1084. An attempt to determine the mechanism of a natural mineral-forming reaction from examination of the products

Galwey, Andrew K.; Jones, Kenneth A.

doi:10.1039/jr9630005681

Cited by 27 publications

(10 citation statements)

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“…Grains form polyhedra of a uniform size distribution, and the normalized GSD will not change with continued coarsening (Lifshitz & Slyozov 1961; Wagner 1961; Joesten 1991). This may be easily assessed from the apparent GSD measured from sections; the apparent GSD is within 10% of true GSD (Galwey & Jones 1963).…”

Section: Resultsmentioning

confidence: 99%

Grain‐scale permeabilities of faceted polycrystalline aggregates

et al. 2006

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Porous synthetic quartzites and amphibolites, each with faceted pore walls, were synthesized and evaluated to examine the permeability of pore networks similar to those of the lower crust and mantle. Quartzite with a fluid in equilibrium with an Mg-clinopyroxene contained connected networks of pores with a dihedral angle of 30°b ounded by walls that were 10-50% faceted. The relationship of their permeability (k) to porosity (/) is approximated by the previously determined relationship for relatively nonfaceted synthetic quartziteAmphibolite with an HF fluid contained fluorotremolite and a connected network of pores bounded by walls exhibiting 78-90% faceting. These materials showed much lower k for a given /, with an apparent permeability threshold at / c ¼ 0.04. A curve fit to these data yieldsThe results suggest that moderate faceting has little effect on the transmission of fluids through rocks, but extensive faceting significantly alters permeability. This difference is most likely produced through isolation of the fluid to the grain corners at low / with extensive faceting. Rocks with pores that tend toward faceting may impede the flow of fluids and melt.

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Section: Resultsmentioning

confidence: 99%

Grain‐scale permeabilities of faceted polycrystalline aggregates

et al. 2006

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“…Effects of this type have been reported previously by Chinner (1960, p. 193) and by Jones and Galwey (1964). Considering the second aspect, the authors believed that quantitative examination of crystal size distribution may give information about the kinetics of reactions in the nucleation and growth of the product phase (Galwey and Jones, 1963).…”

Section: Introductionmentioning

confidence: 87%

Crystal Size Frequency Distribution of Garnets in Some Analysed Metamorphic Rocks from Mallaig, Inverness, Scotland

Galwey

Jones²

1966

Geol. Mag.

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In an attempt to obtain information about garnet nucleation a series of eleven apparently homogeneous metamorphic rocks, from a small area near Mallaig, Inverness, Scotland, have been analysed to determine bulk chemical and modal compositions, garnet grain size and number of garnet crystals occurring in unit volume of rock (N). No correlation of N with any function of chemical and modal compositions could be found, and it is therefore concluded that, if the influence of trace components can be neglected, externally imposed factors (for example, time-temperature variation) or internal physical factors (for example, the surface area of the rock just prior to garnet formation) must exert a controlling influence on garnet nucleation. It was found, however, that in each specimen, there was a preferred crystal radius and the relative frequency of occurrence about this preferred value was constant for all samples studied. Preliminary comparison with other systems, investigated by the authors, suggested that the nature of this relationship may provide evidence of the conditions under which these rocks recrystallized.

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“…These tools of quantitative textural analysis (QTA) were first introduced by Galwey and Jones (1963;1966), Jones and Galwey (1964;1966), Kretz (1966;1969;1973;1974) Kretz 1993), which require arduous effort to obtain information on relatively small populations of crystals. These obstacles can now be overcome, however, by means of high-resolution X-ray CT. With instruments similar to the CAT scanners long used for medical diagnosis, but with higher intensity X-ray sources and much higher resolution, it is now possible to obtain complete three-dimensional information with sub-millimetre resolution on the sizes and locations of thousands of crystals within rock samples several centimetres in maximum dimension (Carlson and Denison 1992).…”

Section: Quantitative Textural Measurements Using Computed X-ray Tomomentioning

confidence: 99%

“…Quantitative characterization of metamorphic textures focuses on measurement of the spatial disposition of crystals and their size frequency distributions, and in favourable cases on the record of growth preserved in minerals such as garnet that acquire and retain prograde chemical zonation. These tools of quantitative textural analysis (QTA) were first introduced by Galwey and Jones (1963;1966), Jones and Galwey (1964;1966), Kretz (1966;1969;1973;1974) and Jones et al (1972), who demonstrated that such measurements Figure 2. Planar sections through three-dimensional arrays of porphyroblasts corrupt the measurement of crystal sizes and separations that are fundamental to the quantitative analysis of textures.…”

Section: Quantitative Textural Measurements Using Computed X-ray Tomomentioning

confidence: 99%

Controls on the nucleation and growth of porphyroblasts: Kinetics from natural textures and numerical models

1995

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Quantitative textural analysis of garnetiferous rocks from diverse metamorphic environments has demonstrated that diffusionally influenced nucleation and thermally accelerated diffusion-controlled growth are commonly among the dominant controls on porphyroblast crystallization. A new numerical model of diffusion-controlled nucleation and growth that incorporates time as an explicit variable is capable of replicating the essential features of many of these natural porphyroblastic textures using geologically reasonable values for the kinetic parameters governing crystallization. This model has been used to interpret quantitative textural data from four rocks in which garnet grew during prograde regional metamorphism, by assuming constant heating rates and by accepting a previously published estimate for the activation energy for intergranular diffusion. From fits of the model to natural textures, estimates have been extracted for three previously undetermined kinetic quantities that control the nucleation and growth of garnet porphyroblasts, namely the activation energy for nucleation and the pre-exponential rate constants for nucleation and intergranular diffusion. The uncertainty in derived values for the pre-exponential rate constant for intergranular diffusion is probably not much larger than a factor of two because it is proportional to the uncertainty in prograde heating rates, given a defined temperature interval over which Crystallization occurs. The uncertainty in estimates of the activation energy and pre-exponential rate constant for nucleation is larger, perhaps a factor of ten, because values for these quantities are derived from fits of the model to natural crystal size distributions; the precision of these estimates appears to be limited by the fact that the crystal size distributions are affected by factors not encompassed within the model (probably variable heating rates and inhomogeneity in the distribution of nutrients in the rock's precursor).

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1084. An attempt to determine the mechanism of a natural mineral-forming reaction from examination of the products

Abstract: Mineral-forming Reaction from Examination of the Products.

Cited by 27 publications

References 0 publications

Grain‐scale permeabilities of faceted polycrystalline aggregates

Grain‐scale permeabilities of faceted polycrystalline aggregates

Crystal Size Frequency Distribution of Garnets in Some Analysed Metamorphic Rocks from Mallaig, Inverness, Scotland

Controls on the nucleation and growth of porphyroblasts: Kinetics from natural textures and numerical models

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