HR: 1340h
AN: MR23B-1322    [Abstracts]
TI: Quantitative Textural Analysis of Packings of Elongate Crystals
AU: * Rudge, J F
EM: rudge@esc.cam.ac.uk
AF: Bullard Laboratories, Department of Earth Sciences, Madingley Road, Cambridge, CB3 0EZ, United Kingdom
AU: * Rudge, J F
EM: rudge@esc.cam.ac.uk
AF: Department of Applied Mathematics and Theoretical Physics, Wilberforce Road, Cambridge, CB3 0WA, United Kingdom
AU: Holness, M B
EM: marian@esc.cam.ac.uk
AF: Department of Earth Sciences, Downing Street, Cambridge, CB2 3EQ, United Kingdom
AU: Smith, G C
EM: gcs27@esc.cam.ac.uk
AF: Department of Earth Sciences, Downing Street, Cambridge, CB2 3EQ, United Kingdom
AB: The spatial distribution of grains in a solidifying igneous rock controls the physical properties of the crystal mush, and is in turn controlled by the rates of crystal growth and accumulation. The dominance of a non-spherical habit for minerals growing from liquid brings into question the use of spherical particles in reference packings used for the quantification of grain spatial distribution in rocks. Furthermore, details of the way crystal clustering/ordering varies on a range of lengthscales can only be discerned using statistical measures which take into account the distribution of particles beyond nearest neighbours. We advocate the use of spatial distribution functions such as Ripley's K, the pair correlation, and the mark correlation. Using random close packings of spherocylinders we demonstrate the importance of aspect ratio in controlling the aggregation index (usually known as R) and demonstrate that packings of spherical particles have more structure than those of elongate particles. Application of the spatial distribution functions to a sample of the colonnade from the Holyoke flood basalt, dominated by clusters of elongate plagioclase grains, demonstrates that the lengthscale of the clustering is 0.5 mm. Further understanding of the controls on grain spatial distribution in igneous rocks will depend on application of these techniques to rocks from well-understood environments.
DE: 3625 Petrography, microstructures, and textures
DE: 3640 Igneous petrology
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting