Les granites a muscovite du mont Pilat (Massif central)

1966 ◽  
Vol S7-VIII (1) ◽  
pp. 133-149
Author(s):  
Jean Ravier ◽  
Maurice Chenevoy
Keyword(s):  
Chemical Composition ◽  
Low Pressure ◽  
Massif Central ◽  
Potassic Feldspar ◽  
Large Groups ◽  
Metamorphic Series

Abstract Muscovite granites of the Pilat massif (French Central Massif) can be divided into two large groups. Those belonging to the first group appear in the so-called metamorphic series of the Pilat massif and are associated with granulites of rhyolitic origin from which they were directly derived by anatexis. Those of the second group are doubtless of similar origin, although this is more difficult to establish. All these granites have a constant chemical composition. Their magmatic paragenesis includes, in addition to quartz, potassic feldspar and albite, some biotite, a little muscovite, and occasionally andalusite. The data seem to indicate crystallization under conditions of low pressure and temperatures less than 700 degrees C. Subsequently, secondary muscovitization developed at the expense of andalusite. The muscovite granites of the Pilat massif do not present a mineralization sequence. Their mode of formation was quite different from that of the late hololeucocratic granites resulting from a differentiation of granitoid assemblages.

Supergene alteration of metamorphic chlorite in an amphibolite from Massif Central, France

Clay Minerals ◽  
1982 ◽  
Vol 17 (2) ◽  
pp. 159-173 ◽  
Author(s):  
D. Proust
Keyword(s):  
Chemical Composition ◽  
Low Temperature ◽  
Grain Boundaries ◽  
Mixed Layer ◽  
Low Pressure ◽  
Chemical Changes ◽  
Massif Central ◽  
Rock Structure ◽  
Initial Rock

AbstractThe mineralogical and chemical changes of sheridanite were followed in different alteration horizons as weathering of its host amphibolite increased. Microscopic and microprobe analyses of phases produced in or around the chlorite allowed a classification of the different alteration stages relative to their position in the profile. In the unweathered rock, prehnite and a sericite—kaolinite assemblage appear to have formed at grain boundaries between chlorites and plagioclases. These represent low-pressure (PH2O < 2.5 ± 1 Kb) and low-temperature (320–360°C) metamorphic phases. In the saprock, where initial rock structure is still preserved, chlorites weather to a more or less regular mixed-layer chlorite-vermiculite. In the saprolite, large-grain (20 µm) vermiculite forms in the clayey zones (plasma) when rock structure is destroyed. The chemical composition of these newly-formed minerals is influenced by the original chlorites and mixed-layer minerals.

scholarly journals Research Regarding the Quality of Lambs Carcass Resulted from Tsigaia Purebred Compared with Hybrids of Tsigaia Ewes Crossed with Blanc du Massif Central Rams

2017 ◽  
Vol 74 (1) ◽  
pp. 7
Author(s):  
Mihai Marian BORZAN ◽  
Dana PUSTA ◽  
Liviu BOGDAN ◽  
Alexandra TABARAN ◽  
Attila MATE ◽  
...  
Keyword(s):  
Body Weight ◽  
Chemical Composition ◽  
Massif Central ◽  
Live Body Weight ◽  
Almost All ◽  
Qualitative Characteristics

Abstract: The research aims to compare some qualitative characteristics of purebred Tsigaia lambs and Tsigaia crossed with Blanc du Massif Central lambs. The criteria assessed were: chemical composition of purebred and Tsigaia crossed meat, the live body weight, the slaughtering performance, the weight of different carcass cut. For almost all criteria chosen the crossed individuals registered better results.

scholarly journals Uraninite, Coffinite and Ningyoite from Vein-Type Uranium Deposits of the Bohemian Massif (Central European Variscan Belt)

Minerals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 123 ◽  
Author(s):  
Miloš René ◽  
Zdeněk Dolníček ◽  
Jiří Sejkora ◽  
Pavel Škácha ◽  
Vladimír Šrein
Keyword(s):  
Chemical Composition ◽  
Electron Microprobe ◽  
Bohemian Massif ◽  
Uranium Deposit ◽  
Ore Deposits ◽  
Metamorphic Rocks ◽  
Uranium Deposits ◽  
Massif Central ◽  
Vein Type ◽  
Ore District

