From outcrop to synthetic seismic: 2D and 3D modelling of igneous intrusions at Botneheia, central Spitsbergen
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The use of seismic reflection data and seismic modelling of igneous intrusions has greatly improved the understanding of igneous intrusions in sedimentary basins. However, there are still uncertainties in the seismic images of such intrusions, because they can have a complex architecture and their imaging potential is dependent on several factors. For instance, igneous intrusions crystallise from magma, which introduce heat to the host rocks in which they enter, resulting in a zone of contact metamorphism. Therefore, the present study analyses the effect a contact metamorphic aureole has on the seismic expression of igneous intrusions, and how intrusion geometries are imaged in both 2D- and 3D-seismic data. Digital outcrop models from the locality of Botneheia, Svalbard, from both lidar-data and photogrammetry, are first used to generate realistic 2D- and 3D-geological models. A modelling workflow is then applied to efficiently turn outcrops of intruded rocks into synthetic seismic images, both in 2D and 3D, and to perform sensitivity analyses. The study highlights which impact a change in dominant frequency has on the detail-level for intrusions in seismic data, this without and with contact aureoles, two types of the latter being tested in the 2D cases. The contact aureoles lead to lowered reflection amplitudes and influence how the reflections of the intrusions are resolved, i.e. a strong combined reflection and/or individual ones, and thus add to the list of factors complicating the imaging of igneous intrusions. The obtained results demonstrate that the seismic expression of intrusions may vary from case to case, i.e. dependent on local factors, and that seismic modelling should aid interpretation of real seismic data. This study also opens the door for more comprehensive 3D modelling of igneous intrusions, especially by including detailed contact aureoles.
PublisherThe University of Bergen
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