Controls on the expression of igneous intrusions in seismic reflection data

Craig Magee, Shivani M. Maharaj, Thilo Wrona, Christopher A.-L. Jackson
2015 Geosphere  
The architecture of subsurface magma plumbing systems influences a variety of igneous processes, including the physiochemical evolution of magma and extrusion sites. Seismic reflection data provides a unique opportunity to image and analyze these sub-volcanic systems in 3-D and has arguably revolutionized our understanding of magma emplacement. In particular, the observation of (i) interconnected sills, (ii) transgressive sill limbs, and (iii) magma flow indicators in seismic data suggest that
more » ... data suggest that sillcomplexes can facilitate significant lateral (10's-100's km) and vertical (<5 km) magma transport. However, it is often difficult to determine the validity of seismic interpretations of igneous features because: (i) they are rarely drilled; and (ii) our ability to compare seismically imaged features to potential field analogues is hampered by the limited resolution of seismic data. Here, we use field observations to constrain a series of novel seismic forward models that examine how different sill morphologies may be expressed in seismic data. By varying the geologic architecture (e.g., host rock lithology and intrusion thickness) and seismic properties (e.g., frequency), the models demonstrate that seismic amplitude variations and reflection configurations can be used to constrain intrusion geometry. However, our results also highlight that stratigraphic reflections can interfere with reflections generated at the intrusive contacts, and may thus produce seismic artefacts that could be misinterpreted as real features. This study emphasizes the value of seismic data to understanding magmatic systems and demonstrates the role that synthetic seismic forward modelling can play in bridging the gap between seismic data and field observations. Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation Click here to download Cover Letter: Magee_cover letter_revised.docx Controls on the expression of igneous intrusions in seismic reflection data 1 2 Abstract 8 The architecture of subsurface magma plumbing systems influences a variety of igneous 9 processes, including the physiochemical evolution of magma and extrusion sites. Seismic 10 reflection data provides a unique opportunity to image and analyze these sub-volcanic 11 systems in 3-D and has arguably revolutionized our understanding of magma emplacement. 12 In particular, the observation of (i) interconnected sills, (ii) transgressive sill limbs, and (iii) 13 magma flow indicators in seismic data suggest that sill-complexes can facilitate significant 14 lateral (10's-100's km) and vertical (<5 km) magma transport. However, it is often difficult 15 to determine the validity of seismic interpretations of igneous features because: (i) they are 16 rarely drilled; and (ii) our ability to compare seismically imaged features to potential field 17 analogues is hampered by the limited resolution of seismic data. Here, we use field 18 observations to constrain a series of novel seismic forward models that examine how 19 different sill morphologies may be expressed in seismic data. By varying the geologic 20 architecture (e.g., host rock lithology and intrusion thickness) and seismic properties (e.g., 21 frequency), the models demonstrate that seismic amplitude variations and reflection 22 configurations can be used to constrain intrusion geometry. However, our results also 23 highlight that stratigraphic reflections can interfere with reflections generated at the intrusive 24 contacts, and may thus produce seismic artefacts that could be misinterpreted as real features. 25 Manuscript Click here to download Manuscript: Magee et al 2014 -synthetic intrusions and host rock III__revised.docx This study emphasizes the value of seismic data to understanding magmatic systems and 26 demonstrates the role that synthetic seismic forward modelling can play in bridging the gap 27 between seismic data and field observations. 28 29
doi:10.1130/ges01150.1 fatcat:bkbfcor7fvemzhvp64nlrnyyp4