Modelling the structural controls of primary kaolinite formation
Reason for embargo
An abundance of kaolinite was formed within the St Austell granite pluton of Cornwall, southwest England, by the hydrous dissolution of feldspar crystals. The permeability of Cornish granites is low and alteration acts pervasively from discontinuity features, with montmorillonite recognised as an intermediate assemblage in partially kaolinised material. Structural features allowed fluids to channel through the impermeable granite and pervade deep into the rock. Areas of high structural control are hypothesised to link well with areas of advanced alteration. As kaolinisation results in a loss of competence, we present a method of utilising discontinuity orientations from nearby unaltered granites alongside the local tectonic history to calculate strain rates and delineate a discrete fracture network. Simulation of the discrete fracture network is demonstrated through a case study at Higher Moor, where kaolinite is actively extracted from a pit. Reconciliation of fracture connectivity and permeability against measured subsurface data show that higher values of modelled properties match with advanced kaolinisation observed in the field. This suggests that the technique may be applicable across various industries and disciplines
We acknowledge and are grateful for use of the Move Software Suite granted by Midland Valley's Academic Software Initiative. We would also like to thank Imerys Minerals Ltd. for the contribution of drill data and field access. Richard Hooper and Chris Yeomans are thanked for their help and advice. We thank two anonymous reviewers for their helpful comments and suggestions. One of the authors (HG) would like to acknowledge funding as part of the Sustainable Technologies for Calcined Industrial Minerals (STOICISM) project funded by the European Union's seventh Framework Program (FP7/2007–2013) under grant agreement number 310645.
This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.