Volume expansion (∼1-5% volume strain with ΔVmeltingpositive) and fluid-absent partial melting, in which ΔVmeltingis positive, of continental crust by intruding basaltic magma is a strongly irreversible process involving the dissipation of both thermal energy and matter (partial melt). Using a simple random graph model we show by analogy how isolated fractures that form during rapid thermal perturbation in the source region can combine to form a single, interconnected structure with high permeability. Once connected, the fracture network may be thought of as a single structure or pattern that will remain stable so long as a strong temperature gradient is maintained in the source region. Estimates of fracture permeability that take into account changes in connectivity and fracture spacing range from approximately 10-10to 10-5m2, many orders of magnitude greater than values considered typical during large-scale crustal deformation and prograde regional metamorphism. The ability of the isotropic fracture network to develop a top-bottom directionality is crucial for buoyancy-driven melt transport. A physical model based on non-linear evolution rules during thermal expansion is given that predicts the emergence of directionality (vertical fracture alignment) on a time scale of the order of 105y. The necessary ingredients are a deviatoric strain path, a heterogeneous medium and a stiffness that evolves as a function of the local strain. © 1998 Elsevier Science Ltd. All rights reserved.
|Title of host publication||Journal of Structural Geology|
|Number of pages||10|
|Publication status||Published - 1 Sep 1998|
|Name||Journal of Structural Geology|
Petford, N., & Curt Koenders, M. A. (1998). Self-organisation and fracture connectivity in rapidly heated continental crust. In Journal of Structural Geology (Vol. 20, pp. 1425-1434). (Journal of Structural Geology; Vol. 20). Elsevier Ltd. https://doi.org/10.1016/S0191-8141(98)00081-9