Abstract - The thickness and spacing systematics of 30 line
samples of vein arrays at ten localities have been analysed. The analytical
methods were tested on four synthetic data sets. The synthetic and natural
data sets were each analysed with respect to (i) cumulative thickness vs
distance, (ii) thickness population, (iii) spacing population, (iv) the
coefficient of variation of spacing, which measures clustering and (v)
the mass function, which measures the scaling of strain heterogeneity.
A fundamental distinction is apparent between stratabound arrays, vein
arrays in layered rocks where the veins are confined to individual mechanical
units, and non-stratabound arrays which occur in rock volumes lacking persistent
crack-stopping discontinuities. The stratabound arrays show regular spacing
controlled by layer thickness and non power-law thickness distributions.
The non-stratabound arrays are clustered and have power-law thickness
distributions, resulting from the lack of a controlling length scale. Exponents
of the thickness distributions have a modal value of 0.8 and do not vary
significantly with lithology. Ore mineralisation is favoured in non-stratabound
arrays as they are more likely than stratabound arrays to form large clusters
connected to a remote fluid source.
In: Fractures, fluid flow and mineralisation. Geological
Society of London, Special Publication, 155, 35-65, 1999.