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Thesis (Ph. D.)--University of Wisconsin--Madison, 1964. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Results from experiments in this work have been combined with existing data to yield tracer diffusivities of divalent cations in natural multicomponent garnets at 10-40 kb, 1100 - 1475°C. For the garnet compositions studied in this work, the activation energy for tracer diffusion of Mn < Fe ≃ Mg, while activation volumes increase in the order Mg < Fe < Mn. These data may be used with theoretical models to calculate the full multicomponent diffusion coefficient matrix as a function of pressure, temperature, composition and oxygen fugacity. An analytical model has been developed to describe the relaxation of compositional zoning in metapelitic garnets during metamorphism. It is found that a significant amount of relaxation occurs during heating and the composition at the core of a garnet crystal is disturbed very early in the process. The extent of relaxation depends on a number of factors which include the grain size, the initial shape of the compositional profile, details of the thermal history and the textural mode of occurrence of the garnet. Complications such as oscillations in a compositional profile may be explained by the mathematical form of the equations describing the process. Graphical representation of the results of this model have been provided that allow quick and easy determination of the extent of relaxation or time scale of metamorphic processes. Calculations using the diffusion data indicate that Fe-Mg exchange geothennometry and Sm-Nd geochronology involving garnets may not yield the peak metamorphic conditions for certain geologically realistic situations. Model calculations on natural assemblages suggest that the diffusion data may be used to yield infonnation on metamorphic processes ranging from time scales to crystal growth rates during metamorphism. Veracity of P-T paths calculated from garnet zoning may also be checked using the diffusion data. Illustrative examples of such calculations have been provided.

No description available.

The mineralogy and particle size distribution of a large number of till samples from eastern England were studied. Only two members of the Devensian till succession of the Holderness area of Yorkshire are recognised, not three as earlier supposed. These two tills, the Purple and Drab, car be distinguished texturally, mineralogically, and by their colour. However, both weather by oxidation to a reddish brown till, and are then virtually indistinguishable in the field; this weathered material was previously thought to represent a distinct unit, the Hessle Till. The lower Devensian till (the Drab) extends on to the eastern foot slopes of the Yorkshire Wolds, and is correlated with the Marsh Tills of Lincolnshire and the Hunstanton Till of north-west Norfolk. The upper Purple Till occupies only an arcuate area of south-eastern Holderness. A grey older till at Welton-le-Wold (Lincolnshire) is tentatively correlated with the pre-Devensian Basement Till of Holderness. Soil development on these tills was investigated, mainly in a profile on the Purple Till at Tunstall in eastern Holderness. Particle size, mineralogical and chemical analyses were used to establish the uniformity of the original parent material in this profile, and to quantify weathering and other changes that occurred during its development in post-Devensian times. The calculations were based on the method outlined by Barshad (1964), using the quarts and felspar content as an index of weathering. The profile is oxidised to a depth of about and leached of calcium carbonate to 0.7m. Gleying is prominent at depths of 0.2 - 2m. Pock fragments have been disaggregated and fine clay formed from coarser fractions in the upper part of the profile. Much of this fine clay has been translocated to lower horizons (O.3-1.4m depth), but there is little remaining evidence for translocated clay in the micromorphology of these horizons. The main mineralogical charge in fine soil fractions was the weathering of mica to fine clay sized vermiculite.

Thesis (M.S.)--Miami University, Dept. of Geology, 2002. / Title from first page of PDF document. Document formatted into pages; contains vi, 182 p. : ill. Includes bibliographical references (p. 128-130).

Thesis (Ph. D.)--University of Missouri, 1937. / Vita. Published also as Bulletin, Technical series, v. 12, no. 3, March, 1937, of the University of Missouri School of Mines, with F.J. Zvanut, L.J. Wood, C.M. Dodd and W.T. Schrenk given as authors. Bibliography: p. 37-42.