The alkali feldspars of the Ardara pluton, Donegal

1966 ◽  
Vol 35 (273) ◽  
pp. 693-703 ◽  
Author(s):  
A. Hall
Keyword(s):  
Structural State ◽  
Significant Variation ◽  
Reciprocal Lattice ◽  
Bulk Composition ◽  
Alkali Feldspar ◽  
Ray Method ◽  
X Ray ◽  
Before And After ◽  
Different Parts ◽  
Alkali Feldspars

SummaryThe alkali feldspars in the Ardara pluton are microcline- and orthoclase-microperthites. Their compositions have been determined by the 20 X-ray method, both before and after homogenization. The bulk compositions are very rich in potassium as a result of postmagmatic recrystallization of the alkali feldspar. There is no significant variation in either the bulk composition or the composition of the potassic phase in different parts of the intrusion. The structural state of the feldspars has been studied by measurement of 2V and obliquity of the potassic phases, and the reciprocal lattice angles α* and γ* of the potassic and sodic phases in selected crystals. Most of the specimens contain near-maximum microcline, but there is a decrease in the obliquity of the potassic phase at the eastern end of the intrusion. This can be related to the subsequent intrusion of the Main Donegal Granite.

Twin memory and twin amnesia in anorthoclase

2000 ◽  
Vol 64 (2) ◽  
pp. 195-200 ◽  
Author(s):  
S. A. Hayward ◽  
E. K. H. Salje
Keyword(s):  
Phase Transitions ◽  
Transition Temperature ◽  
Alkali Feldspar ◽  
Spatial Distributions ◽  
X Ray Diffraction ◽  
Alkali Cations ◽  
X Ray ◽  
Natural Minerals ◽  
Synthetic Materials ◽  
Before And After

AbstractMany natural minerals and synthetic materials display twin microstructures resulting from displacive phase transitions. These microstructures may be removed temporarily from the sample by heating above the relevant transition temperature, though the twinning generally returns on subsequent cooling.In anorthoclase, the spatial distributions of twins before and after brief annealing above TC are often identical. This property appears to be a common feature in many materials which undergo ferroelastic phase transitions, and is known as ‘twin memory’. The atomic mechanisms responsible for this twin memory may be investigated by studying the annealing regimes required to remove the memory effect; how long must a sample be annealed, and at what temperature, to induce ‘twin amnesia’.High-resolution X-ray diffraction (XRD) has been used to investigate twin memory and twin amnesia in anorthoclase. In anorthoclase, the primary constraint on twin amnesia is thermodynamic, rather than kinetic. The critical temperature to induce amnesia correlates well with the top of the (Na, K) solvus in disordered alkali feldspar. For this reason, the proposed mechanism for twin memory involves the segregation of alkali cations in thin lamellae at the twin boundaries.

The feldspars of the Rosses Granite Complex, Donegal, Ireland

1966 ◽  
Vol 35 (275) ◽  
pp. 975-982 ◽  
Author(s):  
A. Hall
Keyword(s):  
Low Temperature ◽  
Structural State ◽  
Alkali Feldspar ◽  
Temperature State ◽  
Granite Complex ◽  
Higher Temperature ◽  
Alkali Feldspars

SummaryAn examination has been made of the composition and structural state of the feldspars in each of the units of the Rosses granite complex. The compositions of the plagioclases are systematically related to the compositions of the rocks, but the alkali feldspars are much more uniform as a result of postmagmatic recrystallization. In the granites both alkali feldspar and plagioclase are in low-temperature structural states, but alkali feldspar phenocrysts from one of the porphyry dykes associated with the complex show a higher-temperature state.

Composition and structural state of coexisting feldspars, Salton Sea geothermal field

1986 ◽  
Vol 50 (355) ◽  
pp. 75-84 ◽  
Author(s):  
S. Douglas McDowell
Keyword(s):  
Excellent Agreement ◽  
Structural State ◽  
Alkali Feldspar ◽  
Geothermal Field ◽  
Salton Sea ◽  
Geothermal System ◽  
Temperature Range ◽  
Fine Grained ◽  
Alkali Feldspars

AbstractActive metamorphism of fine grained sandstone in the c.16000 year old Salton Sea geothermal system has produced a suite of chemically equilibrated coexisting authigenic alkali feldspars and re-equilibrated detrital feldspars in the 250–360°C temperature range. At c.335°C the average compositions, 2 Vs, and (t1o+t1m) and Z ordering parameters of coexisting authigenic feldspars are [Or0.52Ab97.40An2.08, 2Vx = 91.3±4.8, (t1o + t1m) = 0.89±0.05, Z = 0.79±0.09], and [Or94.42 Ab5.10An0.48, 2Vx = 70, (t1o + t1m) = 0.90, Z = 0.81]. At c.360°C authigenic albite becomes more An-rich and less ordered [Or1.21Ab92.83An5.97, 2Vx = 87.5±3.4, (t1o + t1m) = 0.85±0.03, Z = 0.70±0.07] and K-feldspar is no longer stable. Detrital plagioclase (An up to 40%) is preserved metastably to temperatures up to c.190°C in strongly carbonate-cemented sandstone which forms part of a geothermally produced permeability cap. It undergoes rapid alkali exchange at temperatures near 200°C, and by 250°C no plagioclase with An-content over 12% is observed. At > 250°C authigenic and most detrital alkali feldspar compositions are in excellent agreement with the Bachinski and Muller (1971) microcline-low-albite solvus.

