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Articles 211 - 219 of 219

Full-Text Articles in Geology

Dunes And Vegetation: Natural Recovery On A Damaged Barrier Island, C. John Burk, H. Allen Curran, Teresa M. Czerniak Jan 1981

Dunes And Vegetation: Natural Recovery On A Damaged Barrier Island, C. John Burk, H. Allen Curran, Teresa M. Czerniak

Geosciences: Faculty Publications

No abstract provided.

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Normalizations Of Thermodynamic Properties And Some Implications For Graphical And Analytical Problems In Petrology, John B. Brady, James H. Stout Feb 1980

Normalizations Of Thermodynamic Properties And Some Implications For Graphical And Analytical Problems In Petrology, John B. Brady, James H. Stout

Geosciences: Faculty Publications

Petrologic problems may be analyzed using any of a variety of possible choices of units. Although gram-formula units (moles) are commonly used, other units of quantity arc more appropriate for many applications. Gram-atom units offer the numerical simplicity of gram-formula units and have the advantage of being conserva­tive. A conservative unit of quantity is one for which the sum of the units of reactants equals the sum of the units of products in a chemical reaction. For many graphical problems, a conservative unit of quantity, such as gram-atom or mass units, should be used. Since gram-formula units are not conservative, …

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Interdiffusion Of S And Se In Tiemannite, Nabil Z. Boctor, John B. Brady Jan 1980

Interdiffusion Of S And Se In Tiemannite, Nabil Z. Boctor, John B. Brady

Geosciences: Faculty Publications

Diffusion coefficients for S-Se interdiffusion in tiemannite (HgSe) single crystals have been determined in the temperature range 500"-700oC. The measured diffusivities may be fit by the equation...

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A Micro-Analytical Technique For Determination Of Aluminum In Aqueous Solutions, John B. Brady, John D. Frantz Jan 1980

A Micro-Analytical Technique For Determination Of Aluminum In Aqueous Solutions, John B. Brady, John D. Frantz

Geosciences: Faculty Publications

A flow-cell colorimetric technique has been developed by which Al concentrations of 0.0003to 0.1 wt. percent can be analyzed in one-microliter fluid samples.An A1-complexing reagent (Ferron) continuously flowing through teflon capillary tubing is spiked with one-microliter aliquots of solutions containing A1. The sample reacts with the reagent and subsequently passes through a microcolorimeter. Measurement of less than one nanomole A1 is possible by comparing the integrated absorbance of unknown samples with standard solutions.

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Magic Gems, Minerals, And Fossils, Mary Margaret Murphy, H. Allen Curran May 1977

Magic Gems, Minerals, And Fossils, Mary Margaret Murphy, H. Allen Curran

Geosciences: Faculty Publications

No abstract provided.

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Chemical Components And Diffusion, John B. Brady Nov 1975

Chemical Components And Diffusion, John B. Brady

Geosciences: Faculty Publications

Chemical components for use in the description of a system involved in a diffusion process may be selected according to the same criteria followed in the selec­tion of components for an equilibrium system. The various possible sets of components are not independent and may be interrelated through a component transformation. Actual components are preferred over nonvariable components, since they simplify descriptions and avoid theoretically nonmeasureable quantities. Two systems involved in an interdiffusion process may always be described using components that are actual components of both systems. For example, ternary reciprocal exchange of alkalis be­ tween alkali feldspars and dioctahedral alkali …

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Reference Frames And Diffusion Coefficients, John B. Brady Oct 1975

Reference Frames And Diffusion Coefficients, John B. Brady

Geosciences: Faculty Publications

No abstract provided.

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Problems In Interpreting Unusually Large Burrows, Richard G. Bromley, H. Allen Curran, Robert W. Frey, Raymond C. Gutschick, Lee J. Suttner Jan 1975

Problems In Interpreting Unusually Large Burrows, Richard G. Bromley, H. Allen Curran, Robert W. Frey, Raymond C. Gutschick, Lee J. Suttner

Geosciences: Faculty Publications

Although marine burrows of unusually large dimensions have long been known in certain areas, they are probably much more widespread in the rock record than is generally recognized. Such burrows constitute a heterogeneous group, having little in common other than "exceptional" size. Yet their size alone unites them in difficulty of interpretation: e.g., densely spaced-dwelling burrows of combined dwelling-escape burrows as much as 12 cm in diameter and 5 m long; vertical dwelling burrows only 0.5 cm in diameter but up to 9 m long; possible escape structures as much as 24 cm in diameter and 3 m long, subsequently …

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Coexisting Actinolite And Hornblende From West-Central New Hampshire, John B. Brady Jan 1974

Coexisting Actinolite And Hornblende From West-Central New Hampshire, John B. Brady

Geosciences: Faculty Publications

The coexistence of actinolite and hornblende and of cummingtonite and hornblende has been observed in garnet-zone and staurolite-kyanite-zone amphibolites of the Ammonoosuc Volcanics near Hanover, New Hampshire. The amphibole pairs occur both as separate grains and as intergrowths with boundaries that are optically and chemically sharp, but geometrically irregular; no exsolution lamellae were observed.Electron microprobe analyses of the amphibole pairs show that: (1) hornblende is richer in Al, Na, K, Ti, and Fea+,and has a lower Mg/(Me f Fe) ratio than the coexisting actinolite; (2) hornblende is enriched in Al, Na, and Ca, but has a similar Mel(Mg f Fe) …

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