TY - JOUR
T1 - The building blocks of igneous sheet intrusions
T2 - Insights from 3-D seismic reflection data
AU - Köpping, Jonas
AU - Magee, Craig
AU - Cruden, Alexander R.
AU - Jackson, Christopher A.L.
AU - Norcliffe, James R.
N1 - Funding Information:
We are grateful to Geoscience Australia for making the seismic reflection and borehole data publicly available at https://nopims.dmp.wa.gov.au/nopims. We also thank Down Under Geo-Solution and Schlumberger for the use of DUG Insight 4 and Petrel seismic interpretation software. We gratefully acknowledge helpful reviews by Eric Horsman and an anonymous reviewer and additional commentary from associate editor Robert Miller. We thank Shanaka de Silva for his editorial handling of the manuscript. J. Köpping acknowledges a Monash Graduate Scholarship. A.R. Cruden, C.A.-L. Jackson, and C. Magee acknowledge funding from Australian Research Council Discovery Grant DP190102422. We thank Andy Bunger for fruitful discussions on element geometries.
Funding Information:
We are grateful to Geoscience Australia for making the seismic reflection and borehole data publicly available at https://nopims.dmp.wa.gov.au/nopims. We also thank Down Under GeoSolution and Schlumberger for the use of DUG Insight 4 and Petrel seismic interpretation software. We gratefully acknowledge helpful reviews by Eric Horsman and an anonymous reviewer and additional commentary from associate editor Robert Miller. We thank Shanaka de Silva for his editorial handling of the manuscript. J. K?pping acknowledges a Monash Graduate Scholarship. A.R. Cruden, C.A.-L. Jackson, and C. Magee acknowledge funding from Australian Research Council Discovery Grant DP190102422. We thank Andy Bunger for fruitful discussions on element geometries.
Publisher Copyright:
© 2022 The Authors. All Rights Reserved.
PY - 2022
Y1 - 2022
N2 - The propagating margins of igneous sills (and other sheet intrusions) may divide into laterally and/or vertically separated sections, which later inflate and coalesce. These components elongate parallel to and thus record the magma flow direction, and they can form either due to fracture segmentation (i.e., “segments”) or brittle and/or non-brittle deformation of the host rock (i.e., “magma fingers”). Seismic reflection data can image entire sills or sill-complexes in 3-D, and their resolution is often sufficient to allow us to identify these distinct elongate components and thereby map magma flow patterns over entire intrusion networks. However, seismic resolution is limited, so we typically cannot discern the centimeter- to meter-scale host rock deformation structures that would allow the origin of these components to be interpreted. Here, we introduce a new term that defines the components (i.e., “elements”) of sheet-like igneous intrusions without linking their description to emplacement mechanisms. Using 3-D seismic reflection data from offshore NW Australia, we quantify the 3-D geometry of these elements and their connectors within two sills and discuss how their shape may relate to emplacement processes. Based on seismic attribute analyses and our measurements of their 3-D geometry, we conclude that the mapped elements likely formed through non-elastic-brittle and/or non-brittle deformation ahead of the advancing sill tip, which implies they are magma fingers. We show that thickness varies across sills, and across distinct elements, which we infer to represent flow localization and subsequent thickening of restricted areas. The quantification of element geometries is useful for comparisons between different subsurface and field-based data sets that span a range of host rock types and tectonic settings. This, in turn, facilitates the testing of magma emplacement mechanisms and predictions from numerical and physical analogue experiments.
AB - The propagating margins of igneous sills (and other sheet intrusions) may divide into laterally and/or vertically separated sections, which later inflate and coalesce. These components elongate parallel to and thus record the magma flow direction, and they can form either due to fracture segmentation (i.e., “segments”) or brittle and/or non-brittle deformation of the host rock (i.e., “magma fingers”). Seismic reflection data can image entire sills or sill-complexes in 3-D, and their resolution is often sufficient to allow us to identify these distinct elongate components and thereby map magma flow patterns over entire intrusion networks. However, seismic resolution is limited, so we typically cannot discern the centimeter- to meter-scale host rock deformation structures that would allow the origin of these components to be interpreted. Here, we introduce a new term that defines the components (i.e., “elements”) of sheet-like igneous intrusions without linking their description to emplacement mechanisms. Using 3-D seismic reflection data from offshore NW Australia, we quantify the 3-D geometry of these elements and their connectors within two sills and discuss how their shape may relate to emplacement processes. Based on seismic attribute analyses and our measurements of their 3-D geometry, we conclude that the mapped elements likely formed through non-elastic-brittle and/or non-brittle deformation ahead of the advancing sill tip, which implies they are magma fingers. We show that thickness varies across sills, and across distinct elements, which we infer to represent flow localization and subsequent thickening of restricted areas. The quantification of element geometries is useful for comparisons between different subsurface and field-based data sets that span a range of host rock types and tectonic settings. This, in turn, facilitates the testing of magma emplacement mechanisms and predictions from numerical and physical analogue experiments.
UR - https://www.scopus.com/pages/publications/85124962902
U2 - 10.1130/GES02390.1
DO - 10.1130/GES02390.1
M3 - Article
AN - SCOPUS:85124962902
SN - 1553-040X
VL - 18
SP - 156
EP - 182
JO - Geosphere
JF - Geosphere
IS - 1
ER -