The Mathematics of Cation Diffusion and Exchange Between Silicate Minerals During Retrograde Metamorphism

1977 ◽  
pp. 353-388 ◽  
Author(s):  
A. C. Lasaga ◽  
S. M. Richardson ◽  
H. D. Holland
Keyword(s):  
Retrograde Metamorphism ◽  
Cation Diffusion ◽  
Silicate Minerals

scholarly journals MN-ANDALUSITE, SPESSARTINE, MN-GROSSULAR, PIEMONTITE AND MN-ZOISITE/CLINOZOISITE FROM TRIKORFO, THASSOS ISLAND, GREECE

2017 ◽  
Vol 50 (4) ◽  
pp. 2068 ◽  
Author(s):  
P. Voudouris ◽  
I. Graham ◽  
K. Mavrogonatos ◽  
S. Su ◽  
K. Papavasiliou ◽  
...  
Keyword(s):  
Sustainable Development ◽  
Greenschist Facies ◽  
Contact Metamorphism ◽  
Retrograde Metamorphism ◽  
Prograde Metamorphism ◽  
Silicate Minerals ◽  
Vein Formation ◽  
Mineral Associations ◽  
Silicate Layers ◽  
Iron Bearing

Mylonitized manganiferous schists and calc-silicate layers intercalated within amphibolite- to greenschist facies mica schists from the Trikorfo area (Thassos Island, Greece), host an unusual Mn-rich paragenesis of metamorphic silicate minerals, most of them in large, gemmy crystals. The silicates occur both in layers subparallel to the foliation and within discordant veins cross-cutting the metamorphic fabric. Piemontite (up to 12.7 wt. % Mn2O3), Mn-rich epidote (up to 7.8 wt. % Mn2O3), Mn-rich andalusite (up to 15.6 wt. % Mn2O3), Mn-poor pink clinozoisite-epidote (up to 0.87 wt. % Mn2O3), Mn-poor pink zoisite (up to 0.21 wt. % Mn2O3), spessartine (up to 47.7 wt. % MnO) and Mn-rich grossular (up to 3.6 wt. % MnO) are associated with diopside, hornblende, phlogopite, muscovite, tourmaline, hematite and iron-bearing kyanite. The studied assemblages are indicative of high fO2 conditions due to the presence of highly oxidized pre-metamorphic Mn-rich mineral associations. They developed during prograde metamorphism of a Mn-rich sedimentary protolith(s), followed by re equilibration to post-peak metamorphic conditions, vein formation and metasomatism during retrograde metamorphism accompanying the exhumation of the Thassos Island during the Oligocene-Miocene. Alternatively, the skarn similar mineralogy of the calc-silicate layers could have been formed by fluids released by granitoids during contact metamorphism. The studied area represents a unique mineralogical geotope. Its geological-mineralogical heritage should be protected through establishment of a mineralogical-petrological geopark that will also promote sustainable development of the area.

Electron energy-loss near-edge structure in silicate minerals

1992 ◽  
Vol 50 (2) ◽  
pp. 1258-1259
Author(s):  
D W McComb ◽  
R S Payne ◽  
P L Hansen ◽  
R Brydson
Keyword(s):  
Solid State ◽  
Energy Loss ◽  
Electron Energy ◽  
State Energy ◽  
Local Environment ◽  
Edge Structure ◽  
Silicate Minerals ◽  
Two Samples ◽  
Electron Energy Loss ◽  
Careful Processing

Electron energy-loss near-edge structure (ELNES) is an effective probe of the local geometrical and electronic environment around particular atomic species in the solid state. Energy-loss spectra from several silicate minerals were mostly acquired using a VG HB501 STEM fitted with a parallel detector. Typically a collection angle of ≈8mrad was used, and an energy resolution of ≈0.5eV was achieved.Other authors have indicated that the ELNES of the Si L2,3-edge in α-quartz is dominated by the local environment of the silicon atom i.e. the SiO4 tetrahedron. On this basis, and from results on other minerals, the concept of a coordination fingerprint for certain atoms in minerals has been proposed. The concept is useful in some cases, illustrated here using results from a study of the Al2SiO5 polymorphs (Fig.l). The Al L2,3-edge of kyanite, which contains only 6-coordinate Al, is easily distinguished from andalusite (5- & 6-coordinate Al) and sillimanite (4- & 6-coordinate Al). At the Al K-edge even the latter two samples exhibit differences; with careful processing, the fingerprint for 4-, 5- and 6-coordinate aluminium may be obtained.