Uraninite-coffinite vein-type mineralisation with significant predominance of uraninite over coffinite occurs in the Příbram, Jáchymov and Horní Slavkov ore districts and the Potůčky, Zálesí and Předbořice uranium deposits. These uranium deposits are hosted by faults that are mostly developed in low- to high-grade metamorphic rocks of the basement of the Bohemian Massif. Textural features and the chemical composition of uraninite, coffinite and ningyoite were studied using an electron microprobe. Collomorphic uraninite was the only primary uranium mineral in all deposits studied. The uraninites contained variable and elevated concentrations of PbO (1.5 wt %–5.4 wt %), CaO (0.7 wt %–8.3 wt %), and SiO2 (up to 10.0 wt %), whereas the contents of Th, Zr, REE and Y were usually below the detection limits of the electron microprobe. Coffinite usually forms by gradual coffinitization of uraninite in ore deposits and the concentration of CaO was lower than that in uraninites, varying from 0.6 wt % to 6.5 wt %. Coffinite from the Jáchymov ore district was partly enriched in Zr (up to 3.3 wt % ZrO2) and Y (up to 5.5 wt % Y2O3), and from the Potůčky uranium deposit, was distinctly enriched in P (up to 8.8 wt % P2O5), occurring in association with ningyoite. The chemical composition of ningyoite was similar to that from type locality; however, ningyoite from Potůčky was distinctly enriched in REE, containing up to 22.3 wt % REE2O3.

Smectite, chlorite and a regular interlayered chlorite-vermiculite in soils developed on a small serpentinite body Massif Central, France

Clay Minerals ◽  
1976 ◽  
Vol 11 (2) ◽  
pp. 121-135 ◽  
Author(s):  
J. Ducloux ◽  
A. Meunier ◽  
B. Velde
Keyword(s):  
Chemical Composition ◽  
Clay Minerals ◽  
Closed System ◽  
Soil Profile ◽  
Crystalline Rocks ◽  
Soil Profiles ◽  
Massif Central ◽  
Three Stages ◽  
Image Position ◽  
Chemical Migration

AbstractThree soil profiles developed on a serpentinite body (La Rochel'Abeille, near Limoges) show three stages of weathering. All soils contain iron-rich smectites and secondary chlorites. The latter are very silica-rich, more so than 14 Å chlorites from crystalline rocks. In the (B)1g horizon of the hydromorphic profile, these minerals seem to give a reaction of the type:This reaction, typical of a closed system, appears to be operative in a soil profile which is certainly, in part, open to chemical migration. The chemistry of the weathered serpentinite and the chemical composition of newly formed minerals as well as those of the serpentinite are used to indicate the chemiographic relations of clay minerals formed in the weathering profiles.

scholarly journals Vertical zonality of fractionated granite plutons reflected in zircon chemistry: the Cínovec A-type versus the Beauvoir S-type suite

2012 ◽  
Vol 63 (5) ◽  
pp. 383-398 ◽  
Author(s):  
Karel Breiter ◽  
Radek Škoda
Keyword(s):  
Czech Republic ◽  
Chemical Composition ◽  
Vertical Section ◽  
Chemical Compositions ◽  
Massif Central ◽  
Intermediate Unit ◽  
Type Granite ◽  
Vertical Changes ◽  
High Degree ◽  
Vertical Zonality

Abstract We studied vertical changes in the chemical composition of zircon from two contrasting Variscan granite systems. The Beauvoir system (Massif Central, France) composed of three successive intrusions (B1, B2, B3) represents typical peraluminous S-type granite extremely enriched in P, F, Li, Rb, Cs, Be, Sn, Nb, Ta, and poor in Zr, Th, REE and Y. The Cínovec system (Krušné hory Mts/Erzgebirge, Czech Republic/Germany) composed of two successive intrusions (protolithionite granite, zinnwaldite granite) is only slightly peraluminous, P-poor, F, Li, Rb, Cs, U, Th, REE, Y, Sc, Sn, W, Nb, Ta-rich granite, which may be classified as A-type. In both localities, the most fractionated intrusions are located on the top of the system. Samples from borehole GPF-1 (Beauvoir) represent an 800 m long vertical section through the entire granite stock, while CS-1 borehole (Cínovec) reached a depth of 1600 m. Chemical compositions of zircons from both granite systems show distinct vertical zonality, but their shape and elemental speciation is highly contrasting. At Beauvoir, zircon shows a remarkable increase in Hf-content from 2-4 wt. % HfO2 (~0.03 apfu Hf) in the deepest B3-unit to 15-19 wt. % HfO2 (up to 0.18 apfu Hf) in the uppermost B1-unit. The highest contents of F, P, and U were detected in the intermediate unit B2 at a depth of 400-600 m. At Cínovec, Hf shows only moderate enrichment from ca. 2 wt. % HfO2 in the deeper protolithionite granite to 5-10 wt. % HfO2 in the uppermost part of the zinnwaldite granite. High contents of Th (3-8 wt. % ThO2) are entirely bound in the uppermost section of the granite copula to a depth of 200 m, but below this level the contents only sporadically exceed 1 wt. % ThO2. Concentrations of U, Y, HREE, Sc and Bi also reach their highest values in the uppermost parts of the zinnwaldite granite, but their decrease downward is much gentler. Extreme enrichment of outer zones of zircon crystals from some granites with Hf or high contents of Th, U, REE, Y, Nb and of some other elements in zircons from other localities is not considered to be a specific phenomenon characterizing melts of A- or S-type granite, but reflects a high degree of fractionation of systems rich in Na and F.

