature, 10-13 kb for the pressure. These P-T conditions do not show any significant variation between different regional occurrences, but well between various petrographical types, the maximum conditions being recorded in pyroxenites. These results suggest that some clinopyroxene at least has been formed by mantle metasomatism caused by ephemeral carbonate magmas, in a mantle plume located under the Arabic plate.

Bulletin de Minéralogie

... Mots-clés anglais / English Keywords. Fluid inclusions. ; Fluid inclusion. ; Nitrogen. ; Quar... more ... Mots-clés anglais / English Keywords. Fluid inclusions. ; Fluid inclusion. ; Nitrogen. ; Quartz. ; Metasedimentary rocks. ; Devonian. ; Ardennes Department. ; Ardennes. ; Belgium. ; PT conditions. ; Metamorphic rocks. ; Paleozoic. ; Paris Basin. ; France. ; Europe. ; Champagne. ; ...

Granulites constitute a major part of the (lower) continental crust, occurring on a regional scal... more Granulites constitute a major part of the (lower) continental crust, occurring on a regional scale in many metamorphic belts. Their origin is generally discussed in terms of vapour-absent melting and fluid-assisted dehydration. This last model is notably supported by the occurrence of two immiscible free fluids at peak-and retrograde conditions, viz. CO 2 and highly saline brines. Evidence includes fluid remnants preserved in mineral inclusions, but also large scale metasomatic effects. The current paper discusses the presence and action of these fluids in granulites, with special attention to amphibolite to granulite facies transition zones (e.g. the Bamble sector, south Norway). Metasomatic effects induced by fluid percolation at different scales and stages include: (1) Control of state variables (H 2 O activity or O 2 fugacity), regional oxidation and so-called 'granulite facies' islands. (2) Small scale metasomatism at mineral intergrain boundaries (e.g. K-feldspar microveins and/or myrmekites). (3) Large scale metasomatism at the amphibolite to granulite facies transition zone, evidenced by: (a) Incipient charnockites, (b) Metasomatic redistribution of elements traditionally considered as immobile (e.g. Zr, Th, REE), (c) Peak metamorphic to retrograde bulk chemical processes (scapolitization, albitization), (d) Long distance action of granulite fluids. The importance and widespread occurrence of these effects call for large fluid quantities stored in the lower crust at peak metamorphic conditions, later expelled towards shallower crustal levels during retrogradation. Fluid origin, only briefly discussed in this paper, is complicated, not unique. Some fluids are crustal, either far remnants of sedimentary waters (brines) or linked to metamorphic/melt reactions. But, especially for high-temperature granulites, the greatest amount, notably for CO 2 , is issued from the upper mantle, which contain also the same fluid remnants as those found in the lower crust.

Geological Society, London, Special Publications

Abstract Shoksha quartzite is a heritage stone of international importance. This stone, a hematit... more Abstract Shoksha quartzite is a heritage stone of international importance. This stone, a hematitic quartzite composed predominantly of quartz with subordinate amounts of chalcedony and sericite, is Jatulian (2.3–2.0 Ga) in age. The sarcophagus of Napoleon I, Emperor of France, inside the Dôme des Invalides in Paris was cut from Shoksha quartzite quarried by Lake Onega, Russia. The details of the sarcophagus were cut and polished in Paris using steam machinery, an early use of this method. A monument to Russian Emperor, Nicholas I, in St Petersburg is also made in part of this quartzite. This stone also has been utilized in the Grave of the Unknown Soldier and the monument to Heroic Cities near the Kremlin in Moscow, as well as for other uses.