The Petrological Data Allow to Evaluate Magnitudes of Crustal Uplift Resulting from the Retrograde Metamorphism

2018 ◽  
Vol 482 (1) ◽  
pp. 56-59
Author(s):  
P. Chekhovich ◽  
◽  
E. Artyuishkov ◽  
S. Korikovsky ◽  
H.-J. Massonne ◽  
...  
Keyword(s):  
Retrograde Metamorphism ◽  
Crustal Uplift

USING SILICATE MINERALS AS MICROMODELS TO ACCESS THE RELATIONSHIP BETWEEN TRANSPORT AND REACTION AT THE PORE SCALE

2016 ◽  
Author(s):  
Heewon Jung ◽  
◽  
Alexis K. Navarre-Sitchler ◽  
Nathan Worts ◽  
Erica Block ◽  
...  
Keyword(s):  
Pore Scale ◽  
Silicate Minerals ◽  
The Relationship

Trace Element Composition of Silicate Minerals in the Chondrules and Matrix of the Buschhof Meteorite

2020 ◽  
Vol 58 (12) ◽  
pp. 1321-1330
Author(s):  
K. G. Sukhanova ◽  
S. G. Skublov ◽  
O. L. Galankina ◽  
E. V. Obolonskaya ◽  
E. L. Kotova
Keyword(s):  
Trace Element ◽  
Trace Element Composition ◽  
Element Composition ◽  
Silicate Minerals

scholarly journals Risk assessment of Ni, Cr, and Si release from alkaline minerals during enhanced weathering

2020 ◽  
Vol 5 (1) ◽  
pp. 166-175
Author(s):  
Fatima Haque ◽  
Yi Wai Chiang ◽  
Rafael M. Santos
Keyword(s):  
Risk Assessment ◽  
Environmental Protection Agency ◽  
Hazard Index ◽  
Carcinogenic Risk ◽  
Contamination Level ◽  
Potential Threat ◽  
Silicate Minerals ◽  
Guideline Value ◽  
Quality Guideline ◽  
Index Value

AbstractCalcium- and magnesium-rich alkaline silicate minerals, when applied to soil, can aid in carbon dioxide sequestration via enhanced weathering. The weathering of these silicate minerals is also associated with the release of heavy metals such as Ni and Cr, depending on the composition of the parent rock, and also labile Si. This paper critically analyses the risk associated with the release of Ni, Cr, and Si from alkaline silicate minerals as a result of enhanced weathering to evaluate its potential to be applied as a soil amendment. Based on the available data in the literature, this study evaluates the soil contamination level and quantifies the risk these elements pose to human health as well as the environment. To assess these potential threat levels, the geoaccumulation index was applied, along with the method recommended by the US Environmental Protection Agency for health risk assessment. The main findings of this study indicate the potential release of Ni, Cr, and Si to exceed the soil quality guideline value. The geochemical index suggests that the analyzed samples are in the class 0–3 and represents sites that lie between uncontaminated zones to highly contaminated zones. The hazard index value for Ni and Cr is greater than unity, which suggests that Ni and Cr release poses a non-carcinogenic risk. The probability of labile Si concentration in the soil to exceed the critical value is found to be 75%.

Non-Stoichiometry and Cation Tracer Diffusion Studies in the Magnetite-UlvÖSpinel Solution, (Fe,Ti)3-δO4

1994 ◽  
Vol 369 ◽  
Author(s):  
Sanjeev Aggarwal ◽  
Rudiger Dieckmann
Keyword(s):  
Diffusion Coefficients ◽  
Tracer Diffusion ◽  
Oxygen Activity ◽  
Spinel Solid Solution ◽  
Low Oxygen ◽  
Cation Diffusion ◽  
Deviation From Stoichiometry ◽  
Diffusion Studies ◽  
Tracer Diffusion Coefficients ◽  
Point Defect Structure

AbstractCation diffusion in the spinel solid solution (Fe1-xTix)3-δO4 (0≤ x ≤ 0.3) was investigated at 1200 ºC as a function of oxygen activity, aO2 and cationic composition, x. At different cationic compositions, cation tracer diffusion coefficients, D*Me of Me = Fe and Ti were measured as a function of oxygen activity. Plots of log DMe vs. loga0 show V-shaped curves, indicating that different types of point defects prevail at high anc low oxygen activities. Thermogravimetric experiments were conducted, using a high resolution microbalance, to determine the deviation from stoichiometry in (Fe1-xTix)3-δO4 at 1200 °C. δversus log aO2 curves are S-shaped. An analysis of the oxygen activity dependences of thecation diffusion coefficients and the deviation from stoichiometry with regardto the point defect structure suggests that at high oxygen activities cation vacancies are the predominant defects governing the deviation from stoichiometry and the diffusion ofcations. At low oxygen activities, and at small values of x, cation interstitials determine the deviation from stoichiometry, while they dominate for 0 ≤ x ≤ 0.3 inthe cation diffusion.

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