0.3.3 The chemical composition of metamorphic rocks

2005 ◽  
pp. 32-34
Author(s):  
H.-G. Huckenholz
Keyword(s):  
Chemical Composition ◽  
Metamorphic Rocks

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.

Variation in the Composition of Muscovite and Biotite in some Metamorphic Rocks near Bancroft, Ontario

1973 ◽  
Vol 10 (6) ◽  
pp. 869-880 ◽  
Author(s):  
Ermanno R. Rambaldi
Keyword(s):  
Chemical Composition ◽  
Chemical Equilibrium ◽  
Element Distribution ◽  
Metamorphic Grade ◽  
Chemical Data ◽  
Metamorphic Rocks ◽  
Exchange Equilibrium ◽  
Metamorphic Terrain ◽  
Fe Content ◽  
Compositional Study

A study of mica composition in a metamorphic terrain which displays a variation in metamorphic grade from the garnet to the sillimanite–garnet–biotite zone, has revealed that muscovite and phengite occur over the whole range of metamorphic conditions that were encountered. The distribution of Mn, Li, Ti, Na, Fe, and Mg between these minerals and coexisting biotite shows many regularities which are interpreted in relation to exchange equilibrium. Two trends of element distribution are suggested, corresponding to the association phengite–biotite and muscovite–biotite. The chemical composition of the mica minerals is not correlative with metamorphic grade.A compositional study of phengite has revealed that the Fe2+/Fe3+ ratio in this mineral is higher in rocks that contain epidote than in rocks that are free of epidote.The distribution of Na and K between muscovite and plagioclase is affected by the Fe content of muscovite and the An content of plagioclase.Mineralogical and chemical data from the study area provide an indication that a generalized chemical equilibrium was established in the rocks during metamorphism.

Les relations petrogenetiques entre les eclogites et les amphibolites dans le massif cristallophyllien du mont Snieznik

1964 ◽  
Vol S7-VI (2) ◽  
pp. 232-239 ◽  
Author(s):  
Kazimierz Smulikowski
Keyword(s):  
Chemical Composition ◽  
Metamorphic Rocks ◽  
Equilibrium Conditions ◽  
Rock Types ◽  
Temperature And Pressure ◽  
Depth Of Burial

Abstract Two different lithologic series of metamorphic rocks, granulite-eclogite and amphibolite-eclogite, in adjoining areas of the Snieznik massif of the Sudetes mountains on the Czech-Polish frontier, underwent different equilibrium conditions yet both had the paragenetic conditions for development of eclogite. Differences in the chemical composition of the original rocks and in the properties of intergranular solutions during metamorphism, rather than differences in temperature and pressure resulting from differences in depth of burial, determined the rock types resulting from metamorphism.

scholarly journals THE PALEOARCHEAN (3.3 Ga) AND MESOARCHEAN (3.0 Ga) TTGs OF THE WESTERN AZOV AREA, THE UKRAINIAN SHIELD

2021 ◽  
pp. 35-47
Author(s):  
G.V. Artemenko ◽  
L.V. Shumlyanskyy
Keyword(s):  
Chemical Composition ◽  
Detrital Zircons ◽  
Geochemical Characteristics ◽  
Ukrainian Shield ◽  
Metamorphic Rocks ◽  
The West ◽  
Siliceous Rocks ◽  
Zircon Crystallization ◽  
Greenstone Belts ◽  
Archean Greenstone Belts