Internal stress in titanium G4 before and after metal forming in increased temperature and shot-peening determinated by sin2ψ method

2020 ◽  
Vol 25 (1-2) ◽  
pp. 31-37
Author(s):  
Jerzy Jeleńkowski ◽  
Joanna Zdunek ◽  
Piotr Nawrocki ◽  
Grzegorz Mońka
Keyword(s):  
Shot Peening ◽  
Metal Forming ◽  
Source Material ◽  
Internal Stresses ◽  
Ray Method ◽  
X Ray ◽  
Plastic Processing ◽  
Before And After ◽  
Titanium Grade ◽  
Structure Diversity

The article presents the assessment of the macroscopic residual stresses in titanium, grade G4, determined by the sin2ψ X-ray method. The values of stresses measured in the source material and in samples of sub/microstructure obtained after plastic processing in the Gleeble plastometer at the temperature 875 K, optimized strain ε and strain velocity έ were compared. After shot peening, regardless of the structure diversity, the roughness of the polished surfaces of the samples sometimes increased even about 10 times. Small differences occurred in hardness, higher in the more plastic sub/microstructure, which was also reflected in the magnitude of internal stresses.

The determination of the orthoclase content of homogenized alkali feldspars using the 2̄01 X-ray method

1969 ◽  
Vol 37 (288) ◽  
pp. 489-496 ◽  
Author(s):  
J. B. Jones ◽  
R. W. Nesbitt ◽  
P. G. Slade
Keyword(s):  
Ray Method ◽  
High Potassium ◽  
X Ray ◽  
Cation Deficiency ◽  
Alkali Feldspars

SummaryForty-three natural alkali feldspars have been homogenized and used to correlate with wt % K2O. The regression of Or on is Or (wt %) = 465·5 (Å)-1877·5, and is comparable to that obtained on an exchanged orthoclase (Wright, 1968). A deviation from the Orville (1963, 1967) determinative line for synthetic sanidine-albite is greatest at the high potassium end of the series. The discrepancy is not caused by failure to homogenize or incomplete disorder. The presence of cations other than potassium and sodium, or cation deficiency, or both cannot be discounted as a cause.

A Study of the Interaction of Pb-Sn Solder with O2, H2O, and NO2 by X-Ray Photoelectron (ESCA) and Auger (AES) Spectroscopy

1979 ◽  
Vol 33 (3) ◽  
pp. 287-293 ◽  
Author(s):  
Yasuaki Okamoto ◽  
William J. Carter ◽  
David M. Hercules
Keyword(s):  
Reaction Time ◽  
Relative Humidity ◽  
Room Temperature ◽  
Bulk Composition ◽  
Binding Energies ◽  
Nitrogen Species ◽  
Surface Enrichment ◽  
X Ray ◽  
Before And After ◽  
O 10

An ESCA and AES study of the corrosion of 1:1 Pb-Sn solder is reported. The solder was reacted at room temperature with O2 (1 Torr), H2O (10 Torr), 100 ppm of NO2 in N2 (1 atm), and the latter at 50% relative humidity. Pb and Sn foils were examined under similar conditions. The Pb/Sn ratios observed by ESCA and AES for unmelted solder are close to those expected from bulk composition. After melting, a 50% decrease in Pb/Sn was obtained by ESCA; no AES signal for Pb was observed. Before melting, 90% of the Pb and 100% of the Sn were oxidized; after melting 18% Pb and 70% Sn were oxidized. Exposure of solder to O2 (1 Torr) resulted in a Pb/Sn ratio which decreased as a function of time to a minimum value, rapidly increased through a maximum around 60 min and then decreased to an equilibrium value. The O/(Pb + Sn) ratio increased rapidly to an equilibrium value. The interaction of solder with 10 Torr of H2O vapor for 5 min resulted in surface enrichment of Sn with the formation of Sn and Pb oxides. The results obtained with dry NO2 were similar to those with O2; Pb/Sn decreased rapidly to a minimum and went through a small maximum to an equilibrium value. The distribution of species determined by ESCA before and after the reaction were essentially the same as for O2 except the oxidation of Pb was suppressed. No nitrogen species were observed. Solder exposed to at 100 ppm of NO2 in N2 50% relative humidity gave similar results to O2 and dry NO2. The Pb/Sn maximum occurred at a reaction time approximately 2 to 3 times that of O2 and dry NO2 (40 to 60 min). Two nitrogen species were observed for solder treated with 100 ppm of NO2 in N2 at 50% relative humidity; binding energies were ∼404 and 400 eV. These have been attributed to NO2− and NO−, respectively. Mechanisms are proposed for reaction of solder with O2, dry NO2, and NO2 at 50% relative humidity.

The alkali feldspars from microsyenitic dylces of southern Greenland

1966 ◽  
Vol 35 (275) ◽  
pp. 903-919 ◽  
Author(s):  
H. G. Scharbert
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Structural State ◽  
Reciprocal Lattice ◽  
Rich Phase ◽  
Range Of Variation ◽  
Alkali Feldspars

Summary26 b-axis oscillation photographs of alkali feldspars of microsyenitic dykes of Southern Greenland are presented. The crystals are rather restricted in composition (Or42·4 to Or35·3) but are rather rich in Ca (up to 14 % An). The range of variation of the optic axial angles, 2 V 45° to 71° (exceptions up to 87°), puts the crystals between sanidine-anorthoclase cryptoperthite and orthoclase microperthite, as classified by Tuttle (1952).Since the syenitic magma cooled down rather rapidly some peculiarities in the structural state of the alkali feldspars are to be expected. The potassium-rich phase is (nearly) monoclinic. According to the values of the reciprocal lattice angles α* and γ* the sodium-rich phases can be divided into three groups: high-temperature pericline-twinned and high-temperature albite-twinned phases, high-temperature pericline-twinned and low-temperature albite-twinned phases, and high-temperature pericline-twinned and low-temperature albite-twinned phases with nearly identical values of the reciprocal lattice angle γ*.

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