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.

Variation in the Composition of Plagioclase and Epidote in some Metamorphic Rocks near Bancroft, Ontario

1973 ◽  
Vol 10 (6) ◽  
pp. 852-868 ◽  
Author(s):  
Ermanno R. Rambaldi
Keyword(s):  
Chemical Reactions ◽  
Metamorphic Grade ◽  
Chemical Data ◽  
Metamorphic Rocks ◽  
General Increase ◽  
Al Content ◽  
Metamorphic Terrain ◽  
Anorthite Content ◽  
Normal Zoning

A Precambrian metamorphic terrain near Bancroft displays a variation in metamorphic grade, as indicated by the presence of the following metamorphic zones: garnet, staurolite–biotite, kyanite–biotite, sillimanite, and sillimanite–garnet–biotite.In rocks that contain plagioclase and epidote, there is a general increase in the anorthite content of plagioclase and a decrease in the Al content of epidote with increasing metamorphic grade. Plagioclase crystals are commonly zoned, becoming richer in anorthite toward the rims, and epidote crystals may also be zoned, becoming enriched in iron toward the rims. Various chemical reactions are proposed to account for these changes.In rocks that do not contain epidote, plagioclase is typically albitic in composition, regardless of metamorphic grade.In rocks containing microcline, some albite has evidently exsolved from the microcline, resulting in the development of sodic rims about plagioclase crystals and normal zoning in these crystals.The distribution of albite between plagioclase and microcline is in agreement with the results from other metamorphic terrains of similar grade. Observed irregularities in this distribution may be attributed to exsolution of albite from microcline.Mineralogical and chemical data from the study area provide an opportunity to propose various chemical reactions, some of which may closely approach those that have taken place within the rocks.

Saponite, Corrensite and Chlorite-Saponite Mixed-Layers in the Sancerre-Couy Deep Drill-Hole (France)

Clay Minerals ◽  
1994 ◽  
Vol 29 (1) ◽  
pp. 47-61 ◽  
Author(s):  
D. Beaufort ◽  
A. Meunier
Keyword(s):  
Chemical Composition ◽  
Drill Hole ◽  
X Ray Diffraction ◽  
Parental Relationships ◽  
Clay Deposits ◽  
Fe Content ◽  
Three Samples ◽  
Structural Formulae ◽  
Layer Mineral ◽  
Mixed Layers

AbstractThe clay deposits in fractures of the metamorphic basement under the Paris Basin sedimentary formations at Sancerre-Couy (France) are composed of trioctahedral species which are exceptionally well crystallized. Three samples were chosen in order to study the chemical composition of 100% expandable saponite, 50% expandable corrensite and 10% expandable chlorite-saponite mixed-layer mineral C90–S10 Two sets of microchemical analyses were performed in order to determine the variations of the composition on large and small numbers of particles. X-ray diffraction (XRD) and Mössbauer spectrometry were performed on purified samples.The mathematical decomposition of Si, Al and Mg histograms established from microanalyses of a large number of crystals of saponite, corrensite and C90–S10 evidences bimodal populations. The total Fe content of the three species is unimodal whatever the chemical composition of the surrounding rock and the Fe2+/Fe3+ ratio. The structural formulae established from a large number of microanalyses of a few particles show that there are no parental relationships between saponite, corrensite and C90–S10. The expandable layer of corrensite is characterized by a high charge. It is proposed that the tetrahedral sheets adjacent to the brucitic sheet and the exchangeable interlayer in a 2 : 1 unit are identical in corrensite.

scholarly journals Chemosystematics of Porella (Marchantiophyta, Porellaceae)

2011 ◽  
Vol 6 (3) ◽  
pp. 1934578X1100600 ◽  
Author(s):  
Agnieszka Ludwiczuk ◽  
S. Rob Gradstein ◽  
Fumihiro Nagashima ◽  
Yoshinori Asakawa
Keyword(s):  
Chemical Composition ◽  
Secondary Metabolites ◽  
Plant Morphology ◽  
The Other ◽  
Chemical Data ◽  
Type I ◽  
Separate Section ◽  
The Family ◽  
Chemosystematic Markers

The taxonomy of the liverwort genus Porella based on plant morphology has been regarded as difficult. Recent DNA-based studies have brought new insights into the systematics of these liverworts and have uncovered some novel relationships that allowed the resolution of controversial treatments based on morphology. One of the outstanding features of these plants, in addition to their form, is their chemical composition, which is characterized by great diversity of secondary metabolites. In this paper the sesqui- and diterpenoids occurring in Porella species are described and their chemosystematic relevance is explored. On the basis of chemical data, the Porella species have been divided into six chemotypes: the drimane- (I), sacculatane- (II), pinguisane-sacculatane- (III), guaiane-germacrane- (IV), pinguisane- (V) and africane- (VI) types. Species belonging to type I are characterized by their hot taste, whereas the other chemotypes are comprised of non-pungent species. Consideration of recent DNA data shows striking correlations between molecular groups and their terpenoid chemistry. The chemical data suggest that the P. vernicosa complex (chemotype I) deserves recognition as a separate section of Porella and that terpenoids are important chemosystematic markers in the family Porellaceae.