A large anticline structure that includes the West Azov and Remivka blocks occurs in the western part of the Azov Domain of the Ukrainian Shield. These blocks are composed of rocks of the Mesoarchean (3.2-3.0 Ga) granite-greenstone association and relics of an older basement. The anticline is divided into two parts by the Bilotserkivka structure of sub-latitudinal strike; the northern part includes the Huliaipole and Remivka blocks, and the southern part is comprised of the Saltycha anticline. The Archean plagiogranitoids of the West Azov underwent intense dislocation metamorphism during the Paleoproterozoic. In many areas they were transformed into plagioclase gneisses that were attributed to the Paleoarchean “Kainkulak thickness” of the Azov Series. Detailed geological-structural and geochronological studies are required to define the age of these gneisses.We have chosen two areas for our studies: the Lantsevo anticline within the Bilotserkivka structure, and the Ivanivka area in the eastern part of the Saltycha anticline. The Bilotserkivka structure is composed of rocks of the Central Azov Series and highly deformed Archean formations. We have dated plagiogneisses of the Lantsevo anticline. These rocks contain large relics of metamorphic rocks of unknown age, including two-pyroxene and pyroxene crystalline schists, and pyroxenemagnetite quartzites (BIF). In terms of chemical composition, two-pyroxene crystalline schists correspond to tholeiitic basalts and basaltic komatiites. Ferruginous-siliceous rocks belong to the Algoma type typical for the Archean greenstone belts. Biotite gneisses are similar to the medium-pressure tonalite-trondhjemite-granodiorite rocks (TTGs). The U-Pb age of zircon crystallization from biotite gneisses is 3299 ± 11 Ma. At 30 km in the western part of the Bilotserkivka structure, we have previously identified quartz diorites having an age of 3297 ± 22 Ma. In terms of geochemical characteristics, they correspond to low-pressure TTGs. These data show that the Bilotserkivka structure is a block representing an ancient basement. In the Ivanivka area in the eastern part of the Saltycha anticline, the strike of the Archean rocks was reorientated from northwestern to latitudinal. The studied dislocated trondhjemites of the Ivanivka area correspond to TTGs in terms of the geochemical characteristics. They contain numerous relics of highly altered amphibolites. The U-Pb age of zircon crystallization from trondhjemite is 3013 ± 15 Ma. These rocks are of the same age as TTGs of the Shevchenko Complex cutting through the sedimentary-volcanogenic rocks of the greenstone structures of the Azov Domain. They share age and geochemical characteristics with biotite and amphibole-biotite gneisses of the “Kainkulak thickness” in Zrazkove village located at the Mokra Konka river (3.1-3.0 Ga) and with biotite gneisses in the lower reaches of the Kainkulak river (2.92 Ga). Thus, gneisses of the “Kainkulak thickness” in fact represent the Mesoarchean TTGs of the Shevchenko Complex, which were transformed in the Paleoproterozoic time due to the dislocation metamorphism. Late Paleoarchean (3.3 Ga) tonalites are known in the West Azov and the KMA domains; they probably also occur in the basement of the Middle Dnieper domains, where detrital zircons of this age have been reported. These data allow us to conclude the existence of a large Late Paleoarchean (3.3 Ga) protocraton, in which the Mesoarchean (3.2-3.0 Ga) greenstone belts and TTGs of the eastern part of the Ukrainian Shield and the KMA Domain were formed.

Sur l'existence et la nature de l'apport chimique dans certaines series cristallophylliennes

1945 ◽  
Vol S5-XV (4-6) ◽  
pp. 255-310 ◽  
Author(s):  
Pierre Lapadu-Hargues
Keyword(s):  
Chemical Composition ◽  
Special Reference ◽  
Metamorphic Rocks ◽  
Calc Alkaline ◽  
Physicochemical Factors ◽  
Alkaline Material

Abstract Distinguishes seven groups of metamorphic rocks according to chemical composition, ranging from argillaceous schists to granites and granulites, and discusses the physicochemical factors involved in the transformation of the pre-existing rocks during metamorphism, with special reference to the addition of calc-alkaline material from deep-seated magmas, the behavior of component elements, and the migration of ions during alteration.

