Spontaneous development of concentric layering in a solidified siliceous dike, East Greenland
A meter-wide rhyolitic dike near the eastern margin of the Skaergaard Intrusion developed fine concentric layering in a small section where a fault appears to have fractured the dike and enhanced its interaction with meteoric water. Layers two or three millimeters thick consist of quartz alternating with low-temperature albite and potassium feldspar around a core of radiating clots of the same minerals. The layering seems to have resulted from late-stage crystallization and "self-organization" during devitrification in a warm hydrous environment. The development of fine-scale layering can be modeled quantitatively using the model for competitive particle growth (CPG) of Ortoleva and co-workers. Owing to the small differences of surface energy of grains of differing sizes, large crystals tend to grow at the expense of smaller ones, and a repetitive pattern of layering develops from a small initial perturbation of grain size. The spacing of layers predicted by a numerical model using reasonable estimates for the physical parameters, such as diffusivity and the rate of cooling, is in good agreement with the observed geometry and dimensions. © 1990.
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Related Subject Headings
- Geology
- 3709 Physical geography and environmental geoscience
- 3706 Geophysics
- 3705 Geology
- 04 Earth Sciences
Citation
Published In
DOI
ISSN
Publication Date
Volume
Issue
Start / End Page
Related Subject Headings
- Geology
- 3709 Physical geography and environmental geoscience
- 3706 Geophysics
- 3705 Geology
- 04 Earth Sciences