Sill complex geometry and internal architecture: a 3D seismic perspective

Abstract

Abstract Seismic volume visualization techniques demonstrate that saucer-shaped sill complexes consist of a series of radiating principal flow units rising from an inner saucer and fed by principal magma tubes. Such flow units contain smaller scale secondary flow units, each being fed by a secondary magma tube branching from the principal magma tube. This pattern is repeated down to scales of approximately 100 m with successively smaller flow units being fed from magma tubes repeatedly branching from higher order tubes. The data demonstrates that each sill complex is independently fed from a centrally located point source, that sills grow by climbing from the centre outwards and that peripheral dyking from the upper surface is a common feature. These features suggest a laccolith emplacement style involving peripheral fracturing and dyking during inner saucer growth and thickening.