scholarly journals Plasma-assisted oxidation of Cu(100) and Cu(111)

2021 ◽  
Author(s):  
Sebastian Kunze ◽  
Liviu C. Tănase ◽  
Mauricio J. Prieto ◽  
Philipp Grosse ◽  
Fabian Scholten ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Surface Structure ◽  
Room Temperature ◽  
Oxygen Plasma ◽  
Low Pressure ◽  
Time Dependent ◽  
Pressure Oxygen

A low-pressure oxygen plasma oxidized Cu(100) and Cu(111) surfaces at room temperature. The time-dependent evolution of surface structure and chemical composition is reported in detail for a range of exposure times up to 30 min.

New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. XI. Anatolyite, Na6(Ca,Na)(Mg,Fe3+)3Al(AsO4)6

2019 ◽  
Vol 83 (5) ◽  
pp. 633-638 ◽  
Author(s):  
Igor V. Pekov ◽  
Inna S. Lykova ◽  
Vasiliy O. Yapaskurt ◽  
Dmitry I. Belakovskiy ◽  
Anna G. Turchkova ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Chemical Composition ◽  
Electron Microprobe ◽  
New Mineral ◽  
Single Crystal Xrd ◽  
Xrd Pattern ◽  
Potassic Feldspar ◽  
Tolbachik Volcano ◽  
Mohs Hardness ◽  
Heteropolyhedral Framework

AbstractThe new mineral anatolyite Na6(Ca,Na)(Mg,Fe3+)3Al(AsO4)6 was found in the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. It is associated with potassic feldspar, hematite, tenorite, cassiterite, johillerite, tilasite, ericlaxmanite, lammerite, arsmirandite, sylvite, halite, aphthitalite, langbeinite, anhydrite, wulffite, krasheninnikovite, fluoborite, pseudobrookite and fluorophlogopite. Anatolyite occurs as aggregates (up to 2 mm across) of rhombohedral–prismatic, equant or slightly elongated along [001] crystals up to 0.2 mm. The mineral is transparent, pale brownish–pinkish, with vitreous lustre. It is brittle, cleavage was not observed and the fracture is uneven. The Mohs’ hardness is ca 4½. Dcalc is 3.872 g cm–3. Anatolyite is optically uniaxial (–), ω = 1.703(4) and ε = 1.675(3). Chemical composition (wt.%, electron microprobe) is: Na2O 16.55, K2O 0.43, CaO 2.49, MgO 5.80, MnO 0.16, CuO 0.69, ZnO 0.55, Al2O3 5.01, Fe2O3 7.94, TiO2 0.18, SnO2 0.17, SiO2 0.04, P2O5 0.55, As2O5 60.75, SO3 0.03, total 101.34. The empirical formula based on 24 O apfu is (Na5.90K0.10)Σ6.00(Ca0.50Na0.13Zn0.08Mn0.03)Σ0.74(Mg1.63Fe3+1.12Al0.15Cu0.10)Σ3.00(Al0.96Ti0.03Sn0.01)Σ1.00(As5.97P0.09Si0.01)Σ6.07O24. Anatolyite is trigonal, R$\bar{3}$c, a = 13.6574(10), c = 18.2349(17) Å, V = 2945.6(4) Å3 and Z = 6. The strongest reflections of the powder XRD pattern [d,Å(I)(hkl)] are: 7.21(33)(012), 4.539(16)(113), 4.347(27)(211), 3.421(20)(220), 3.196(31)(214), 2.981(17)(223), 2.827(100)(125) and 2.589(18)(410). The crystal structure was solved from single-crystal XRD data to R = 4.77%. The structure is based on a 3D heteropolyhedral framework formed by M4O18 clusters [M1 = Al and M2 = (Mg,Fe3+)] linked with AsO4 tetrahedra. (Ca,Na) and Na cations centre A1O6 and A2O8 polyhedra in voids of the framework. Anatolyite is isostructural with yurmarinite. The new mineral is named in honour of the outstanding Russian crystallographer, mineralogist and mathematician Anatoly Kapitonovich Boldyrev (1883–1946).

