Diffusion Of Mg Research Articles

THE PETROLOGY OF TWO ZONED SCAPOLITE SKARNS

A spheroidal skarn body at Gib Lake, Pontiac County, Quebec, occurs in phlogopite marble, and shows concentric zones several centimeters thick. The zonal sequence is (a) core of blue scapolite; (b) pargasite–albite intergrowth; (c) pure phlogopite; (d) serpentinized forsterite–dolomite marble. The minerals have been analyzed. A zoned skarn with a similar sequence was found 15 miles south on Calumet Island.Phase assemblages are consistent with upper amphibolite facies metamorphism. The zonal sequence is explained by reaction between a spheroidal quartzo-feldspathic mass and an enveloping dolomitic marble through radial diffusion of Mg (inward) and Si, Al (outward), establishing local equilibrium between adjacent phases. Mg, Al, and Si behaved as phase-determining inert components, Ca was probably in excess, while Na, K, H, Cl, C, F, S were perfectly mobile.

Predicting concentrations of solutes in water percolated through a column of soil

A procedure was developed for calculating the concentration of solutes present in waters leached through soils containing gypsum and exchangeable Ca++ and Mg++. A program of the procedure, prepared for a 1620 IBM computer, was used to predict the concentration of solutes in the effluent from a Yolo clay-loam soil that was being leached with a 0.025 N MgCl2 solution. The theoretical results are compared with experimentally determined values. It is apparent that diffusion of Mg++ caused variation between some of the calculated and measured values; the predicted values, however, are sufficiently close to the measured concentrations to be useful in most investigations.

Selective Oxidation of Silver-Magnesium Alloys in Water Vapor

A simple method is described for measuring low rates of selective oxidation of Ag–Mg alloys at elevated temperatures when water vapor is used as oxidizing agent. It is found that the MgO layer builds up on the surface of the alloy according to a parabolic law over a range of the water vapor pressure from 7×10 -3 to 6×10 -2 mm Hg, and the oxide growth begins to follow a linear law rather than a parabolic law at a pressure of 1 mm Hg. In the region where the parabolic law holds, the growth of the oxide layer seems to be controlled by the diffusion of Mg through the layer. 20.7 kcal/mol is obtained as the activation energy of diffusion. Applyjng the transition state theory of gas-metal reaction, as developed by Gulbransen, the diffusion of Mg through the oxide layer is given by D (cm 2 /sec)=2.17×10 -9 exp (-20,700/RT).

Selective Oxidation of Silver-Magnesium Alloys in Water Vapor

A simple method is described for measuring low rates of selective oxidation of Ag–Mg alloys at elevated temperatures when water vapor is used as oxidizing agent. It is found that the MgO layer builds up on the surface of the alloy according to a parabolic law over a range of the water vapor pressure from 7×10 -3 to 6×10 -2 mm Hg, and the oxide growth begins to follow a linear law rather than a parabolic law at a pressure of 1 mm Hg. In the region where the parabolic law holds, the growth of the oxide layer seems to be controlled by the diffusion of Mg through the layer. 20.7 kcal/mol is obtained as the activation energy of diffusion. Applyjng the transition state theory of gas-metal reaction, as developed by Gulbransen, the diffusion of Mg through the oxide layer is given by D (cm 2 /sec)=2.17×10 -9 exp (-20,700/RT).