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.

scholarly journals Chemical equilibrium of groundwater with minerals of the host rocks in Upper Jurassic sediments (Arctic regions of Western Siberia)

2019 ◽  
Vol 98 ◽  
pp. 01037 ◽  
Author(s):  
Dmitry A. Novikov
Keyword(s):  
Chemical Composition ◽  
Chemical Equilibrium ◽  
Western Siberia ◽  
Upper Jurassic ◽  
The Arctic ◽  
Geochemical Environment ◽  
Rock System ◽  
Arctic Regions ◽  
Host Rocks ◽  
Mineral Changes

The results of thermodynamic calculations for a water-rock system in the Upper Jurassic deposits of the Arctic regions of Western Siberia are presented. In the area under investigation the groundwaters have been identified with mineralization up to 63.3 g/L and various chemical composition and genesis. Despite the long interaction with the rock (150-160 ma) equilibrium with endogenous minerals (albite, microcline and anorthite) is practically not observed. At the same time, groundwaters are in equilibrium with clay minerals and micas, such as: Caand Na-montmorillonites, kaolinite, paragonite, margarite, illite, muscovite and Mg-chlorite. The establishment of a balance of groundwater with primary aluminosilicate minerals is also affected by interactions with carbonate minerals. The differences in composition of groundwater in equilibrium with certain aluminosilicates and carbonates indicate that the mineral changes are formed from a solution of a strictly defined chemical composition in an appropriate geochemical environment.

Chemical composition of Archean Pontiac metasediments, southwestern Abitibi Belt, Superior Province

1984 ◽  
Vol 21 (6) ◽  
pp. 727-731 ◽  
Author(s):  
Osamu Ujike
Keyword(s):  
Chemical Composition ◽  
Chemical Data ◽  
Superior Province ◽  
Upper Crust ◽  
The Mean

Three mica schists from the Pontiac Group have a La/Yb ratio of ~19, a La content of ~32 ppm, and a Th content of ~6 ppm. These values are higher than those of the average Archean upper crust (La/Yb, ~7; La, ~13 ppm; Th, ~3.5 ppm) and the mean compositions of Blake River (La/Yb, ~2.6 (184 analyses); La, ~10 ppm (184 analyses); Th, ~1.3 ppm (143 analyses)) and other subalkalic volcanic groups in the Kirkland Lake–Noranda region. Hence it is unlikely that the latter are exclusive sources of Pontiac detritus. The chemical data reveal that Timiskaming-type alkalic rocks (La/Yb, ~ 45; La, ~95 ppm; Th, ~21 ppm (means of 29 analyses)) are likely contributors to Pontiac metasediments. However, the Timiskaming Group itself is generally considered to be younger than the Pontiac Group. This implies the presence of an undetected or unpreserved terrane characterized by Timiskaming-type alkalic rocks.

Ganophyllite from Franklin, New Jersey; Pajsberg, Sweden; and Wales new chemical data

1983 ◽  
Vol 47 (345) ◽  
pp. 563-566 ◽  
Author(s):  
Pete J. Dunn ◽  
Donald R. Peacor ◽  
Joseph E. Nelen ◽  
Robert A. Ramik
Keyword(s):  
Solid Solution ◽  
New Jersey ◽  
Chemical Composition ◽  
Water Content ◽  
General Structure ◽  
Chemical Data ◽  
Upper Limit ◽  
Octahedral Cations

AbstractGanophyllite from Franklin, New Jersey, Pajsberg, Sweden, and the Benallt Mine, Wales, has been chemically reinvestigated. Twelve new analyses confirm the general structure of Kato (1980) and yield the tentative formula (K,Na,Ca)2Mn8(Si,Al)12(O,OH)32(OH)4·8H2O. There is little solid solution among octahedral cations, and the Si:Al ratio is nearly constant at 10:2. Ca and (Na + K) are apparently differentiated, but all examined ganophyllites are K-rich. Much of the water content is loosely bound and the upper limit of water content is not well defined. Ganophyllite is relatively invariant in chemical composition from locality to locality.

The petrology and chemical composition of a tholeiite sill on Schaapkraal 68JT, Lydenburg District, Transvaal, South Africa

1970 ◽  
Vol 37 (292) ◽  
pp. 909-915
Author(s):  
C. Frick
Keyword(s):  
South Africa ◽  
High Pressure ◽  
Chemical Composition ◽  
Chemical Analysis ◽  
Chemical Data ◽  
Chemical Analyses ◽  
Residual Glass ◽  
Iron Enrichment ◽  
Crystallization Differentiation

SummaryA glass-bearing dolerite, which consists of orthopyroxene phenocrysts (γ 1·689, α 1·678, β 1·680, 2Vα 81°, S.G. 3·35) and a glassy mesostasis (n 1·568, S.G. 3·25), is described petrologically. Three new chemical analyses are given. From the petrological and chemical data it can be concluded that the orthopyroxene formed under intratelluric conditions and probably under high pressure. According to the recalculated chemical analysis of the orthopyroxene 0·22 Al3+ is in the Y position and much less Al3+ in the Z position. The chemical analysis of the residual glass is compared with similar residual glasses, and it shows that iron enrichment characterizes the earlier stages of crystallization differentiation, whereas the later stages are marked by an increase in Si4+, K+, and Na+.

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