Une nouvelle serie polymetamorphique du Massif Central francais; le Livradois meridional

1959 ◽  
Vol S7-I (8) ◽  
pp. 854-856 ◽  
Author(s):  
Francois-Hubert Forestier
Keyword(s):  
Late Stage ◽  
Crystalline Rocks ◽  
Mica Schist ◽  
Massif Central ◽  
Metamorphic Series

Abstract A retrograde metamorphic series in the southern Livradois zone is described and compared with other retrograde metamorphic zones in the crystalline rocks of the Central Massif of France. The second metamorphism is not merely a late stage of the first; its microcataclastic character indicates that it affected completely consolidated rocks of the deep migmatite to the lower mica schist stage. Two distinct pre-Stephanian orogenies are apparently represented, but they cannot be dated more precisely at present.

Thermal maturation and exhumation of a middle orogenic crust in the Livradois area (French Massif Central)

2011 ◽  
Vol 182 (1) ◽  
pp. 5-24 ◽  
Author(s):  
Véronique Gardien ◽  
Olivier Vanderhaeghe ◽  
Nicolas Arnaud ◽  
Alain Cocherie ◽  
Marion Grange ◽  
...  
Keyword(s):  
Final Stage ◽  
Crustal Melting ◽  
Early Permian ◽  
French Massif Central ◽  
Rapid Cooling ◽  
Massif Central ◽  
Upper Carboniferous ◽  
Peak Metamorphism ◽  
Metamorphic Series ◽  
Granitic Dome

AbstractUpper Carboniferous heating and melting of the middle orogenic crust associated with the emplacement of syntectonic granitoids are documented in the Upper Gneissic Unit of the Livradois area (central part of the French Massif Central). Crustal melting post-dates peak metamorphism conditions (800-625°C, 10-8 kb) dated at 360 ± 4 Ma (U-Th-Pb on monazite). The P-T evolution of the metamorphic series indicates that Barrovian metamorphism was followed by a decompression (from 10 ± 1 kbar to 6 ± 1 kbar) associated with either a decrease in temperature in the southern part of the series or with an increase in temperature (of about 150°C) in the northern part of the series. This evolution records the first step of the exhumation of the series coeval with granitoids intrusion, of which the emplacements were dated at 315 ± 4 and 311 ± 18 Ma (U-Pb on zircon). The final stage of the exhumation is associated with an isobaric cooling of the whole series. Similarity of 40Ar/39Ar ages for biotite in the paragneisses (307-300 Ma) and K-feldspar in the granitoids (306-300 Ma) document rapid cooling for this stage. Moreover dextral reverse mylonites, at the border and the northern part of the metamorphic series indicate north-south compression coeval with the unroofing of the series. Youngest 40Ar-39Ar ages on K-feldspar (274.6 ± 5 Ma) combined with normal shearing in mylonites limiting the Carboniferous Brassac-les-Mines basin document the late Carboniferous-early Permian stage of extension coeval with the upwelling of the Velay granitic dome.

Mathematical Modelling the Low-Pressure Nitriding Process

2013 ◽  
Vol 421 ◽  
pp. 377-383 ◽  
Author(s):  
Emilia Wolowiec ◽  
Piotr Kula ◽  
Bartłomiej Januszewicz ◽  
Maciej Korecki
Keyword(s):  
Neural Networks ◽  
Artificial Neural Networks ◽  
Chemical Composition ◽  
Mathematical Modelling ◽  
Computational Methods ◽  
Thermochemical Treatment ◽  
Low Pressure ◽  
Computer Support ◽  
Effect Relationship ◽  
Relationship Of

This paper discusses the issues of modelling and smart computer support for low-pressure nitriding aimed at achieving more effectively the compatibility between the actual post-treatment properties of a material and the designed properties, which will contribute to improved repeatability of the processes. The principal objective of the experiment was to acquire better understanding of the cause and effect relationship of the low-pressure nitriding processes and to develop the methodology of designing functional and effective processes of low-pressure thermochemical treatment, using effective computational methods. The paper proposes a method of steel classification based on its chemical composition and a model used to forecast the properties of material after low-pressure nitriding, based on the artificial neural networks.

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