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1 Golders Associates (UK) Ltd. Clyde House, Reform Road, Maidenhead, Berkshire, SL6 8BY, UK
3 BP Amoco Exploration, Chertsey Road, Sunbury-on-Thames, Middlesex, TX16 7LN
2 Department of Earth Sciences and Engineering, Royal School of Mines, Imperial College of Science, Technology & Medicine, London SW7 2BP, UK
Fluid flow through fractured media is dependent upon a variety of parameters including fracture length, orientation and density, and also on the relative magnitude of the lithostatic stress and the fluid pressure. Because of this it is often difficult to determine the fluid pathway through a particular fracture system even when the geometry of the network is known. Although many fluids (e.g. gas, water etc.) leave little or no evidence of their passage through the rock others such as magmas and fluidized sediments preserve the pathways they follow by forming dykes and sills.
It is found that the pathways preserved by the two types of fluids are different i.e. the spacing of the clastic dykes follows a power-law distribution and that of the igneous dykes a log-normal distribution. It is suggested that this in part might reflect the different properties of the dyke material (specifically its permeability) which determines whether or not the fracture containing the dyke can continue to act as a channel of easy fluid migration once the dyke has been emplaced.