The Principle of Constituent Analysis, with Special Reference to the Calculation of Weight Percentages of Minerals in Metamorphic Rocks

1973 ◽  
Vol 10 (5) ◽  
pp. 657-669 ◽  
Author(s):  
Tsu-Min Fuh
Keyword(s):  
Chemical Composition ◽  
Metamorphic Rock ◽  
Dimensional Space ◽  
Metamorphic Rocks ◽  
Chemical Compositions ◽  
Bulk Chemical Composition ◽  
Orthogonal Axis ◽  
Bulk Chemical ◽  
Axis I ◽  
End Members

The principle of constituent analysis is introduced. Assuming that a component (end member) consists of n variables in percentage form and that m different components (m ≤ n) constitute each of N samples, the samples can be treated as N points in m-dimensional space. Points represented by m end members are characterized by being non-coplanar and non-collinear in m-dimensional space. The amount of the mth end member contained in a sample is calculated as Xm−1i/Xm−1 m, where Xm−1 is the length of (m−1)th orthogonal axis; i and m in subscript Xm−1 are for the sample and mth end member, respectively; and the end members are successively put on the origin of the coordinate, X1, X1−X2, X1−X2−X3,…, and X1−X2 …−Xm−1 axes.In a metamorphic rock, m points are equivalent to constituent minerals. If the chemical compositions of constituent minerals and the bulk chemical composition of the rock are known, the method outlined in this paper provides information on equilibrium assemblages and allows computation of the amounts of constituent minerals.

4. Rocks transformed

2016 ◽  
pp. 51-65
Author(s):  
Jan Zalasiewicz
Keyword(s):  
Chemical Composition ◽  
High Pressures ◽  
Regional Metamorphism ◽  
Contact Metamorphism ◽  
Metamorphic Rocks ◽  
Mountain Belt ◽  
Different Types ◽  
High Pressures And Temperatures ◽  
Contact And Impact

‘Rocks transformed’ outlines the processes of metamorphism and describes the different types of metamorphism: regional, contact, and impact. Regional metamorphism is the most common form and occurs in mountain belt zones where the crust is much thicker. High pressures and temperatures result in recrystallization in the rocks. As temperatures and pressures increase, the new crystals that form are bigger. The original chemical composition of the rocks affects the resulting metamorphic rocks. Muds become slates and mica-schists, while limestones become marbles. Contact metamorphism takes place at the boundaries of magma bodies and impact metamorphism is seen when meteorites crash into the Earth’s surface.

Zussmanite in ferruginous metasediments from Southern Central Chile

1998 ◽  
Vol 62 (6) ◽  
pp. 869-876 ◽  
Author(s):  
H.-J. Massonne ◽  
F. Hervé ◽  
O. Medenbach ◽  
V. Muñoz ◽  
A. P. Willner
Keyword(s):  
Chemical Composition ◽  
Metamorphic Rocks ◽  
Stability Field ◽  
Low Grade ◽  
Central Chile ◽  
X Ray ◽  
Fine Grained ◽  
Southern Central ◽  
Similar Phase

AbstractZussmanite KFe13[AlSi17O42](OH)14, a modulated 2:1 layer silicate, has so far been found only in iron-rich metasediments from Laytonville, California (Agrellet al.), 1965). A new occurrence is reported here from Punta Nihue north of Valdivia, Chile, in banded stilpnomelane-schists. These are intercalated in the ‘Western Series’, a complex of low-grade metamorphic rocks with local high-pressure, low-temperature overprint (e.g. blueschists).The rock contains conspicuous porphyroblasts of zussmanite of mm size and is composed of chemically distinct bands with the subsequent assemblages: (1) zussmanite-stilpnomelane-quartz, (2) siderite-quartz±stilpnomelane (3) apatite-stilpnomelane-quartz±siderite. The chemical composition of zussmanite, (K0.80Na0.05Ba0.01)(Fe11.292+Mg1.11Mn0.25Fe0.143+Cr0.01Al0.19Ti0.01)[Al1.23Si16.77O42](OH)14, its optical properties and X-ray data correlate well with the Californian occurrence. Additionally, we present new IR data. In type (2) bands of fine-grained crystals of a K,Al poor mineral formed from siderite and quartz. Its chemical composition is close to that of zussmanite. A similar phase was also reported from Laytonville, California (Muir Wood, 1980).The rarity of rock-forming zussmanite can be explained by its occurrence in strongly Fe-rich and reduced rocks, as well as, by a possibly narrowP-Tstability field.

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