Precambrian Research, 2014

Evidence is accumulating from experimental petrology and thermodynamic calculations based on deta... more Evidence is accumulating from experimental petrology and thermodynamic calculations based on detailed descriptions of key natural occurrences that H2O activity at the regional amphibolite facies- granulite boundaries in high-grade Precambrian gneiss terranes (coincident with the orthopyroxene isograd) is considerably higher (0.3–0.6) than previously thought (0.15–0.3). This revision provides insight into the significance of fluid inclusions in minerals of the incipient charnockites characteristic of the granulite facies transitions in several Precambrian gneiss terranes. Observations on NaCl-dominated brine inclusions in minerals, including some new data in this paper, in rocks from such places as the Kabbal–Satnur–Halagur area of the Archean Shield of South India have salt concentrations conso- nant with the stabilization of orthopyroxene relative to calcic amphibole and biotite; closely associated CO2-dominated fluid inclusions can have substantial H2O contents at typical incipient granulite facies conditions (700–750 ◦ C and 0.5–0.7 GPa) and can thus have been in equilibrium with the associated brines as immiscible metamorphic fluids. Observed densities of the best-preserved CO2-rich fluid inclusions in quartz are consistent with those expected from the equation of state of CO2 at incipient granulite facies pressure-temperature conditions.
It seems likely that the role of fluids in granulite facies metamorphism of the deep crust has been considerably underemphasized in discussions, still prevalent, which concentrate on the role of fluid- deficient partial melting as the primary agent, to the exclusion of a possible role of metamorphic fluids and metasomatism.

Pendant la plus grande partie du XIXe siecle, la geologie francaise a ete dominee par la personna... more Pendant la plus grande partie du XIXe siecle, la geologie francaise a ete dominee par la personnalite ecrasante de Leonce Elie de Beaumont, inventeur du " reseau pentagonal ". On detaille les principes et l'illustration de ce modele, premier essai de tectonique globale, dont l'oubli actuel parait aussi immerite que la confiance aveugle que lui ont accordee bon nombre de ses contemporains.

Hydrothermal graphite vein deposits hosted in granulite facies metamorphic rocks in Sri Lanka are... more Hydrothermal graphite vein deposits hosted in granulite facies metamorphic rocks in Sri Lanka are unique because of their large size and high crystallinity. In this paper, we present a review of the structural-meta-morphic setting of the graphite veins and of the graphite stable carbon isotope data, and we present fluid inclusion data from quartz in the graphite veins and in the host rocks from several graphite deposits in Sri Lanka. The studied host rocks show decompression rims of plagioclase and orthopyroxene after garnet. The quartz in these decompression rim textures comprise, in order of abundance, high-salinity brine, H 2 O-CO 2 , and low-salinity aqueous fluid inclusions. The brine fluid is responsible for metasomatic features observed in garnet decompression rims, including feldspar leaching and re-precipitation. Quartz cogenetic with vein graphite comprises, in order of abundance, low-salinity aqueous, CO 2 , high-salinity brine, and H 2 O-CO 2 fluid inclusions. Published ...

Bulletin de Minéralogie

Remarques historiques sur le developpement de l'etude des inclusions fluides et vitreuses. Ac... more Remarques historiques sur le developpement de l'etude des inclusions fluides et vitreuses. Actualite de l'œuvre de Sorby (1858).

Vestnik of Saint Petersburg University. Arts

The crypt and sarcophagus of Napoleon in the Dôme des Invalids in Paris which were constructed by... more The crypt and sarcophagus of Napoleon in the Dôme des Invalids in Paris which were constructed by an Italian-born French architect and designer Louis Tullius Joachim Visconti evince an extraordinarily expressive and harmonic colour combination in French and Italian marbles with those of so called porphyries in Napoleon's tombstone (they are really green andesite from France and purple quartzite from Russia). Works continued over a twenty year period (1840-1861) which saw in France three Kings, one Republic and one Emperor, and in Russia two emperors. Every political change in France exerted critical influence on the continuation of these works. The events surrounding the constructing the crypt and tombstone, applying steam machinery to cut and polish the sarcophagus, the budgets of the work is described from archival documents in detail. J.-F. Bujatti (an Italian from St Petersburg) played an important role in the quarrying of the Russian ornamental stone and in its transport to Paris. Refs 16. Figs 3.